Engines, Apu R 01

737-300/400 ENGINES, AUXILIARY POWER UNIT (APU)

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Engine Instruments-Primary Panel

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Engine Instruments-Primary Panel REVERSER UNLOCKED Lights: Illuminated – Indicates the respective engine thrust reverser sleeves are unlocked.

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Engine Instruments-Primary Panel N1 RPM Indicators: • Displays N1% RPM for respective engine. • Analog needle corresponds with rolling digital display. Note: Failure of the N1 indicator or the transmitter results in the digital display blanking and the needle moving to zero.

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Engine Instruments-Primary Panel N1 Cursors: With N1 manual set knob pushed in – • Positioned by FMC. • Based on N1 limit page and takeoff reference page. With N1 manual set knob pulled out – • Displays N1 selected by flight deck crew.

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Engine Instruments-Primary Panel N1 Manual Set Indication Windows: • Set by N1 manual set knob. • Digital readout of N1 cursor position. • Blank when manual set knob is pushed in.

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Engine Instruments-Primary Panel N1 Warning Lights: Illuminated – • Indicates the N1 limit has been reached or exceeded on respective engine. • Remains illuminated until N1 is reduced below the limit.

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Engine Instruments-Primary Panel N1 Manual Set Knobs: Pushed in – • N1 cursor set by FMC based on N1 limit page and takeoff reference page. • Blanks respective N1 manual set indication window. Pulled out – • Disables FMC input signal. • Rotation sets desired N1 RPM in the respective N1 manual set indication window and moves the N1 cursor to the corresponding location.

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Engine Instruments-Primary Panel

EGT Indicators: • Displays engine EGT in °C. • Analog needle corresponds with rolling digital display. Note: Failure of the EGT indicator or the transmitter results in the digital display blanking and the needle moving to zero.

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Engine Instruments-Primary Panel

EGT Warning Lights: Illuminated – • Indicates the EGT limit has been reached or exceeded on respective engine. • Remains illuminated until EGT reduced below the limit.

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Engine Instruments-Primary Panel

N2 RPM Indicators: • Displays N2% RPM for respective engine. • Analog needle corresponds with rolling digital display. Note: Failure of the N2 indicator or the transmitter results in the digital display blanking and the needle moving to zero.

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Engine Instruments-Primary Panel

Warning Lights: Illuminated – • Indicates the N2 limit has been reached or exceeded on respective engine. • Remains illuminated until N2 reduced below the limit.

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Engine Instruments-Primary Panel

FF (Fuel Flow) Indicators: • Displays rate of fuel flow in pounds per hour at all times. • Analog needle corresponds with rolling digital display. Slide 13 of 73

Engine Instruments-Primary Panel

Fuel Flow Switch: Three position switch, spring-loaded to RATE position.

Fuel Flow Digital Displays (RATE/USED): • With the fuel flow switch in the RATE position, indicates rate of fuel consumption in poundsper-hour X 1000. • With the fuel flow switch held in the USED position, indicates the amount of fuel consumed (in pounds) since last reset. • With the fuel flow switch held in the RESET position, resets display on both fuel flow indicators to zero. Slide 14 of 73

Engine Instruments-Secondary Panel

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Engine Instruments-Secondary Panel START VALVE OPEN Lights: Illuminated – Respective engine start valve is open and air is being supplied to the starter.

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Engine Instruments-Secondary Panel LOW OIL PRESSURE Lights: Illuminated – Respective engine oil pressure is at or below the red radial.

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Engine Instruments-Secondary Panel OIL FILTER BYPASS Lights: Illuminated – Indicates and impending or actual bypass of the respective scavenge oil filter.

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Engine Instruments-Secondary Panel

OIL PRESS Indicators: Displays engine oil pressure in psi.

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Engine Instruments-Secondary Panel

Low Oil Pressure Yellow Band: • Indicates minimum oil pressure limit. • Valid only on the ground with takeoff thrust set.

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Engine Instruments-Secondary Panel

OIL TEMP Indicators: Displays engine oil temperature in °C.

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Engine Instruments-Secondary Panel

ENG OIL QTY TEST Switch: Push – OIL QUANTITY indicators move toward zero.

OIL QUANTITY Indicators: Displays engine oil quantity in gallons.

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Engine Instruments-Secondary Panel

VIB (Airborne Vibration Monitors): Indicates engine vibration level.

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Engine Instruments-Secondary Panel This concludes the review of the Engine Instrument Panels. The next section will discuss various other engine panels and controls. Click Next to continue.

Off Index Mark: Indicates system is inoperative if needle is pointing to blue line.

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Engine Start Panel

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Engine Start Panel ENGINE START Switches: GRD – • Opens start valve. • Closes engine bleed air valve. • Provides ignition to selected igniter(s) when engine start lever is positioned to IDLE. • Switch automatically releases to OFF position at starter cutout. OFF – Ignition off. CONT – Provides ignition to selected igniter(s) when engine start lever is in IDLE position. FLT – Bypasses ignition select switch and provides ignition to both igniters when engine start lever is in IDLE position.

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Engine Start Panel Ignition Select Switch: IGN L – Selects the left igniter on each engine for use on respective engine. BOTH – Selects both igniters on each engine for use on respective engine. IGN R – Selects the right igniter on each engine for use on respective engine.

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Engine Panel

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Engine Panel REVERSER Lights: If Illuminated, one or more of the following three non-normal scenarios has occurred – • Thrust reverser selector valve or thrust reverser isolation valve are not in commanded position. • Thrust reverser sleeve position sensors on same engine are in disagreement. (Example: The left thrust reverser sleeve position sensor on the No. 1 engine is in disagreement with the right thrust reverser sleeve position sensor on the No. 1 engine.) • Auto-restow circuit has been activated (see slide 66). Note: The REVERSER lights will also normally illuminate when the thrust reverser sleeves are commanded to the stow position (see slide 65).

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Engine Panel PMC (Power Management Control) Switches: ON (white ON in view) – PMC is selected on. INOP (amber INOP in view) – PMC is inoperative when engine speed is above 46% N2, or the PMC is selected OFF. Note: Both PMC switches guarded by a plastic lens cover. Cover is hinged on top to rotate upward.

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Engine Panel LOW IDLE Light: Illuminated – • The thrust lever for either engine is near idle and the MEC on either engine is not commanded to maintain high idle RPM in flight. • The speed of either engine is below 25% N1 in flight. Note: If an engine start lever is in CUTOFF, the light is deactivated.

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Engine Controls Forward Thrust Levers: • Controls respective engine thrust. • Cannot be advanced if the respective reverse thrust lever is in the deployed position.

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Engine Controls Reverse Thrust Levers: • Controls respective engine reverse thrust. • Cannot select reverse thrust unless respective forward thrust lever is at IDLE. Note: Reverse thrust lever is blocked at reverse idle position until respective thrust reverser sleeves are more than 60% deployed. Note: Movement of reverse thrust lever into reverse thrust engages locking pawl preventing forward thrust lever movement. Terminating reverse thrust removes locking pawl and restores forward thrust lever movement ability.

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Engine Controls Engine Start Levers: IDLE – • Energizes the ignition system. • Electronically opens the engine fuel shutoff valve. This valve is attached to the wing front spar and located just outboard of the engine pylon. • Mechanically opens the MEC fuel shutoff valve. CUTOFF – • De-energizes the ignition system. • Electronically closes the engine fuel shutoff valve. • Mechanically closes the MEC fuel shutoff valve.

This concludes the review of Engine Panels and Controls. The next section will discuss the APU panels. Click Next to continue. Slide 34 of 73

APU Panel

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APU Panel

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MAINT/LOW OIL QUANTITY Light: Illuminated – APU maintenance problem exists. • APU oil quantity may be insufficient for extended operations. • APU may still be operated. Note: Light is disarmed when APU switch is OFF.

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APU Panel

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LOW OIL PRESSURE Light: Illuminated – • Oil pressure is low, therefore initiating an automatic shutdown of the APU (after start cycle is complete). • During start, light is normally illuminated until sufficient oil pressure is achieved. Note: Light is disarmed when APU switch is OFF.

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APU Panel FAULT/HIGH OIL TEMP Light: Illuminated – • Oil temperature is excessive, therefore initiating an automatic shutdown of the APU. 1

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Note: Light is disarmed when APU switch is OFF.

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APU Panel

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OVERSPEED Light: Illuminated – • APU RPM limit (110%) has been exceeded, therefore initiating an automatic shutdown of the APU. • APU start has been manually aborted prior to reaching its governed speed of 100%. When a re-start is attempted, light will extinguish following a normal start. • During a normal shutdown, the overspeed shutdown protection feature has failed its selftest. Note: Light is disarmed when APU switch is OFF.

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APU Panel EGT Indicator: Displays APU EGT.

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APU Panel APU AMPS (APU Generator AC Ammeter): Displays APU generator current load.

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APU Switch APU Switch: OFF – Normal position when APU is not operating. Positioning the switch from ON to OFF while the APU is operating will accomplish the following: • Initiates an APU shutdown. • Closes the APU fuel shutoff valve and the APU fuel solenoid valve. • Disconnects the APU from the generator bus(es), if connected. • Closes the APU bleed air valve. • Closes the APU air inlet door. ON – Normal position when APU is operating.

This concludes the review of the APU panels. The remainder of the presentation will discuss the engines and APU in greater detail. Click Next to continue.

START (momentary) – Initiates an automatic start sequence when momentarily positioning the switch from OFF to START, and then releasing it back to the ON position. Slide 42 of 73

Engines The 737-300/400 is powered by two General Electric CFM56-3 engines. The engine is a dual rotor axial flow turbofan of high compression ratio and high bypass ratio. Approximately 20% of the air entering the engine inlet is utilized for combustion, while the remaining 80% is bypassed (fan air). The N1 rotor consists of a fan and a three stage booster section which is connected by a through shaft to a four stage low pressure turbine. The N2 rotor consists of a high pressure compressor and a single stage high pressure turbine. The N1 and N2 rotors are mechanically independent.

CFM56-3 Slide 43 of 73

Engines Fan Air (80%)

Air utilized for combustion (20%)

Fan Air (80%)

The CFM-56 has a high bypass ratio Slide 44 of 73

Engines

Fan Blades (N1 rotor) Slide 45 of 73

Engines

Three stage booster section (N1 rotor) Slide 46 of 73

Engines

Four stage low pressure turbine (N1 rotor) Slide 47 of 73

Engines

Nine stage high pressure compressor (N2 rotor) Slide 48 of 73

Engines

Single stage high pressure turbine (N2 rotor) Slide 49 of 73

Engines

See picture of gearbox

Gearbox Slide 50 of 73

Engines

Combustion chamber Slide 51 of 73

MEC and PMC The thrust control system consists of a hydro-mechanical Main Engine Control (MEC) unit and a Power Management Control (PMC) unit mounted on each engine. The PMC is an electronic system with limited authority over the MEC. The PMC uses MEC power lever angle, N1 speed, inlet temperature, and inlet pressure to adjust the MEC to obtain the desired N1 speed. The PMC adjusts fuel flow as a function of thrust lever angle. The PMC provides a constant thrust climb feature once the thrust lever is set at the beginning of climb. Thus, when thrust is set for climb, the PMC automatically maintains that thrust throughout the climb profile with no further thrust lever adjustments. If the thrust lever is repositioned, the PMC maintains the setting corresponding to the new thrust lever angle.

See picture of MEC and PMC temperature probes

See picture of MEC and PMC

CFM56-3 Slide 52 of 73

Idle Speeds There are two engine idle speeds: low idle and high idle. • The minimum engine speed for all flight phases is high idle, which varies with flight conditions. As temperature and airspeed decrease, high idle speed also decrease. The average high idle speed is approximately 32% N1. • The minimum engine speed for all ground phases is low idle. There is one exception to the previous sentence: For the first four seconds after touchdown, the engines remain in high idle to enhance engine speed acceleration for reverse thrust, and therefore reduce braking activity. The average low idle speed is approximately 22% N1.

CFM56-3 Slide 53 of 73

Engine Schematic FAN AIR 5TH STAGE BLEED AIR 9TH STAGE BLEED AIR

ENGINE IDLE CONTROL ENGINE FUEL SYSTEM ACCESSORIES OIL, FUEL & HYDRAULIC PUMPS GENERATOR CSD STARTER TACHOMETER

AIR DRIVEN STARTER

POWER MANAGEMENT CONTROL FLIGHT DECK CONTROLS & INDICATORS

ENGINE START & IGNITION SYSTEM

FROM PNEUMATIC SYSTEM

FROM FUEL SYSTEM

FROM ENGINE INDICATING SYSTEM

FROM ELECTRICAL SYSTEM

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Engine Fuel System Fuel is delivered under pressure the from fuel pumps located in the fuel tanks. The fuel enters the engine through the engine fuel shutoff valve. Once through this valve, the fuel passes through the first stage engine fuel pump where fuel pressure is increased. It then passes through a fuel/oil heat exchanger where the engine oil heats the fuel. A fuel filter then removes contaminants. (If the fuel filter becomes saturated with contaminates, fuel automatically bypasses the fuel filter and continues its flow to the engine. Before this bypass occurs, the FILTER BYPASS light illuminates, which is located on the fuel panel.) Next, a second stage fuel pump further increases the pressure of the fuel. As the fuel leaves the second stage fuel pump, a majority of the fuel passes through another fuel filter an then eventually to the MEC, via the MEC fuel shutoff valve. (The MEC will ensure that the correct amount of fuel is delivered to the combustion chamber.) However, prior to the MEC, a portion of the fuel is diverted back to the fuel/oil heat exchanger and then routed to operate the hydro-mechanical portion of the MEC to ensure clean, icefree fuel for servo operation. The engine fuel shutoff valve and MEC fuel shutoff valve allow fuel flow to the engine when both valves are open. The valves are open when the respective engine fire warning switch is “down” and the respective start lever is in the IDLE position. The MEC fuel shutoff valve closes only when the respective start lever is in the CUTOFF position. The engine fuel shutoff valve closes when the start lever is positioned back to CUTOFF, or the engine fire warning switch is pulled “up”. The FUEL VALVE CLOSED light, located on the fuel panel, indicates the position of the engine fuel shutoff valve. For example, if the light glows “dim”, the valve is closed. If the light glows “bright,” the valve is in transit or is in disagreement with the switch position. If the light is extinguished, the valve is open.

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Engine Oil System Both engines have their own oil tank. Oil from the tank is circulated under pressure through the engine to lubricate the engine bearings and accessory gearbox. Oil quantity is displayed on the oil quantity indicator. The oil system is pressurized by the engine driven oil pump. Oil from the pump is filtered and then flows to the engine bearings and gearbox. Sensors for the oil pressure indicator and the LOW OIL PRESSURE light are located downstream of the oil filter, prior to engine bearing and gearbox lubrication. After lubrication, oil is returned to the oil tank by engine driven scavenge pumps. From the scavenge pumps, oil passes through a scavenge filter. If the scavenge filter becomes saturated with contaminates, the oil automatically bypasses the filter and continues to flow to the oil tank. Before this bypass occurs, the OIL FILTER BYPASS light illuminates. As the oil returns to the tank, oil temperature is sensed and consequently displayed on the oil temperature indicator. The oil now passes through the fuel/oil heat exchanger, where it is cooled by engine fuel prior to returning to the oil tank.

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Engine Fuel/Oil Schematic TO BEARINGS & GEARBOX

OIL RETURN

OIL PRESS

FUEL FLOW TRANSMITTER MEC FUEL SHUTOFF VALVE

FUEL FLOW IDLE CONTROL

B

SCAVENGE PUMPS

OIL FILTER

MEC

SCAVENGE FILTER

B

FUEL FILTER SECOND STAGE FUEL PUMP

OIL TEMP

B

C

B

PMC

FUEL FILTER

OIL QUANT

OIL PUMP

C

FUEL / OIL HEAT EXCHANGER

OIL TANK

FIRST STAGE FUEL PUMP ENGINE FUEL SHUTOFF VALVE

FUEL OIL

FROM FUEL TANK

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Engine Start System Starter operation requires pressurized air and electrical power. Air from the bleed air system powers the starter motor. Bleed air sources are either the APU, an external ground cart, or the other operating engine. In the GRD position, the engine start switch uses DC power (from the battery bus) to close the engine bleed air valve and open the start valve to allow pressure to rotate the starter. When the start valve opens, the START VALVE OPEN light illuminates. The starter rotates the N2 high pressure compressor through the gearbox. When the engine accelerates to the recommended value (25% N2 or max motoring), moving the engine start lever from the CUTOFF to the IDLE position opens the fuel valves. (The engine fuel shutoff valve is electrically opened and the MEC fuel shutoff valve is mechanically opened.) With both fuel valves now open, the MEC meters the fuel to the combustion chamber where the fuel ignites. At starter cutout (approximately 46% N2), power is removed from the engine start switch holding solenoid, which returns the start switch to the OFF position. Also occurring at starter cutout are: engine bleed air valve returns to the selected position, start valve closes, START VALVE OPEN light extinguishes, and a rise in pressure can be witnessed on the bleed air duct pressure indicator (respective needle).

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Engine Start System Each engine has two igniters (left and right). The ignition select switch selects either the left, right, or both igniters for both engines. The ignition select switch is bypassed when the engine start switch is in the FLT position. The left igniter on each engine is powered by its respective AC transfer bus. The right igniter on each engine is powered by the AC standby bus. Both igniters provide high energy ignition.

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Start and Ignition Schematic NO. 1 ENGINE CONDITION: • ENGINE NO. 1 BEING STARTED • N2 ROTATION BELOW STARTER CUTOUT SPEED

AIR DRIVEN STARTER

BATTERY BUS

GRD OFF

S

START VALVE

CONT FLT START SWITCH HOLDING RELAY

HIGH N2

ENGINE BLEED AIR VALVE

FROM PNEUMATIC SYSTEM

STARTER CUTOUT SWITCH

COMBUSTION CHAMBER

LOW N2

MEC

NO. 1 TRANSFER BUS

AC STANDBY BUS

NO. 1 START LEVER IN IDLE POSITION

GRD OFF

IGN L BOTH

IDLE

CONT FLT

IGN R

CUTOFF

GRD OFF CONT FLT

IGN R

LEFT IGNITER RIGHT IGNITER

IGN L BOTH

FROM FUEL SYSTEM

IDLE

BLEED AIR FUEL

CUTOFF

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Thrust Reverse Each engine is equipped with a hydraulically operated thrust reverser, consisting of left and right translating sleeves. As the reverser sleeves translate aft, ten blocker doors rotate into a blocking position which forces fan air in a reverse direction, through cascade vanes, thereby producing reverse thrust. The thrust reverser is for ground operations only and is utilized after touchdown to slow the aircraft, reducing stopping distance and brake wear. Hydraulic pressure for the operation of engine No. 1 and engine No. 2 thrust reversers comes from hydraulic systems “A” and “B” respectively. If hydraulic system “A” or “B” fails, alternate operation for the affected thrust reverser is available through the standby hydraulic system. When the standby system is being utilized, the affected thrust reverser deploys and retracts at a slower rate, and therefore some thrust asymmetry can be anticipated.

See picture of cascade vanes

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737-300/400 Hydraulic Schematic (specific to thrust reverse)

Pneumatic air

“A” system reservoir

Return Standpipe (quantity 25%)

No. 1 fuel tank

Standpipe (quantity 50%) Hydraulic shutoff

Hydraulic heat exchanger

Hydraulic heat exchanger

Electric pump To return

No. 2 fuel tank

Motor

Electric pump

P

P

No. 1 thrust reverser

Engine driven pump

To reservoir

Motor Motor

Hydraulic pressure for the operation of engine No. 1 and engine No. 2 thrust reversers comes from hydraulic systems “A” and “B” respectively. If hydraulic system “A” or “B” fails, alternate operation for the affected thrust reverser is available through the standby hydraulic system.

Standpipe (quantity 0%). 1 gallon remaining for PTU use only.

Return

To reservoir

To return

Pneumatic air Return

Standby system reservoir

Hydraulic shutoff

Engine driven pump

“B” system reservoir

To return

No. 2 thrust reverser

Supply “A” system pressure “B” system pressure Standby system pressure Case drain return

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Thrust Reverse When reverse thrust is selected, the isolation valve opens and the thrust reverser control valve moves to the deploy position, thereby allowing hydraulic pressure to unlock and deploy the thrust reverser system. An interlock mechanism restricts movement of the reverse thrust lever until the reverser sleeves are more than 60% deployed. As the thrust reverser reaches the fully deployed position, the reverse thrust lever can be raised to detent No. 2. This position provides adequate reverse thrust for normal operations. When necessary, the reverse thrust lever can be pulled beyond detent No. 2, providing maximum reverse thrust. When either reverser sleeve moves from the stowed position, the amber REVERSER UNLOCKED light on the center instrument panel illuminates. Downward motion of the reverse thrust lever past detent No. 1 commands the reverser to stow. Once the thrust reverser is commanded to stow, the control valve moves to the stow position allowing hydraulic pressure to stow and lock the reverser sleeves. After the thrust reverser is stowed, the isolation valve closes.

Thrust reverser levers Slide 63 of 73

Thrust Reverse Schematic DETENT NO. 2

MAXIMUM REVERSE THRUST

DETENT NO. 1 INTERLOCK STOWED

FORWARD THRUST LEVER

REVERSE THRUST (STOWED) SYS. STBY SYS “A” SYS “B” ENGINE NO. 1 SYSTEM “A” HYDRAULIC PRESSURE

ENGINE NO. 2 SYSTEM “B” HYDRAULIC PRESSURE

ISOLATION VALVE (CLOSED) CONTROL VALVE (STOW)

ACTUATOR (STOWED & LOCKED)

ENG. NO. 1 SYS “A” HYD. PRESS.

ENGINE NO. 2 SYSTEM “B” HYDRAULIC PRESSURE

ISOLATION VALVE (OPEN)

CONTROL VALVE (DEPLOY)

ACTUATOR (DEPLOY)

BLOCKER DOOR

FAN AIR FLOW

FAN AIR FLOW

CASCADE VANES

REVERSE THRUST (DEPLOYED) STBY SYS SYS. SYS “B” “A”

TRANSLATING SLEEVE

CASCADE VANES

TRANSLATING SLEEVE

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Thrust Reverse The REVERSER lights, located on the aft overhead panel, normally illuminate whenever the thrust reverser sleeves are commanded to the stow position. In this situation, the REVERSER lights illuminate because the selector valve has been commanded to the “stow” position, while the isolation valve remains “open” to allow hydraulic fluid to flow to the hydraulic actuators which close the translating sleeves. This is disagreement between the two valves, thereby illuminating the respective REVERSER light. The isolation valve will remain “open” for approximately ten seconds, allowing enough time for the hydraulic actuators to fully stow the thrust reverser sleeves (the MASTER CAUTION and ENG system annunciator lights are not signaled to illuminate during the ten seconds that the selector valve and isolation valve are in disagreement). When the thrust reverser sleeves are fully stowed, the isolation valve closes and the respective REVERSER light extinguishes. If a REVERSER light remains illuminated for more than approximately twelve seconds, a malfunction has occurred and the MASTER CAUTION and ENG system annunciator lights now illuminate.

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Thrust Reverse An auto-restow circuit compares actual thrust reverser sleeve position to the commanded thrust reverser sleeve position. In the event of an incomplete stowage or un-commanded movement of the thrust reverser sleeves toward the deployed position, the auto-restow circuit opens the isolation valve and commands the control valve to the stow position, thereby directing hydraulic pressure to stow the thrust reverser sleeves. This will result in the illumination of the respective REVERSER light. Once the auto-restow circuit is activated, the isolation valve remains open and the control valve is held in the stowed position until the thrust reverser is commanded to deploy or until corrective maintenance action is taken.

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APU The Auxiliary Power Unit (APU) is a self-contained gas turbine engine consisting of a compressor, turbine, and accessory drive section. It is installed within a fireproof compartment located in the tail of the aircraft. Gear driven units in the accessory drive section control the APU from startup to shutdown. The APU can be operated up to the aircraft maximum certified altitude. The APU supplies bleed air for engine starting and air conditioning. In flight or on the ground, the APU can supply bleed air to one air conditioning pack. An AC electrical generator on the APU provides an auxiliary AC power source. While on the ground, both generator bus 1 and generator bus 2 can be powered from the APU. In flight, only one generator bus can be powered from the APU.

EXHAUST OUTLET

ACCESSORY COOLING AIR DUCT APU DUCT AIR DIFFUSER DUCT

EXHAUST MUFFLER

VORTEX GENERATOR

APU FUEL LINE AIR INLET DOOR APU BLEED AIR DUCT

Slide 67 of 73

APU When the AC powered fuel pumps are operating, fuel to start and operate the APU comes from the left side of the fuel manifold. If the fuel pumps are not operating, fuel is suction fed from the No. 1 fuel tank. During APU operating, fuel is automatically heated to prevent icing. APU engine air is routed to the APU through an automatically operated air inlet door located on the right side of the fuselage. APU exhaust gases are discharged overboard through an exhaust muffler. A portion of the air entering the air inlet door is drawn in by a gear driven fan and then routed to cool the electrical generator and engine oil.

EXHAUST OUTLET

ACCESSORY COOLING AIR DUCT APU DUCT AIR DIFFUSER DUCT

EXHAUST MUFFLER

VORTEX GENERATOR

APU FUEL LINE AIR INLET DOOR APU BLEED AIR DUCT

Slide 68 of 73

APU APU operation requires the following: • APU fire handle on the overheat/fire panel must be “down”. • APU fire control handle on the APU ground control panel must be “up”. • Battery (BAT) switch must be ON. Electrical power to start the APU comes from the aircraft battery. While on the ground, if the battery (BAT) switch is positioned to OFF, the APU will shutdown due to the loss of power to the APU fire detector loop.

EXHAUST OUTLET

ACCESSORY COOLING AIR DUCT APU DUCT AIR DIFFUSER DUCT

EXHAUST MUFFLER

VORTEX GENERATOR

APU FUEL LINE AIR INLET DOOR APU BLEED AIR DUCT

Slide 69 of 73

APU The automatic start sequence begins by moving the APU start switch momentarily to the START position. This initiates opening of the APU fuel shutoff valve (located in the wheel well) and the air inlet door. When the air inlet door is fully open, the start sequence begins. If the APU does not reach the proper speed with the proper acceleration rate within the time limit of the starter, the start cycle automatically terminates. The start cycle may take as long as 135 seconds. When the APU reaches the proper speed, ignition and fuel are provided for combustion. When the APU is ready to accept a bleed air or electrical load, the APU GEN OFF BUS light illuminates. It is recommended that the APU be operated for at least one full minute before utilizing as a bleed source. This one minute stabilization period is to extend the service life of the APU.

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APU The APU will automatically shutdown if it encounters LOW OIL PRESSURE, HIGH OIL TEMP (FAULT), OVERSPEED or a FIRE. These four auto-shutdown features stop the operation of the APU by closing the fuel solenoid valve, which is attached to the APU fuel control unit. A combination of electrical loads and bleed air extraction may cause the EGT to rise above acceptable levels. In this scenario, the APU bleed valve will automatically modulate towards the closed position, which will result in a lower EGT.

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APU Engine Cross Section Accessory section

Compressor section

Turbine section H

G

E B

C A) B) C) D) E) F) G) H) I) J)

D

Output shaft Inlet plenum First stage compressor Second stage compressor Turbine plenum Bleed air valve Fuel nozzle A Igniter Combustor Turbine

I

J F

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APU Schematic ACCELERATION / LOAD CONTROL THERMOSTAT

3-WAY CONTROL VALVE

NO. 1 FUEL TANK

IGNITER

FCU

S

ACCELERATION CONTROL

FUEL SOLENOID VALVE

OVERBOARD

SPEED CONTROL

M

FUEL PUMP

TURBINE

ACCESSORY GEAR BOX

STARTER

COMPRESSOR

OIL PUMP

FUEL SHUTOFF VALVE

OIL COOLER

TO ELECTRICAL LOADS

GENERATOR

SPEED SWITCH

1

BLEED AIR VALVE 1 TO BLEED LOADS

FUEL APU BLEED AIR APU CONTROL AIR RAM AIR 1 AS INSTALLED PT. METRO BATAVIA Directorate of Operational

AIR INLET DOOR

M Slide 73 of 73