b737-300/400 flight controls

of 73PT. METRO BATAVIAPT. METRO BATAVIADirectorate of OperationalDirectorate of Operational

737-300/400737-300/400FLIGHT CONTROLSFLIGHT CONTROLS

NextNextMain MenuMain Menu QuitQuit


Flight Control Surface Locations

Flight Spoilers (4 total)

Ground Spoilers (6 total)

Rudder

Elevators

Balance Tabs

Horizontal Stabilizer

Trailing Edge Flaps

AileronBalance Tab

Leading Edge Slats

(6 total)

Leading Edge Flaps

(4 total)


737-300/400 Hydraulic Schematic (specific to primary flight

controls)

Both “A” and “B” hydraulic systems

simultaneously supply pressure to the primary flight controls;

ailerons, elevator (elevator feel), and rudder. In addition, the

standby hydraulic system will

supply pressure to the rudder

when operating under non-normal

conditions.

“B” system pressure

“A” system pressure

Supply

Standby system pressure

Case drain return

Aileron

Rudder

Elevator and Elevator feel

Standby rudder

To return

Standby system

reservoir

Motor

Return

To return P P To return

Hydraulic shutoff

No. 1fuel tank

To reservoir Hydraulic heat exchanger

Engine driven pump

Hydraulic shutoff

No. 2fuel tank

To reservoirHydraulic heat exchanger

Motor

Electric pump

Electric pump

Motor

“A” system

reservoir

Pneumatic air

ReturnStandpipe

(quantity 25%)

Engine driven pump

“B” system

reservoirPneumatic air

Return

Standpipe(quantity 50%)

Standpipe (quantity 0%). 1 gallon remaining for

PTU use only.


Flight Control PanelFlight Control Panel(top half)(top half)



FLIGHT CONTROL Switches:FLIGHT CONTROL Switches:STBY RUD –STBY RUD –Activates standby pump and opens Activates standby pump and opens standby rudder shutoff valve to standby rudder shutoff valve to pressurize standby rudder power pressurize standby rudder power control unit (PCU).control unit (PCU).

OFF –OFF –Closes flight control shutoff valve Closes flight control shutoff valve isolating ailerons, elevators, and isolating ailerons, elevators, and rudder from associated hydraulic rudder from associated hydraulic system pressure.system pressure.

ON (guarded position) –ON (guarded position) –Normal operating position.Normal operating position.



Flight Control LOW PRESSURE Lights:Flight Control LOW PRESSURE Lights:Illuminated –Illuminated –• Indicates low hydraulic system Indicates low hydraulic system

("A" or “B”) pressure to ailerons, ("A" or “B”) pressure to ailerons, elevator, and rudder.elevator, and rudder.• Deactivated when associated Deactivated when associated FLIGHT CONTROL switch is FLIGHT CONTROL switch is positioned to STBY RUD positioned to STBY RUD andand standby rudder shutoff valve is standby rudder shutoff valve is fully fully open.open.• On airplanes with the rudder On airplanes with the rudder pressure reducer installed, the “A” pressure reducer installed, the “A”

system light indicates “A” system system light indicates “A” system pressure is low when normal system pressure is low when normal system pressure is commanded.pressure is commanded.



STANDBY HYD LOW QUANTITY Light:STANDBY HYD LOW QUANTITY Light:Illuminated –Illuminated –Indicates low quantity in standby Indicates low quantity in standby hydraulic reservoir (approximately 50%).hydraulic reservoir (approximately 50%).

Note: This light is always armed.Note: This light is always armed.

STANDBY HYD LOW PRESSURE Light:STANDBY HYD LOW PRESSURE Light:Illuminated –Illuminated –Indicates output pressure of standby Indicates output pressure of standby pump is low.pump is low.

Note: This light is armed only when Note: This light is armed only when standby pump operation has been standby pump operation has been selected or automatic standby function selected or automatic standby function is activated. is activated.



ALTERNATE FLAPS Master Switch:ALTERNATE FLAPS Master Switch:OFF (guarded position) –OFF (guarded position) –Normal operating position.Normal operating position.

ARM –ARM –• Closes the trailing edge flap bypass valve Closes the trailing edge flap bypass valve

(to prevent hydraulic lock of flap drive unit)(to prevent hydraulic lock of flap drive unit) ..• Arms the ALTERNATE FLAPS position Arms the ALTERNATE FLAPS position switch.switch.• Activates standby pump.Activates standby pump.• Arms the standby hydraulic LOW Arms the standby hydraulic LOW PRESSURE light. PRESSURE light. • Arms the leading edge standby drive Arms the leading edge standby drive extension shutoff valve.extension shutoff valve.



ALTERNATE FLAPS Position Switch:ALTERNATE FLAPS Position Switch:Functions only when the Functions only when the ALTERNATE FLAPS master switch ALTERNATE FLAPS master switch is in the ARM position. is in the ARM position.

UP –UP –• Electrically retracts trailing edge flaps.Electrically retracts trailing edge flaps.• Leading edge devices remain Leading edge devices remain extended and cannot be retracted by extended and cannot be retracted by

the alternate flaps system.the alternate flaps system.

OFF –OFF –Normal operating position.Normal operating position.

DOWN (spring-loaded to OFF) –DOWN (spring-loaded to OFF) –• (Momentary) Opens the leading edge (Momentary) Opens the leading edge

standby drive extension shutoff valve standby drive extension shutoff valve and fully extends leading edge devices and fully extends leading edge devices using standby hydraulic pressure.using standby hydraulic pressure.• (Hold) Electrically extends trailing edge (Hold) Electrically extends trailing edge

flaps flaps (no asymmetry protection is provided).(no asymmetry protection is provided).


Flight Control PanelFlight Control Panel(bottom half)(bottom half)



Flight SPOILER Switches:Flight SPOILER Switches:(guarded to ON)(guarded to ON)OFF –OFF –Closes the respective flight spoilers Closes the respective flight spoilers shutoff valve.shutoff valve.

Used for maintenance purposes only.Used for maintenance purposes only.



FEEL DIFF PRESS Light:FEEL DIFF PRESS Light:Armed when the trailing edge flaps Armed when the trailing edge flaps are up.are up.

Illuminated –Illuminated –Indicates excessive differential Indicates excessive differential pressure in the elevator feel pressure in the elevator feel computer.computer.



SPEED TRIM FAIL Light:SPEED TRIM FAIL Light:Armed when the trailing edge flaps Armed when the trailing edge flaps are not up.are not up.

Illuminated –Illuminated –• If illuminated continuously, indicates If illuminated continuously, indicates

failure of both channels of the speed failure of both channels of the speed trim system.trim system.• If illuminated only when the MASTER If illuminated only when the MASTER

CAUTION light recall is activated, CAUTION light recall is activated, indicates failure of a single channel indicates failure of a single channel of the speed trim system. Light of the speed trim system. Light extinguishes when master caution extinguishes when master caution system is reset.system is reset.



MACH TRIM FAIL Light:MACH TRIM FAIL Light:Armed when the trailing edge flaps Armed when the trailing edge flaps are up.are up.

Illuminated –Illuminated –• If illuminated continuously, indicates If illuminated continuously, indicates

failure of both channels of the mach failure of both channels of the mach trim system.trim system.• If illuminated only when the MASTER If illuminated only when the MASTER

CAUTION light recall is activated, CAUTION light recall is activated, indicates failure of a single channel indicates failure of a single channel of the mach trim system. Light of the mach trim system. Light extinguishes when master caution extinguishes when master caution system is reset.system is reset.



AUTO SLAT FAIL Light:AUTO SLAT FAIL Light:Illuminated –Illuminated –• If illuminated continuously, indicates If illuminated continuously, indicates

failure of both autoslat computers.failure of both autoslat computers.• If illuminated only when the MASTER If illuminated only when the MASTER

CAUTION light recall is activated, CAUTION light recall is activated, indicates failure of a single autoslat indicates failure of a single autoslat computer. Light extinguishes when computer. Light extinguishes when master caution system is reset.master caution system is reset.



YAW DAMPER Light:YAW DAMPER Light:Illuminated –Illuminated –Yaw damper is not engaged.Yaw damper is not engaged.



YAW DAMPER Switch:YAW DAMPER Switch:OFF –OFF –Disengages yaw damper.Disengages yaw damper.

ON –ON –Engages yaw damper to rudder Engages yaw damper to rudder power control unit (PCU).power control unit (PCU).

This concludes the review of the Flight Control Panel. The remainder of the presentation This concludes the review of the Flight Control Panel. The remainder of the presentation will discuss the flight control system in greater detail. Click will discuss the flight control system in greater detail. Click NextNext to continue. to continue.


Roll ControlRoll Control

Control Wheel:Control Wheel:Rotate –Rotate –Operates ailerons and flight Operates ailerons and flight spoilers in desired direction.spoilers in desired direction.


Roll ControlRoll ControlAILERON Trim Switches:AILERON Trim Switches:(spring-loaded to center)(spring-loaded to center)Movement of both switches in Movement of both switches in same direction repositions the same direction repositions the aileron neutral control position. aileron neutral control position. Control wheel automatically Control wheel automatically moves in the respective direction.moves in the respective direction.

AILERON TRIM Indicator:AILERON TRIM Indicator:(located on top of control column, (located on top of control column, behind control wheel)behind control wheel)Indicates units of aileron trim. Indicates units of aileron trim.


Roll ControlRoll control surfaces consist of hydraulically powered ailerons and flight spoilers, which provide roll control around the aircraft’s longitudinal axis. The ailerons and flight spoilers are controlled by rotating either control wheel. With a loss of both “A” and “B” hydraulic systems, the ailerons and flight spoilers are capable of being mechanically positioned (manual reversion). The aileron balance tab functions to reduce the force required to position the aileron. Balance tab travel is opposite to aileron travel, i.e., an upward movement of the aileron produces a downward movement of the balance tab.

Flight Spoilers

Aileron

Flight Spoilers

Aileron

Balance Tab

Balance Tab


Roll ControlFlight spoilers are utilized either inflight or on the ground to increase drag and reduce lift. They also supplement roll control in response to control wheel commands. A spoiler mixer (located in the main wheel well) controls the hydraulic power control units (PCUs) on each flight spoiler panel to provide flight spoiler movement proportional to aileron movement.

Flight Spoilers

Aileron

Flight Spoilers

Aileron

Balance Tab

Balance Tab


Roll ControlAt the base of the First Officer’s control column is the Aileron Transfer Mechanism. This mechanism will allow the pilots to bypass a jammed roll control system (aileron or flight spoiler). Applying force to either the Captain’s or First Officer’s control wheel will determine which system is jammed and therefore which control surface (ailerons or flight spoilers) and which control wheel (Captain’s or First Officer’s) will be utilized for roll control…

Flight Spoilers

Aileron

Flight Spoilers

Aileron

Balance Tab

Balance Tab


Roll Control…For example, if the aileron system is jammed, applying force the the First Officer’s control wheel will result in roll control from the flight spoilers (in this case the Captain’s control wheel and ailerons are inoperative). If the flight spoiler system is jammed, applying force the the Captain’s control wheel will result in roll control from the ailerons (in this case the First Officer’s control wheel and flight spoilers are inoperative).

Flight Spoilers

Aileron

Flight Spoilers

Aileron

Balance Tab

Balance Tab


Roll Control

AILERONTRIM

AILERONFEEL AND

CENTERINGUNIT

SPOILERMIXER

FLIGHTSPOILERS

AILERON

AILERON TRANSFERMECHANISM

2 3 6 7

FIRST OFFICER’SCONTROL WHEEL

CAPTAIN’SCONTROL WHEEL

FLIGHTSPOILERS

AILERON

BALANCETAB

BALANCETAB

AILERONPOWER

CONTROLUNIT “A”

AILERONPOWER

CONTROLUNIT “B”

HYDRAULIC SYSTEM“A’

HYDRAULIC SYSTEM“B’


Pitch ControlPitch Control

Control Column:Control Column:Push/Pull –Push/Pull –• Operates elevators in the desired Operates elevators in the desired

direction.direction.• Movement in opposite direction of Movement in opposite direction of

stabilizer trim will stop electric stabilizer trim will stop electric trimming.trimming.

Stabilizer Trim Switches:Stabilizer Trim Switches:(spring-loaded to neutral)(spring-loaded to neutral)Push (both) up/down –Push (both) up/down –• Electrically commands stabilizer Electrically commands stabilizer

trim in desired direction.trim in desired direction.• Autopilot disengages, if engagedAutopilot disengages, if engaged


Pitch ControlPitch ControlStabilizer Trim Wheels:Stabilizer Trim Wheels:• Provides for manual operation of Provides for manual operation of

horizontal stabilizer.horizontal stabilizer.• Overrides any other horizontal Overrides any other horizontal

stabilizer inputs.stabilizer inputs.• Rotates when horizontal stabilizer is in Rotates when horizontal stabilizer is in

motion.motion.


Pitch ControlPitch ControlSTAB TRIM Green Band Range:STAB TRIM Green Band Range:Corresponds to allowable range of Corresponds to allowable range of trim settings for takeoff.trim settings for takeoff.

STAB TRIM Indicator:STAB TRIM Indicator:Indicates units of trim on the adjacent Indicates units of trim on the adjacent green band range scale.green band range scale.


Pitch ControlPitch ControlSTAB TRIM AUTO PILOT CUTOUT Switch:STAB TRIM AUTO PILOT CUTOUT Switch:NORMAL –NORMAL –Normal operating position.Normal operating position.

CUTOUT –CUTOUT –• Deactivates autopilot stabilizer trim Deactivates autopilot stabilizer trim operation.operation.• Autopilot disengages if engaged.Autopilot disengages if engaged.

STAB TRIM MAIN ELECT CUTOUT Switch:STAB TRIM MAIN ELECT CUTOUT Switch:NORMAL –NORMAL –Normal operating position.Normal operating position.

CUTOUT –CUTOUT –Deactivates stabilizer trim switch operation.Deactivates stabilizer trim switch operation.

STAB TRIM Override Switch:STAB TRIM Override Switch:NORMAL –NORMAL –Normal operating position.Normal operating position.

OVERRIDE –OVERRIDE –Bypasses the control column actuated Bypasses the control column actuated stabilizer trim cutout switches to restore stabilizer trim cutout switches to restore power to the stabilizer trim switches.power to the stabilizer trim switches.


Pitch ControlPitch control surfaces consist of hydraulically powered elevators and an electrically powered horizontal stabilizer. The elevators are controlled by forward or aft movement of the control column. The horizontal stabilizer is controlled by either the stabilizer trim switches, autopilot or stabilizer trim wheel (manual trim). The elevator balance tab functions to reduce the force required to position the elevator.

ElevatorsHorizontal Stabilizer

Balance Tabs


Left Pitot Probe (for elevator feel system)


Pitch ControlThe elevators provide pitch control around the airplane’s lateral axis. Cables connect the pilots’ control columns to elevator PCUs. The PCUs are powered by “A” and “B” hydraulic system. With a loss of both “A” and “B” hydraulic systems, the elevators can be mechanically positioned (manual reversion).


Balance Tabs




Pitch ControlThe elevator feel computer provides simulated aerodynamic forces using airspeed (from pitot probe on vertical stabilizer) and horizontal stabilizer position. This “artificial feel” is transmitted to the control columns via the elevator feel and centering unit. The elevator feel computer utilizes either “A” or “B” hydraulic systems. If an undesirable pressure difference exists between the two hydraulic systems, or an elevator feel pitot probe fails, the FEEL DIFF PRESS light will automatically illuminate.


Balance Tabs




Pitch ControlThe Mach Trim system provides speed stability at higher Mach numbers (above Mach .615). As aircraft speed increases, the Mach Trim system will automatically reposition the elevators via the elevator feel and centering mechanism, which in turn adjusts the control column neutral position. If one channel of the Mach Trim system fails, the MACH TRIM FAIL light will illuminate when the Master Caution system annunciator panel (recall) is pressed. If both channels of the Mach Trim system fail, the MACH TRIM FAIL light will automatically illuminate.


Balance Tabs




Pitch ControlThe horizontal stabilizer is positioned by the main electric trim motor (utilizing the stabilizer trim switches on the control wheel) or by the autopilot trim motor. The horizontal stabilizer may also be positioned by manually rotating the stabilizer trim wheel. The stabilizer trim wheels in the flight deck rotate whenever electric stabilizer trim is actuated.


Balance Tabs




Pitch ControlControl column actuated stabilizer trim cutout switches (located under the flight deck floor) stop operation of the main electric and autopilot trim motors when control column movement opposes trim direction. When the STAB TRIM override switch is positioned to OVERRIDE, main electric trim can be used regardless of control column position.


Balance Tabs




Pitch ControlThe Speed Trim system provides automatic trim inputs to the horizontal stabilizer to maintain positive speed stability. This usually occurs during takeoff or go-around with an aft center of gravity, high thrust setting, and a low gross weight. Other inputs into the Speed Trim system include horizontal stabilizer position, thrust lever position, airspeed, and vertical speed. During Speed Trim operation, trimming of the horizontal stabilizer is via the autopilot trim motor. Conditions for Speed Trim operation are listed below:

Speed Trim operates when: • Flaps not up• N1 above 60%• Airspeed 100-300 KIAS• Autopilot not engaged• Ten seconds after takeoff• Five seconds following release of trim switches• Sensing of trim requirement


Balance Tabs




Pitch Control

FLIGHTCONTROL

COMPUTERSAIR DATA

COMPUTERS

L PITOTPROBE

R PITOTPROBE

ELEVATORFEEL

COMPUTER

MACH TRIM ACTUATOR

ELEVATOR FEEL& CENTERING UNIT

STABILIZERTRIMSTABILIZER

POSITION

“A”HYDRAULIC

SYSTEM

“B”HYDRAULIC

SYSTEM

HORIZONTALSTABILIZER

ELEVATOR

BALANCE TABS

HORIZONTALSTABILIZER

ELEVATOR


Yaw ControlYaw ControlRudder Pedals:Rudder Pedals:Push –Push –• Controls rudder position.Controls rudder position.• Permits limited nose wheel steering up to 7Permits limited nose wheel steering up to 7°°

left or right of center.left or right of center.

RUDDER Trim Control Knob:RUDDER Trim Control Knob:(spring-loaded to center)(spring-loaded to center)Rotate –Rotate –Electrically trims the rudder in the desired Electrically trims the rudder in the desired direction.direction.

RUDDER TRIM Indicator:RUDDER TRIM Indicator:Indicates units of rudder trim.Indicates units of rudder trim.

YAW DAMPER Indicator:YAW DAMPER Indicator:• Indicates yaw damper movement of rudder.Indicates yaw damper movement of rudder.• Pilot rudder pedal inputs are not indicated.Pilot rudder pedal inputs are not indicated.


Yaw Control

Rudder

Vertical Stabilizer

Yaw control is accomplished by a hydraulically powered rudder, and a yaw damper system. The rudder provides yaw control around the aircraft’s vertical axis, and is controlled by displacing the rudder pedals. Both sets of rudder pedals are connected via cables to the main and standby rudder PCUs through the rudder feel and centering unit. The rudder can only be operated when hydraulic power is available, i.e. manual reversion is not available for the rudder.


Yaw ControlThe main rudder PCU is powered by “A” and “B” hydraulic system. The standby rudder PCU is powered by the standby hydraulic system. The standby hydraulic system serves as a backup if “A” and/or “B” hydraulic system pressure is lost. The standby hydraulic pump and standby rudder PCU can be manually activated by positioning either FLT CONTROL switch to STBY RUD (standby rudder). They can also be automatically activated when all of the conditions listed below exist:

Standby pump and PCU automatic activation: • Loss of one hydraulic system

(“A” or “B”)• Trailing edge flaps extended• Airborne OR wheel speed greater than 60 kts.

Rudder

Vertical Stabilizer


Yaw ControlThe yaw damper system prevents unwanted (Dutch) roll, and provides turn coordination. When necessary, the yaw damper system will provide inputs to the rudder via the main rudder PCU. At higher airspeeds the amount of yaw damper rudder deflection decreases. No rudder pedal movement results from yaw damper operation. The yaw damper utilizes “B” hydraulic system only. If “B” pressure is lost, the yaw damper system is inoperative, but the YAW DAMPER switch remains in the ON position until the “B” FLT CONTROL switch is positioned to OFF or STBY RUD.

Rudder

Vertical Stabilizer


Yaw Control

RUDDERTRIM

RUDDER FEELAND CENTERING

UNIT

YAW DAMPERRATE GYRO

YAWDAMPER

RUDDERPCU

STANDBYRUDDER PCU

RUDDER

STANDBYRUDDERSHUTOFF

VALVE

STANDBY HYDRAULIC SYSTEM

“B” HYDRAULIC SYSTEM

CAPTAIN’SRUDDERPEDALS

FIRST OFFICER’SRUDDERPEDALS

“A” HYDRAULIC SYSTEM


Speed BrakesSpeed BrakesSPEED BRAKE Lever:SPEED BRAKE Lever:DOWN –DOWN –All flight and ground spoiler panels in faired All flight and ground spoiler panels in faired position.position.

ARMED –ARMED –• Automatic speed brake system armed.Automatic speed brake system armed.• Upon touchdown, the speed brake lever Upon touchdown, the speed brake lever moves to the UP position and all flight and moves to the UP position and all flight and ground spoilers extend.ground spoilers extend.

FLIGHT DETENT –FLIGHT DETENT –All flight spoilers are extended to their All flight spoilers are extended to their maximum position for inflight use.maximum position for inflight use.

UP –UP –All flight and ground spoilers are extended to All flight and ground spoilers are extended to their maximum position for ground use.their maximum position for ground use.


Speed BrakesSpeed BrakesSPEED BRAKE DO NOT ARM Light:SPEED BRAKE DO NOT ARM Light:Illuminated –Illuminated –Indicates abnormal condition or test inputs to Indicates abnormal condition or test inputs to the automatic speed brake system.the automatic speed brake system.

Note: Light is deactivated when speed brake Note: Light is deactivated when speed brake lever is in the DOWN position.lever is in the DOWN position.

SPEED BRAKE ARMED Light:SPEED BRAKE ARMED Light:Illuminated –Illuminated –Indicates valid automatic speed brake system Indicates valid automatic speed brake system inputs.inputs.

Note: Light is deactivated when speed brake Note: Light is deactivated when speed brake lever is in the DOWN position.lever is in the DOWN position.


737-300/400 Hydraulic Schematic (specific to spoilers)

“A” system hydraulics powers

the six ground spoilers and the

two inboard flight spoilers. “B”

system hydraulics powers the two outboard flight

spoilers.“B”

system pressure


Supply


Case drain return

To return P

Hydraulic shutoff

No. 1fuel tank


Electric pump

Motor

“A” system

reservoir

Pneumatic air

ReturnStandpipe

(quantity 25%)

Engine driven pump

P To return

Engine driven pump

Hydraulic shutoff

No. 2fuel tank


Motor

Electric pump

“B” system


Return



PTU use only.

Ground spoilers

Inboard flight spoilers Outboard flight spoilers


Speed BrakesThe speed brakes consist of four flight spoilers and six ground spoilers. “A” hydraulic system powers all six ground spoilers and the two inboard flight spoilers. “B” hydraulic system powers the two outboard flight spoilers. The speed brake lever controls the spoilers. On the ground, when the speed brake lever is actuated, all ten spoilers deploy. In flight, when the speed brake lever is actuated, only the flight spoilers deploy.

Flight Spoilers

Flight Spoilers

Ground Spoilers

Ground Spoilers


Speed BrakesIn flight operation:Operating the speed brake lever in flight will result in the four flight spoiler panels to deploy symmetrically to act as speed brakes. When the flight spoilers are in an intermediate position, roll rates increase significantly. Moving the speed brake lever past the FLIGHT detent results in buffeting and is not recommended in flight.

Flight Spoilers

Flight Spoilers

Ground Spoilers

Ground Spoilers


Speed BrakesGround operation:During landing, the auto speed brake system operates when the following conditions exist: • Speed brake lever in the ARMED position• SPEED BRAKE ARMED light illuminated• Both thrust levers in the idle position• Upon main landing gear wheel spin-up of greater than 60 knots, the speed brake lever will automatically

move to the UP position and all four flight spoilers deploy. • Upon air/ground sensing system detecting aircraft being on the ground, the six ground spoilers deploy.

If a wheel spin-up signal is not detected, the speed brake lever automatically moves to the UP position and all ten spoilers deploy when the air/ground sensing system detects being on the ground.

Flight Spoilers

Ground Spoilers

Ground Spoilers

Flight Spoilers


Speed BrakesGround operation (RTO):During a rejected takeoff (RTO), the auto speed brake system operates when the these conditions exist: • Main landing gear wheel speed greater than 60 kts. • Both thrust levers in the idle position.• Application of reverse thrust mechanically lifts the speed brake handle out of the DOWN detent. The

speed brake handle will now automatically move to the UP position resulting in all ten spoilers deploying.

All ten spoilers may be stowed manually by repositioning the speed brake handle to the DOWN detent. The spoilers may be automatically stowed by advancing the thrust levers until the speed brake handle moves to the DOWN detent.

Flight Spoilers

Ground Spoilers

Ground Spoilers

Flight Spoilers


Speed Brakes

SPEED BRAKELEVER

01 2 3

4 56 7 8 9

“A” HYDRAULICSYSTEM

GROUND SPOILERSHUTOFF VALVE

GROUND SPOILERCONTROL VALVE

SPOILERMIXER

RIGHT MAINLANDING GEAR

FLIGHT SPOILERS: 2, 3, 6, 7GROUND SPOILERS: 0, 1, 4, 5, 8, 9

“B” HYDRAULICSYSTEM


Trailing and Leading Edge DevicesTrailing and Leading Edge DevicesFLAP lever:FLAP lever:• Selects position of flap control valve, directing Selects position of flap control valve, directing

hydraulic pressure for flap drive unit.hydraulic pressure for flap drive unit.• Position of the leading edge devices is Position of the leading edge devices is determined by selecting trailing edge flap determined by selecting trailing edge flap position.position.• Flap position 40 arms the flap load relief Flap position 40 arms the flap load relief system.system.

FLAPS LIMIT PlacardFLAPS LIMIT Placard

Flap Position Indicator:Flap Position Indicator:• Indicates position of left and right trailing edge Indicates position of left and right trailing edge

flaps in “units,” not “degrees”.flaps in “units,” not “degrees”.• Provides trailing edge flaps asymmetry Provides trailing edge flaps asymmetry protection.protection.


737-300/400 Hydraulic Schematic (specific to leading and

trailing edge devices)

“B” system hydraulics powers both the leading and trailing edge devices. If “B”

hydraulic system pressure is lost,

the standby hydraulic system can extend, but not retract, the leading edge

devices.



Supply


Case drain return

P To return

Engine driven pump

Hydraulic shutoff

No. 2fuel tank


Motor

Electric pump

“B” system


Return



PTU use only.

Trailing edge flaps

Leading edge flaps & slats

Leading edge devices standby extension

Return

Standby system

reservoir

Motor

To return


Trailing and Leading Edge DevicesThe leading edge flaps and slats (LE devices) are high lift devices that increase wing lift and decrease stall speed during takeoff, low speed maneuvering, and landing. Leading edge devices consist of four Krueger flaps (two inboard of each engine), and six slats (three outboard of each engine). Slats extend to form a sealed or slotted leading edge depending on the trailing edge flap setting.

Leading Edge Flaps

Leading Edge Slats

Leading Edge SlatsLeading Edge

Flaps

Trailing Edge Flaps

Trailing Edge Flaps


Trailing and Leading Edge DevicesThe trailing edge devices (TE devices) consist of triple-slotted flaps inboard and outboard of each engine. TE flap positions 1-15 provide increased lift; positions 15-40 provide increased lift and drag. Flap positions 15, 30, and 40 are normal landing flap positions.

Leading Edge Flaps

Leading Edge Slats

Leading Edge SlatsLeading Edge

Flaps

Trailing Edge Flaps

Trailing Edge Flaps


Leading Edge Annunciator PanelLeading Edge Annunciator Panel



LE DEVICES (Leading Edge Devices) LE DEVICES (Leading Edge Devices) Annunciator Panel:Annunciator Panel:Indicates position of individual leading edge Indicates position of individual leading edge flaps and slats.flaps and slats.

Extinguished –Extinguished –Related leading edge device retracted.Related leading edge device retracted.



The four flaps have two positions:The four flaps have two positions:• Fully retractedFully retracted• Fully extendedFully extended



The six slats have three positions:The six slats have three positions:• Fully retractedFully retracted• ExtendedExtended• Fully extendedFully extended



LE DEVICES TRANSIT Lights:LE DEVICES TRANSIT Lights:Illuminated –Illuminated –Related leading edge device in transit.Related leading edge device in transit.



LE DEVICES EXT Lights:LE DEVICES EXT Lights:Illuminated –Illuminated –Related leading edge slat in extended Related leading edge slat in extended position.position.



LE DEVICES FULL EXT Lights:LE DEVICES FULL EXT Lights:Illuminated –Illuminated –Related leading edge flap or slat in Related leading edge flap or slat in fully extended position.fully extended position.



LE DEVICES TEST Switch:LE DEVICES TEST Switch:Press –Press –Tests all annunciator panel lights.Tests all annunciator panel lights.


Leading EdgeLeading EdgeTransit / Extend LightsTransit / Extend Lights



LE FLAPS TRANSIT Light:LE FLAPS TRANSIT Light:Illuminated –Illuminated –Any leading edge device in transit, or not in Any leading edge device in transit, or not in programmed position with respect to trailing programmed position with respect to trailing edge flaps.edge flaps.

Note: Light is inhibited during autoslat Note: Light is inhibited during autoslat operation in fight.operation in fight.



LE FLAPS EXT Light:LE FLAPS EXT Light:Illuminated –Illuminated –• All leading edge flaps fully extended and All leading edge flaps fully extended and all leading edge slats in extended all leading edge slats in extended position (trailing edge flap positions 1, 2, position (trailing edge flap positions 1, 2, and 5).and 5).

• All leading edge devices in fully extended All leading edge devices in fully extended position (trailing edge flap positions position (trailing edge flap positions

10 thru 40).10 thru 40).


Trailing and Leading Edge Device Trailing and Leading Edge Device SequencingSequencing

TE flaps selected from UP to 1, 2 or 5:TE flaps selected from UP to 1, 2 or 5:

TE devices and flap gauge move to TE devices and flap gauge move to commanded position (TE flaps 1 shown).commanded position (TE flaps 1 shown).

LE annunciator panel initially indicates LE annunciator panel initially indicates LE devices in “transit,” then indicates LE devices in “transit,” then indicates flaps in fully extended position and slats flaps in fully extended position and slats in extended position.in extended position.

LE transit / extend lights initially indicate LE transit / extend lights initially indicate LE FLAPS TRANSIT, then LE FLAPS EXT LE FLAPS TRANSIT, then LE FLAPS EXT when when allall LE devices in commanded LE devices in commanded position.position.

TE and LE devices are normally powered by the “B” hydraulic system. When the flap lever is in the UP TE and LE devices are normally powered by the “B” hydraulic system. When the flap lever is in the UP position, all TE and LE devices are commanded to the fully retracted position. LE device deployment is position, all TE and LE devices are commanded to the fully retracted position. LE device deployment is sequenced as a function of TE device deployment. Sequencing is as follows: sequenced as a function of TE device deployment. Sequencing is as follows:


Trailing and Leading Edge Device Trailing and Leading Edge Device SequencingSequencing

TE and LE devices are normally powered by the “B” hydraulic system. When the flap lever is in the UP TE and LE devices are normally powered by the “B” hydraulic system. When the flap lever is in the UP position, all TE and LE devices are commanded to the fully retracted position. LE device deployment is position, all TE and LE devices are commanded to the fully retracted position. LE device deployment is sequenced as a function of TE device deployment. Sequencing is as follows: sequenced as a function of TE device deployment. Sequencing is as follows:

TE flaps selected from 1, 2 or 5 to 10 or greater:TE flaps selected from 1, 2 or 5 to 10 or greater:

TE devices and flap gauge move to TE devices and flap gauge move to commanded position (TE flaps 15 shown).commanded position (TE flaps 15 shown).

LE annunciator panel initially indicates LE annunciator panel initially indicates slats in “transit,” then indicates slats in slats in “transit,” then indicates slats in fully extended position. Flaps remain in fully extended position. Flaps remain in fully extended position.fully extended position.

LE transit / extend lights initially indicate LE transit / extend lights initially indicate LE FLAPS TRANSIT, then LE FLAPS EXT LE FLAPS TRANSIT, then LE FLAPS EXT when slats are fully extended.when slats are fully extended.


Alternate Extension/Retraction of Trailing Edge Devices

Trailing Edge Flaps

Trailing Edge Flaps

In the event of “B” system hydraulic failure, an alternate method of extending and retracting the TE flaps is provided via the ALTERNATE FLAPS master switch. Unguarding and positioning the red ALTERNATE FLAPS master switch to ARM, arms the ALTERNATE FLAPS position switch. The ALTERNATE FLAPS position switch controls a flap drive unit which electrically extends and retracts the TE flaps. The switch must be held in the DOWN position until the TE flaps reach the desired position. No asymmetry protection is provided when using this alternate extension/retraction method.

See picture of See picture of Flap Drive UnitFlap Drive Unit


Alternate Extension of Leading Edge Devices

In the event of “B” system hydraulic failure, an alternate method of extending the LE devices is provided via the ALTERNATE FLAPS master switch. Unguarding and positioning the red ALTERNATE FLAPS master switch to ARM, arms the ALTERNATE FLAPS position switch and activates the standby hydraulic pump. When the ALTERNATE FLAPS position switch is momentarily held in the DOWN position, all LE devices drive to the fully extended position. The LE devices cannot be retracted utilizing the standby hydraulic system.

Leading Edge Flaps

Leading Edge Flaps

Leading Edge Slats

Leading Edge Slats


Trailing and Leading Edge Device Schematic

TE FLAPHANDLE

AIR DATACOMPUTER

TE FLAP BYPASSVALVE

SLATS SLATS

FLAPSFLAPS3 4 4

65

1 21

32

STBYRES

AUTOSLATCONTROL

LECONTROL

FROM “B”SYSTEM

RESERVOIR

“A” SYSTEM HYDRAULICS“B” SYSTEM HYDRAULICS

PTU

. . TE FLAPCONTROL

FLAPDRIVEUNIT

M

M

..

TE FLAPS.COMPARATOR

SWITCH

L R


Flap Load ReliefA flap load relief limiter provides a TE flap load relief function which protects the flaps from excessive air loads. This function is operative at the flaps 40 position only. When the TE flaps are at 40, the TE flaps will retract to 30 if the airspeed exceeds 158 kts. When airspeed is reduced to 153 kts., the TE flaps will re-extend to 40. The flap handle does not move during flap load relief operation, but the FLAP LOAD RELIEF light illuminates.

Trailing Edge Flaps

Trailing Edge Flaps


AutoslatsWhen TE flaps 1, 2 or 5 are selected, an autoslat function is available to automatically extend the LE slats to the fully extended position if the aircraft approaches a stall condition. The autoslat system is designed to enhance aircraft stall characteristics at high angles of attack during takeoff and approach to landing. As the aircraft approaches the stall angle, the LE slats automatically drive from extended to the fully extended position prior to stick shaker activation. The LE slats return to the extended position when the pitch angle is sufficiently reduced below the stall critical attitude. To summarize, autoslat operation is automatic when all of the following conditions exist:• Airborne• Trailing edge flaps 1, 2 or 5• Aircraft approaching stall condition

Leading Edge Slats

Leading Edge Slats


AutoslatsThe normal power source for autoslats is “B” system hydraulics. If the “B” system engine driven pump pressure falls below limits, an alternate source of power for autoslats is provided via the Power Transfer Unit (PTU). The PTU consists of a hydraulic motor connected to a hydraulic pump. The PTU motor is driven by “A” system hydraulics. The motor pressurizes the PTU pump, which supplies “B” system hydraulic pressure to the LE slats. There is no fluid interchange between “A” and “B” hydraulic systems. The PTU is automatically activated for autoslat operation when all of the following conditions exist:

• Airborne• Trailing edge flaps 1, 2 or 5• Aircraft approaching stall condition• “B” hydraulic system engine driven pump pressure falls below

limits

Leading Edge Slats

Leading Edge Slats


737-300/400 Hydraulic Schematic (specific to alternate autoslat operation; PTU)

“B” system hydraulics is the

normal power source for autoslat

operation. If the “B” system engine

driven pump pressure falls

below limits, an alternate source of

power for autoslats is

provided via a Power Transfer

Unit (PTU).



Supply


Case drain return

To return P

Hydraulic shutoff

No. 1fuel tank


Electric pump

Motor

“A” system

reservoir

Pneumatic air

ReturnStandpipe

(quantity 25%)

Engine driven pump

Autoslat operationPTU control valve “A”

Motor“B”

Pump

Power Transfer Unit (PTU)

P To return

Engine driven pump

Hydraulic shutoff

No. 2fuel tank


Motor

Electric pump

“B” system


Return



PTU use only.

b737-300/400 flight controls

Engineering