Aircraft Mass & Balance

031 AIRCRAFT MASS & BALANCE

© G LONGHURST 1999 All Rights Reserved Worldwide

COPYRIGHT All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the author. This publication shall not, by way of trade or otherwise, be lent, resold, hired out or otherwise circulated without the author's prior consent. Produced and Published by the CLICK2PPSC LTD EDITION 2.00.00 2001 This is the second edition of this manual, and incorporates all amendments to previous editions, in whatever form they were issued, prior to July 1999. EDITION 2.00.00

© 1999,2000,2001

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The information contained in this publication is for instructional use only. Every effort has been made to ensure the validity and accuracy of the material contained herein, however no responsibility is accepted for errors or discrepancies. The texts are subject to frequent changes which are beyond our control.

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TABLE OF CONTENTS Introduction The Composition of Aeroplane Weight The Calculation of Aircraft Weight Weight and Balance Theory Centre of Gravity Calculations Adding, Removing and Repositioning Loads The Mean Aerodynamic Chord Structural Limitations Manual and Computer Load/Trim Sheets Joint Aviation Regulations

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TABLE OF CONTENTS The Weighing of Aeroplanes Documentation Definitions CAP 696 - Loading Manual

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Introduction 1. As a professional pilot you will deal with aircraft loading situations on every flying day of your working life. The course that you are about to embark upon considers the inter-relationship between aircraft loading and other related subjects (principally aircraft performance and flight planning), and the very important airmanship aspects of proper aircraft loading. In general (nonaircraft type specific) terms, the ways in which the centre of gravity of both unladen and laden aircraft can be determined and checked as being within safe limits will be discussed. As and when you are introduced to new aircraft types, both during your flight training and during your subsequent career, you will be taught the loading procedures which are specific to that particular aircraft type. 2. In the Aircraft Performance book the problem of determining the maximum permitted takeoff weight for an aircraft in a given situation is addressed. The Flight Planning book addresses the determination of the maximum payload, which can be carried on a given flight. In Aircraft Loading the problems of distributing the load within the aircraft such that the resultant centre of gravity is, firstly, within the safe limits laid down for the aircraft and, secondly, positioned so as to enhance the efficient performance of the aircraft, are addressed. 3. The Joint Aviation Authority has the task of ensuring that all public transport aircraft, irrespective of size or number of engines, are operated to the highest possible level of safety. To discharge this commission the JAA periodically introduces legislation in the form of operating rules or regulations and minimum performance requirements, which are complementary. All public transport aircraft are divided into Classes in which the types have similar levels or performance. There is a set of rules and requirements for each Class of aeroplanes, which dictate the maximum mass at which an aeroplane may be operated during any particular phase of flight.

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4. With the introduction of the Joint Aviation Authority syllabus the word ‘mass’ is used instead of the word ‘weight’. In all British and American publications, weight is still preferred and used to express the downward force exerted by mass. The reason the JAA use mass is because weight = mass x acceleration i.e. weight = mass x 1. Therefore weight and mass are synonymous. Throughout this book the word ‘weight’ has been used and may be exchanged for the word ‘mass’ if preferred. 5. In addition to this the metric system of measuring weight and volume is preferred by the JAA and it may be necessary to convert Imperial or American quantities to metric equivalents. If such is the case use the following method.

Conversion between Weight and Volume 6. The weights and volumes obtained for the purpose of centre of gravity calculations are frequently given as a mixture of metric and imperial measures. For example a British or American built aircraft may well have its weights presented in the Aeroplane Flight Manual (AFM) in pounds and when loaded on the continent the load may be quoted in kilograms. Fuel is delivered in litres, imperial gallons or US gallons, but of course must figure in the load sheet calculations in pounds or kilograms. Although the conversion between differing units of weight and volume, and indeed the conversion between volume and weight for fluids with a given specific gravity, is covered elsewhere in the course, the following paragraphs are included in this manual for your guidance. 7. To convert a volume of liquid to weight and vice versa the density of the liquid must be considered. The density is expressed as a specific gravity (SG). 1 litre of pure water weighs 1 kg and 1 imperial gallon pure water weights 10 lb. The SG of pure water is taken as the datum SG of 1.0.

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8. When converting litres of any liquid to kilograms the volume must be multiplied by the specific gravity, or when converting kilograms to litres the weight must be divided by the specific gravity. Similarly, when converting imperial gallons to pounds the volume must be multiplied by (10 x the specific gravity), or to convert pounds to imperial gallons the volume must be divided by (10 x the specific gravity) of the liquid. 9. Aviation fuels and oils are lighter than pure water, therefore their specific gravities will be less than 1.0. 10. The diagram at Figure 0-1 may help you with these conversions. When using the diagram at Figure 0-1 and moving in the direction of the arrows, multiply (as shown). Conversely, when moving in the opposite direction, divide.

Volume Conversions 11. In some problems the oil is measured in quarts. They may be in Imperial measurements or American. It does not matter, the conversion is the same as shown below in Paragraph 12. 12.

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2 Pints

= 1 Quart

4 Quarts

= 1 Gallon

8 Pints

= 1 Gallon

FIGURE 0-1 Weight/Volume Conversion

13. When travelling in the direction of the arrows multiply, when travelling in the opposite direction divide.

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031 Aircraft Mass & Balance

The Composition of Aeroplane Weight Weight Limitations

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The Composition of Aeroplane Weight

The Composition of Aeroplane Weight 1

1. The total weight of an aeroplane is the weight of the aeroplane and everyone and everything carried on it or in it. Total weight comprises three elements, the basic weight, the variable load and the disposable load.

Basic Weight.

This is the aeroplane weight plus basic equipment, unusable fuel and undrainable oil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulic fluid.

Variable Load.

This includes the role equipment, the crew and the crew baggage. Role equipment is that which is required to complete a specific tasks such as seats, toilets and galley for the passenger role or roller convey or, lashing points and tie down equipment for the freight role.

Disposable Load.

The traffic load plus usable fuel and consumable fluids. The traffic load is the total weight of passengers, baggage and cargo, including any non-revenue load. The disposable load is sometimes referred to as the useful load. 2. Although these are the weight definitions used in the load sheet there are other terms which are commonly used. These are:

Absolute Traffic Load.

The maximum traffic load that may be carried in any circumstances. It is a limitation caused by the stress limitation of the airframe and is equal to the maximum zero fuel weight minus the aircraft prepared for service weight.

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The Composition of Aeroplane Weight All Up Weight (AUW).

The total weight of an aircraft and all of its contents at a specific time.

Design Minimum Weight. The lowest weight at which an aeroplane complies with the structural requirements for its own safety. Dry Operating Weight. The total weight of the aeroplane for a specific type of operation excluding all usable fuel and traffic loads. It includes such items as crew, crew baggage, catering equipment, removable passenger service equipment, and potable water and lavatory chemicals. The items to be included are decided by the Operator. The dry operating weight is sometimes referred to as the Aircraft Prepared for Service (APS) weight. The traffic load is the total weight of passengers, baggage and cargo including non-revenue load. [JAR-OPS 1.607 (a)]. Empty Weight.

(Standard Empty Weight) The weight of the aircraft excluding usable fuel, crew and traffic load but including fixed ballast, engine oil, engine coolants (if applicable) and all hydraulic fluid and all other fluids required for normal operation and aircraft systems, except potable water, lavatory pre-charge water and fluids intended for injection into the engine (demineralised water or water-methanol used for thrust augmentation).

Landing Weight.

The gross weight of the aeroplane, including all of its contents, at the time of

landing.

Maximum Ramp Weight.

The maximum weight at which an aircraft may commence taxiing and its equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed the surface load bearing strength.

Maximum Structural Landing Weight.

The maximum permissible total aeroplane weight on landing in normal circumstances. [JAR-OPS 1.607 (c)].

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The Composition of Aeroplane Weight Maximum Structural Take-Off Weight.

The maximum permissible total aeroplane weight at the start of the take-off run. [JAR-OPS 1.607 (d)].

Maximum Total Weight Authorised (MTWA).

The maximum total weight of aircraft prepared for service, the crew (unless already included in the APS weight), passengers, baggage and cargo at which the aircraft may take-off anywhere in the world, in the most favourable circumstances in accordance with the Certificate of Airworthiness in force in respect of aircraft.

Maximum Zero Fuel Weight.

The maximum permissible weight of an aeroplane with no usable fuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when it is explicitly mentioned in the Aeroplane Flight Manual limitations. This is a structural limitation imposed to ensure that the airframe is not overstressed. [JAR-OPS 1.607 (b)].

Payload.

Anyone or anything on board the aeroplane the carriage of which is paid for any someone other than the operation. In other words anything or anyone carried that earns money for the airline.

Total Loaded Weight.

The sum of the aircraft basic weight, the variable load and disposable

load.

Traffic Load. The total mass of passengers, baggage and cargo, including any non-revenue load. [JAR-OPS 1.607 (f)]. Zero Fuel Weight.

This is the dry operating weight plus the traffic load. In other words it is the weight of the aeroplane without the weight of usable fuel.

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The Composition of Aeroplane Weight

Equipment Ballast.

Additional fixed weights which can be removed, if necessary, that are carried, to ensure the centre of gravity remains within the safe limits, in certain circumstances.

Basic Equipment. The unconsumable fluids and the equipment which is common to all roles for which the operator intends to use the aircraft. Load Spreader.

A mechanical device inserted between the cargo and the aircraft floor to distribute the weight evenly over a greater floor area.

Unusable Fuel.

That part of the fuel carried which is impossible to use because of the shape or position of particular tanks.

Unusable Oil. That part of the oil lubrication system that cannot be removed due to the construction of the system.

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The Composition of Aeroplane Weight FIGURE 1-1 The Composition of Aeroplane Weight

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The Composition of Aeroplane Weight 3. The total weight of an aeroplane comprises many different components, all of which, together with the appropriate lever arms, are recorded in the weight and CG Schedule. 4. The standard empty weight of the aeroplane is the weight of the aircraft excluding the usable fuel, the crew and the traffic load but including any fixed ballast, unusable fuel, all engine coolant and all hydraulic fluid. 5. The basic weight of an aeroplane is essentially the empty weight plus the weight of basic equipment, that is equipment which is common to all roles in which the aircraft may be required to perform. The basic weight and the corresponding CG position, together with the declared basic equipment showing the weight and arm of each item, are shown in Part A of the Weight and CG Schedule or in the Loading and Distribution Schedule as appropriate. 6. To equip an aircraft to perform a particular role it may be necessary to fit additional equipment. This is known as role equipment, an example would be the passenger seats, toilets and galleys, which may vary in quantity for a large public transport aircraft. 7. The role equipment (variable load) detailed in Part B may be for as many roles as the operator wishes, but for every role the weights and moments must be stated. The weight and moment of the crew is included in Part B. Under certain circumstances, standard crew (and passenger) weights are assumed, otherwise the weight of each crew member must be determined by weighing. The occasions on which standard weights may be used are discussed in the Chapter entitled ‘Joint Airworthiness Requirements’. 8. With the role equipment fitted the aircraft is ready to enter service. The weight of the aircraft in this condition is called the Aircraft Prepared for Service (APS) weight, or the Dry Operating Weight (DOW). The total weight of the aeroplane comprises the APS weight plus the disposable load, which is made up of usable fuel and the payload.

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The Composition of Aeroplane Weight 9. Details of the disposable load must be entered in Part C of the Weight and CG Schedule, which contains the lever arm of each cargo stowage position, hold and each row of passenger seats. Full details of all fuel and oil tanks are also included in this part of the Schedule stating the arm, maximum capacity and weight when full for aircraft exceeding an MTWA of 2730 kg. 10. For an aircraft having a valid Certificate of Airworthiness a valid Weight and CG Schedule must be completed every time the aircraft is weighed. Each Schedule must be preserved for a period of six months following the subsequent re-weighing of the aircraft. 11. If the person who is the operator ceases to be the operator, he (or his representative if he dies) must retain the Schedule or pass it on to the new operator for retention for the requisite period.

Weight Limitations 12.

The factors which may limit the maximum Take-Off Weight (TOW) are:

The Structural Limits.

These are weight limits, which are imposed by the manufacturer, and agreed by the Authority, to ensure the aeroplane is not over-stressed. These structural weights include the maximum structural ramp weight, the maximum structural take-off weight, the maximum zero fuel weight and the maximum structural landing weight.

The Field-Length Limited Take-Off Weight.

This is the TOW as limited by the available field lengths and the prevailing meteorological conditions at the departure aerodrome.

The Weight-Altitude-Temperature (WAT) Limit.

This limitation is imposed on TOW by minimum climb gradient requirements, which are specified in Joint Airworthiness Requirements (JARs).

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The Composition of Aeroplane Weight The En-Route Requirements.

The weight of the aircraft at any stage of the flight en-route must be such that the aircraft can safely clear any objects within a specified distance of the aircraft’s intended track. Depending on the aircraft’s performance category, the loss of power from a specified number of engines will be assumed when determining the maximum weight at which the aircraft can safely clear en-route obstacles. En-route terrain clearance may impose a limitation on the take-off weight.

The Maximum Landing Weight.

This may be dictated by the structural limitation, the FieldLength Limit or the WAT Limit at the destination or alternate aerodromes.

The Maximum Take-off Weight. The lowest restricted weight of the field-length limitation, the WAT limitation and the structural limitation is the maximum TOW. 13. As already discussed, the disposable load consists of the usable fuel and the traffic load. In order that the maximum traffic load can be carried it may be necessary to limit the amount of fuel which is carried to a safe minimum. Whether or not the fuel carried actually limits the traffic load, it is normally prudent to reduce the fuel load to a safe minimum in order to reduce the all up weight of the aircraft. This will result in lower operating costs, higher cruise levels, reduced thrust take-offs and/or easier compliance with noise abatement procedures on take-off. The total fuel required on any particular flight comprise the following:

Route Fuel. This is the fuel used from departure to destination aerodromes and may be minimised by operating at the most economical pressure altitude accounting for the temperature and wind component, but not below the minimum safe altitude. Diversion Fuel.

The fuel required to proceed from the destination to the alternate aerodrome in the prevailing conditions.

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The Composition of Aeroplane Weight Holding Allowance. The fuel required to enable the aircraft to hold at a specified pressure altitude and for a specified period of time. Contingency Allowance.

An amount of fuel carried to counter any disadvantage suffered because of unforecast adverse conditions.

Landing Allowance.

The fuel required to be used from overhead the landing aerodrome to the

end of the landing roll. 14. On occasions it is advantageous to carry more than the minimum fuel for a given sector. The obvious example is when fuel will not be available at the destination aerodrome. Alternatively, the cost of fuel at the destination aerodrome may be so high that the cost differential (departure aerodrome fuel cost versus destination aerodrome fuel cost) may be so great that it is cheaper to carry the fuel for the return or subsequent sector outbound from the original departure aerodrome. In either event, when this is done the first sector would be termed a ‘Tankering Sector’. 15. The size of the traffic load may be restricted by reasons other than the disposable load which is available once the fuel load has been decided. It may be impossible to distribute the traffic load such that the centre of gravity of the laden aircraft remains within the safe specified limits, in which case some of the traffic load may have to be off-loaded. Floor loading factors may have to be considered. With a payload which is light in weight but bulky it may be physically impossible to fit the traffic load into the aircraft.

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The Composition of Aeroplane Weight

Operating Overweight 16. A safely loaded aircraft is one in which the total weight of traffic load is equal to or less than the maximum permissible traffic load for a given flight and the distribution of that traffic load is such that the centre of gravity of the laden aircraft lies within the fore and aft limits of centre of gravity which are permitted for that aircraft operating in the specified role. 17.

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The effects of operating in an overweight condition include: (a)

Reduced acceleration on the ground run for take-off. The take-off speeds are increased because of the weight, and this results in an increased take-off run required and an increased take-off distance required.

(b)

Decreased gradient and rate of climb which decreases obstacle clearance capability after take-off and the ability to comply with the minimum climb gradient requirements.

(c)

Increased take-off speeds impose a higher load on the undercarriage and increased tyre and wheel temperatures. Together these reduce the aeroplane’s ability to stop rapidly in the event of an abandoned take-off.

(d)

Increased stalling speed which reduces the safety margins.

(e)

Reduced cruise ceiling which increases the fuel consumption resulting in a decreased operational range. It may also cause en-route terrain clearance problems.

(f)

Impaired manoeuvrability and controllability.

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The Composition of Aeroplane Weight (g)

Increased approach and landing speeds causing a longer landing distance, landing ground run, increased tyre and wheel temperatures and reduced braking effectiveness.

(h)

Reduced one-engine inoperative performance on multi-engined aircraft.

(i)

Reduced structural strength safety martins with the possibility of overstressing the airframe.

18. In addition to ensuring that the maximum permissible all-up weight of an aircraft is not exceeded it is of vital importance to ensure that the distribution of the permissible weight is such that the balance of the aircraft is not upset.

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031 Aircraft Mass & Balance

The Calculation of Aircraft Weight Weight and Traffic Load

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The Calculation of Aircraft Weight

2

The Calculation of Aircraft Weight

From the diagram at Figure 1-1 it can be determined that: •

Aircraft Weight + Basic Equipment = Basic Weight

•

Basic Weight + Usable Oil = Standard Empty Weight

•

Standard Empty Weight + Optional Equipment = Basic Empty Weight

(Note if no optional equipment is added, Standard Empty Weight = Basic Empty Weight). •

Basic Empty Weight + Variable Load = Aircraft Prepared for Service Weight (APS).

•

APS Weight + Removable Ballast = Dry Operating Weight.

(Note if there is no removable ballast, APS Weight = Dry Operating Weight). •

Dry Operating Weight + Traffic Load = Zero Fuel Weight.

•

Zero Fuel Weight + Usable Fuel = All Up Weight

Problems related to these fomulae will be met as follows: (Note optional equipment and removable ballast will not be mentioned unless it is carried).

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The Calculation of Aircraft Weight EXAMPLE 2-1

EXAMPLE Given: Take-off mass 80,000 kgs; Traffic load 12,000 kgs; Usable fuel 10,000 kgs; Crew 1000 kgs. Calculate the dry operating weight.

SOLUTION 80,000 - 12,000 - 10,000 = 58,000 kgs.

EXAMPLE 2-2

EXAMPLE Given: Basic weight 50,000 kgs; Basic equipment 5,000 kgs; Usable oil 500 kgs; Variable load 6000 kgs; Traffic load 3000 kgs; Usable fuel 7000 kgs. Calculate the APS weight.

SOLUTION 50,000 + 500 + 6000 = 56,500 kgs

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The Calculation of Aircraft Weight EXAMPLE 2-3

EXAMPLE Given the same details as Example 2-2, calculate the disposable load.

SOLUTION 3000 + 7000 = 10,000 kgs.

EXAMPLE 2-4

EXAMPLE Given: Take-off mass 77,500 kgs; Disposable load 10,000 kgs; Variable load 4000 kgs. Calculate the basic empty mass.

SOLUTION 77,500 - 10,000 - 4000 = 63,500 kgs.

Weight and Traffic Load 1. Problems concerning the traffic load capacity of an aircraft often occur in the Flight Planning, Navigation or Mass and Balance examination papers. The problems are not complicated because there is no consideration of whether the centre of gravity of the laden aircraft lies within the trim envelope.

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The Calculation of Aircraft Weight 2. To avoid getting lost in a mass of figures and definitions, remember that the All Up Weight of an aircraft at any stage of flight consists of three elements: (a)

The Aircraft Prepared for Service Weight (or Dry Operating Mass).

(b)

The weight of the Fuel Onboard.

(c)

The traffic load carried.

3. The APS weight and the traffic load remain constant throughout the flight whereas the weight of the fuel will progressively decrease. 4. In the examination you will be required to calculate the weight of the traffic load that can be carried, as limited by one of three limiting maximum weights: (a)

Maximum Take-Off Weight.

(b)

Maximum Landing Weight.

(c)

Maximum Zero Fuel Weight.

5. For an aircraft to perform a particular role it may be necessary to fit additional equipment. This is known as role equipment, for example the passenger seats and galleys required in a public transport aircraft, which makes the aircraft ready to enter service. The weight of the aircraft in this condition is called the Aircraft Prepared for Service (APS) weight, or the Dry Operating Weight. The Total Weight of the aeroplane then comprises of the APS weight plus the Disposable Load, which is made up of the usable fuel and traffic load.

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The Calculation of Aircraft Weight 6. To answer this type of question use the layout shown in the following examples and approach the problem in a logical manner remembering the total weight at any time comprises the APS weight, the fuel and the traffic load.

EXAMPLE 2-5

EXAMPLE Given: Maximum Take-Off Weight at A

145,000 kg.

Maximum Landing Weight at B

97,900 kg.

Maximum Zero Fuel Weight

90,100 kg.

Weight Less Fuel and Payload

67,400 kg.

Reserve Fuel (remains unused)

7,500 kg.

Mean TAS

470 kt.

Sector Distance A to B

3,600 nm.

Mean Fuel Flow

5,500 kg/hr.

Wind Component

-20 kt.

Determine the traffic load which can be carried from A to B.

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The Calculation of Aircraft Weight SOLUTION First, calculate the fuel required for the sector. TAS

=

470 kt.

Wind Component

=

-20 kt.

Groundspeed

=

450 Kt.

Sector Time

=

Sector Distance- = --------------3, 600- = 8 hours --------------------------------------Groundspeed 450

Sector Fuel Required

=

Fuel flow x time = 5,500 x 8 = 44,000 kg

MTOW Limit

MLW Limit

MZFW Limit

MTOW

+145,000 kg.

MLW

+ 97,900 kg. MZFW

APS Wt.

– 67,400 kg.

APS Wt.

–67,400 kg.

Res:

- 7,500

+ 90,100 kg

APS Wt. - 67,400 kg

Fuel: Leg - 44,000 kg Res Payload

- 7,500 +26,100 kg.

+23,000 kg.

+22,700kg

Maximum traffic load is the lower of the three calculated values i.e. 22,700 kg. This is the only traffic load that will not exceed either the MTOW, MLW or the MZFW limitations.

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The Calculation of Aircraft Weight In the above example, the Fuel Required calculation could have been conducted in one step using the following method: Sector Distance Sector Fuel Required = ------------------------------------- × Fuel Flow Groundspeed 3, 600 = --------------- × 5, 500 = 44, 000 kg 450

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The Calculation of Aircraft Weight EXAMPLE 2-6

EXAMPLE Given: Maximum Take-Off Weight

150,000 kg.

Maximum Landing Weight

100,000 kg.

Maximum Zero Fuel Weight

90,000 kg.

APS Weight

70,000 kg.

Total Fuel On-Board at Take-Off

50,000 kg.

Reserve Fuel

6,000 kg.

Sector Distance

1,250 nm.

TAS

300 kt.

Wind Component

-50 kt.

Fuel Flow

6,000 kg./hr.

Calculate:

Chapter 2 Page 8

(a)

The maximum Payload that can be carried.

(b)

The Maximum Range with the Payload.

(c)

What Payload can be carried over the Maximum Range of the aircraft.

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The Calculation of Aircraft Weight SOLUTION Calculate the Sector Fuel: Sector Distance 1250 Sector Fuel = ------------------------------------- × Fuel Flow = ------------ × 6000 = 30000 kg Ground speed 250 If the aircraft had a total of 50,000 kg. of fuel at take-off and burnt 30,000 kg. of fuel in transiting the sector distance then there would be 20,000 kg. of fuel remaining in the tanks on landing. MTOW Limit MTOW

+150,000 kg

MLW Limit MLW +100,000 kg

MZFW Limit MZFW +90,000 kg

APS Weight -70,000 kg

-70,000 kg

-70,000 kg

Fuel

-50,000 kg

-20,000 kg

-

Payload

+30,000 kg

+10,000 kg

+20,000 kg

The Limiting Payload is 10,000 kg To calculate the maximum range with this payload, consider that the aircraft has landed with 20,000 kg of fuel on-board although the reserve fuel requirement was only 5,000 kg. This means that there is an additional 15,000 kg of fuel available to increase the sector distance. We now need to calculate this extra distance. Fuel Available 15000 Distance = ----------------------------------- × Groundspeed = --------------- × 250 = 625 Nm Fuel Flow 6000 Maximum Range = Original Sector Distance of 1250 + 625 = 1,875 nm.

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The Calculation of Aircraft Weight EXAMPLE 2-7

EXAMPLE An aircraft is to fly from A to B and then on to C without refuelling at B. Given: APS weight 23,500kgs Maximum Take-Off Weight at A

41,800 kg.

Maximum Take-Off Weight at B

37,000 kg.

Maximum Landing Weight at B

38,000 kg.

Maximum Landing Weight at C

36,500 kg.

Maximum Taxi Weight at B

37,320 kg.

Maximum Zero Fuel Weight

31,300 kg.

APS Weight

23,500 kg.

Distance A to B

521 nm.

Distance B to C

703 nm.

Mean Groundspeed A to B

453 kt.

Mean Groundspeed B to C

388 kt.

Mean Fuel Consumption A to B

3,100 kg/hr.

Mean Fuel Consumption B to C

2,950 kg/hr.

Reserve Fuel (Unused)

2,000 kg.

Determine the maximum payload that could be loaded at A and B.

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The Calculation of Aircraft Weight SOLUTION 521 Calculate fuel required A to B = --------- × 3100 = 3565 kg 453 703 Calculate fuel required B to C = --------- × 2950 = 5345 kg 388 Note the taxi fuel at B (the difference between the Maximum Taxi Weight and the Maximum TakeOff Weight) is also to be considered in the calculation of the fuel on-board the aircraft from the point of take-off at A. MTOW A

MLW B

MZFW

MTOW B

MLW C

Limitation

+41,800

+38,000

+31,300

+37,000

+36,500

APS Weight

-23,500

-23,500

-23,500

-23,500

-23,500

Fuel A - B

-3,565

Fuel B - C

-5,345

-5,345

-320

-320

Reserve Fuel

-2,000

-2,000

Payload

+7,070

+6,835

Taxi Fuel at B

-5,345

+7,800

The maximum payload that can be loaded at A is 6,835 kg. The maximum payload that can be loaded at B is 6,155 kg.

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-2,000

-2,000

+6,155

+11,000

031 Aircraft Mass & Balance

Weight and Balance Theory Reference Datum The Centre of Gravity Envelope The Newton Aeroplane Weight Determination

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Weight and Balance Theory

3

Weight and Balance Theory

1. In order to understand the concept of weight and balance as it applies to aeroplanes it is essential to have a thorough knowledge of the basic theory of balance and force moments. This is best described by using a child’s seesaw to illustrate the terms, cause and effect. 2. If the bar of a seesaw having a uniform density and cross section is placed on a fulcrum (or pivot) for support such that the fulcrum is exactly half way along the length of the seesaw, the weight of the seesaw will act vertically downwards through the fulcrum. In this case at any specified distance from the fulcrum, the turning moment (that is the downward force imposed at that point) will be equal on both sides of the fulcrum. The seesaw is said to be in equilibrium or to be balanced, and will therefore rest in a horizontal position. 3. The turning moment at any particular point can be determined by multiplying the weight (the downward force) by the arm (the distance of that point from the fulcrum). Moments can be expressed foot pounds (ft. lb.) inch pounds (in. lb.) or metre kilograms (m. kg.). 4. The position through which all of the weight acts in a vertically downward direction is referred to as the Centre of Gravity (CG). In the case considered above and illustrated at Figure 3-1, the CG of the seesaw is immediately above the fulcrum.

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Weight and Balance Theory FIGURE 3-1 Balanced Condition

5. If a weight is placed on one side of the seesaw it will impart an unbalancing force or turning moment about the fulcrum. The moment of this force is equal to the product of the weight and the distance at which it is placed from the fulcrum. For example, if a 20 kg weight is placed on the seesaw at a distance of 80 cm from the fulcrum the moment (20 kg x 80 cm) is equal to 1600 cm kg or 16 m kg as shown at Figure 3-2.

FIGURE 3-2 Unbalanced Condition

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Weight and Balance Theory 6. In order to restore the balance or equilibrium of the seesaw the unbalancing moment of 16 m kg must be counterbalanced. This may be done by placing a weight on the opposite side of the fulcrum such that the moment produced is equal and opposite to the unbalancing force. Therefore any product combination of weight and arm which gives a moment of 16 m kg will suffice. Figure 3-3 shows only three of the infinite combinations possible.

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Weight and Balance Theory FIGURE 3-3 Restored Balanced Condition

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Weight and Balance Theory 7. At Figure 3-3 (b) the same effect is achieved by placing a 40 kg weight at a distance of 40 cm from the fulcrum (40 kg x 40 cm = 16 m kg). 8. Figure 3-3 (c) the same effect is achieved by placing a 80 kg weight at a distance of 20 cm from the fulcrum (80 kg x 20 cm = 16 m kg).

NOTE: All of the weights used in the above examples are assumed to be of uniform density and construction such that the weight acts vertically downward through the centre of the weight.

Reference Datum 9. The point from which the arms of force moments are measured is termed the reference datum. In the preceding examples the reference datum was the centre of gravity of the unladen seesaw, which was coincident with the fulcrum. 10. The CG of an aircraft is the point through which all of its weight is assumed to act in a vertically downward direction. The position of the CG measured along the fore and aft axis of the aircraft will change due to changes in aircraft configuration (passenger configuration with seats in, freight configuration with seats out), total weight and distribution of the fuel load at any given point in the flight, total weight and distribution of the payload, and so on. It is therefore important to appreciate that with an aircraft the reference datum cannot be the position of the CG, but will instead be a fixed point on the aircraft structure, or indeed a point on the extension of the aircraft’s fore and aft axis which is in fact forward of the aircraft’s nose.

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Weight and Balance Theory 11. On large aircraft the bulkhead separating crew and passenger compartments is frequently used as a reference datum, whereas in single engine aircraft the fire wall between cabin and engine bay is often specified as the reference datum, or alternatively the tip of the propeller spinner. 12. In order to determine the position of the CG of a laden aircraft the weight and distance fore or aft of the datum (arm) of each piece of equipment, cargo and person on board the aircraft must be known. By convention any weight which is positioned forward of the reference datum has a negative arm and therefore produces a negative moment. 13. Conversely, by convention, any weight which is aft of the reference datum has a positive arm and therefore produces a positive moment.

The Centre of Gravity Envelope 14. In order to ensure that an aeroplane can be safely controlled by the aerodynamic control surfaces the CG must remain within safe limits. The distance between the maximum safe forward position of the CG and the maximum safe aft position of the CG is termed the CG envelope. The envelope dimensions are determined by the manufacturer, approved by the CAA, and subsequently described in the Approved Flight Manual (AFM), which is part of the Certificate of Airworthiness. It is a legal requirement that the CG remains within the CG envelope at all times. Some aircraft have more than one CG envelope. 15. Public transport aeroplanes may have two CG envelopes, one for public transport flights and one for use on ferry or training flights. The CG envelope will be wider in the latter case, however it may still be necessary to use ballast in order to position the CG of the essentially empty aeroplane within limits.

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Weight and Balance Theory 16. Similarly, some light aircraft are certified in two categories, semi-aerobatic category CG envelope will be significantly narrower than the non-aerobatic CG envelope (or utility, or normal) category, the aft limit is likely to be especially restrictive. The maximum weight at which semiaerobatic manoeuvres may be conducted may also be limited.

The Newton 17. The mass of a body is the amount of matter which it contains. The weight of a body is the force due to gravity acting on that mass. Weight and mass are often taken to be synonymous. 18. When considering SI units, the unit of mass is the kilogram and the unit of force is the Newton. From Newton’s second law it is known that: Force = Mass x Acceleration and therefore 1 Newton=1 kilogram x 1 metre/second/second 19. The acceleration due to gravity at the earth’s surface is 9.81 metres/second2, and therefore the weight force of gravity acting on a 1 kilogram mass is 9.81 Newtons. 20. If one now accepts mass and weight as being synonymous, then 1 kilogram is equal to 9.81 Newtons. 21. It is possible, although presently unlikely, that you may encounter aircraft weights expressed in Newtons. In the examination, you may find that gravity is given as 10m/s/s in which case 1kg is equal to 10 Newtons.

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Weight and Balance Theory

The Forces Acting On An Aeroplane In Flight 22. The centre of gravity is that point on the longitudinal axis through which all of the weight acts vertically downward. The centre of pressure is that point on the longitudinal axis through which all of the lift is assumed to act upward at 90° to the axis. 23. The four forces which act on an aircraft in straight and level flight are lift, weight, thrust and drag. Lift acts through the centre of pressure and weight through the centre of gravity. For simplicity, thrust and drag forces are considered as acting parallel to the longitudinal axis, and their displacement from this axis depends on the design of the aircraft, high wing or low wing, the position of the engine(s), and so on. 24. In order to maintain steady flight the forces acting on an aeroplane must be in balance, with no turning moment about any axis. In this condition the aircraft is said to be trimmed. The condition is achieved by balancing the lift, weight, thrust and drag forces acting at the aircraft’s C of G and C of P so that: (a)

Lift equals weight, otherwise the aircraft would climb or descend.

(b)

Thrust equals drag, otherwise the aircraft would accelerate or decelerate.

25. Providing that the centre of gravity and the centre of pressure are not coincident a force couple will be set up by the lift and the weight forces, and this will result in a pitching moment, as shown at Figure 3-4.

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Weight and Balance Theory FIGURE 3-4 The Forces on an Aeroplane in Level Flight

26. The magnitude of the pitching moment will depend on the magnitude of lift and weight forces, but also on the distance between the centre of gravity and the centre of pressure. 27. The position of the C of G will depend on the way in which the aircraft is loaded, and on the manner in which fuel is transferred/consumed in flight. The position of the centre of pressure depends on the angle of attack, with the C of P moving slowly forward as the angle increases, and then rapidly backwards at the stalling angle. 28. It is rarely possible to design an aircraft in which the forces of lift, weight, thrust and drag are exactly in equilibrium in flight. The centre of pressure moves with changing angle of attack, as does the drag line. The centre of gravity moves with changes in the distribution of load and fuel. The pitching couples are set up when the weight line is not coincident with the lift line or the drag line is not coincident with the thrust line and are offset by the tailplane and/or elevators.

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Weight and Balance Theory 29. Consequently, the forward and aft limits of the centre of gravity are determined by the capability of the elevators (or stabilator or all moving tailplane) to control the aircraft in pitch at the lowest flight speed. These limits are established by the aircraft manufacturer. 30. The forward centre of gravity limit is established to ensure there is sufficient elevator movement available at minimum flight airspeed. In other words to avoid a situation where the elevators are fully deflected in order to maintain a level pitch attitude. 31. The aft centre of gravity limit is the most rearward position at which the centre of gravity can be located for the most critical manoeuvre or operation. As the centre of gravity moves rearwards aircraft longitudinal stability decreases. This means that the aircraft’s natural ability to return to stable flight after a disturbance, a manoeuvre or a gust, is degraded. 32. It is therefore of paramount importance to safe flight that the aircraft is never operated with the centre of gravity beyond the limits set down by the manufacturer and agreed by the Authority. 33. The effects of operating with the centre of gravity forward of the permitted forward limit include:

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(a)

Difficulty in rotating to take-off altitude.

(b)

Difficulty in flaring, rounding-out, or holding the nose-wheel off the ground after touchdown on landing.

(c)

Possible damage to nose-wheel, nose oleo and propeller tips.

(d)

Restricted elevator trim resulting in an unstable approach.

(e)

Increased stalling speed against full up elevator.

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Weight and Balance Theory

34.

(f)

Additional tail down force requires more lift from wing resulting in greater induced drag, higher fuel consumption and reduced range.

(g)

Slow rotation on take-off.

(h)

Inability to trim out elevator stick forces.

The effects of operating with the centre of gravity aft of the permitted aft limit include: (a)

Pitch up at low speeds causing early rotation on take-off or inadvertent stall in the climb.

(b)

Difficulty in trimming especially at high power.

(c)

Longitudinal instability, particularly in turbulence, with the possibility of a reverssal of control forces.

(d)

Degraded stall qualities to an unknown degree.

(e)

More difficult spin recovery, unexplored spin behaviour, delayed or even inability to recover.

Aeroplane Weight Determination 35. In order to determine the weight and the arm of the basic aircraft, the first step is to determine the aircraft empty weight (without fuel and payload) by measuring the weight acting through each wheel (on a small aircraft) or through each jacking point (on larger aircraft).

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Weight and Balance Theory 36. Since the position of each wheel or jacking point (relative to the datum) is known, it is now a simple step to determine the position of the CG of the empty aircraft, and to express this position relative to the datum. 37. The following examples illustrate the method of calculating the weight and arm of empty aircraft with various datum positions.

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Weight and Balance Theory EXAMPLE 3-1

EXAMPLE The main wheels of a light aircraft are in line with the datum, and the nose-wheel is 75 inches forward of the datum. The weights measured through each wheel are: Left Hand Main Wheel

810 lb.

Right Hand Main Wheel

815 lb.

Nose-Wheel

320 lb.

Determine the weight of the aircraft, and the position of the aircraft CG relative to the datum.

SOLUTION The situation is as shown at Figure 3-5.

FIGURE 3-5

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Weight and Balance Theory The simple calculation is completed in the following manner: Weight

Arm

Moment

Nose-Wheel

320 lb.

-75 in

-24,000 in lb.

Left Main Wheel

810 lb.

0

0

Right Main Wheel

815 lb.

0

Total

1945 lb.

0 -24,000 in lb.

– 24000 in lb CG = ------------------------------ = – 12.34 in 1945 lb The aircraft weight is therefore 1945 pounds, and the CG lies 12.34 inches forward of the datum.

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Weight and Balance Theory EXAMPLE 3-2

EXAMPLE The datum is in line with the tip of the propeller spinner of a single engined light aircraft. The nose-wheel is 10 inches aft of the datum and the main wheels are 120 inches aft of the datum. The weights measured through each wheel are: Left Hand Main Wheel

810 lb.

Right Hand Main Wheel

815 lb.

Nose-Wheel

320 lb.

Determine the weight of the aircraft, and the position of the aircraft CG relative to the datum.

SOLUTION The situation is as shown at Figure 3-6.

FIGURE 3-6

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Weight and Balance Theory The calculation is now completed as follows: Weight

Arm

Moment

Nose-Wheel

320 lb.

+10 in

+3,200 in lb.

Left Main Wheel

810 lb.

+120 in

+97,200 in lb.

Right Main Wheel

815 lb.

+120 in

+97,800 in lb.

Total

1945 lb.

+198,200 in lb.

+ 198,200 in lb CG = ------------------------------------ = +101.9 in 1945 lb The aircraft weight is therefore 1945 pounds, and the CG lies 101.9 inches aft of the datum.

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Weight and Balance Theory EXAMPLE 3-3

EXAMPLE The datum is positioned between the nose and the main wheels of a single engined light aircraft. The nose-wheel is 45 inches forward of the datum and the main wheels are 55 inches aft of the datum. The weights measured through each wheel are: Left Hand Main Wheel

810 lb.

Right Hand Main Wheel

815 lb.

Nose-Wheel

320 lb.

Determine the weight of the aircraft, and the position of the aircraft CG relative to the datum.

SOLUTION The situation is as shown at Figure 3-7.

FIGURE 3-7

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Weight and Balance Theory The calculation is now completed as follows:

Nose-Wheel

Weight

Arm

Moment

320 lb.

-45 in

-14,400 in lb.

Left Main Wheel

810 lb.

+55 in

+44,550 in lb.

Right Main Wheel

815 lb.

+55 in

+44,825 in lb.

Total

1945 lb.

+74,975in lb.

+74,975 in lb CG = -------------------------------- = +38.55 in 1945 lb The aircraft weight is therefore 1945 pounds and the CG lies 38.55 inches aft of the datum.

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Weight and Balance Theory Self Assessed Exercise No. 1 QUESTIONS: QUESTION 1. List the elements of basic weight. QUESTION 2. What does all up weight minus disposable load equal? QUESTION 3. Given: MTOW 48t; MLW44t; MZFW 36t; Taxi fuel 0.5t; Contingency fuel 1t; Alternate fuel 1t; Final reserve 1.5t; Trip fuel 8t. Calculate the actual TOW if ZFW = MZFW. QUESTION 4. Define reference datum. QUESTION 5. What is the difference between zero fuel weight and dry operating weight? QUESTION 6. What consideration limits maximum ramp weight? QUESTION 7. Define maximum zero fuel weight.

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Weight and Balance Theory QUESTION 8. Specify the maximum weight to which an aeroplane may be loaded prior to starting the engines. QUESTION 9. If the CG is at the forward limit state the stability of the aeroplane. QUESTION 10. How will the elevators feel if the CG moves AFT? QUESTION 11. The total weight of the aeroplane excluding the usable fuel and traffic load is called? QUESTION 12. Define the CG of an aeroplane. QUESTION 13. Given: Dry operating weight 30,000kgs; Maximum take-off weight 52,000kgs; Maximum zero fuel weight 43,000 kgs; Maximum landing weight 46,000kgs: Fuel at take-off 10,000kgs; Trip fuel 5,000kgs. Calculate the maximum traffic load. QUESTION 14. Does traffic load include the crew?

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Weight and Balance Theory QUESTION 15. Who determines the structural limitations of an aeroplane? QUESTION 16. List the factors that may limit the take-off weight. QUESTION 17. What effect does an overweight take-off have on stalling speed? QUESTION 18. Define a Newton. QUESTION 19. How does stalling speed change if the CG moves to the AFT of the envelope? QUESTION 20. What determines the value of the maximum zero fuel weight.

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Weight and Balance Theory ANSWERS: ANSWER 1. Page 1-4 ANSWER 2. Page 1-4. Dry operating weight ANSWER 3. Page 2-1. Taxi fuel will be used before take-off. The total fuel required for the flight = Contingency + Alternative + Final reserve + Trip fuel = 1t + 1t + 1.5t + 8t = 11.5t ZFW + Fuel = TOW = 36t + 11.5t = 47.5t which does not exceed MTOW. LW = TOW – Trip fuel = 47.5t – 8t = 39.5t which does not exceed MLW ANSWER 4. Page 3-3 ANSWER 5. Page 1-4. Zero fuel weight – Dry operating weight = Traffic load ANSWER 6. Page 1-2

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Weight and Balance Theory ANSWER 7. Page 1-2 ANSWER 8. Page 1-2. – Maximum ramp weight ANSWER 9. Page 3-6 Paragraph 31. – Extremely stable ANSWER 10. Page 3-6 Paragraph 31. – Very light ANSWER 11. Page 1-4. Dry operating weight ANSWER 12. Page 3-1. The CG is the point on the longitudinal axis through which all of the weight acts vertically downward.

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Weight and Balance Theory ANSWER 13. Page 2-3 Example 2-5 MTOW

MLW

MZFW

+ 52000 kgs

+ 46000 kgs

+ 43000 kgs

DOW

- 30,000 kgs

- 30,000 kgs

- 30,000 kgs

Fuel

- 10,000 kgs

- 5,000 kgs

––

Traffic Load

+ 12000 kgs

+ 11000 kgs

+13,000 kgs

Maximum Traffic Load = 11,000 kgs ANSWER 14. Page 1-4. No ANSWER 15. Page 3-4 Paragraph 14. The Manufacturer ANSWER 16. Page 1-6 Paragraph 12 ANSWER 17. Page 1-8 Paragraph 17 (d). Increases stalling speed

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Weight and Balance Theory ANSWER 18. Page 3-4 Paragraph 18 ANSWER 19. Page 3-5 Paragraph 33. By inference stalling speed decreases ANSWER 20. Page 1-2. The strength of the wing roots.

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031 Aircraft Mass & Balance

Centre of Gravity Calculations

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Centre of Gravity Calculations

4

Centre of Gravity Calculations

1. The CG of an aeroplane is determined by calculating the moments of the basic aeroplane and together with the moments of all additional items (fuel, passengers, freight and so on) contained within the aeroplane and dividing the sum of these moments by the total weight. 2. In order to determine the individual moments the weight of each specific item is multiplied by its arm (distance from the reference datum). It is vital that you remember that the arm and the resulting moment is, by convention, considered to be negative if the item is forward of the datum and positive if the item is aft of the datum. Frequently the reference datum is given as a point on an extension of the fore and aft axis forward of the nose of the aircraft. The advantage of such a reference datum is that all arms and moments will be positive. 3. In the event that the position of the undercarriage (extended or retracted) will significantly affect the position of the basic aircraft CG, the loading information contained in Part C of the Weight and CG Schedule will contain a statement of the total moment change which occurs when the undercarriage is lowered. This is because the position of the basic aircraft CG is given with the undercarriage the aircraft weight is therefore 1945 pounds and the CG lies 38.55 inches aft of the datum extended. 4. In order to demonstrate how the position of the loaded aircraft CG can be determined a small twin piston aircraft is considered in Figure 4-1 and Figure 4-2. A general description of the CG limits for this aeroplane is given at Figure 4-1 and is shown diagrammatically at Figure 4-2. Figure 4-3 shows the load form, which is appropriate to this aeroplane. The layout of the seats, baggage stowage areas and fuel tanks is shown at Figure 4-4 and Figure 4-5.

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Centre of Gravity Calculations FIGURE 4-1 Centre of Gravity Limits (Gear Extended)

Weight in Pounds

Forward Limit Inches Aft of Datum

Aft Limit Inches Aft of Datum

7045 (Max. Ramp Weight)

126

135

7000 (Max. Take-off Weight)

126

135

6200

122

135

5200 or less

120

135

NOTE: Straight line variation between the points given. Datum line is located 137 in ahead of the wing main spar centreline. Maximum landing weight 7000 lb.

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Centre of Gravity Calculations FIGURE 4-2 Aeroplane CG Envelope

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Centre of Gravity Calculations FIGURE 4-3 Blank Load Sheet Item

Weight Lb.

Arm Inches

Basic Aeroplane Pilot’s Seat

+ 95.0

Co-Pilot’s Seat

+ 95.0

Seat No.3

+ 137.0

Seat No.4

+ 137.0

Seat No.5

+ 195.0

Seat No.6

+ 195.0

Seat No.7

+ 229.0

Seat No.8

+ 242.0

Forward Baggage

+ 19.0

Rear Baggage

+ 255.0

Right Nacelle Locker Forward

+ 145.0

Right Nacelle Locker Aft

+ 192.0

Left Nacelle Locker Forward

+ 145.0

Left Nacelle Locker Aft

+ 192.0

Inboard Fuel

+ 126.8

Outboard Fuel

+ 148.0

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Moment Inches Lbs.

Centre of Gravity Calculations Other Total Weight

Total Moment CG Location for Take-Off

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Centre of Gravity Calculations FIGURE 4-4 Layout of Aeroplane Weight

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Centre of Gravity Calculations FIGURE 4-5 Profile of Aeroplane

NOTE: Note that on the form shown at Figure 4-3 that neither the weight nor the arm appropriate to the aircraft itself is given. The information is contained within the aircraft weight schedule, and is appropriate to one particular airframe.

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Centre of Gravity Calculations 5. When loading the aeroplane care must be taken not to exceed the maximum weight permitted in specific baggage areas. Floor loading/maximum weight details are not given in the form at Figure 4-3, but are listed separately in the operating manual or, for larger aircraft, in the loading manual, and are normally placarded in the aircraft itself.

EXAMPLE 4-1

EXAMPLE Given that the aircraft described at Figure 4-2, Figure 4-3, and Figure 4-4, is loaded in the following manner, determine the take-off weight and the position of the CG at take-off. Basic aircraft Arm

122.5 inches

Captain

170 lb.

Co-pilot

150 lb.

Seat 3

120 lb.

Seat 4

145 lb.

Seat 5

80 lb.

Seat 6

0 lb.

Seat 7

0 lb.

Seat 8

Chapter 4 Page 8

4,600 lb.

0 lb.

Forward baggage hold

40 lb.

Rear baggage hold

120 lb.

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Centre of Gravity Calculations The left and right forward and the left and right aft nacelle lockers each contain 50 lb. of baggage. Inboard fuel tanks

200 litres port

200 litres starboard

Outboard fuel tanks

200 litres port

200 litres starboard

SG of fuel 0.72

SOLUTION First calculate the weight of fuel in pounds. 200 litres x 0.72

=

144 kg

144 kg x 2.205

=

317.5 lb

Therefore the weight of fuel in the inboard tanks is 635 lb., and in the outboard tanks is 635 lb. Now complete the table to appear as Figure 4-6.

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Centre of Gravity Calculations FIGURE 4-6 Item

Weight Lb.

Basic Aeroplane

4

0

0

+ 122.5

Pilot’s Seat

1

7

0

+ 95.0

Co-Pilot’s Seat

1

5

0

+ 95.0

Seat No.3

1

2

0

+ 137.0

Seat No.4

1

4

5

+ 137.0

8

0

+ 195.0

Seat No.6

0

+ 195.0

Seat No.7

0

+ 229.0

Seat No.8

0

+ 242.0

4

0

+ 19.0

2

0

+ 255.0

Seat No.5

Fwd Baggage Rear Baggage

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Arm Inches

6

1

Right Nacelle Locker Forward

5

0

+ 145.0

Right Nacelle Locker Aft

5

0

+ 192.0

Left Nacelle Locker Forward

5

0

+ 145.0

Left Nacelle Locker Aft

5

0

+ 192.0

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Moment Inches Lbs.

Centre of Gravity Calculations

Inboard Fuel

6

3

5

+ 126.8

Outboard Fuel

6

3

5

+ 148.0

8

9

5

Tot Moment

Other Total Weight

6

Check that the total weight is within the permitted limits shown at Figure 4-1, which it is. Next calculate the moments by multiplying the weights by their associated arms. Now add all of the moments together to get, in this case, 885,363 inch-pounds. Finally divide the total moment by the total weight to get: 885, 363 inch-pounds ---------------------------------------------------- = +128.4in 6, 895 lb The completed table should now appear as shown at Figure 4-7.

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Centre of Gravity Calculations FIGURE 4-7 Item

Weight Lb.

Basic Aeroplane

4

Moment Inches Lbs.

6

0

0

+ 122.5

6

3

5

0

0

Pilot’s Seat

1

7

0

+ 95.0

1

6

1

5

0

Co-Pilot’s Seat

1

5

0

+ 95.0

1

4

2

5

0

Seat No.3

1

2

0

+ 137.0

1

6

4

4

0

Seat No.4

1

4

5

+ 137.0

1

9

8

6

5

8

0

+ 195.0

1

5

6

0

0

Seat No.6

0

+ 195.0

0

Seat No.7

0

+ 229.0

0

Seat No.5

Seat No.8

0

+ 242.0

4

0

+ 19.0

2

0

+ 255.0

Right Nacelle Locker Forward

5

0

Right Nacelle Locker Aft

5

Left Nacelle Locker Forward

5

Left Nacelle Locker Aft

5

Fwd Baggage Rear Baggage

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Arm Inches

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1

5

0 7

6

0

0

6

0

0

+ 145.0

7

2

5

0

0

+ 192.0

9

6

0

0

0

+ 145.0

7

2

5

0

0

+ 192.0

9

6

0

0

3

Centre of Gravity Calculations Inboard Fuel

6

3

5

+ 126.8

8

0

5

1

8

Outboard Fuel

6

3

5

+ 148.0

9

3

9

8

0

8

9

5

Tot Moment

8

5

3

6

3

Other Total Weight

6

8

885,363 inch-pounds -------------------------------------------------- = +128.4in 6, 895lb Take the planned take-off weight and the calculated CG and go to Figure 4-2. You can now see that the CG lies within the envelope on take-off. This is shown at Figure 4-8. You should of course appreciate that, although the C of A maximum take-off weight has not been exceeded, the actual take-off weight may in fact be limited by aircraft performance considerations (such as the runway length available, obstacles in the take-off flight path and so on); by the requirement to clear obstacles en-route to the destination of any nominated alternate aerodrome; or by the landing weight (with aircraft where the maximum landing weight is lower than the maximum take-off weight).

Chapter 4 Page 13

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Centre of Gravity Calculations FIGURE 4-8

Chapter 4 Page 14

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Centre of Gravity Calculations EXAMPLE 4-2

EXAMPLE The aircraft in Example 4-1 is planned to burn 650 litres of fuel en-route. The outboard tanks will be used initially until they contain only 20 litres each, the inboard tanks will then be used for the remainder of the flight. Determine the landing weight and position of the CG on touchdown.

SOLUTION The question doesn't indicate that we've lost any passengers en-route, and therefore the only change is going to be the weight of fuel, and the change in the position of the CG which has resulted from the reduction in fuel load. Fuel remaining 150 litres. 20 litres in each of the outboard tanks weigh 31.75 lb. per tank, total 64 lb. (to the nearest lb.) 55 litres in each of the inboard tanks weigh 87.32 lb. per tank, total 175 lb. (to the nearest lb.) The amended table should now appear as at Figure 4-9. With this aircraft the maximum landing weight is the same as the maximum take-off weight and so there is no problem (but the landing distance required will need checking). The new CG falls well within the envelope as shown at Figure 4-10.

Chapter 4 Page 15

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Centre of Gravity Calculations FIGURE 4-9 Item

Weight Lb.

Basic Aeroplane

4

6

0

+ 122.5

Moment Inches Lbs. (+) 5

6

3

5

0

0

Pilot’s Seat

1

7

0

+ 95.0

1

6

1

5

0

Co-Pilot’s Seat

1

5

0

+ 95.0

1

4

2

5

0

Seat No.3

1

2

0

+ 137.0

1

6

4

4

0

Seat No.4

1

4

5

+ 137.0

1

9

8

6

5

1

5

6

0

Seat No.5

0

+ 195.0

Seat No.6

8

0

+ 195.0

0

Seat No.7

0

+ 229.0

0

Seat No.8

0

+ 242.0

0

Fwd Baggage

4

0

+ 19.0

2

0

+ 255.0

Right Nacelle Locker Fwd

5

0

Right Nacelle Locker Aft

5

Left Nacelle Locker Fwd Left Nacelle Locker Aft

Rear Baggage

Chapter 4 Page 16

0

Arm Inches

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1

0

7

6

0

0

6

0

0

+ 145.0

7

2

5

0

0

+ 192.0

9

6

0

0

5

0

+ 145.0

7

2

5

0

5

0

+ 192.0

9

6

0

0

3

Centre of Gravity Calculations

Inboard Fuel

1

Outboard Fuel

7

5

+ 126.8

6

4

+ 148.0

6

4

Total Moment

2

2

1

9

0

9

4

7

2

2

5

2

7

Other Total Weight

5

8

CG Location for Landing 742, 527 --------------------- = 126.6 in 5864

Chapter 4 Page 17

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7

4

Centre of Gravity Calculations FIGURE 4-10

Chapter 4 Page 18

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Centre of Gravity Calculations Example 4-2 Alternative Solution. An alternative procedure is shown below for determining the position of the CG on landing. The fuel used from the outboard tanks (400 - 40) is 360 litres or 571 lb. The moment change for the outboard tanks (571 x 148) is 84,508 in. lb. The fuel used from the inboard tanks (650 - 360) is 290 litres or 460 lb. The moment change for the inboard tanks (460 x 126.8) is 58,328 in. lb. The total weight change during flight (571 + 460) is 1031 lb. The landing weight is the take-off weight less the total weight of fuel used in flight. The landing weight (6895 - 1031) is therefore 5864 lb. The total moment change during flight (84,508 + 58,328) is 142,836 in. lb. The landing moment is the take-off moment less the total moment change during flight. The landing moment (885,363 - 142,836) is therefore 742,527 in. lb. The position of the CG on landing (742,527 ÷ 5864) is 126.6". #

Chapter 4 Page 19

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Centre of Gravity Calculations EXAMPLE 4-3

EXAMPLE Determine the position of the CG of an aircraft at take-off, given the following information: Maximum weight for take-off and landing 8000 lb. CG envelope from 1 inch to 4 inches forward of the datum at all weights. Aeroplane Details for Example 4-3.

FIGURE 4-11

Chapter 4 Page 20

Item

Weight or Volume

Arm

Basic Aircraft

6000 lb.

5" forward of datum

Crew

350 lb.

40" forward of datum

Passengers

330 lb.

Fuel

150 Imp gallons SG 0.72

Engine Oil

8 Imp gallons SG 0.875

© G LONGHURST 1999 All Rights Reserved Worldwide

36" aft of datum 11" aft of datum 6" forward of datum

Centre of Gravity Calculations SOLUTION Figure 4-12 shows schematically the distribution of the various weights about the datum and illustrates the need in this example to consider both positive and negative moments.

FIGURE 4-12

150 Imperial gallons of fuel (150 x 10 x 0.72) weigh 1080 lb. 8 Imperial gallons of oil (8 x 10 x 0.875) weigh 70 lb.

Chapter 4 Page 21

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Centre of Gravity Calculations Solution to Example 4-3

FIGURE 4-13 Item

Weight Lb.

Arm Inches

Moment Inch / lbs

Basic Aircraft

6000

-5

-30,000

Crew

350

-40

-14,000

Passengers

330

+36

+11,880

Fuel

1080

+11

+11,880

Oil

70

-6

7830

-420 -44,420 -20,660

- 20,660 inch pound CG = ------------------------------------------------ = – 2.64 inches 7830 lb The CG therefore lies within the approved envelope for take-off.

Chapter 4 Page 22

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+23,760

Centre of Gravity Calculations EXAMPLE 4-4

EXAMPLE Given that the aircraft described in Example 4-3 flies for 3 hours and that the mean rate of fuel consumption is 32 Imperial gallons per hour, determine the position of the CG on landing.

SOLUTION Fuel used in flight (3 x 32 x 10 x 0.72) is 691 lb. (to the nearest lb.). Fuel remaining (1080 691) is 389 lb.

FIGURE 4-14 Item

Weight Lb.

Arm Inches

Moment Inch/lbs

Basic Aircraft

6000

-5

-30,000

Crew

350

-40

-14,000

Passengers

330

+36

+11,880

Fuel

389

+11

+4,279

Oil

70

-6

7139

-420 -44,420 -28,261

Chapter 4 Page 23

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+16,159

Centre of Gravity Calculations - 28,261 inch pound CG = ------------------------------------------------ = -3.96 inches 7139 lb The CG on touchdown lies close, but within, the forward limit of the envelope. Alternative Solution: 96 gallons of fuel weighing 691 lb. is burnt off during the flight. The aircraft weight is reduced by this amount to become 7139 lb. The positive moments are reduced by (691 lb. x 11"), or 7601 inch pounds. The revised algebraic sum of the moments is [(-20,660) - (+7601)], or -28,261 inch-pounds. The new position of the CG is therefore (-28,261 ÷ 7139), or -3.96" (forward of the datum).

Chapter 4 Page 24

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Centre of Gravity Calculations EXAMPLE 4-5

EXAMPLE The following details apply to a six-seat twin engined aircraft. Maximum take-off and landing weight 6000 lb. Maximum baggage weights: Port and starboard wing lockers

120 lb. each

Nose bay

350 lb.

Aft cabin baggage area

340 lb.

Fuel capacities Main tanks (x 2)

50 US gallons each

Auxiliary tanks (x 2)

30 US gallons each 80 x 2 = 160 US gallons

Specific gravity of the fuel Basic aircraft:

Chapter 4 Page 25

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0.72

Centre of Gravity Calculations

Basic aircraft: Weight 3900 lb., CG is 143 inches aft of datum. Relevant arms, given in inches aft of the datum: Nose bay baggage area

77

Pilot/Co-pilot

137

Row 1 passengers

175

Row 2 passengers

204

Aft cabin baggage area

242

Main fuel tanks

150

Auxiliary fuel tanks

162

Loading:

Chapter 4 Page 26

Two pilots

340 lb

Two pax row 1

320 lb

One pax row 2

80 lb

Nose baggage bay

50 lb

Aft cabin baggage

310 lb

Fuel main tanks

100 US gallons

Fuel auxiliary tanks (If take-off weight permits)

60 US gallons

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Centre of Gravity Calculations The centre of gravity limits for the aircraft in this example are shown graphically below.

FIGURE 4-15

Determine whether or not the CG will lie within the envelope at take-off, with the aircraft loaded as described.

Chapter 4 Page 27

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Centre of Gravity Calculations SOLUTION The first thing is to decide whether or not the maximum permitted weight for take-off (6000 lb.) will permit full auxiliary fuel tanks: The maximum fuel weight is therefore 1000 lb. The weight of aircraft plus crew, passengers and baggage is 5000 lb. The main tanks are full and contain (100 ÷ 1.2 x 10 x 0.72), 600 lbs. of fuel. If filled, the auxiliary tanks will between them hold (60 ÷ 1.2 x 10 x 0.72), 360 lb. of fuel. It is therefore possible to fill the auxiliary tanks, and take-off at maximum all-up weight minus 40 lb. Now construct and complete a table in the approved manner.

FIGURE 4-16 Item

Weight Lb.

Arm Inches

Moment Inch Pounds

Basic Aircraft

3900

+143

+557,700

Crew

340

+137

+46,580

Row 1 Passengers

320

+175

+56,000

Row 2 Passengers

80

+204

+16,320

Nose Bay Bags

50

+77

+3850

Aft Cabin Bags

310

+242

+75,020

Main Tanks

600

+150

+90,000

Aux Tanks

360

+162

+58,320

5960

Chapter 4 Page 28

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+903,790

Centre of Gravity Calculations 903, 790 Position CG = --------------------- = +151.6 inches (aft of datum) 5960 Plotting CG against weight gives us a point outside of the envelope, see Figure 4-17. Plotted Answer to Example 4-5

FIGURE 4-17

The aircraft cannot fly whilst loaded in this manner and quantity of baggage will have to be moved from the aft baggage area to the nose bay baggage area in order to move the CG to within safe limits.

Chapter 4 Page 29

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Centre of Gravity Calculations EXAMPLE 4-6

EXAMPLE Determine the minimum amount of baggage that must be moved from the aft baggage area to the nose bay baggage area, in order to move the CG calculated in Example 4-5 to the aft safe limit. The baggage to be moved comprises individual packages each weighing 10 lb.

SOLUTION The maximum aft safe CG position is 149", see Figure 4-17. The movement of baggage will not change the total weight of the aircraft but it will alter the total moments. The required total moments, that is the moments which will result from a CG at 149" and a total (unchanged) weight of 5960 lb., will be 888,040 in. lb. The change of moment caused by moving 1 lb. of baggage from the aft baggage area (at an arm of +242") to the nose bay baggage area (at an arm of +77") is -165 in. lb. The change of moment is minus since load is being moved forward. The total change of moment required is determined by subtracting the total moments for a CG at +149" from the total moments for a CG at +151.6" from Example 4-5. The total change of moment required (903,790 - 888,040) is therefore 15,750 in/lb. The amount of baggage which must be moved from the aft baggage area to the nose bay baggage area (15,750 ÷ 165) is therefore 95.45 lb. The baggage can only be moved in 10 lb. increments and therefore it is necessary to move 100 lb. The revised baggage distribution is therefore as shown in the table which follows.

Chapter 4 Page 30

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Centre of Gravity Calculations FIGURE 4-18 Item

Weight Lb.

Arm Inches

Moment Inch Pounds

Basic Aircraft

3900

+143

+557,700

Crew

340

+137

+46,580

Row 1 Passengers

320

+175

+56,000

Row 2 Passengers

80

+204

+16,320

Nose Bay Bags

150

+77

+11,550

Aft Cabin Bags

210

+242

+50,820

Main Tanks

600

+150

+90,000

Aux Tanks

360

+162

+58,320

5960

+887,290

887, 290 Position CG = --------------------- = +148.9 in (aft of datum) 5960 Plotting CG against weight gives us a point inside of the envelope, see Figure 4-19.

Chapter 4 Page 31

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Centre of Gravity Calculations FIGURE 4-19

Chapter 4 Page 32

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Centre of Gravity Calculations EXAMPLE 4-7

EXAMPLE The mean fuel consumption for the flight is 180 lb. per hour, and the flight time is 4.5 hours. Given that the aircraft is loaded as described in Example 4-5, and that the fuel which remains on touchdown is all contained in the main tanks, check that the CG lies within the envelope on landing.

SOLUTION

Chapter 4 Page 33

Fuel on take-off

960 lb.

Fuel consumed in flight

810 lb.

Fuel on touchdown

150 lb.

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Centre of Gravity Calculations FIGURE 4-20 Item

Weight Lb.

Arm Inches

Moment Inch/lbs

Basic Aircraft

+557,700

Crew

+46,580

Row 1 Passengers

+56,000

Row 2 Passengers

+16,320

Nose Bay Bags

+11,550

Aft Cabin Bags

+50,820

Main Tanks

150

+150

+22,500

Aux Tanks

-

-

-

5960

+761,470

-810 5150 761, 470 Position CG = --------------------- = 147.9 in (aft of datum) 5150

Chapter 4 Page 34

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Centre of Gravity Calculations The CG lies within the envelope, see Figure 4-21. Plotted Answer to Example 4-7.

FIGURE 4-21

The conventional graph used to present the CG envelope, which we have used so far, employs a vertical ‘total aircraft weight’ axis and a horizontal ‘distance from datum’ axis. An alternative presentation is shown at Figure 4-22.

Chapter 4 Page 35

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Centre of Gravity Calculations At Figure 4-22 the vertical axis of the graph remains as ‘total aircraft weight’, in this case using pounds as the unit of weight. The horizontal axis has changed and now represents the ‘total aircraft moments’, in this case using units of ‘total inch-pounds divided by 1000’. Dividing the total moment by 1000 is simply a device which is used in order to keep the numbers to a manageable magnitude.

FIGURE 4-22

Chapter 4 Page 36

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Centre of Gravity Calculations

Transverse Loading 6. So far all of the calculations concerning the position of the CG of an aircraft have considered the position along the fore and aft axis. It is important that an aircraft be loaded such that it is reasonably balanced about the centreline. The most common reason for an aircraft to be unbalanced about the centreline is that the wing fuel is unevenly loaded. Wing tanks, especially outboard tanks and possibly wingtip tanks, have a considerable arm from the centreline. Aircraft operating and/or loading manuals will frequently contain limits as to the amount of permissible imbalance in respect of lateral fuel distribution. 7. Should it be necessary to determine the position of the CG relative to the centreline, appreciate that, by convention, arms to the left (port) of the centreline are positive and arms to the right (starboard) of the centreline are negative.

Chapter 4 Page 37

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Centre of Gravity Calculations EXAMPLE 4-8

EXAMPLE An aircraft is loaded such that the weight is evenly distributed about the centreline, with the exception of the fuel, which is loaded such that there is 400 lb. of fuel in the left wing and 500 lb. of fuel in the right wing. The lateral arm for the wing fuel tanks is 127". If the loaded weight of the aeroplane is 9000 lbs, determine the lateral position of the CG.

SOLUTION Total moments

Lateral CG

Chapter 4 Page 38

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=

(+ 400 x 127) + ( - 500 x 127)

=

50,800 - 63,500

=

- 12,700 in. lb.

=

-12,700 -----------------9000

=

-1.41"

=

1.41" right of the centreline

Centre of Gravity Calculations C of G Practice Calculations Question 1 Aeroplane Data

Chapter 4 Page 39

Maximum Authorised Weight

8000 lbs

C of G limits 4" to 0.5"

forward of datum

Basic weight 6000 lbs

arm 5" forward of datum

Fuel 150 Imp. gals

arm 11" aft of datum

Oil 8 Imp. gals

arm 6" forward of datum

Crew 340 lbs

arm 40" forward of datum

Passengers 340 lbs

arm 36" aft of datum

SG of fuel 0.72

SG of oil 0.90

(a)

Calculate the C of G arm

(b)

If the fuel consumption is 40 Imp. gals/hr and the oil consumption is 2 Imp. gals/hr, calculate the arm of the C of G after three hours.

© G LONGHURST 1999 All Rights Reserved Worldwide

Centre of Gravity Calculations Question 2 Aeroplane Data Maximum Authorised Weight

60,000 lbs

C of G limits 1.5 ft. aft of datum to 2.5 ft. aft of datum

Chapter 4 Page 40

Basic weight 26,000 lbs

arm 1 ft. aft of datum

Crew 300 lbs

arm 5 ft. forward of datrum

Freight in hold A 10,400 lbs

arm 6 ft. aft of datum

Freight in hold B 800 lbs

arm 1 ft. forward of datrum

Fuel 2000 Imp. gals

on the datum

Oil 25 Imp. gals

arm 1 ft. forward of datum

SG of fuel 0.72

SG of oil 0.90

(a)

Calculate the arm of the C of G at take-off

(b)

If the fuel consumption is 204 Imp. gals/hr and the oil consumption is 4 pints/hr, what is the arm of the C of G after 4 hours?

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Centre of Gravity Calculations Question 3 Aeroplane Data

Chapter 4 Page 41

Maximum Authorised Weight

8500 lbs

C of G limits 18 to 29"

aft of datum

Basic weight 5000 lbs

arm 30" aft of datum

Crew 340 lbs

arm 30" forward of datum

Fuel 200 US gals

arm 10" forward of datum

Oil 15 US gals

arm 8" aft of datum

Passengers 340 lbs

arm 40" aft of datum

SG of fuel 0.72

SG of oil 0.90

Fuel consumption

50 US gals/hr

Oil consumption

2 US gals/hr

(a)

Calculate the C of G for take-off

(b)

Calculate the C of G for landing after three hours.

© G LONGHURST 1999 All Rights Reserved Worldwide

Centre of Gravity Calculations C of G Practice Calculation Answers Answer 1 C of G limits -4" to -0.5" (a)

Weight

Arm

Moment

APS

6000 lbs

-5"

-30,000 ins/lbs

Fuel

1080 lbs

+11"

+11,880 ins/lbs

Oil

72 lbs

-6"

-432 ins/lbs

Crew

340 lbs

-40"

-13,600 ins/lbs

PAX

340 lbs

+36"

+12,240 ins/lbs

Totals

7832 lbs

– 19912 C of G arm ------------------ = – 2.542″ 7832

Chapter 4 Page 42

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-19,912 ins/lbs

Centre of Gravity Calculations (b)

Fuel used

40 x 3 = 120 Imp. gals = 864 lbs

Oil used

2 x 3 = 6 Imp. gals = 54 lbs

Weight change

- 918 lbs

Moment change

(-864 x +11) - (54 x-6) = -9180

Revised weight

7832 - 918 = 6914 lbs

Revised moment

-19,912 - 9180 = 29092 ins/lbs

– 29092 C of G arm ------------------ = – 4.208 ″ (out of limits) 6914

Chapter 4 Page 43

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Centre of Gravity Calculations Answer 2 (a) APS

Arm

Moment

26,000 lbs

+1 ft

+26,000 ft/lbs

Crew

300 lbs

-5 ft

- 1500 ft/lbs

Hold A

10,400 lbs

+ 6ft

+ 62,400 ft/lbs

Hold B

800 lbs

- 1ft

- 800 ft/lbs

Fuel

14,400 lbs

0

0

Oil

225 lbs

- 1ft

-225 ft/lbs

Totals

52,125 lbs

+85, 875 C of G arm --------------------- = +1.647 ft 52, 125

Chapter 4 Page 44

Weight

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Centre of Gravity Calculations (b)

4 hrs fuel

816 gals = 5875.2 lbs

4 hrs oil

2 gals = 18 lbs

Change of weight

- 5893.2 lbs

Revised AUW

46,231.8 lbs

Moment change

fuel = 0 oil = -18 x = 85,893 ft/lbs

Revised moment

85, 893 C of G arm ---------------------- = 1.8579 ft 46, 231.8

Chapter 4 Page 45

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85,875 + 18 = 85,893 ft/lbs

Centre of Gravity Calculations Answer 3 (a) APS

Arm

Moment

5000 lbs

+30"

+150,000 ins/lbs

Crew

340 lbs

- 30"

-10,200 ins/lbs

Fuel

1200 lbs

-10"

-12,000 ins/lbs

Oil

112.5 lbs

+8"

+900 ins/lbs

PAX

340 lbs

+40"

+13,600 ins/lbs

Totals

6992.5 lbs

+142.300 C of G arm ---------------------- = +20.35″ 6992.5

Chapter 4 Page 46

Weight

© G LONGHURST 1999 All Rights Reserved Worldwide

+ 142,300 ins/lbs

Centre of Gravity Calculations (b)

3 hrs fuel

150 US gals = 125 Imp. gals = 900 lbs

3 hrs oil

6 US gals = 5 Imp. gals = 45 lbs

Revised AUW

6992.5 - 45 = 6047.5 lbs

Moment change

- 900 x -10 = +9000 ins/lbs - 45 x +8 total

Revised moment

+150,940 C of G arm ---------------------- = +24.96″ 6047.5

Chapter 4 Page 47

© G LONGHURST 1999 All Rights Reserved Worldwide

= -360

ins/lbs

+8640 ins/lbs

+142,300 + 8640 = +150,940 ins/lbs

031 Aircraft Mass & Balance

Adding, Removing and Repositioning Loads Adding or Removing Load Repositioning a Load

© G LONGHURST 1999 All Rights Reserved Worldwide

Adding, Removing and Repositioning Loads

Adding, Removing and Repositioning Loads 5

1. When a detailed description of the weight and arms of an aeroplane and all of its contents is available, the method used to determine the position of the laden aircraft CG is to complete a trim sheet. Having done this, if the CG is outside of the approved envelope it is necessary to redistribute the load in order to move the CG to within limits, if possible. If this is not possible then some of the load will need to be removed from the aircraft altogether in order to put the CG within the envelope. 2. Frequently, once the trim sheet is complete, additional payload is added (last minute changes) and it is essential that the new CG is calculated in order to ensure that it is still within limits.

Adding or Removing Load 3. To facilitate the rapid and easy calculation of either the new CG position, when a load is added or removed, or the amount of load which must be removed in order to achieve a given CG position there is an algebraic solution. By introducing an algebraic value for the unknown quantity into the following formula, the value of the unknown quantity can be determined. The formula is: New Total Moments

=

Old Total Moments + or – Load Moment

4. In the formula above the ‘Load moment’ is the product of the weight and arm of the load which is added or removed from the aircraft. The symbol will therefore appear as a + if a load is added or a – if a load is removed.

Chapter 5 Page 1

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Adding, Removing and Repositioning Loads 5. If the formula is to be utilised to account the use of fuel it may be modified (by replacing ‘Load Moment’ with ‘Fuel Moment’) and used to recalculate the CG position for landing if a larger or smaller quantity of fuel has been consumed in flight than was originally planned.

EXAMPLE 5-1

EXAMPLE Given an aeroplane all up weight of 120,000 lb. and CG arm 4 ft aft of the reference datum. Determine how much load must be removed from a cargo hold 33 ft aft of the datum in order to move the CG 1–ft forward from its original position.

Chapter 5 Page 2

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Adding, Removing and Repositioning Loads SOLUTION Let W be the unknown, in this case the amount of load to be removed. New Total Moments

=

Old Total Moments – Load Moment

New CG arm

=

+4 ft – 1 ft.

=

+3 ft.

New weight

=

120,000 – W lb.

New Total Moments

=

(120,000 – W) x (+3) ft. lb.

=

360,000 – 3W ft. lb.

Old Total Moments

=

120,000 x (+4) ft. lb.

=

+480,000 ft. lb.

Load moment

=

W (+33) ft. lb.

=

33W ft. lb.

=

Old Total Moments – Load Moment

New Total Moments 360,000 –3W

=

480,000 – 33W

33W – 3W

=

480,000 – 360,000

30W

=

120,000

W

=

4000 lb.

In order to position the CG 3–ft aft of the datum it is therefore necessary to remove 4000 lb. of load.

Chapter 5 Page 3

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Adding, Removing and Repositioning Loads EXAMPLE 5-2

EXAMPLE Given an all up weight of 80,000 kg and a CG 16 metres aft of the datum which is the nose of the aircraft, determine the change in the position of the CG, if 5,000 kg of freight is now loaded in a hold 23 metres aft of the datum.

SOLUTION Let D

=

The unknown distance of the New CG Arm.

New Total Moments

=

Old Total Moments + Load moment

(80,000 + 5,000) x D

=

(80,000 x (+16)) + (5,000 x (+23))

85,000 x D

=

1,280,000 + 115,000

D

=

D

=

+16.412 m.

Change to CG Arm

=

New CG Arm – Old CG Arm

Change

=

(+16.412 – (+16))

=

+0.412 m.

1, 395, 000 --------------------------85, 000

The CG has therefore moved 0.412 metres aft of its original position.

Chapter 5 Page 4

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Adding, Removing and Repositioning Loads EXAMPLE 5-3

EXAMPLE Given an all up weight of 65,000 lb. and a CG 18.5–ft aft of the datum, which is the nose of the aircraft. Determine the change in the position of the CG if 3,200 lb. of freight is removed from a hold 14 ft aft of the datum.

SOLUTION New Total Moments

=

Old Total Moments – Load Moment

(65,000 – 3200) x D

=

(65,000 x (+18.5)) – (3200 x (+14))

61,800 x D

=

1,202,500 – 44,800

D

=

D

=

+18.733 ft

Change to CG Arm

=

New CG Arm – Old CG Arm

Change

=

(+18.733 – (+18.5))

=

+0.233 ft

Let D be the new CG arm.

1, 157, 700 --------------------------- ft 61, 800

The CG has therefore moved 0.233 metres aft of its original position.

Chapter 5 Page 5

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Adding, Removing and Repositioning Loads 6. If freight or fuel is added or removed from an aeroplane and the cargo hold or fuel tank is measured relative to the present CG position, the change to the CG can be determined by a simple formula. If the freight or fuel is added, then the weight value is positive and if it is removed it is a negative value. If the distance of the hold or fuel tank is ahead of the present CG the distance is a negative value and if it is aft of the present CG it is a positive value. The formula is: Freight/fuel × distance from present CG ------------------------------------------------------------------------------------------------- = change to CG New aircraft weight

EXAMPLE 5-4

EXAMPLE Given: Aircraft weight 150,000 kgs, if 5000 kgs of freight is added to a hold 10 m ahead of the present CG, determine the change to the CG

SOLUTION 5000 × – 10 --------------------------- = – 0.323m . New CG is 0.323 m ahead of old CG. 155000

Chapter 5 Page 6

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Adding, Removing and Repositioning Loads EXAMPLE 5-5

EXAMPLE Given: Aircraft weight 30,000 lbs, if 2000 lbs of fuel is used from a fuel tank positioned 5 ft forward of the present CG, determine the change to the CG.

SOLUTION – 2000 × – 5 --------------------------- = +0.357 ft The new CG is 0.357 ft aft of the old CG. +28000

Repositioning a Load 7. As already discussed, the CG position is influenced by the relocation of the load. When dealing with this type of problem it is convenient to use the following formula: Wt of load to be moved Change to CG arm -------------------------------------------------------- = -------------------------------------------------Total weight Distance load moved or w cc ----- = ----W d 8. The signs to be used in this formula for ‘cc’ and ‘d’ are + for a rearward movement of the load and – for a forward movement of the load.

Chapter 5 Page 7

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Adding, Removing and Repositioning Loads NOTE: Note this formula can only be used with ‘moving load within an aeroplane’ problems. It cannot be used for problems involving removing loads, using fuel or adding loads or increasing the fuel on board. However, the original formula: New Total Moments = Old Total Moments + Load Moment can be used for ‘moving loads within an aeroplane’ problems. It is used in this manner: New Total Moments = Old Total Moments – Load Moment + Load Moment. The – Load Moment is used for removing it from the original hold and the + Load Moment is used for loading it back on the aeroplane in the new hold.

Chapter 5 Page 8

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Adding, Removing and Repositioning Loads EXAMPLE 5-6

EXAMPLE Given an All Up Weight of 60,000 kg and a CG 22 metres aft of the datum, which is the nose of the aircraft. Determine the change in the position of the CG if 3,000 kg of load is moved from a hold 14 metres aft of the datum to a hold 29 metres aft of the datum.

SOLUTION The load (3,000 lb.) is to be moved aft by 15 metres as illustrated below.

Chapter 5 Page 9

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Adding, Removing and Repositioning Loads

w ----W

=

cc ----d

3000 -----------------60, 000

=

cc --------+15

3000x + 15 --------------------------60, 000

= cc

cc

= –0.75 metres (aft movement)

New Total Moments

= Old Total Moments – Load Moment + Load Moment

(600,000 x D)

= 60,000 x (+22)] – [3,000 x (+14)] + [3,000 x (+29)]

60,000 D

= 132,000 – 42,000 + 87,00

60,000 D

= 1,365,000

D

= 22.75 m.

Change to CG Arm

= New C G Arm – Old CG Arm = 22.75 m. – 22 m. +0.75 m. = 0.75 m. Aft.

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Adding, Removing and Repositioning Loads EXAMPLE 5-7

EXAMPLE Given an All Up Weight of 25,000 kg and a CG 9 metres aft of the datum. Determine the change in the position of the CG if 1,000 kg of load is moved from a hold 12 metres aft of the datum to another 5 metres aft of the datum.

SOLUTION The load (1,000 kg) is to be moved forward by 7 metres as illustrated here.

Chapter 5 Page 11

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Adding, Removing and Repositioning Loads

w ----W

=

cc ----d

1000 -----------------25, 000

=

cc ------7

1000x – 7 -----------------------25, 000 cc

= cc

= –0.28 metres or –28cm (forward movement)

Chapter 5 Page 12

New Total Moments

= Old Total Moments – Load Moment + Load Moment

(25,000 x D)

= 25,000 x (+9)] [1,000 x (+12)] + [1,000 x (+5)]

25,000 D

= 225,000 – 12,000 + 5,000

25,000 D

= 218,000

D

= 8.72 m.

Change

= 8.72 –9 = –0.28 m. = 0.28 m. forward

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Adding, Removing and Repositioning Loads EXAMPLE 5-8

EXAMPLE Given an All Up Weight of 145,000 lb. And a CG 21 ins. forward of the datum. Determine how much freight must be moved from a hold 96 ins. forward of the datum to a hold 84 ins. aft of the datum in order to move the CG 1.5 ins. aft of its original position.

SOLUTION

Chapter 5 Page 13

w ----W

=

cc ----d

w --------------------145, 000

=

+1.5 -----------+180

w

=

+1.5 x 145,000 -----------------------------------+180

w

= 1208 lb

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Adding, Removing and Repositioning Loads EXAMPLE 5-9

EXAMPLE Given an All Up Weight of 120,000 lb and a CG 4 ft aft of the reference datum. Determine how much load must be moved from a hold 35 ft aft of the datum to a hold 25 ft forward of the datum in order to move the CG to a point 3 ft aft of the datum.

SOLUTION

Chapter 5 Page 14

w ----W

=

w --------------------120, 000

=

w

=

w

= 2000 lb

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cc ----d –1 --------60 – 1 x 120,000 ------------------------------– 60

Adding, Removing and Repositioning Loads It should be understood that fuel usage in flight can move the position of the CG, particularly in longer aircraft with heavy fuel loads in numerous tanks. Faithful adherence to the fuel management procedures as laid down in the AFM will ensure that the CG remains within the specified limits during the flight. With large aircraft the usage of fuel can be arranged such that the CG is kept as close as possible to the optimum position for significant periods of the flight, again in accordance with AFM Procedures. This procedure ensures the CG remains just forward of the Aft Limit, and is referred to as flying the ‘Flat’ aeroplane. It results in a significant increase in range.

Formula Practice Questions Question 1 Given

AUW 60,000 lbs. C of G 2 ft. forward of datum.

Calculate:

How much freight must be added to hold arm 5 ft. aft of datum to move the C of G to 1 ft. forward of datum?

Question 2

Chapter 5 Page 15

Given

AUW 100,000 kgs. Datum at nose. C of G 15m aft of datum.

Calculate:

The change to C of G arm if 4,000 kgs of freight is removed from hold 25m aft of datum.

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Adding, Removing and Repositioning Loads Question 3 Given

AUW 60,000 kgs. C of G arm 6m aft of datum.

Calculate:

The change to C of G arm if 10,000 kgs of fuel is used from tank arm 1m forward of datum.

Question 4 Given

AUW 12,000 lbs. C of G 2 ft aft of datum.

Calculate:

How much freight must be removed from hold 4 ft aft of datum to move C of G 6 inches forward?

Question 5

Chapter 5 Page 16

Given

AUW 50,000 kgs datum at nose. C of G 25m. aft of datum.

Calculate:

Change to C of G arm if 1,000 kgs of freight is moved from hold 50m aft of datum to hold 30m aft of datum.

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Adding, Removing and Repositioning Loads Question 6 Calculate:

If the freight in Question 5 is removed, what is the arm of the new C of G?

Question 7 Given

AUW 30,000 lbs. C of G arm 3 ft aft of datum.

Calculate:

How much freight must be removed from hold 5 ft aft of datum to move C of G 6 inches forward?

Formula Practice Answers Answer 1 New Total Moments = Old Total Moments ± Freight/Fuel Moment Let w = Unknown freight (60,000 + w) x (-1) = [60,000 x (-2)] + [(w x (+5)] - 60,000 - w = 120,000 + 5w 120,000 - 60,000 lbs = 5w + w 60,000 lbs = 6w 10,000 lbs = w

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Adding, Removing and Repositioning Loads Answer 2 Let d = New C of G arm (96,000 x d) = [100,000 x (+15)] - [4,000 x (+25)] 96,000 d = 1,500,000 - 100,000 d = 1,400,000 ÷=96,000 = +14.58m Change to C of G

= +14.58 - 15.0 = -0.42m = 0.42m Forward

Answer 3 Let d = New C of G Arm (50,000 x d) = [60,000 x (+6)] - [10,000 x (-1)] 50,000 d = 360,000 + 10,000 d = 370,000 ÷ 50,000 = +7.4m Change to C of G Arm = 7.4 - 6 = +1.4m

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Adding, Removing and Repositioning Loads Answer 4 Let w = Freight to be removed (12,000 - w) x 1.5 = [12,000 x (+2)] - [w x (+4)] 18,000 - 1.5w = 24,000 - 4w 4w - 1.5w = 24,000 - 18,000 2.5w = 6,000 w = 2.4000 lbs.

Answer 5 Let d = New C of G Arm (50,000 d) = [50,000 x (+25)] - [1,000 x (+50)] + [1,000 x (+30)] 50,000 d = 1,250,000 - 50,000 + 30,000 d = 1,230,000 ÷ 50,000 = +24.6m Change to C of G Arm = +24.6 - 25.0 = -0.4m = 0.4m Forward

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Adding, Removing and Repositioning Loads Answer 6 Let d = New C of G Arm (1) 49,000 d = [50,000 x (+25)] - [1,000 x (+50)] 49,000 d = 1,250,000 - 50,000 = 1,200,000 d = 1,200,000 ÷ 49,000 = +24.49m or (2) 49,000 d = [50,000 x (+24.6)] - [1,000 x (+30)] 49,000 d = 1,230,000 - 30,000 = 1,200,000 d = 1,200,000 ÷ 49,000 = +24.49m

Answer 7 Let w = Freight to be removed (30,000 - w) x 2.5 = [30,000 x (+3)] - (w x5) 75,000 - 2.5w = 90,000 - 5w 5w - 2.5w = 90,000 - 75,000 2.5 w = 15,000 w = 6,000 lbs

Chapter 5 Page 20

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Adding, Removing and Repositioning Loads

Chapter 5 Page 21

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031 Aircraft Mass & Balance

The Mean Aerodynamic Chord

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The Mean Aerodynamic Chord

6

The Mean Aerodynamic Chord

1. On large transport aircraft the position of the CG is often expressed in relation to the aircraft’s Mean Aerodynamic Chord (MAC). The MAC is precisely what the name implies. If you take the plan view of a swept and tapered wing and draw a number of chord lines across the wing, each chord will necessarily be of a different length (longer at the wing root and shorter at the wing tip) and a different distance from the nose of the aircraft (the shorter distance at the wing root and the furthest distance at the wing tip). If you now take the mathematical mean of all these chord lines you have the MAC, expressed as a single length starting at a stated distance from the reference datum of the aircraft. For example an aircraft’s MAC might be expressed as 205 inches in length extending from 790 to 995 inches aft of the reference, as shown at Figure 6-1.

Chapter 6 Page 1

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The Mean Aerodynamic Chord FIGURE 6-1 Example Mean Aerodynamic Chord

2. The following examples illustrate how to convert the position of a CG which is given as a percentage of the MAC into a position which is relative to the reference datum, and the reverse.

Chapter 6 Page 2

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The Mean Aerodynamic Chord EXAMPLE 6-1

EXAMPLE The MAC limits of an aircraft are 802.7 inches to 1020.5 inches aft of datum. The CG is 31% of the MAC. Determine the position of the CG relative to the datum.

SOLUTION See Figure 6-2. MAC (1020.5 – 802.7) = 217.8 inches. 217.8 31% MAC = ------------- × 31 = 67.5 inches 100 CG Position = 802.7 + 67.5 = 870.2 inches aft of datum.

Chapter 6 Page 3

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The Mean Aerodynamic Chord FIGURE 6-2

Chapter 6 Page 4

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The Mean Aerodynamic Chord EXAMPLE 6-2

EXAMPLE The CG of a loaded aircraft is given as 503.6 inches aft of the datum. The MAC for this aircraft extends from 482.2 inches to 536.7 inches aft of the datum. Express the position of the CG as a percentage of the MAC.

SOLUTION See Figure 6-3. MAC (536.7 – 482.2) = 54.5 inches CG Position= 503.6 – 482.2 = 21.4 inches aft (Relative to forward MAC Limit) 21.4 CG as % MAC = ---------- × 100 = 39.3 % 54.5

Chapter 6 Page 5

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The Mean Aerodynamic Chord FIGURE 6-3

Chapter 6 Page 6

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031 Aircraft Mass & Balance

Structural Limitations Securing Aircraft Loads Weight Limits

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Structural Limitations

7

Structural Limitations

1. In addition to the weight and C of G limitations already described it is necessary to impose further restrictions to ensure that the aeroplane floor is not overloaded or that the aeroplane structure is not over-stressed. These limitations are divided into overall limitations and floor loading limitations.

Overall Limitations.

An aeroplane is constructed about its main spar because it is this that must support it in flight. Most large aeroplanes have a double main spar. The forward spar supporting the weight in front of it whilst the rear spar supports the weight aft of it. Hence it may be considered to be two cantilever beams, as shown in Figure 7-1. If the weight of the aeroplane is unevenly distributed about the double spar the fuselage will bend about the spar bending greatest toward the heavier weight. Although the bending caused by unevenly distributed loading will not be immediately apparent the forces do exist and if the unequal division of the load is overmuch are a serious potential source of damage to the aeroplane.

Chapter 7 Page 1

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Structural Limitations FIGURE 7-1 The Effect of Uneven Load Distribution

2. The fact that the C of G is within limits does not necessarily mean that the loaded aeroplane is within the bending limitations. Nor does the fact that the load is within the individual compartment load limitations ensure that it is loaded within the bending limits. 3. There are Tables and Graphs provided by the manufacturer to check the compliance of the loaded aeroplane with the requirements.

Floor Loading Limitations.

The strength of the aeroplane floor varies throughout its length and width according to the construction and location of the individual panels and their supporting beams. There are two limitations imposed on floor panels to protect them and the aircraft from damage. They are the linear and area load maxima.

Linear Limitations. This is the maximum weight per unit length of the floor. The width of the load does not affect this limitation. The limitation may be expressed in lbs/linear ft or kgs/linear metre. This restriction therefore requires that due consideration be given to the way in which the items loaded are orientated. The linear load limitation is often referred to as the ‘Running Load’.

Chapter 7 Page 2

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Structural Limitations FIGURE 7-2 Linear Loading

Chapter 7 Page 3

Box A

loaded laterally equals 300 kg/linear m.

Box B

Same weight and length as A but loaded longitudinally, equals 60 kg/linear m.

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Structural Limitations Area Limitations. To provide protection for individual floor panels an area limitation is imposed and is expressed in kg/sq.m. or lbs./sq. ft. Items which have a large surface area impose a low area floor load. However, those having a small area of contact with the floor have a high area floor load e.g. the wheels of a vehicle. Often ‘Load Spreaders’ are used with this type load, this is some type of material, usually wood, which has a larger contact area with the floor and is placed by the item’s contact points and the floor. Thus the weight of the item is distributed over a larger area reducing the area floor load. Again orientation of the load is all important. In the following example Figure 7-3 is loaded in five different ways producing three different floor loads.

Chapter 7 Page 4

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Structural Limitations FIGURE 7-3 Area Loading

Chapter 7 Page 5

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Structural Limitations 4. All five boxes are the same size and weight 600 kgs. But each has a different effect on the floor. In the example the area floor loading limitation is 100 kgs/sq.m. and linear load limitation is 200 kgs/linear m. 5.

To find the area load divide the weight by the floor area.

6.

To calculate the linear load divide the weight by the longitudinal length.

Box 1 - 300 kgs/sq.m. and 600 kgs/linear m. (exceeds both limitations). Box 2 - 200 kgs/sq.m. and 600 kgs/linear m. (exceeds both limitation). Box 3 - 100 kgs/sq.m. and 300 kgs/linear m. (exceeds linear limitation). Box 4 - 200 kgs.sq.m. and 200 kgs/linear m. (exceeds area limitation). Box 5 - 100 kgs.sq.m. and 200 kgs/linear m. (complies with both limitations). 7. To keep the area and linear loads to a minimum, the longest side must be along the longitudinal axis and the second longest side should be along the athwartships axis.

Securing Aircraft Loads 8. The safety of an aeroplane is of paramount importance and depends on many different people competently completing their individual tasks. Incorrect loading of the aircraft could have immediate and devastating consequences.

Weight Limits 9.

Chapter 7 Page 6

The weight of any particular load may be restricted by one of three limitations:

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Structural Limitations (a)

The total weight of the aeroplane including its load must not exceed the maximum permitted take-off weight.

(b)

The load must not exceed the maximum permissible floor loading, measured in kg/m2 or lb/ft2, for each individual cargo or baggage compartment.

(c)

The load must not exceed the capacity of the load restraint.

Floor Loading 10. It is important to minimise the floor loading. If the load has a flat base, which is all in contact with the aircraft floor, then the weight of the load is distributed over the whole base area. However, if by virtue of its shape, the weight of the load is imposed on the floor through a small area in contact with the floor then it may exceed the maximum floor load. To distribute the load over a greater floor area and thus reduce the floor load a mechanical device known as a load spreader may be inserted between the load and the aircraft floor. See Chapter 2.

Load Factor 11.

The load factor is the ratio of an externally applied force to a load with a given weight: ForceLoad Factor = Applied ----------------------------------Weight

Chapter 7 Page 7

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Structural Limitations 12. The load factor is described using multiples of the gravitational force (g) acting on the load. The load factor is therefore +1g under normal gravity conditions. The plus sign indicates that the load is acting vertically downwards. In a 60° bank turn the aircraft, and its contents, are subject to a load factor of +2g. In a bunt manoeuvre the aircraft and its contents are subject to negative g (a negative load factor), which will tend to lift unsecured items off the floor. Similarly, rapid accelerations will tend to move loads backwards and rapid decelerations will tend to move the loads forwards, under the effects of inertia.

Load Restraint 13. In order to ensure that the load does not move during any phase of flight it must be adequately secured in all directions using the most suitable equipment in a planned tie-down scheme. Failure to prevent movement of the load could hazard the safety of the aeroplane by virtue of the momentum or inertia of the load. 14. The restraint factor for fixed wing aircraft is expressed in multiples of the force of gravity. This determines the strength of the lashing and tie-down equipment required to secure the load. The current restraint load factors are:

Chapter 7 Page 8

Forwards

3g

Rearwards

1.5g

Lateral

1.5g

Vertical

2g

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Structural Limitations 15. On flights where passengers and cargo are required to share the same compartment, the restraint load factors are increased to coincide with the load factors for passenger seats. These load factors are listed shortly.

Restraint Equipment 16. On a cargo aeroplane there are many different types of equipment that may be used individually or together to secure a load. Most require attachment to aircraft floor points, which, although they are strong points, have a maximum strength, which must not be exceeded. They include:

Lashing Chains. These should be applied symmetrically between 30° and 45° both with the aircraft floor and the longitudinal axis. Tensioners.

These are mechanical devices used to take any slack out of the tie-down scheme and tighten the lashing equipment.

Cargo Nets.

These are strong webs of nylon or similar material which may be used to secure a number of small items together as one load by covering them all and securing the net at specific points to the aircraft floor.

Side Guidance.

This is a means of protecting the aircraft structure from damage when loading and unloading the cargo bay.

Grab Hooks.

Chapter 7 Page 9

These are a means of securing a cargo net to a lashing point.

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Structural Limitations

Passenger Seats 17. Aircraft seats are specifically designed to fit into secure floor points. Aircraft seats are equipped with seat belts. The floor securing system together with the seat belt are intended to enable the occupant to escape serious injury in the event that the seat and occupant are exposed to the following load factors: Upward

3.0g

Forwards

9.0g

Sideways

4.0g

Downward

6.0g

Rearward

1.5g

18. In the event of an emergency landing, the deformation of seats and other items of cabin equipment should not be such that they would impede rapid evacuation from the aircraft cabin. Any items of significant size or weight within the passenger compartment, galleys or flight deck must be restrained to prevent their movement during an emergency landing. [JAR-25 561 (b) (3)].

Load Shift 19. If the load is not correctly secured using an approved tie-down scheme, it may move and cause a hazard to the aeroplane. Load shift is likely to occur:

During Take-Off.

At VR the aircraft attitude will cause any loose load to move aft causing the aircraft to pitch up even further, making the aircraft unstable and possibly causing it to stall.

Chapter 7 Page 10

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Structural Limitations Nose-Down Pitching. On pitching nose down any loose cargo will move forward, causing the aircraft to pitch further nose down. With a severe load shift it may be impossible to return the aircraft to level flight. A forward load shift which occurs during the landing may make it difficult or impossible to round out. Deceleration. A rapid deceleration (notably during the landing roll) of the aircraft will cause an unsecured load to move forward due to inertia. Load Spreaders. A load spreader is material, usually thick wood, placed between the aircraft floor and heavy load items which exceed the floor load intensity limitation and/or have hard or sharp contact areas. Its purpose is to extend the load intensity over a larger floor area than the base of the item and at the same time protect the aircraft floor from damage. The effectiveness of a load spreader is established by its thickness, not its overall size. To utilise its full potential its area must be large enough to contain a 45° angle from the base of the load item to the aircraft floor.

Chapter 7 Page 11

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Structural Limitations FIGURE 7-4

Dunnage. Material, usually thick wood, utilised to protect the aircraft floor, including ramps, and provide a continuous pathway over which wheeled vehicles may transit when being positioned in the fuselage prior to lashing down without exceeding the maximum area limit at any point.

Chapter 7 Page 12

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031 Aircraft Mass & Balance

Manual and Computer Load/Trim Sheets Manual Load and Trim Sheets Load and Trim Sheet Completion Procedure Computer Load and Trim Forms Last Minute Changes Aircraft Load and Trim Slide Rule

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Manual and Computer Load/Trim Sheets

Manual and Computer Load/Trim Sheets 8

1. A load and trim sheet may be produced either manually or by computer. It is most important that it is thoroughly checked by the aircraft commander and signed by him (or her) as accepting the load and its distribution within the aircraft. A trim slide rule, discussed later in this chapter, may be used for this purpose. 2. A load and trim sheet is a record of the weight of an aircraft and the distribution of its contents. It must be drawn up by a person qualified in the loading and security of load for flight. The load sheet must be signed in duplicate before flight by the person supervising the loading and passed to the aircraft commander. If the aircraft commander is satisfied that the load carried is of such weight and is so distributed and secured that the flight can be safely conducted then he is to sign the load sheet as accepting the load. [JAR-OPS 1.625 (a)]. 3. If the payload weight and distribution is unchanged from the previous flight and the aircraft is refuelled with the same weight and distribution of fuel as on the previous flight the load sheet for the previous flight may be used. The aircraft commander must endorse the load sheet of the previous flight with signature, date and place of departure of the next intended flight and intended destination. 4. If it is necessary for an aircraft to stop en-route in order to refuel it is likely that the payload weight and distribution will be unchanged, however the fuel load may differ from the previous sector. In this case an abbreviated load and trim sheet, known as a Nil Change of Payload Form may be completed.

Chapter 8 Page 1

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Manual and Computer Load/Trim Sheets 5. One copy of the load sheet is to be carried in the aircraft during the flight to which it relates. One copy is to be kept on the ground by the operator and retained for 3 months. [Appendix 1 to JAR-OPS 1.1065]. If this is not practical then the second copy must be kept in a special container in the aircraft provided for the purpose and deposited with the operator at the first opportunity. [JAR-OPS 1.140 (a) (1) (iii)]. 6. These load sheet requirements do not apply to an aircraft with an MTWA of 1150 kg or less. Nor do they apply to aircraft with an MTWA of 2730 kg if the flight time is 60 minutes or less and it is a crew training flight or a flight intended to begin and end at the same aerodrome. Helicopters with an MTWA of 3000 kg or less and a seating capacity of five persons or less are also exempt from the load sheet requirements.

Manual Load and Trim Sheets 7. The manual load and trim sheet may be completed by the agent or alternatively, by the Captain or First Officer. 8. The manual load and trim sheet shown at Figure 8-1 looks complex but is in fact straightforward. Let's go through it step by step, which unfortunately isn't from top left to bottom right. Standard weights are assumed for this exercise.

Chapter 8 Page 2

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Manual and Computer Load/Trim Sheets FIGURE 8-1 Example Load and Trim Sheet

Chapter 8 Page 3

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Manual and Computer Load/Trim Sheets

Load and Trim Sheet Completion Procedure

Chapter 8 Page 4

(a)

Fill in boxes 1 (aircraft registration), 2 (flight number), 3 (seating configuration, in this case 167 passenger seats, all in tourist class configuration), 4 (crew configuration, in this case 2 flight deck and 5 cabin crew), 5 (departure aerodrome, in this case Lanzerote), 6 (destination aerodrome, in this case London Gatwick), 7 (date) and 8 (Captain's name).

(b)

Look up the APS weight and index in the loading manual, which is carried on board the aircraft, and insert the figures in Boxes 9, 10, 11, 12 and 13 as appropriate. The index is the position of the CG relative to the datum of the aircraft in the APS state (the empty aircraft plus the weight of crew, crew baggage, safety equipment and catering etc). We have assumed that there are no adjustments to the APS weight or index, as would result, for example, from the carriage of additional catering or the removal of seats in order to accommodate a stretcher bound passenger and associated medical equipment.

(c)

Insert the take-off fuel (total fuel less taxi fuel) in box 14 and determine the wet operating weight (Box 15).

(d)

Enter the maximum zero fuel weight in box 16, add to it the take-off fuel (Box 17) and determine the ZFW limiting take-off weight (Box 18). Next determine the maximum performance limited take-off weight and enter it at box 19. Similarly enter the performance or C of A limited maximum landing weight at Box 20, add to it the trip fuel (Box 21) to achieve the landing weight limited take-off weight (Box 22).

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Manual and Computer Load/Trim Sheets

Chapter 8 Page 5

(e)

Determine which of the three take-off weights (ZFW, take-off or landing, Boxes 18, 19 and 22) is the most limiting, in this case it is the take-off itself which is limiting. Subtract from this weight the wet operating weight (Box 23) to determine the allowed traffic load (Box 24).

(f)

Transfer the allowed traffic load to Box 25.

(g)

Establish from the agent the passenger breakdown (in this case 69 adult males at 165 lb., 73 adult females at 143 lb., 25 children at 86 lb., and complete Boxes 26 and 27. In this example the total passenger weight is 23,974 lb., so insert this weight in Box 28. Insert at Box 29 the baggage weight (167 x 7lb) giving 1169 lb.

(h)

Establish from the agent the number of pieces of hold baggage (167) and determine the weight (167 x 29 lb.) 4843 lb. Complete Boxes 30 and 31. Add the weights in Boxes 28, 29 and 31 to determine the total traffic load, which is inserted in Boxes 32 and 33.

(i)

Subtract the total traffic load (Box 33) from the allowed traffic load (Box 25) to get the underload before last minute changes (LMCs). The underload is entered in Box 34.

(j)

Enter the dry operating weight in Box 35 and add the total traffic load to the dry operating weight to obtain the zero fuel weight (Box 36). Add the take-off fuel (Box 37) to the zero fuel weight to obtain the take-off weight (Box 38).

(k)

Add the take-off weight (Box 38) to the underload before LMC (Box 34) and confirm that the sum of the two is equal to the maximum allowed take-off weight (in this case Box 19). If it isn't you must find your error before proceeding.

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Manual and Computer Load/Trim Sheets

Chapter 8 Page 6

(l)

Subtract from the take-off weight (Box 38) the trip fuel (Box 39) to achieve the landing weight (Box 40). We have now completed the load form and can start on the trim form.

(m)

Establish from the loaders or the agent (and confirm by visual inspection) the distribution of the hold baggage. In this example we have 100 bags in hold 4 (aft) and 67 bags in hold 3 (mid aft). Armed with this information complete Boxes 41 and 42 ensuring that the maximum hold weights are not exceeded.

(n)

With less than a full complement of passengers we would need to establish where the passengers are sitting, however in this example we have a full load so complete Boxes 43 to 46.

(o)

We know how the fuel load is distributed (there is no trim fuel in this example) and so we can complete Boxes 47 and 48. With this aeroplane the limiting trim is that associated with the ZFW rather than the fuel laden aircraft and consequently it is the position of the ZFW CG within the trim envelope which is important. The trim envelope (A) looks complex but it isn't. It is the white portion of the envelope within the two shaded (ferry) portions, which is the area within which the ZFW CG must fall. Ignore the "MZFW - Limited Wing Fuel" hatched line, it is relevant to an alternative fuel loading regime, which is used for ferry, and training flights.

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Manual and Computer Load/Trim Sheets (p)

Start at B with the APS index and drop the line going left or right in the direction of the arrows for distances dictated by the diagonal lines and the actual passenger/ baggage distribution. Having made the correction for the 24 passengers in bay D take the drop line vertically downwards ignoring for the moment the fuel load. Mark the point on this vertical line which coincides with the actual zero fuel weight and check that this point lies within the envelope. Fortunately it does, it is towards the forward end of the envelope, at 5.25% of the MAC.

(q)

Return to the drop line and correct for the 18,500 lb. of fuel in the wings and the 16,500 lb. of fuel in the centre tank at take-off. Mark the point on the resultant drop line which coincides with the actual take-off weight and read the TOW CG position as a % MAC, in this case 8.9%. The TOW % MAC goes in box 49. It is this value which is used to set the trim on the variable incidence tail plane for take-off. Assuming that you've done your sums right and that the load is distributed as shown, this should mean that the stick force required to rotate the aircraft at VR will be light but positive.

Computer Load and Trim Forms 9. The computer generated equivalent of the manual load and trim sheet previously considered is shown at Figure 8-2. As you can see, there are no graphics on the computer form and it appears that you are taking a lot on trust. Experience will tell you whether or not the computer generated trim position is appropriate to the type of flight (scheduled, holiday charter, ski flight etc) and the number of passengers carried.

Chapter 8 Page 7

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Manual and Computer Load/Trim Sheets

Last Minute Changes 10. Both the manual and the computer load and trim sheets make provision for last minute changes (LMCs). This is basically the out of breath family that has made it from check-in to the gate in record time and arrived just as you are about to push back. It is obviously necessary that the weight of the LMCs be considered, however providing that the total weight of LMCs does not exceed a given figure, the effect of this additional weight on the trim of the aircraft can be ignored. The figure in question is agreed between the operator and the CAA, for your guidance it is normally in the order of 500 kg or 1000 lb. for medium passenger transport aircraft.

Aircraft Load and Trim Slide Rule 11. The trim slide rule is a mechanical means of solving the mathematical problem of locating the CG of an aeroplane. Although mainly of historical interest they are still used on rare occasions.

FIGURE 8-2

LOADSHEET

CHECKED

APPROVED

All Weights in lb

Chapter 8 Page 8

From / To

Flight

A/C REG

Version

Crew

Date/Time

ACE LGW

454

GRJER

167Y

2/5

2 Feb 95 1847

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Manual and Computer Load/Trim Sheets Weight Load in compartments

4843

1/-

Passenger / Cabin Load

25143

69/73/25/-

Total Traffic Load

29886

Dry Operating Weight

86606

Zero Fuel Weight

116592

Take-Off Fuel

35000

Take-Off Weight Actual

151592

Trip Fuel

26000

Landing Weight Actual

125592

Balance

2/-

3/1943

4/2900

TTL 167

MAX 122000 MAX 154760 MAX 139500 Last Minute Changes

MAXZFW

5.25

MAXTOW

8.9

STD PAX WTS

3168 LMC TOTAL + -

12. The slide rule consists of a main block body in which several sliders are contained. Each slide represents a loading cargo bay or compartment, which is etched with incremental weight.

Chapter 8 Page 9

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Manual and Computer Load/Trim Sheets 13. On each slide is a datum arrow, which is positioned against the appropriate value on the slide above. When using the trim slide rule a moment is referred to as an index. The index for the basic weight of the aircraft is a known value. 14. To use the slide rule the moment of the basic weight, known as the basic index is located on the body of the rule and the datum arrow of the first slider positioned against it. The slides are moved left for negative moments and right for positive moments. 15. The final position is drawn down from the lowest slide on a chart on which the forward and aft limits of the CG envelope are depicted together with the maximum take-off weight, the maximum landing weight and the maximum zero fuel weight. If the intersection of the weight and the final line fall within the envelope it is safe. If it is outside the envelope then it is unsafe. 16. The main advantage of this method of determining the CG is that of speed, with a secondary advantage of the ability of making adjustments for ‘last minute changes’. The major disadvantage is that no record is kept and unless each slide can be locked in position, errors are difficult to trace; furthermore large transport aircraft would require a considerable number of slides making the instrument unwieldy to manage. 17. Recently this type of slide rule has been superseded by a circular slide rule, which has rotating scales.

Chapter 8 Page 10

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Manual and Computer Load/Trim Sheets EXAMPLE 8-1

EXAMPLE Given: Maximum take-off weight

36,000 lb.

Maximum landing weight

33,000 lb.

Maximum zero fuel weight

30,000 lb

Basic aircraft weight

22,000 lb

Crew weight

300 lb.

15 pax @ 170 lb. aft cabin

2,550 lb.

12 pax @ 170 lb. fwd cabin

2,040 lb.

Aft cargo

445 lb.

Forward cargo

50 lb.

Zero fuel weight

27,385 lb.

Fuel 700 Imperial gallons

5,040 lb.

Take-off weight

32,425 lb

Index 5.0

SG 0.72

Sector fuel to touch down 300 Imperial gallons

-2,160 lb.

Landing weight

30,265 lb.

SG 0.72

Determine whether or not it is safe to take-off and land with the aircraft loaded in this way.

Chapter 8 Page 11

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Manual and Computer Load/Trim Sheets SOLUTION It should be noted that the slide rule illustrated at Figure 8-3 assumes a fixed passenger weight of 170 lb., consequently the passenger slides are indexed in passenger numbers, as shown. The fuel slide is indexed in Imperial gallons. As can be seen from Figure 8-3, the CG is within limits for both take-off and landing.

Chapter 8 Page 12

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Manual and Computer Load/Trim Sheets FIGURE 8-3

Figure 8-3. The Trim Slide Rule Solution to Example 8-1

Chapter 8 Page 13

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Manual and Computer Load/Trim Sheets The MRJT Trim Sheet The specimen aeroplane that will be used in any questions in the JAA examination is the MRJT. It is therefore advantageous to be familiar with the load and trim sheet used for this aeroplane. As you can see from the following diagram the method of use is precisely the same as the previous example. It is simply the layout that is different. At the top right is a table of passenger seats in each compartment, which corresponds to those listed to the left of the trim diagram. The method of determining the C of G position is as before. Start at the top of the diagram at the dry operating index and work downward moving in the direction indicated by each arrow the appropriate number of divisions. In the final C of G envelope plot the TOW and landing weight. Both positions must fall within the envelope. If they don’t adjustments must be made to the load distribution to bring the C of G back into the envelope.

Chapter 8 Page 14

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Manual and Computer Load/Trim Sheets FIGURE 8-4

Chapter 8 Page 15

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Manual and Computer Load/Trim Sheets EXAMPLE 8-2

EXAMPLE Given: Dry Operating Mass 35,000 kgs; Index 48; Take-off Fuel 10,000 kgs; Cargo Hold 1 2,000 kgs; Cargo Hold 4 4,000 kgs; Passengers 10a, 15b, 20c, 20d, 20e, 15f and 10g. All at standard mass 84 kgs; Fuel Index –10; Trip Fuel 8,000 kgs; Taxi Fuel 200 kgs. Determine the underload and the MAC for Zero Fuel Mass, Take-Off Mass and Landing Mass.

Chapter 8 Page 16

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Manual and Computer Load/Trim Sheets SOLUTION 1. Extract from Loading Manual. Maximum Take-Off Mass 62,800 kgs. Insert at (1), (8) and (16). Maximum Landing Mass 54,900 kgs. Insert at (2) and (9). Maximum Zero Fuel Mass 51,300 kgs. Insert at (3) and (10). Dry Operating Mass 35,000 kgs. Insert at (4) and (11). 2. Calculate fuel at take-off = 10,200 –200 = 10,000 kgs. Insert at (5), (6) and (7). 3. Add DOM to take-off fuel, insert at (12) and (13) = 45,000 kgs. 4. Insert Trip Fuel at (14) and (24) = 8,000 kgs. 5. Add Trip Fuel to Maximum Landing Mass to derive landing limited maximum TOM, insert at (15). 6. Add Take-off Fuel to Maximum Zero Fuel Mass to obtain structurally limited TOM, insert at (17). 7. The lowest of (15), (16) and (17) is the maximum TOM permitted. 8. Subtract the Operating Mass from the maximum permitted TOM to obtain the allowed Traffic Load, insert at (18). 9. Calculate the total Passenger Mass = 84 x 110 = 9,240 kgs. 10. Add passenger to total Fuel Mass to obtain total traffic load = 9,240 +6000 = 15,240 kgs. Insert at (19) and (20). 11. Subtract total Traffic Load from allowed Traffic Load to obtain underload = 1060 kgs. Insert at (21).

Chapter 8 Page 17

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Manual and Computer Load/Trim Sheets 12. Add total Traffic Load to Dry Operating Mass to obtain the Zero Fuel Mass = 50,240 kgs. Insert at (22). 13. Add Take-Off Fuel to Zero Fuel Mass to obtain Take-Off Mass = 60,240 kgs. Insert at (23). 14. Subtract Trip Fuel from Take-Off Mass to obtain Landing Mass = 52,040 kgs. Insert at (25). 15. Insert cargo at Hold 1 at (26) and Hold 4 at (27). 16. Insert Dry Operating Index at (28) and mark on the index scale (29). 17. Insert the number of passengers in each of the stations (a) to (g). 18. Commence the plot at the Dry Operating Index and continue as in Example 8-1.

Chapter 8 Page 18

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Manual and Computer Load/Trim Sheets FIGURE 8-5

Chapter 8 Page 19

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031 Aircraft Mass & Balance

Joint Aviation Regulations Mass and Balance

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Joint Aviation Regulations

9

Joint Aviation Regulations

Mass and Balance Mass values for Crew JAR-OPS 1.615: 1.

An operator shall use the following mass values to determine the dry operating mass: (i)

Actual masses including any crew baggage; or

(ii)

Standard masses, including hand baggage, of 85 kg for flight crew members and 75 kg for cabin crew members; or

(iii)

Other standard masses acceptable to the Authority.

2. An operator must correct the dry operating mass to account for any additional baggage. The position of this additional baggage must be accounted for when establishing the centre of gravity of the aeroplane.

Chapter 9 Page 1

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Joint Aviation Regulations

Mass Values for Passengers and Baggage JAR-OPS 1.620: 3. An operator shall compute the mass of passengers and checked baggage using either the actual weighed mass of each person and the actual weighed mass of baggage or the standard mass values specified in Tables 9-1 to 9-3 below except where the number of passenger seats available is less than 10, when the passenger mass may be established by a verbal statement by or on behalf of each passenger or by estimation. The procedure specifying when to select actual or standard masses must be included in the Operations Manual. 4. If determining the actual mass by weighing an operator must ensure that passenger’s personal belongings and hand baggage are included. Such weighing must be conducted immediately prior to boarding and at an adjacent location. 5. If determining the mass of passengers using standard mass values, the standard mass values in Tables 9-1 and 9-2 below must be used. The standard masses include hand baggage and the mass of any infant below 2 years of age carried by an adult on one passenger seat. Infants occupying separate passenger seats must be considered as children for the purpose of this sub-paragraph.

Mass values for Passengers – 20 seats or more

Chapter 9 Page 2

(a)

Where the total number of passenger seats available on an aeroplane is 20 or more, the standard masses of male and female in Figure 9-1 are applicable. As an alternative, in cases where the total number of passenger seats available is 30 or more, the ‘All Adult’ mass values in Figure 9-1 are applicable.

(b)

For the purpose of Figure 9-1, holiday charter means a charter flight solely intended as an element of a holiday travel package.

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Joint Aviation Regulations JAR-OPS 1.620(d) Table 1

FIGURE 9-1 Aircraft with 20 or more Passenger Seats

Chapter 9 Page 3

Passenger Seats

20 or More

30 or More

Male

Female

All flights except Holiday Charters

88kg

70kg

84kg

Holiday Charters

83kg

69kg

76kg

Children

35kg

35kg

35kg

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All Adult

Joint Aviation Regulations JAR-OPS 1.620(e) Table 2

FIGURE 9-2 Mass Values for Aircraft with 19 or less Passenger Seats

Passenger Seats

1-5

6-9

10 - 19

Male

104kg

96kg

92kg

Female

86kg

78kg

74kg

Children

35kg

35kg

35kg

6. Where the total number of passenger seats available on an aeroplane is 19 or less, the standard masses in Figure 9-2 are applicable. 7. On flights where no hand baggage is carried in the cabin or where hand baggage is accounted for separately, 6 kg may be deducted from the above male and female masses. Articles such as an overcoat, an umbrella, a small handbag or purse, reading material or a small camera are not considered as hand baggage for the purpose of this sub-paragraph. 8.

Chapter 9 Page 4

Mass Values for Baggage

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Joint Aviation Regulations (c)

Where the total number of passenger seats available on the aeroplane is 20 or more the standard mass value given in Figure 9-3 are applicable for each piece of checked baggage. For aeroplanes with 19 passenger seats or less, the actual mass of checked baggage, determined by weighing, must be used.

For the purpose of Figure 9-3: (i)

Domestic flight means a flight with origin and destination within the borders of one State.

(ii)

Flights within the European region means flights, other than Domestic flights, whose origin and destination are within the area specified in Appendix 1 to JAR-OPS 1.620 (f); and

(iii)

Intercontinental flight, other than flights within the European region, means a flight with origin and destination in different continents.

FIGURE 9-3 Aircraft with 20 or more Seats

JAR-OPS 1.620(f) Table 3 Type of Flight

Chapter 9 Page 5

Baggage Standard Mass

Domestic

11 kg

Within the European Region

13 kg

Intercontinental

15 kg

All Other

13 kg

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Joint Aviation Regulations

Chapter 9 Page 6

(iv)

If an operator wishes to use standard mass values other than those contained in Figure 9-1 to Figure 9-3 above, he must advise the Authority of his reasons and gain its approval in advance. He must also submit for approval a detailed weighing survey plan and apply the statistical analysis method given in Appendix 1 to JAR-OPS 1.620 (g). After verification and approval by the Authority of the results of the weighing survey, the revised standard mass values are only applicable to that operator. The revised standard mass values can only be used in circumstances consistent with those under which the survey was conducted. Where revised standard masses exceed those in Figure 9-1 to Figure 9-3, then such higher values must be used. [See IEM-OPS 1.620 (g)].

(v)

On any flight identified as carrying a significant number of passengers whose masses, including hand baggage, are expected to exceed the standard passenger mass, an operator must determine the actual mass of such passengers by weighing or by adding an adequate mass increment. [See IEM-OPS 1.620 (h) and (i)].

(vi)

If standard mass values for checked baggage are used and a significant number of passengers check in baggage that is expected to exceed the standard baggage mass, an operator must determine the actual mass of such baggage by weighing or by adding an adequate mass increment. [See IEM-OPS 1.620 (h) and (i)].

(vii)

An operator shall ensure that a commander is advised when a non-standard method has been used for determining the mass of the load and that this method is stated in the mass and balance documentation.

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Joint Aviation Regulations

Appendix 1 to JAR-OPS 1.620 (f) Definition of the Area for Flights within the European Region 9. For the purpose of JAR-OPS 1.620 (f), flights within the European region, other than domestic flights, are flights conducted within the area bounded by rhumb lines between the following points: N7200

E04500

N4000

E04500

N3500

E03700

N3000

E03700

N3000

W00600

N2700

W00900

N2700

W03000

N6700

W03000

N7200

W01000

N7200

E04500

As depicted in Figure 9-4 below.

Chapter 9 Page 7

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Joint Aviation Regulations FIGURE 9-4

Chapter 9 Page 8

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Joint Aviation Regulations

Appendix to JAR-OPS 1.620 (g) Procedure for Establishing Revised Standard Mass Values for Passengers and Baggage. [See IEM to Appendix 1 to JAR-OPS 1.620 (g)] Passengers 10. Weight Sampling Method. The average mass of passengers and their hand baggage must be determined by weighing, taking random samples. The selection of random samples must by nature and extent be representative of the passenger volume, considering the type of operation, the frequency of flights on various routes, in/outbound flights, applicable season and seat capacity of the aeroplane. 11.

Sample Size. The survey plan must cover the weighing of at least the greatest of: (a)

A number of passengers calculated from a pilot sample, using normal statistical procedures and based on a relative confidence range (accuracy) of 1% for all adult and 2% for separate male and female average masses. The statistical procedure, complemented with a worked example for determining the minimum required sample size and the average mass, is included in IEM-OPS 1.620 (g), and;

(b)

For Aeroplanes: (i)

Chapter 9 Page 9

With a passenger seating capacity of 40 or more, a total of 2000 passengers, or;

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Joint Aviation Regulations (ii)

With a passenger seating capacity of less than 40, a total number of 50 x (the passenger seating capacity).

Passenger Masses 12. Adults and Children. Adults are defined as persons of an age of 12 years and above. They are further classified as male or female. No differentiation according to sex shall be made for children, who are defined as persons of an age of two years but who have not yet reached their twelfth birthday. Passenger masses must include the mass of the passengers’ belongings, which are carried when entering the aeroplane. 13. Infants. Infants are defined as persons who have not yet reached their second birthday. When taking random samples of passenger masses, infants shall be weighed together with the accompanying adult. 14. Weighing Location. The location for the weighing of passengers shall be selected as close as possible to the aeroplane, at a point where a change in the passenger mass by disposing of or by acquiring more personal belongings is unlikely to occur before the passenger’s board the aeroplane. 15. Weighing Machine. The weighing machine to be used for passenger weighing shall have a capacity of at least 150 kg. The mass shall be displayed at minimum graduations of 500 g. The weighing machine must be accurate to within 0.5% or 200 g whichever is the greater. 16. Recording of Mass Values. For each flight the mass of the passengers, the corresponding passenger category (i.e. male/female/children) and the flight number must be recorded.

Chapter 9 Page 10

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Joint Aviation Regulations Checked Baggage 17. The statistical procedure for determining revised standard baggage mass values based on average baggage mass values based on average baggage masses of the minimum required sample size is basically the same as for passengers and as specified in sub-paragraph (a) (1) [See also IEM-OPS 1.620 (g)]. For baggage, the relative confidence range (accuracy) amounts to 1%. A minimum of 2000 pieces of checked baggage must be weighed.

Determination of Revised Standard Mass Values for Passengers and Checked Baggage

Chapter 9 Page 11

(a)

To ensure that, in preference to the use of actual masses determined by weighing, the use of revised standard mass values for passengers and checked baggage does not adversely affect operational safety; a statistical analysis (see IEM-OPS 1.620 (g)) must be carried out. Such an analysis will generate average mass values for passengers and baggage as well as other data.

(b)

On aeroplanes with 20 or more passenger seats these averages apply as revised standard male and female mass values.

(c)

On smaller aeroplanes, the following increments must be added to the average passenger mass to obtain the revised standard mass value:

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Joint Aviation Regulations FIGURE 9-5 Revised Standard Mass Increments for Aircraft with 19 or less Passenger Seats

Number of Passenger Seats

Required Mass Increment

1 – 5 Inclusive

16 kg

6 – 9 Inclusive

8 kg

10 – 19 Inclusive

4 kg

18. Alternatively, all adult revised standard (average) mass values may be applied on aeroplanes with 30 or more passenger seats. Revised standard (average) checked baggage mass values are applicable to aeroplanes with 20 or more passenger seats.

Chapter 9 Page 12

(d)

Operators have the option to submit a detailed survey plan to the Authority for approval and subsequently a deviation form the revised standard mass value providing this deviating value is determined by use of the procedure explained in the Appendix. Such deviations must be reviewed at intervals not exceeding five years. [See AMC to Appendix 1 to JAR-OPS 1.620 (g), sub-paragraph (c) (4)].

(e)

All adult revised standard mass values must be based on a male/female ratio of 80/20 in respect of all flights except holiday charters which are 50/50. If an operator wishes to obtain approval for use of a different ratio on specific routes or flights then data must be submitted to the Authority showing that the alternative male/female ratio is conservative and covers at least 84% of the actual male/female ratios on a sample of at least 100 representative flights.

(f)

The average mass values found are rounded to the nearest whole number in kg. Checked baggage mass values are rounded to the nearest 0.5 kg figure, as appropriate.

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031 Aircraft Mass & Balance

The Weighing of Aeroplanes Joint Airworthiness Requirement Determination of the Dry Operating Mass of an Aeroplane Special Standard Masses for the Traffic Load

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The Weighing of Aeroplanes

10

The Weighing of Aeroplanes

Joint Airworthiness Requirement 1. The weight and C of G of an aeroplane must be established by the operator by actually weighing it prior to initial entry into service and every four years thereafter if individual aeroplane weights are used or every nine years if fleet weights are used. The cumulative effect of modifications and/or repairs have on the weight and balance must be accounted and documented. Aeroplanes that have been modified but the effects on the weight and balance are unknown must be re-weighed. [JAR-OPS 1.605 (1) (b)].Appendix 1 to JAR-OPS 1.605 and Mass and Balance – General (See JAROPS 1.605)

Determination of the Dry Operating Mass of an Aeroplane Weighing of an Aeroplane (a)

Chapter 10 Page 1

New aeroplanes are normally weighed at the factory and are eligible to be placed into operation without re-weighing if the mass and balance records have been adjusted for alterations or modifications to the aeroplane. Aeroplanes transferred from one JAA operator with an approved mass control programme to another JAA operator with an approved programme need not be weighed prior to use by the receiving operator unless more than four years have elapsed since the last weighing.

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The Weighing of Aeroplanes (b)

The individual mass and centre of gravity (CG) position of each aeroplane shall be reestablished periodically. The maximum interval between two weighings must be defined by the operator and must meet the requirements of JAR-OPS 1.605 (b). In addition, the mass and the CG of each aeroplane shall be re-established either by: (i)

Weighing, or;

(ii)

Calculation, if the operator is able to provide the necessary justification to prove the validity of the method of calculation chosen.

whenever the cumulative changes to the dry operating mass exceed + 0.5% of the maximum landing mass or the cumulative change in CG position exceeds 0.5% of the mean aerodynamic chord. [Appendix to JAR-OPS 1.605 (a) (1)].

Fleet Mass and CG Position (a)

Chapter 10 Page 2

For a fleet or group of aeroplanes of the same model and configuration, an average dry operating mass and CG position may be used as the fleet mass and CG position, provided that the dry operating masses and CG positions of the individual aeroplanes meet the tolerances specified below. Furthermore, the criteria specified in ‘Use of Fleet-Values’ and ‘Number of Aeroplanes to be Weighed’ below are applicable.

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The Weighing of Aeroplanes Tolerances

Chapter 10 Page 3

(i)

If the dry operating mass of any aeroplane weighed, or the calculated dry operating mass of any aeroplane of a fleet, varies by more than + 0.5% of the maximum structural landing mass from the established dry operating fleet mass or the CG position varies by more than + 0.5% of the mean aerodynamic chord from the fleet CG, that aeroplane shall be omitted from that fleet. Separate fleets may be established, each with differing fleet mean masses.

(ii)

In cases where the aeroplane mass is within the dry operating fleet mass tolerance but its CG position falls outside the permitted fleet tolerance, the aeroplane may still be operated under the applicable dry operating fleet mass but with an individual CG position.

(iii)

If an individual aeroplane has, when compared with other aeroplanes of the fleet, a physical, accurately accountable difference (e.g. galley or seat configuration), that causes exceedance of the fleet tolerances, this aeroplane may be maintained in the fleet provided that appropriate corrections are applied to the mass and/or CG position for that aeroplane.

(iv)

Aeroplanes for which no mean aerodynamic chord has been published must be operated with their individual mass and CG position values or must be subjected to a special study and approval.

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The Weighing of Aeroplanes Use of Fleet Values

Chapter 10 Page 4

(i)

After the weighing of an aeroplane, or if any change occurs in the aeroplane equipment or configuration, the operator must verify that this aeroplane falls within the tolerances specified in ‘Tolerances’ above.

(ii)

Aeroplanes which have not been weighed since the last fleet mass evaluation can still be kept in a fleet operated with fleet values, provided that the individual values are revised by computation and stay within the tolerances defined in ‘Tolerances’ above. If these individual values no longer fall within the permitted tolerances, the operator must either determine new fleet values fulfilling the conditions of ‘Fleet-Mass and CG Position’ and ‘Tolerances’ above, or operate the aeroplanes not falling within the limits with their individual values.

(iii)

To add an aeroplane to a fleet operated with fleet values, the operator with fleet values, the operator must verify by weighing or computation that its actual values fall within the tolerance specified in ’Tolerances’ above.

(iv)

To comply with ‘Fleet Mass and CG Position’ above, the fleet values must be updated at least at the end of each fleet mass evaluation. [Appendix to JAROPS 1.605 (a) (2)].

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The Weighing of Aeroplanes

Number of Aeroplanes To Be weighed to Obtain Fleet Values (a)

FIGURE 10-1

If ‘n’ is the number of aeroplanes in the fleet using fleet values, the operator must at least weigh, in the period between two fleet mass evaluations, a certain number of aeroplanes defined in Figure 10-1: Number of Aeroplanes in the Fleet

Minimum Number of Weighings

2 or 3

n

4 to 9

n+3 -----------2

10 or More

n + 51 --------------10

(b)

In choosing the aeroplanes to be weighed, aeroplanes in the fleet which have not been weighed for the longest time should be selected.

(c)

The interval between 2 fleet mass evaluations must not exceed 48 months.

Weighing Procedure (a)

Chapter 10 Page 5

The weighing must be accomplished either by the manufacturer or by an approved maintenance organisation.

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The Weighing of Aeroplanes (b)

Normal precautions must be taken consistent with good practices such as: (i)

Checking for completeness of the aeroplane and equipment.

(ii)

Determining that fluids are properly accounted for.

(iii)

Ensuring that the aeroplane is clean, and;

(iv)

Ensuring that weighing is accomplished in an enclosed building.

2. Any equipment used for weighing must be properly calibrated, zeroed, and used in accordance with the manufacture’s instructions. Each scale must be calibrated either by the manufacturer, by a civil department of weights and measures or by an appropriately authorised organisation within two years or within a time period defined by the manufacturer of the weighing equipment, whichever is less. The equipment must enable the mass of the aeroplane to be established accurately. [Appendix to JAR-OPS 1.605 (a) (4)].

Special Standard Masses for the Traffic Load 3. In addition to standard masses for passengers and checked baggage, an operator can submit for approval to the Authority standard masses for other load items.

Aeroplane Loading (a)

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An operator must ensure that the loading of its aeroplanes is performed under the supervision of qualified personnel.

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The Weighing of Aeroplanes (b)

An operator must ensure that the loading of the freight is consistent with the data used for the calculation of the aeroplane mass and balance.

(c)

An operator must comply with additional structural limits such as the floor strength limitations, the maximum load per running metre, the maximum mass per cargo compartment and/or the maximum seating limits. [Appendix to JAR-OPS 1.605 (a) (4)].

Centre of Gravity Limits Operational CG Envelope.

Unless seat allocation is applied and the effects of the number of passengers per seat row, of cargo in individual cargo compartments and of fuel in individual tanks is accounted for accurately in the balance calculation, operational margins must be applied to the certificated centre of gravity envelope. In determining the CG margins, possible deviations from the assumed load distribution must be considered. If free seating is applied, the operator must introduce procedures to ensure corrective action by flight or cabin crew if extreme longitudinal seat selection occurs. The CG margins and associated operational procedures, including assumptions with regard to passenger seating, must be acceptable to the Authority. [See IEM to Appendix 1 to JAR-OPS 1.605 (d)].

In-Flight Centre of Gravity. Further to sub-paragraph above, the operator must show that the procedures fully account for the extreme variation in CG travel during flight caused by passenger/ crew movement and fuel consumption/transfer.

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The Weighing of Aeroplanes

British Civil Airworthiness Requirement 4. The above are the requirements of the Joint Aviation Authority (JAA), however, these will not be legally enforceable until a statute has been passed by Parliament to make JAR-OPS a legally binding document. Until such time the legal requirements of British Civil Airworthiness requirements remain in force and have different requirements with respect to the weighing of aeroplanes and are as follows:

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(a)

An aircraft is weighed when all manufacturing processes are complete. It must be reweighed within two years of the date of manufacture and subsequently at intervals not exceeding five years and at such times as the CAA may require if the maximum total weight authorised exceeds 5700 kg. If the MTWA does not exceed 5700 kg the aeroplane must be re-weighed at such times as the CAA may require.

(b)

The aircraft should be re-weighed after a major servicing has been carried out or when a modification or engine change has been done which may have a significant effect on the aircraft weight and balanced. It would be prudent to re-weigh the aircraft if it is not attaining is scheduled performance level.

(c)

With the approval of the Authority, when an operator has three or more aircraft of the same type, the fleet mean weight and CG may be used for the whole fleet, except for those that differ significantly from the remainder of the fleet.

(d)

For an aircraft having a valid Certificate of Airworthiness a valid Weight and CG Schedule must be completed every time the aircraft is weighed. Each Schedule must be preserved for a period of six months following the subsequent re-weighing of the aircraft.

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The Weighing of Aeroplanes (e)

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If the person who is the operator ceases to be the operator, he (or his representative if he dies) must retain the Schedule or pass it on to the new operator for retention for the requisite period. [BCAR Section A, Chapter A5-47].

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The Weighing of Aeroplanes Self Assessed Exercise No. 2 QUESTIONS: QUESTION 1. List four items not considered to be hand baggage when using the standard mass value of JAR-OPS1. 620(e) table 2. QUESTION 2. According to JAR-OPS1, when should an aeroplane be weighed? QUESTION 3. What precautions should be taken when weighing an aircraft? QUESTION 4. What are the floor area maximum load intensity and the running load maximum between balance arm 343 and 500 for the cargo compartments of the MRJT? QUESTION 5. What is the purpose of Dunnage? QUESTION 6. Specify the current restraint load factor forward for lashing and tie-down equipment for fixed wing aircraft.

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The Weighing of Aeroplanes QUESTION 7. State the load factor formula. QUESTION 8. Given the mean aerodynamic chord is from 750ins to 1000ins aft of the Datum. Express the GG 850ins AFT of the Datum as a % of MAC. QUESTION 9. What determines the maximum zero fuel weight? QUESTION 10. How is the stalling speed affected by the position of the CG? QUESTION 11. Given: AUW 30,000lbs. CG 1ft AFT of Datum. How much freight must be added to a hold 10ft forward of Datum to move the CG 1ft forward. QUESTION 12. If 300lbs of cargo is moved from a hold 10ft aft of the Datum to hold 5ft forward of the Datum what change will occur to the CG for an aeroplane weighing 5000lbs. QUESTION 13. If 2,000kgs of freight added to a hold 5m ahead of the present CG of an aeroplane weighing 10,000kgs. The change to the CG is?

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The Weighing of Aeroplanes QUESTION 14. If the main wheels retract athwarships and the nose wheel retracts forward. How will the CG move on lowering the undercarriage to land? QUESTION 15. What is the critical angle between the edge of freight and the edge of load spreader for it to be fully effective: QUESTION 16. If the centre tank of the MRJT contains 500kgs of fuel how much fuel must be in the wing tanks? QUESTION 17. Given: Cargo 1500kgs in hold 10m forward of Datum and cargo 1000kgs in a hold 15m AFT of Datum. What are the total freight moments? QUESTION 18. Given: Fuel at take-off 6000lbs in tank 10ft forward of Datum. The fuel in the same tank on Landing 2000lbs calculate the change of moments. QUESTION 19. At what age is a child assumed to be an adult for the purposes of mass and balance?

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The Weighing of Aeroplanes QUESTION 20. What increment must be added to the average mass for a passenger of an aeroplane having 6 to 9 passenger seats?

ANSWERS: ANSWER 1. Page 9-2 paragraph 7 ANSWER 2. Page 10-1 paragraph 1 ANSWER 3. Page 10-4 paragraph 1 (b) ANSWER 4. CAP 696 Page 24 ANSWER 5. Page 7-7 ANSWER 6. Page 7-5

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The Weighing of Aeroplanes ANSWER 7. Page 7-4 ANSWER 8. ( 850 – 750 ) 100 -------------------------------% = --------- % = 40% of MAC ( 1000 – 750 ) 250 ANSWER 9. The strength of the wing roots. Page 1-2 ANSWER 10. Page 3-6 and 3-7 ANSWER 11. (30000 + w) x 0 = (30000 x +1) + (w x –10) 0 = 30,000 – 10w 10w = 30,000 w= 3000 lbs

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The Weighing of Aeroplanes ANSWER 12. w CC ----- = -------W d

300 CC ------------ = --------5000 – 15

– 4500 CC = --------------- = – 0.9ft 5000

ANSWER 13. 2000 × – 5 ------------------------ = -0.83m = 0.83 ahead of old CG 12, 000 ANSWER 14. CG moves with the nose wheel. CG moves AFT. ANSWER 15. 45° Page 7-7 ANSWER 16. The wing tanks must be full. CAP 696 Page 22 ANSWER 17. (1500 x –10) + (1000 x +15) = 0

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The Weighing of Aeroplanes ANSWER 18. Moments at take-off = 6000 x –10 = -60,000 ft. lbs. Moments at landing = 2000 x –10 = -20,000 ft. lbs. Change in moments = -20,000 – (-60,000) = + 40,000 ft. lbs. ANSWER 19. 12 years old Page 9-6 ANSWER 20. 8 kgs Page 9-8

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031 Aircraft Mass & Balance

Documentation UK National Requirements

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Documentation

11

Documentation

Mass and Balance Documentation JAR-OPS 1.625 [See Appendix 1 to JAR-OPS 1.625] 1. An operator shall establish mass and balance documentation prior to each flight specifying the load AND its distribution. The mass and balance documentation must enable the commander to determine by inspection that the load and its distribution is such that the mass and balance limits of the aeroplane are not exceeded. The person preparing the mass and balance documentation must be named on the document. The person supervising the loading of the aeroplane must confirm by signature that the load and its distribution are in accordance with the mass and balance documentation. This document must be acceptable to the commander, his acceptance being indicated by countersignature or equivalent. [See also IEM-OPS 1.1055 (a) (12)]. 2.

An operator must specify procedures for Last Minute Changes to the load.

3. Subject to the approval of the Authority, an operator may use an alternative to the procedures required by paragraphs (a) and (b) above.

Signature or Equivalent IEM-OPS 1.1055 (a) (12) [See JAR-OPS 1.1055 (a) (12)] 4. JAR-OPS 1.1055 requires a signature or its equivalent. This IEM gives and example of how this can be arranged where normal signature by hand is impracticable and it is desirable to arrange the equivalent verification by electronic means.

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Documentation 5. The following conditions should be applied in order to make an electronic signature the equivalent of a conventional hand-written signature:

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(a)

Electronic ‘signing’ should be achieved by entering a Personal Identification Number (PIN) code with appropriate security etc.

(b)

Entering the PIN code should generate a print-out of the individual’s name and professional capacity on the relevant document(s) in such a way that it is evident to anyone having a need for that information, who has signed the document.

(c)

The computer system should log information to indicate when and where each PIN codes has been entered.

(d)

The use of PIN code is, from a legal and responsibility point of view, considered to be fully equivalent to signature by hand.

(e)

The requirements for record keeping remain unchanged, and

(f)

All personnel concerned should be made aware of the conditions associated with electronic signature and should confirm this in writing.

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Documentation Appendix 1 to JAR-OPS 1.625 Mass and Balance Documentation [See IEM to Appendix 1 to JAR-OPS 1.625]

Mass and Balance Documentation Contents (a)

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The mass and balance documentation must contain the following information: (i)

The aeroplane registration and type.

(ii)

The flight identification number and date.

(iii)

The identity of the Commander.

(iv)

The identity of the person who prepared the document.

(v)

The dry operating mass and the corresponding CG of the aeroplane.

(vi)

The mass of the fuel at take-off and the mass of trip fuel.

(vii)

The mass of consumables other than fuel.

(viii)

The components of the load including passengers, baggage, freight and ballast.

(ix)

The Take-Off Mass, Landing Mass and Zero Fuel Mass.

(x)

The load distribution.

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Documentation (xi)

The applicable aeroplane CG positions; and

(xii)

The Limiting Mass and CG Values.

6. Subject to the approval of the Authority, an operator may omit some of this Data from the mass and balance documentation. 7. Last Minute Change. If any last minute change occurs after the completion of the mass and balance documentation, this must be brought to the attention of the Commander and the last minute change must be entered on the mass and balance documentation. The maximum allowed change in the number of passengers or hold load acceptable as a last minute change must be specified in the Operations Manual. If this number is exceeded, new mass and balance documentation must be prepared.

Computerised Systems 8. Where mass and balance documentation is generated by a computerised mass and balance system, the operator must verify the integrity of the output data. He must establish a system to check that amendments of his input data are incorporated properly in the system and that the system is operating correctly on a continuous basis by verifying the output data at intervals not exceeding six months.

Onboard Mass and Balance Systems 9. An operator must obtain the approval of the Authority if he wishes to use an onboard mass and balance computer system as a primary source for despatch.

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Documentation Datalink 10. When mass and balance documentation is sent to aeroplane via datalink, a copy of the final mass and balance documentation as accepted by the Commander must be available on the ground.

Mass and Balance Documentation [See IEM to Appendix 1 to JAROPS 1.625] 11. For Performance Class B aeroplanes, the CG position need not be mentioned on the mass and balance documentation if for example the load distribution is in accordance with a pre-calculated balance table or if it can be shown that for the planned operations a correct balance can be ensured, whatever the real load is.

UK National Requirements The Weight and Balance Report 12.

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The following are the requirements of the CAA as specified in BCAR, Section A. (a)

Weight and Balance Report – Aircraft Exceeding 5700 kg.

(b)

A Weight and Balance Report shall be produced for each Prototype, Variant and Series aircraft the Maximum Weight Authorised of which exceeds 5700 kg.

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Documentation

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(c)

The Weight and Balance Report shall record such loading data as is essential to enable the particular aircraft to be correctly loaded, and shall include sufficient information for an operator to produce written loading instructions in compliance with the requirements of the Air Navigation Order.

(d)

The Weight and Balance Report shall apply to the aircraft in the condition in which it is to be delivered to the user.

(e)

One copy of the Weight and Balance Report shall be sent to the CAA Safety Regulation Group.

(f)

The Weight and Balance Report shall include the following items:

(g)

Reference Number and date.

(h)

Designation, nationality, and registration marks of the aircraft, or if these are not known the constructor’s serial number.

(i)

A copy of the Weighing Record.

(j)

A copy of the Weight and Centre-of-Gravity Schedule including the list of Basic Equipment, if this is separate from Part A of the Schedule.

(k)

A diagram and a description of the datum points which are used for weighing and loading and an explanation of the relationship of these points to the fuselage frame numbering system of other identifiable points, and where applicable, to the Standard Mean Chord (SMC).

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Documentation (l)

Information on the level arms appropriate to items of Disposable Load. (This should include the lever arms of fuel, oil and other consumable fluids or substances in the various tanks (including agricultural material in hoppers) which, if necessary, should be shown diagrammatically or graphically; lever arms of passengers in seats appropriate to the various seating layouts; mean lever arms of the various baggage holds or compartments.)

(m)

Details of any significant effect on the aircraft CG of any change in configuration, such as retraction of the landing gear.

Weight and Centre-of-Gravity Schedule – Aircraft Exceeding 2730 kg 13. A Weight and Centre-of-Gravity Schedule shall be provided for each aircraft the Maximum Total Weight Authorised of which exceeds 2730 kg, except that for an aircraft the Maximum Total Weight Authorised or which exceeds 5700 kg the information contained in Parts B and C of the Schedule may, for a new aircraft, be given as part of the Weight and Balance Report.

NOTE: 1) The Weight and Centre-of-Gravity Schedule may be in the form set down in Appendix 1, but variations are permitted within the Requirements.

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Documentation NOTE: 2) Here reference is made in Appendix 1 to the Flight Manual, but such a document has not been issued, it will be necessary to refer to the Certificate of Airworthiness. 14. Each Schedule shall be identified by the aircraft designation, nationality and registration marks, or if these are not known, by the constructor’s serial number. The date of issue of the Schedule shall be given and the Schedule shall be signed by a representative of an approved Organisation or a person acceptable to the CAA. A statement shall be included indicating that the Schedule supersedes all previous issues. 15. The date and reference number of the Weight and Balance Report, or, as appropriate to the weight, other acceptable information upon which the Schedule is based, shall be given.

NOTE: For aircraft for which a Weight and Balance Report is not mandatory, the Weighing Record would normally used. 16. A copy of each issue of the Schedule shall be retained by the operator, and where the Schedule is re-issued the previous issue shall be retained with the aircraft records. A copy of the current Schedule and any related list of Basic Equipment (see Part A Basic Weight), shall be sent to the CAA Safety Regulation Group.

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Documentation 17. For aircraft the Maximum Total Weight Authorised of which does not exceed 5700 kg, a copy of the Schedule shall be included in the Flight Manual, if a Flight Manual is applicable, or if this is not the case, displayed or retained in the aircraft in a suitably identified stowage. 18. Operators shall issue a revised Weight and Centre-of-Gravity Schedule when the weight and e.g. is known to have changed to an extent greater than that which has been agreed by the CAA as applicable to a particular aircraft type. 19. If the aircraft has not been re-weighed, the revised Weight and Centre-of-Gravity Schedule shall contain a statement that calculations have been based on the last Weight and Balance Report, or other information, and the known weight and CG changes. 20. The datum to which CG limits relate is defined in Part A (see Part A Basic Weight) and this may be different from the datum defined in the Certificate of Airworthiness or Flight Manual. When a different datum is used it shall be adequately defined, its precise relationship to the datum in the Certificate of Airworthiness or Flight Manual shall be given, and any lever arms and moments which appear in any part of the Schedule shall be consistent with the datum so declared.

NOTE: In the case of helicopters, it may be necessary to present lever arms and moments about more than one axis, depending on the CG limits specified in the Flight Manual. 21. Part A Basic Weight. The Basic Weight and the associated position of the CG of the aircraft as derived from the most recent Weight and Balance Report or other information together with any subsequent weight and CG changes shall be stated. The position (retracted or extended) of the landing gear associated with this information shall be stated.

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Documentation 22. Where the Maximum Total Weight Authorised does not exceed 5700 kg, Part A shall also include the list of Basic Equipment showing the weight and lever arm of each item, or this information may form separate pages attached to the Weight and Centre-of-Gravity Schedule, with a suitable reference in Part A of the Schedule to this procedure. 23. Where the Maximum Total Weight Authorised exceeds 5700 kg, Part A shall include the list of basic equipment showing the weight, lever arm moment of each item, or shall make reference to the document in which such a list is included. 24. Part B Variable Load. The Variable Load may be detailed for as many roles as the operator wishes, but for every role the weights and moments shall be given. Weights of crew members may be assumed to be not less than the weights shown in the Air Navigation (General) Regulations, provided that the Maximum Total Weight Authorised exceeds 5700 kg, or the aircraft has a total seating capacity for 12 or more persons. Otherwise the weight of each person must be determined by weighing. 25. Part C Loading Information. This shall include all relevant information so that, knowing the Disposable Load which is intended to be carried, the weight and the position of the Centre-ofGravity of the aircraft can be calculated. At least the following shall be given:

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(i)

The lever arm of the CG of a passenger in each seat.

(ii)

The mean lever arm of each compartment or area in the aircraft where Disposable Load, such as luggage or freight, may be placed.

(iii)

Any significant change in the CG of the aircraft (change in moment) which will result from a change in configuration, such as the retraction and extension of the landing gear.

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Documentation (iv)

The lever arm of the CG of fuel, oil and other consumable fluids or substances in each tank, including any significant variation of the lever arm with the quantity loaded.

(v)

The maximum total usable capacities of the tanks for fuel, oil and other consumable fluids or substances and the weight of fluids or substances when the tanks are filled to their capacities assuming typical densities.

26. A statement shall be made in the Schedule to the effect that it is a requirement of the Air Navigation Order that the Commander satisfies himself before take-off that the load is of such weight, and is so distributed and secured, that it may safely be carried on the intended flight. 27. The weights, distances, moments and quantities may be given in any units provided that these are used consistently and do not conflict with the markings and placards on the aircraft.

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Documentation Weight and Centre-of-Gravity Schedule-Aircraft Not Exceeding 2730 kg 28. For aircraft the Maximum Total Weight Authorised of which does not exceed 2730 kg, either a Weight and Centre-of-Gravity Schedule, which complies with 2 and 3.2, or a Loading and Distribution Schedule which complies with 3.1 shall be provided. 29.

Loading and Distribution Schedule (Figure 11-6)

30. The Loading and Distribution Schedule (hereinafter referred to as ‘the Schedule’) shall contain at least the information in Figure 11-6. 31. Each Schedule shall be identified by the aircraft designation, nationality and registration marks, or if these are not known, by the constructor’s serial number. 32. A copy of each issue of the Schedule shall be retained by the operator, and when the Schedule is re-issued the previous issue shall be retained with the aircraft records. A copy of the current Schedule and any related list of Basic Equipment shall be sent to the CAA Safety Regulation Group. (i)

33.

Operators shall issue a revised Schedule when: (i)

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A copy of the Schedule shall be included in the Flight Manual is applicable, or, if this is not the case, the Schedule shall be displayed or retained in the aircraft in a suitably identified stowage.

The Basic Weight of the aircraft is known to have undergone changes in excess of 0.5% of the Maximum Total Weight Authorised, or

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Documentation (ii)

The total moment applicable to the Basic Weight is known to have changed to an extent greater than that, which has been agreed by the CAA as applicable to a particular aircraft type.

34. If the aircraft has not been re-weighed the revised Schedule shall contain a statement that calculations have been based on the last Weighing Record and the known weight and moment changes. 35.

Instructions for the use of the Schedule, together with the Loading Graphs, shall be included.

36. A statement shall be given in the Schedule to the effect that it is a requirement of the Air Navigation Order that the Commander satisfies himself before the aircraft takes off that the load is of such a weight, and is so distributed and secured that it may safely be carried on the intended flight. 37. The weight, distances, moments and quantities may be given in any units provided that these are used consistently and do not conflict with the markings and placards on the aircraft. 38.

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Part A Basic Data. Part A shall contain the following: (i)

The Basic Weight and the associated moment, and CG position of the aircraft, as derived from the most recent Weighing Record, together with any subsequent changes.

(ii)

The Maximum Total Weight Authorised appropriate to each permitted use (eg. aerobatics).

(iii)

The definition of the CG datum.

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Documentation (iv)

The date and reference number of the Weighing Record and list of Basic Equipment upon which the Schedule is based.

(v)

The date and reference of the Loading Graphs of the Loading and Distribution Schedule shall be given.

(vi)

A statement of the date of preparation and validity of the Schedule, signed by a representative of an approved Organisation, or a person acceptable to the CAA. A statement shall also be included indicating that the Schedule supersedes all previous issues.

39. Part B Loading. Columns shall be provided which list all standard items of Variable Load and make provision for the associated weight and CG moments to be recorded and totalled for a particular flight. Columns shall also be provided for recording an example of a typical aircraft loading calculation. This example shall employ the same weight and CG moment figures as recorded in the Loading Graphs (see Part C). 40. Part C Loading Graphs. Graphs, sufficient to ascertain moments, and to enable the operator to determine that the aircraft loaded weight and CG moment are within the prescribed limits shall be provided. The graphs shall be identified by aircraft designation, date of compilation and source. Suitable sources are the aircraft constructor or other competent person. An example application shall be included using the same figures as employed in the Loading and Distribution Schedule example. 41. Weight and Centre-of-Gravity Schedule (Appendix 2, (3)). In addition the Weight and Centre-of-Gravity Schedule for aircraft the Maximum Total Weight Authorised of which does not exceed 2730 kg, shall contain instructions for the determination of the loaded weight, the total load moments and resultant CG positions.

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Documentation Appendix No. 1 – Weight and Centre-Of-Gravity Schedules For Aircraft Exceeding 2730 kg 42. INTRODUCTION. This Appendix presents a specimen Weight and CG Schedule which constitutes an acceptable means of compliance with the appropriate requirements.

NOTE: Imperial Units are shown on the specimen. Where it is necessary to use S.I Units these should be used throughout

FIGURE 11-1 Specimen Schedule

Reference

NAL/286

Produced by

Loose Aviation Ltd

Aircraft Designation

Flynow 2E

Nationality & Registration marks

G-BZZZ

Constructor

F.L.Y. Co. Ltd

Constructor’s Serial Number

44

Maximum Total Weight Authorised

7300 lb

Centre of Gravity Limits

Refer to Flight Manual Reference Number 90/946

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Documentation Part A Basic Weight The Basic Weight of the aircraft as calculated from Weight and Balance Report/Weighing Record* NAL/W/95 dated 31 August 1988 is

5516 lb

The CG of the aircraft in the same Condition at this weight and with the landing gear extended is

127 in aft of datum

The total moment about the datum In this condition in lb.in/100 is 7015

NOTE: The datum is at fuselage station 0 situated 114 inches forward of the wing leading edge. This is the datum defined in the Flight Manual. All lever arms are distances in inches aft of datum

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Documentation FIGURE 11-2

Weight

Lever Arm

(lb)

(in)

Two Marzell propeller type BL-H3Z30

127 each

76

Two engine driven 100 ampere alternators Type GE-362

27 each

117

One 13 Ah Ni Cd battery CB-7

31

153

Part B Variable Load The weight, lever arms and moments of items of Variable Load are shown below. The Variable Load depends upon the equipment carried for the particular role.

FIGURE 11-3

Weight

Lever Arm

Moment

(lb)

(in)

(100 lb.inc)

Pilot (one)

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108

De-icing fluid 1.5 gal

12

140

17

Lift-jackets (7)

14

135

19

Row 1 passenger seats (two)

60

173

104

Row 2 passenger seats (two)

60

215

129

Row 3 passenger seats (two)

60

248

149

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Documentation Weight

Lever Arm

Moment

(lb)

(in)

(100 lb.inc)

Table

8

256

20

One stretcher and attachments (in place of seat rows 2 and 3)

45

223

100

Medical stores

15

250

37

FIGURE 11-4 Part C Loading Information (Disposable Loads)

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Weight

Lever Arm

Capacity

(lb)

(in)

(imp gal)

Fuel in tanks 1 and 2

1368

145

190

Engine Oil

50

70

5.5

Forward baggage

21

Rear baggage

261

Passengers in Row 1 seats

171

Passengers in Row 2 seats

213

Passengers in Row 3 seats

246

Patient in stretcher

223

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Documentation NOTE: To obtain the total loaded weight of aircraft, add to the Basic Weight the weights of the items of Variable and Disposable Load to be carried for the particular role. This Schedule was prepared (date) ……… and supersedes all previous issues. Signed …………………….Inspector/Engineer On behalf of ………………………………….. Approval Reference …………………………..

NOTE: Not part of the specimen Schedule). In Part B, Variable Load, of this Schedule the actual weight of the pilot is required in accordance with the Air Navigation (General) Regulations for aircraft the Maximum Total Weight Authorised of which does not exceed 4700 kg or with less than 12 persons seating capacity. Hence the pilot’s weight and calculated moment are omitted in the example. *Densities – Petrol 7.2 lb Imp.gal; Kerosone 8.1 lb. Imp.gal; Oil 9.0 lb Imp.gal.

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Documentation Appendix No. 2 – Weight and Centre-of-Gravity and Loading Distribution Schedules Aircraft Not Exceeding 2730kg. 43. INTRODUCTION. This Appendix contains acceptable means of compliance in respect of Weight and Centre-of-Gravity and Loading and Distribution Schedules provided in accordance with the requirements. 44. LOADING AND DISTRIBUTION SCHEDULE. The Schedule (including the graphs) and the List of Basic Equipment should, as far as is practical, take the form of Figure 11-5, Figure 11-6 and Figure 11-7.

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Documentation FIGURE 11-5 Front of Schedule

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Documentation FIGURE 11-6 Reverse of Schedule

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Documentation FIGURE 11-7 List of Basic Equipment

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Documentation 45. WEIGHT AND CENTRE OF GRAVITY SCHEDULE. An acceptable means of compliance with the requirements would be to include in the Schedule instructions on the following lines:

Specimen Instructions

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(a)

By reference to Weight and Centre-of-Gravity Schedule, ascertain the lever arm of each item (Basic Weight, Variable Load, Disposable Load).

(b)

To obtain moment of an item, multiply the weight of the item by the corresponding lever arm, and record the moment for each item of load, giving the moment a positive sign if the item is aft of the datum, and a negative sign if it is forward of the datum. Enter the weight of the item in the weight column.

(c)

Total the weight column.

(d)

Total the moment columns. If (+) and (-) moments are recorded total each column and obtain the total resultant moment, by subtracting the lesser from the greater.

(e)

Divide the total (or total resultant) moment by the total weight to obtain c.g. position, positive or negative, relative to the datum, and check that this is within the prescribed c.g. limits.

(f)

To check that the fuel consumed during a flight does not cause the c.g. position to be outside the prescribed limits, re-total the weights in 3 and the moments in 4, but omitting the total fuel weight and the corresponding moment(s), respectively. Add the weight and moment of the fuel expected to remain in the tanks at the end of the flight. Divide the final total resultant moment by the final total weight to obtain the c.g. position, and check that it is still within the prescribed c.g. limits.

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Documentation NOTE: Note: Where there are any other significant quantities of consumable fluids or substances (e.g. crop spraying), similar account should be taken of them.

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031 Aircraft Mass & Balance

Definitions Weight Load Equipment Passengers

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Definitions

12

Definitions

Weight Basic Weight.

This is the aeroplane weight plus basic equipment, unusable fuel and undrainable oil. Basic equipment is that which is common to all roles plus unconsumable fluids such as hydraulic fluid.

Dry Operating Weight. This is defined in JAR-OPS 1.607 as the total weight of the aeroplane for a specific type of operation excluding all usable fuel and traffic load. It includes such items as crew, crew baggage, catering equipment, removable passenger service equipment, potable water and lavatory chemicals. The dry operating weight is sometimes referred to as the Aircraft Prepared for Service (APS) weight. Empty Weight.

This is the basic weight plus role equipment.

Maximum Zero Fuel Weight.

The maximum permissible weight of an aeroplane with no usable fuel. The weight of fuel contained in particular tanks must be included in the zero fuel mass when it is explicitly mentioned in the aeroplane Flight Manual limitations. This is a structural limitation imposed to ensure that the airframe is not over-stressed.

Maximum Structural Landing Weight. landing in normal circumstances.

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The maximum permissible total aeroplane weight on

Definitions Maximum Structural Take-Off Weight.

The maximum permissible total aeroplane weight at

the start of the take-off run.

Zero Fuel Weight.

This is the dry operating weight plus the traffic load. In other words it is the weight of the aeroplane without the weight of fuel.

Aircraft Prepared for Service (APS) Weight. The weight of the aircraft shown in the weight schedule (the basic weight) plus such additional items in or on the aircraft as the operator thinks fit to include. All Up Weight (AUW).

The total weight of an aircraft and all of its contents at a specific time.

Total Loaded Weight.

The sum of the aircraft basic weight, the variable load and disposable

load.

Design Minimum Weight. The lowest weight at which an aeroplane complies with the structural requirements for its own safety. Maximum Ramp Weight.

The maximum weight at which an aircraft may commence taxiing and is equal to the maximum take-off weight plus taxi fuel and run-up fuel. It must not exceed the surface load bearing strength.

Maximum Total Weight Authorised (MTWA).

The maximum total weight of the aircraft prepared for service, the crew (unless already included in the APS weight), passengers, baggage, cargo and fuel at which the aircraft may take-off anywhere in the world, in the most favourable circumstances in accordance with the Certificate of Airworthiness in force in respect of aircraft.

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Definitions Maximum Take-Off Weight.

The maximum weight at which take-off is permitted, by conditions other than available performance.

Landing Weight.

The gross weight of the aeroplane, including all of its contents, at the time of

landing.

Maximum Landing Weight. The maximum weight at which a landing (except in an emergency) is permitted by considerations other than available performance. Maximum Taxi Weight.

The same as maximum ramp weight.

Load Absolute Traffic Load.

The traffic load plus usable fuel and consumable fluids. The traffic load is the total weight of passengers, baggage and cargo, including any non-revenue load.

Floor Load. Index.

This is the area load at a specific station.

This is the moment divided by a constant usually 1000.

Maximum Floor Load.

The highest area load permitted on any part of the floor of the aeroplane is the maximum floor load.

Running Load. The weight of any object divided by the length of that object measured parallel to the longitudinal axis is the running or linear load. Payload.

Anyone or anything on board the aeroplane the carriage of which is paid for by someone other than the operator. In other words anything or anyone carried that earns money for the airline.

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Definitions Traffic Load.

The total weight of passengers, baggage and cargo including non-revenue load.

Useful Load.

The traffic load plus usable fuel is also referred to as the disposable load.

Variable Load.

This includes the role equipment, the crew and the crew baggage. Role equipment is that which is required to complete a specific task such as seats, toilets, galley for the passenger role or roller conveyor, lashing points and tie down equipment for the freight roles.

Equipment Ballast.

Additional fixed weights which can be removed, if necessary, that are carried, to ensure the centre of gravity remains within safe limits, in certain circumstances.

Basic Equipment. The inconsumable fluids and the equipment which is common to all roles for which the operator intends to use the aircraft. Load Spreader.

A mechanical device inserted between the cargo and the aircraft floor to distribute the weight evenly over a greater floor area.

Unusable Fuel.

That part of the fuel carried which is impossible to use because of the shape or position of particular tanks.

Passengers Adults are defined as persons of an age of 12 years and above. They are further classified as male or female. [Appendix 1 to JAR-OPS 1.620 (g)].

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Definitions are persons of an age of 2 years but who have not yet reached their 12th birthday. They are not differentiated by sex.

Children Infants

are persons who have not yet reached their second birthday. Infants shall be weighed together with their accompanying adult. When taking random samples.

Standard Weight

–is the weight of any item or person as tabulated in JAR-OPS 1.620 or other item weight as approved by the JAA.

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031 Aircraft Mass & Balance

CAP 696 - Loading Manual

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CAP 696 - Loading Manual

13

CAP 696 - Loading Manual

1. The CAP 696 is published by the CAA for examination purposes. The candidate is responsible for taking a copy of this CAP in pristine condition to the examination. The details of three generic aircraft are contained in the manual which are representative of those used for performance and flight planning. Pages 2, 3 and 4 of the manual contain definitions which can be used to advantage to answer some of the theoretical questions. 2. The SEP 1. The green pages of the manual contain all of the details of the single engine piston/propeller aeroplane. The maximum limitations are on page 5 but the floor loading limitations at the bottom of the page apply to Figure 2-2 on Page 6. Figure 2-3 provides the moments for any given quantity of fuel. Page 7 details the procedure to be adopted to determine and plot the CG position on pages 8 and 9. The following two examples demonstrate the use of the SEP 1 pages.

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CAP 696 - Loading Manual EXAMPLE 13-1

EXAMPLE The aeroplane is to carry a pilot and co-pilot each weighing 80 kgs and two passengers each weighing 70 kgs and have 5 kgs of baggage each, which is in Zone B. The fuel on board at startup is 60 US gallons of which 30 US gallons will be used for the flight. Determine the CG for zero fuel weight, take-off and landing. Fill in the pro forma and plot the results.

EXAMPLE 13-2

EXAMPLE The aeroplane is to carry a pilot and co-pilot each weighing 85 kgs and two passengers weighing 185.6 kgs together in third and fourth seats. Each passenger has 10 kgs of baggage which is loaded in Zone C. The fuel on board is 70 US gallons of which 50 US gallons will be used for the flight. Fill in the pro forma and plot the results to determine the CG for the zero fuel weight, take-off and landing weights.

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CAP 696 - Loading Manual FIGURE 13-1 Loading Manifest

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Example 13-1

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CAP 696 - Loading Manual FIGURE 13-2 Centre of Gravity Envelope

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Example 13-1

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CAP 696 - Loading Manual FIGURE 13-3 Loading Manifest

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Example 13-1 Solution

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CAP 696 - Loading Manual FIGURE 13-4 Centre of Gravity Envelope

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Example 13-1 Solution

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CAP 696 - Loading Manual FIGURE 13-5 Loading Manifest

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Example 13-2

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CAP 696 - Loading Manual FIGURE 13-6 Centre of Gravity Envelope

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Example 13-2

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CAP 696 - Loading Manual FIGURE 13-7 Loading Manifest

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Example 13-2 Solution

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CAP 696 - Loading Manual FIGURE 13-8 Centre of Gravity Envelope

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Example 13-2 Solution

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CAP 696 - Loading Manual 3. The MEP 1. The limitations for the multi-engined piston/propeller aircraft are listed on Page 12. Notice the reference datum is at the bulkhead of the nose cargo compartment. Page 13 details the calculation procedure and a worked example is shown on pages 14 and 15. Now complete the pro forma and plot the results for the following examples.

EXAMPLE 13-3

EXAMPLE The aeroplane is to carry:

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(a)

Pilot and front passenger total weight 360 lbs.

(b)

Two centre seat passengers total weight 340 lbs.

(c)

One rear seat passenger weight 90 lbs.

(d)

Baggage in Zone 1 weight 50 lbs.

(e)

Fuel in tanks 120.5 US gallons.

(f)

23 lbs of fuel is used for start, taxi and run-up.

(g)

500 lbs is used for the flight.

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CAP 696 - Loading Manual EXAMPLE 13-4

EXAMPLE The aeroplane is to carry:

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(a)

Pilot and front passengers total weight 170 kgs.

(b)

Two centre seat passengers total weight 150 kgs.

(c)

Two rear seat passengers total weight 100 kgs.

(d)

Baggage in Zone 1 weight 40 kgs.

(e)

Baggage in Zone 4 weight 40 kgs.

(f)

Fuel in tanks 75 US gallons.

(g)

5 US gallons used for start, taxi and run-up.

(h)

50 US gallons used for the flight.

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CAP 696 - Loading Manual FIGURE 13-9 Loading Manifest

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Example 13-3

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CAP 696 - Loading Manual Example 13-3

FIGURE 13-10

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CAP 696 - Loading Manual FIGURE 13-11 Loading Manifest

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Example 13-3 Solution

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CAP 696 - Loading Manual Example 13-3 Solution

FIGURE 13-12

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CAP 696 - Loading Manual FIGURE 13-13 Loading Manifest

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Example 13-4

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CAP 696 - Loading Manual Example 13-4

FIGURE 13-14

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CAP 696 - Loading Manual FIGURE 13-15 Loading Manifest

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Example 13-4 Solution

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CAP 696 - Loading Manual #

Example 13-4 Solution

FIGURE 13-16

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CAP 696 - Loading Manual 4. The MRJT. All the data regarding the medium range jet transport aeroplane are contained in the white pages of the CAP 696. Page 20 details all the stations and their balance arms. BS is an abbreviation for body station and FS for front spar. 5. On Page 21, Figure 4-3 details the change to the moments caused by flap retraction to 0°, therefore if flap is extended on approach and landing it will have the opposite effect to that which is tabulated. Figure 4-4 enables the stabiliser time unit setting to be calculated fro take-off, using either 5° or 15° of flap, for any CG position between 5% and 30% of the mean aerodynamic chord. The dimensions of the MAC are given in paragraph 2.5 and the structural limitations in paragraph 3.1. All details of the fuel are on Page 22, passenger distribution on Page 23 together with standard mass values for the crew and passengers. Precise details regarding the loading of the cargo compartments are on Page 24. 6. The procedure for calculating and plotting the CG is specified on Page 25 using the pro forma on Page 26 and the trim envelope diagram on Page 27. The example load and trim sheet information on Page 28 and 29 illustrates the completion of this form. At the present it is not envisaged that the candidate will have to utilise one to answer any question because each airline has their own version of this form.

Important Points

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(a)

The wing tanks must remain full until the contents of the centre tank are 450 kgs or less.

(b)

The standard mass used for the crew is 90 kgs each instead of the JAR-OPS 1 standard masses of 85 kgs for flight crew and 75 kgs for cabin crew.

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CAP 696 - Loading Manual (c)

The standard passenger mass is 84 kgs which according to the JAR-OPS 1 is the standard mass for all flights except holiday charters.

(d)

The allowance made for hand baggage is 6 kgs.

(e)

The standard mass for baggage is 13 kgs per passenger which according to JAR-OPS 1 is that which should be used for European flights only.

THE MESSAGE IS THAT WHEN USING MRJT 1 LOADING MANIFEST THE VALUES USED FOR STANDARD MASSES ARE NON-STANDARD.

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CAP 696 - Loading Manual EXAMPLE 13-5

EXAMPLE The details of this example are as shown on Page 28 of CAP 696 and depicted on Page 29. Use the trim sheet blank at Figure 13-7 below and follow the instructions on Page 28.

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CAP 696 - Loading Manual FIGURE 13-17 Load and Trim Sheet (Blank)

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