Introduction To Flight Control Systems
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Introduction to Flight Control Systems Bharath Seshadri Honeywell, Bangalore
Agenda Principles of Flight Axes system Flight Control System Design System considerations Software considerations
Terminology - Mach Number Mach
=>
Speed of the Body Speed of sound
Low Subsonic High Subsonic Hypersonic 0 0.3
0.8
1.2
5
Supersonic Transonic
How does an aircraft fly?
Aircraft - A view
Forces acting on an Aircraft
To overcome the aircraft’s own weight--that is, the force of gravity, it is essential to create an upward force called lift That's what an airplane's wings are meant for… Wings generate lift To create lift, forward motion is required by overcoming the resistance of the air--a force called drag. That's what an airplane's engines are for… Engines produce a force called thrust
Airplane Axes - Naming convention
Moments acting on an Aircraft Pitching Moment Moment about Lateral axis
Yawing Moment Moment about Vertical or Normal axis
Rolling Moment Moment about Longitudinal axis
Moments acting on an Aircraft
Control of vehicles
There are many types of vehicles used to transport people and objects from place to place on Earth. How are these vehicles guided to a destination? For Car :- Turning the steering wheel changes a car's direction. For Boat :- The rudder is used to control the direction of a boat. For Bicycle :- A bicycle is controlled by turning the handle bars and shifting the rider's weight. For most land and sea vehicles, directional controls accomplished by moving the front end right or left. Movement in this one axis of rotation or direction is called yaw. Flying an airplane requires control of three axes of rotation or movement. The nose of the plane can be moved right and left (yaw), rotated up and down (pitch) and the fuselage can be rolled left and right (roll). A pilot uses the control wheel or stick inside the airplane to move control surfaces on the wings and tail of the plane These control surfaces turn the airplane by varying the forces of lift.
Boeing-777-200
F-16 C/D Cockpit
A340 Cockpit
A320 FCS - Cockpit
Mechanical Flight Controls
On aircraft of the A300 and A310 type, the pilot commands are transmitted to the servo-controls by an arrangement of mechanical components (rods, cables, pulleys, etc.). In addition, specific computers and actuators driving the mechanical linkages restore the pilot feels on the controls and transmit the autopilot commands
Electrical Flight Controls FBW
The term fly-by-wire has been adopted to describe the use of electrical rather than mechanical signaling of the pilot’s commands to the flying control actuators. One can imagine a basic form of fly-by-wire in which an airplane retained conventional pilot’s control columns and wheels, hydraulic actuators (but electrically controlled), and artificial feel as experienced in the 1970s with the Concorde program. The fly-by-wire system would simply provide electrical signals to the control actuators that were directly proportional to the angular displacement of the pilot’s controls, without any form of enhancement.
Autopilot
Basic Function of autopilot is to control the flight of the aircraft and maintain it on a predetermined path in space without any action being required by the pilot, once the pilot has selected the appropriate control mode of the autopilot. The autopilot can thus relieve the pilot from the fatigue and tedium of having to maintain continuous control of aircraft’s flight path on a long duration flight. A well designed autopilot, properly integrated with FCS can achieve a faster response and maintain a more precise flight path than the pilot. Eg. Auto landing In Military strike aircraft autopilot in conjunction with Terrain Following guidance can provide can provide all weather auto TF capability, enabling the ac to fly at high speed (600kts) automatically follow the terrain profile to stay below the radar horizon of enemy radars.
Autopilot Loop Commande + d Flight Path
Flight Path Deviation
Autopilot
Sensors
Flight Control Loop
Flight Path Kinematic s
Autopilot –guidance function in outer loop- generates commands for FCS in inner loop These are generally attitude commands which operate the aircraft’s control surfaces through a closed loop control system so that the aircraft rotates about the pitch and roll axes until the measured pitch and bank angles are equal to the commanded values. The changes in the aircraft attitude then cause the flight path to change through flight path kinematics.
AFCS Scope and Limited Authority Digital autopilot for three axis control of the airplane Requirements Flight director to provide the guidance up to Cat II precision
approach phase Vertical, lateral and coupled modes of operation Automatic Pitch trim Manual Pitch trim Smooth engagement, disengagement and mode transition of autopilot without transients leading to hazardous conditions Annunciation of warning and status to ACMPS,CWP and EFIS Crew Interface via Autopilot Control and Mode Select Panel, Control wheel Positive and immediate disengagement facility in case of an emergency Power inputs meeting DO-160D section 16, category B Proven and Airworthy Hardware and servo, meeting DO-160D requirements Fail safe architecture Scalable and up-gradable to host additional functions
AFCS in SARAS
AFCS Modes of operation Mode Definition Vertical Modes PAH
Provides guidance to maintain a pilot selected pitch attitude reference.
ALT
Provides guidance to maintain a barometric altitude reference.
ALTSEL
Provides guidance to capture and level off at a pre-selected altitude.
SPD
Provides guidance to track and attain pilot selected speed reference.
VS
Provides guidance to track a pilot selected vertical speed reference.
GS
Provides guidance to capture and track the Glideslope signal for approach.
Lateral Modes RAH
Provides guidance to maintain a roll attitude reference.
HDG
Provides guidance to capture and track a pilot selected heading reference.
HH
Provides guidance to maintain the fixed heading reference.
NAV (VOR)
Provides guidance to capture and track the VOR signal for cruise.
APPR (LOC)
Provides guidance to capture and track the front course localizer signal.
BC
Provides guidance to capture and track the back course localizer signal.
AFCS Control loop
AFCS Interfaces
Grey shaded are AFCS components
Development Lifecycle: IPDS
KMC 9200 - Autopilot Control/Mode Select Panel (ACMSP)
Single Card (.8 In)
ARINC, DISCRETE ANALOG
t re c s
e
Di , N g CA lo a An
Dual GIO Card (1.6 In)
cr e
te
OTHER AIRCARFT SYSTEMS ADCU,AHRS, RADALT,DME, SWS
A429
AFCS HW components – physical view
MAU: Hosts following set of modules per lane • AIOP Module (combines the
Dis
Actuator IO module combined with a PROC module) • Generic I/O Module
SM1000 SERVO – Aileron, Elevator and Rudder
SVO-65 Pitch Trim
• Network Interface Module (NIC)
Servo
• Power Supply
AFCS Application on AIOP card
Data Flow Diagram
Application Launch Sequence
Execution Rates of AFCS Application Processes
AFCS Application Software Partitioning
Partitioning has been decided based on following factors
Safety Directed design Modular Architecture
Provides Scalability Restricts the changes to a module
Allows for upgrading, changing of specific modules to suit different specifications.
Lower regression
Reusability Control and Data Coupling. Easier to maintain
AFCS Application Functional View
Control Law Design
Knowledge of control systems essential Linearize the non-linear system Understand aircraft equations of motion Understand the necessity of control and what parameters to control Ultimate objective is to maintain aircraft in equilibrium under different modes
Sample Control Law
Books for Reference
Introduction to Flight, John Anderson Jr. , McGraw-Hill, 3rd ed, 1989 Fundamentals of Flight Shevell, Richard S., Prentice Hall, 2nd Edition, 1989 Aerodynamics for Engineers Bertin, John J. and Smith, Michael L., Prentice Hall, 3rd edition, 1998 Aircraft Performance, Stability and Control Perkins and Hage
Agenda Principles of Flight Axes system Flight Control System Design System considerations Software considerations
Terminology - Mach Number Mach
=>
Speed of the Body Speed of sound
Low Subsonic High Subsonic Hypersonic 0 0.3
0.8
1.2
5
Supersonic Transonic
How does an aircraft fly?
Aircraft - A view
Forces acting on an Aircraft
To overcome the aircraft’s own weight--that is, the force of gravity, it is essential to create an upward force called lift That's what an airplane's wings are meant for… Wings generate lift To create lift, forward motion is required by overcoming the resistance of the air--a force called drag. That's what an airplane's engines are for… Engines produce a force called thrust
Airplane Axes - Naming convention
Moments acting on an Aircraft Pitching Moment Moment about Lateral axis
Yawing Moment Moment about Vertical or Normal axis
Rolling Moment Moment about Longitudinal axis
Moments acting on an Aircraft
Control of vehicles
There are many types of vehicles used to transport people and objects from place to place on Earth. How are these vehicles guided to a destination? For Car :- Turning the steering wheel changes a car's direction. For Boat :- The rudder is used to control the direction of a boat. For Bicycle :- A bicycle is controlled by turning the handle bars and shifting the rider's weight. For most land and sea vehicles, directional controls accomplished by moving the front end right or left. Movement in this one axis of rotation or direction is called yaw. Flying an airplane requires control of three axes of rotation or movement. The nose of the plane can be moved right and left (yaw), rotated up and down (pitch) and the fuselage can be rolled left and right (roll). A pilot uses the control wheel or stick inside the airplane to move control surfaces on the wings and tail of the plane These control surfaces turn the airplane by varying the forces of lift.
Boeing-777-200
F-16 C/D Cockpit
A340 Cockpit
A320 FCS - Cockpit
Mechanical Flight Controls
On aircraft of the A300 and A310 type, the pilot commands are transmitted to the servo-controls by an arrangement of mechanical components (rods, cables, pulleys, etc.). In addition, specific computers and actuators driving the mechanical linkages restore the pilot feels on the controls and transmit the autopilot commands
Electrical Flight Controls FBW
The term fly-by-wire has been adopted to describe the use of electrical rather than mechanical signaling of the pilot’s commands to the flying control actuators. One can imagine a basic form of fly-by-wire in which an airplane retained conventional pilot’s control columns and wheels, hydraulic actuators (but electrically controlled), and artificial feel as experienced in the 1970s with the Concorde program. The fly-by-wire system would simply provide electrical signals to the control actuators that were directly proportional to the angular displacement of the pilot’s controls, without any form of enhancement.
Autopilot
Basic Function of autopilot is to control the flight of the aircraft and maintain it on a predetermined path in space without any action being required by the pilot, once the pilot has selected the appropriate control mode of the autopilot. The autopilot can thus relieve the pilot from the fatigue and tedium of having to maintain continuous control of aircraft’s flight path on a long duration flight. A well designed autopilot, properly integrated with FCS can achieve a faster response and maintain a more precise flight path than the pilot. Eg. Auto landing In Military strike aircraft autopilot in conjunction with Terrain Following guidance can provide can provide all weather auto TF capability, enabling the ac to fly at high speed (600kts) automatically follow the terrain profile to stay below the radar horizon of enemy radars.
Autopilot Loop Commande + d Flight Path
Flight Path Deviation
Autopilot
Sensors
Flight Control Loop
Flight Path Kinematic s
Autopilot –guidance function in outer loop- generates commands for FCS in inner loop These are generally attitude commands which operate the aircraft’s control surfaces through a closed loop control system so that the aircraft rotates about the pitch and roll axes until the measured pitch and bank angles are equal to the commanded values. The changes in the aircraft attitude then cause the flight path to change through flight path kinematics.
AFCS Scope and Limited Authority Digital autopilot for three axis control of the airplane Requirements Flight director to provide the guidance up to Cat II precision
approach phase Vertical, lateral and coupled modes of operation Automatic Pitch trim Manual Pitch trim Smooth engagement, disengagement and mode transition of autopilot without transients leading to hazardous conditions Annunciation of warning and status to ACMPS,CWP and EFIS Crew Interface via Autopilot Control and Mode Select Panel, Control wheel Positive and immediate disengagement facility in case of an emergency Power inputs meeting DO-160D section 16, category B Proven and Airworthy Hardware and servo, meeting DO-160D requirements Fail safe architecture Scalable and up-gradable to host additional functions
AFCS in SARAS
AFCS Modes of operation Mode Definition Vertical Modes PAH
Provides guidance to maintain a pilot selected pitch attitude reference.
ALT
Provides guidance to maintain a barometric altitude reference.
ALTSEL
Provides guidance to capture and level off at a pre-selected altitude.
SPD
Provides guidance to track and attain pilot selected speed reference.
VS
Provides guidance to track a pilot selected vertical speed reference.
GS
Provides guidance to capture and track the Glideslope signal for approach.
Lateral Modes RAH
Provides guidance to maintain a roll attitude reference.
HDG
Provides guidance to capture and track a pilot selected heading reference.
HH
Provides guidance to maintain the fixed heading reference.
NAV (VOR)
Provides guidance to capture and track the VOR signal for cruise.
APPR (LOC)
Provides guidance to capture and track the front course localizer signal.
BC
Provides guidance to capture and track the back course localizer signal.
AFCS Control loop
AFCS Interfaces
Grey shaded are AFCS components
Development Lifecycle: IPDS
KMC 9200 - Autopilot Control/Mode Select Panel (ACMSP)
Single Card (.8 In)
ARINC, DISCRETE ANALOG
t re c s
e
Di , N g CA lo a An
Dual GIO Card (1.6 In)
cr e
te
OTHER AIRCARFT SYSTEMS ADCU,AHRS, RADALT,DME, SWS
A429
AFCS HW components – physical view
MAU: Hosts following set of modules per lane • AIOP Module (combines the
Dis
Actuator IO module combined with a PROC module) • Generic I/O Module
SM1000 SERVO – Aileron, Elevator and Rudder
SVO-65 Pitch Trim
• Network Interface Module (NIC)
Servo
• Power Supply
AFCS Application on AIOP card
Data Flow Diagram
Application Launch Sequence
Execution Rates of AFCS Application Processes
AFCS Application Software Partitioning
Partitioning has been decided based on following factors
Safety Directed design Modular Architecture
Provides Scalability Restricts the changes to a module
Allows for upgrading, changing of specific modules to suit different specifications.
Lower regression
Reusability Control and Data Coupling. Easier to maintain
AFCS Application Functional View
Control Law Design
Knowledge of control systems essential Linearize the non-linear system Understand aircraft equations of motion Understand the necessity of control and what parameters to control Ultimate objective is to maintain aircraft in equilibrium under different modes
Sample Control Law
Books for Reference
Introduction to Flight, John Anderson Jr. , McGraw-Hill, 3rd ed, 1989 Fundamentals of Flight Shevell, Richard S., Prentice Hall, 2nd Edition, 1989 Aerodynamics for Engineers Bertin, John J. and Smith, Michael L., Prentice Hall, 3rd edition, 1998 Aircraft Performance, Stability and Control Perkins and Hage
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