737-300/400 landing gear

of 56PT. METRO BATAVIAPT. METRO BATAVIADirectorate of OperationalDirectorate of Operational

737-300/400737-300/400LANDING GEARLANDING GEAR

NextNextMain MenuMain Menu QuitQuit


Instrument PanelsInstrument Panels

Landing Gear PanelLanding Gear Panel


Landing Gear PanelLanding Gear PanelLANDING GEAR Lever:LANDING GEAR Lever:UP –UP –Retract landing gear.Retract landing gear.

OFF –OFF –Hydraulic pressure is removed from the landing Hydraulic pressure is removed from the landing gear system.gear system.

DN –DN –Extend landing gear.Extend landing gear.


Landing Gear PanelLanding Gear PanelRed Landing Gear Indicator Lights:Red Landing Gear Indicator Lights:Illuminated –Illuminated –• Respective landing gear is not down and locked Respective landing gear is not down and locked

when either or both forward thrust levers are when either or both forward thrust levers are retarded retarded to idle.to idle.• Respective landing gear is in disagreement with Respective landing gear is in disagreement with

LANDING GEAR lever, i.e. landing gear is in LANDING GEAR lever, i.e. landing gear is in transit or is unsafe.transit or is unsafe.

Extinguished –Extinguished –Respective landing gear is up and locked with Respective landing gear is up and locked with LANDING GEAR lever UP or OFF.LANDING GEAR lever UP or OFF.


Landing Gear PanelLanding Gear PanelGreen Landing Gear Indicator Lights:Green Landing Gear Indicator Lights:Illuminated –Illuminated –Respective landing gear is down and locked. Respective landing gear is down and locked.

Extinguished –Extinguished –Respective landing gear is not down and locked.Respective landing gear is not down and locked.

Note: Landing gear configuration warning horn is Note: Landing gear configuration warning horn is deactivated with all landing gear down and deactivated with all landing gear down and locked.locked.

See picture of See picture of main gear and nose gearmain gear and nose gear

indicator sensorsindicator sensors


Landing Gear PanelLanding Gear PanelLANDING GEAR LIMIT Speed Placard:LANDING GEAR LIMIT Speed Placard:Indicates maximum speed when operating the Indicates maximum speed when operating the landing gear and after gear extension.landing gear and after gear extension.

See closeup picture of See closeup picture of LANDING GEAR LIMITLANDING GEAR LIMIT

speed placardspeed placard


Landing Gear PanelLanding Gear PanelLOCK OVERRIDE (Landing Gear Override) Trigger:LOCK OVERRIDE (Landing Gear Override) Trigger:Pull –Pull –Bypasses the landing gear lever locking system.Bypasses the landing gear lever locking system.

Note: When the aircraft is on the ground, the Note: When the aircraft is on the ground, the air/ground sensing system engages the landing air/ground sensing system engages the landing gear lever locking system and prevents the lever gear lever locking system and prevents the lever from moving to the UP position. When the aircraft from moving to the UP position. When the aircraft becomes airborne, the air/ground sensing system becomes airborne, the air/ground sensing system disengages the landing gear lever locking system disengages the landing gear lever locking system which allows the lever to be moved from DN to UP. which allows the lever to be moved from DN to UP. It is possible, however, for the air/ground sensing It is possible, however, for the air/ground sensing system to remain in the “ground-mode” even system to remain in the “ground-mode” even though the aircraft is in flight. In this case, the though the aircraft is in flight. In this case, the locking system will remain engaged after takeoff locking system will remain engaged after takeoff and the landing gear lever will not move to the UP and the landing gear lever will not move to the UP position. Non-normal procedures may position. Non-normal procedures may recommend pulling the landing gear override recommend pulling the landing gear override trigger to bypass the locking system and trigger to bypass the locking system and consequently raise the gear (reference your consequently raise the gear (reference your company operations manual).company operations manual).


Manual Gear ExtensionManual Gear Extension


Manual Gear ExtensionManual Gear ExtensionManual Gear Extension Handles:Manual Gear Extension Handles:If “A” system hydraulics is inoperative, the If “A” system hydraulics is inoperative, the landing gear may still be extended via the manual landing gear may still be extended via the manual extension system. The manual gear extension extension system. The manual gear extension handles are located in the flight deck floor, aft handles are located in the flight deck floor, aft and to the left of the First Officer’s seat. When and to the left of the First Officer’s seat. When the extension handles are pulled to their limit, the the extension handles are pulled to their limit, the respective gear will release from its locked respective gear will release from its locked position. Gravity and air loads will assist the position. Gravity and air loads will assist the gear in free-falling to the down and locked gear in free-falling to the down and locked position. The main gear manual extension position. The main gear manual extension handles need to be pulled out approximately 14 to handles need to be pulled out approximately 14 to 16 inches (35 to 40 cm) with a force of about 60 16 inches (35 to 40 cm) with a force of about 60 pounds. The nose gear manual extension handle pounds. The nose gear manual extension handle needs to be pulled out approximately 8 inches (20 needs to be pulled out approximately 8 inches (20 cm) with a force of about 80 pounds. Down and cm) with a force of about 80 pounds. Down and locked verification can be made using the green locked verification can be made using the green landing gear indicator lights.landing gear indicator lights.

Note: LANDING GEAR lever must be in DN or Note: LANDING GEAR lever must be in DN or OFF position to prevent hydraulic lockup during OFF position to prevent hydraulic lockup during manual extension. manual extension.


Main Gear ViewerMain Gear Viewer


Main Gear ViewerMain Gear Viewer

Plywood cover installed Plywood cover installed

Plywood cover removed Plywood cover removed

The main gear viewer is located in the main cabin floor. It is opposite the third window that is aft of the The main gear viewer is located in the main cabin floor. It is opposite the third window that is aft of the overwing exit, one foot left of center. After pulling back the carpet that is concealing the viewer, a overwing exit, one foot left of center. After pulling back the carpet that is concealing the viewer, a plywood cover will be exposed and needs to be removed. The pilot will now position their eyes over the plywood cover will be exposed and needs to be removed. The pilot will now position their eyes over the viewer. Two mirrors inside the viewer are used to ensure that the three red paint stripes on each main viewer. Two mirrors inside the viewer are used to ensure that the three red paint stripes on each main gear are visible and in horizontal alignment. It may be necessary to turn on the wheel well lights.gear are visible and in horizontal alignment. It may be necessary to turn on the wheel well lights.

Note: Depending on the aircraft seat configuration, some viewers may be positioned under an aisle seat.Note: Depending on the aircraft seat configuration, some viewers may be positioned under an aisle seat.


Main Gear Paint StripesMain Gear Paint Stripes

The red paint stripes are located on the lower side strut of each main gear. When looking at The red paint stripes are located on the lower side strut of each main gear. When looking at the mirrors in the main gear viewer, the three red paint stripes should be visible and in the mirrors in the main gear viewer, the three red paint stripes should be visible and in horizontal alignment. This is an indication that the respective main landing gear is down and horizontal alignment. This is an indication that the respective main landing gear is down and locked.locked.

See picture of mainSee picture of maingear viewer mirrorsgear viewer mirrors


Nose Gear ViewerNose Gear Viewer


Nose Gear ViewerNose Gear Viewer

Cover plate closed Cover plate closed

Cover plate openCover plate open

The nose gear viewer is located on the flight deck floor, just inside the door. Access to the viewer is The nose gear viewer is located on the flight deck floor, just inside the door. Access to the viewer is made by opening the cover plate. Under the cover plate is a small circular viewing window. As the made by opening the cover plate. Under the cover plate is a small circular viewing window. As the pilot looks into the viewing window, two red arrow heads should be visible. If the two red arrow pilot looks into the viewing window, two red arrow heads should be visible. If the two red arrow heads are facing each other and appear to be in alignment (in contact), the nose gear is down and heads are facing each other and appear to be in alignment (in contact), the nose gear is down and locked.locked.


Nose Gear Arrow HeadsNose Gear Arrow Heads

One nose gear arrow head is located on the nose gear lock brace and the other arrow head is located One nose gear arrow head is located on the nose gear lock brace and the other arrow head is located on the nose gear lock link. When looking into the nose gear viewing window the two red arrows on the nose gear lock link. When looking into the nose gear viewing window the two red arrows should be visible. If the two red arrow heads are facing each other and appear to be in alignment should be visible. If the two red arrow heads are facing each other and appear to be in alignment (in contact), the nose gear is down and locked. It may be necessary to turn on the wheel well lights.(in contact), the nose gear is down and locked. It may be necessary to turn on the wheel well lights.

See picture ofSee picture ofviewing windowviewing window

in wheel wellin wheel well



Autobrake PanelAutobrake Panel



AUTO BRAKE DISARM Light:AUTO BRAKE DISARM Light:Illuminated –Illuminated –• RTO is selected on the ground.RTO is selected on the ground.

When RTO is selected on the ground, the When RTO is selected on the ground, the AUTO BRAKE DISARM light will illuminate AUTO BRAKE DISARM light will illuminate while the braking while the braking system performs a self-system performs a self-

test. test. One to two seconds later, the light One to two seconds later, the light will will extinguish if the self-test was extinguish if the self-test was successful.successful.

• Manual brakes applied during RTO or landing.Manual brakes applied during RTO or landing.• A fault exists in the automatic braking system.A fault exists in the automatic braking system.• Antiskid has been selected off.Antiskid has been selected off.• Thrust levers are advanced during an RTO or Thrust levers are advanced during an RTO or

landing.landing.• Landing made with RTO selected.Landing made with RTO selected.• SPEED BRAKE lever moved to DOWN detent SPEED BRAKE lever moved to DOWN detent

during an RTO or landing.during an RTO or landing.

Extinguished –Extinguished –• Autobrakes armed.Autobrakes armed.• AUTO BRAKE select switch is positioned to OFF.AUTO BRAKE select switch is positioned to OFF.



AUTO BRAKE Select Switch:AUTO BRAKE Select Switch:OFF –OFF –Automatic braking system deactivated.Automatic braking system deactivated.

1, 2, 3, or MAX –1, 2, 3, or MAX –Selects desired deceleration rate for landing.Selects desired deceleration rate for landing.

Note: Switch must be pulled-out to select MAX Note: Switch must be pulled-out to select MAX deceleration.deceleration.

RTO (Rejected Takeoff) –RTO (Rejected Takeoff) –At or above 90 knots during takeoff, At or above 90 knots during takeoff, automatically applies maximum brake automatically applies maximum brake pressure (3,000 psi) when thrust levers are pressure (3,000 psi) when thrust levers are retarded to idle.retarded to idle.



Antiskid PanelAntiskid Panel



ANTI SKID INOP Light:ANTI SKID INOP Light:Illuminated –Illuminated –• The antiskid fault monitoring system has The antiskid fault monitoring system has detected a system fault.detected a system fault.• Antiskid switch is OFF.Antiskid switch is OFF.

Extinguished –Extinguished –Antiskid system is operating normally.Antiskid system is operating normally.



ANTISKID Control Switch:ANTISKID Control Switch:ON (guarded position) –ON (guarded position) –• Provides power to the antiskid unit for both Provides power to the antiskid unit for both

inboard and outboard antiskid protection.inboard and outboard antiskid protection.

OFF –OFF –• Disables the antiskid system.Disables the antiskid system.• Illuminates the ANTI SKID INOP light.Illuminates the ANTI SKID INOP light.• Illuminates the AUTO BRAKE DISARM light if Illuminates the AUTO BRAKE DISARM light if

the autobrake system is armed.the autobrake system is armed.



Hydraulic Brake Pressure IndicatorHydraulic Brake Pressure Indicator


Hydraulic Brake Pressure IndicatorHydraulic Brake Pressure Indicator

HYD BRAKE PRESS Indicator:HYD BRAKE PRESS Indicator:Indicates brake accumulator pressure.Indicates brake accumulator pressure.• Normal accumulator pressure – 3,000 psiNormal accumulator pressure – 3,000 psi• Maximum accumulator pressure – 3,500 psiMaximum accumulator pressure – 3,500 psi• Normal accumulator precharge pressure – 1,000 Normal accumulator precharge pressure – 1,000 psipsi

Note: The brake accumulator is attached to the aft Note: The brake accumulator is attached to the aft wall in the main gear wheel well, aircraft right. The wall in the main gear wheel well, aircraft right. The accumulator precharge is either compressed air or accumulator precharge is either compressed air or nitrogen.nitrogen.

See picture of See picture of brake accumulatorbrake accumulator


Rudder/Brake PedalsRudder/Brake Pedals

Rudder/Brake Pedals:Rudder/Brake Pedals:Push full pedal –Push full pedal –Turns nose wheel up to 7Turns nose wheel up to 7° ° left or right of center.left or right of center.

Push top of pedal only –Push top of pedal only –Activates wheel brakes.Activates wheel brakes.

Note: See the Flight Controls presentation for a Note: See the Flight Controls presentation for a description of the rudder.description of the rudder.


Control StandControl Stand

Parking BrakeParking Brake



PARKING BRAKE PULL Lever:PARKING BRAKE PULL Lever:Positioned forward –Positioned forward –Parking brake is released.Parking brake is released.

Pulled aft –Pulled aft –Sets the parking brake when either Captain’s Sets the parking brake when either Captain’s or First Officer’s brake pedals are fully or First Officer’s brake pedals are fully depressed.depressed.



PARK BRAKE LIGHT:PARK BRAKE LIGHT:Illuminated –Illuminated –Parking brake is set.Parking brake is set.

Extinguished –Extinguished –Parking brake is released.Parking brake is released.



Nose Wheel Steering SwitchNose Wheel Steering Switch

1111

1111 AS INSTALLEDAS INSTALLED


Nose Wheel Steering SwitchNose Wheel Steering Switch

NOSE WHEEL STEERING Switch:NOSE WHEEL STEERING Switch:NORM (guarded position) –NORM (guarded position) –Hydraulic system “A” is providing power for Hydraulic system “A” is providing power for the nose wheel steering system.the nose wheel steering system.

ALT –ALT –Hydraulic system “B” is providing power for Hydraulic system “B” is providing power for the nose wheel steering system.the nose wheel steering system.

1111

1111 AS INSTALLEDAS INSTALLED


Nose Wheel Steering WheelNose Wheel Steering Wheel



Nose Wheel Steering WheelNose Wheel Steering Wheel::Rotate –Rotate –• Turns nose wheel up to 78Turns nose wheel up to 78° ° left or right of center.left or right of center.• Overrides rudder pedal steering.Overrides rudder pedal steering.

Note: The nose wheel steering wheel is attached Note: The nose wheel steering wheel is attached to the side wall, left of the Captain’s control to the side wall, left of the Captain’s control column. The steering wheel is also known as the column. The steering wheel is also known as the tiller.tiller.



Nose Wheel Steering IndicatorNose Wheel Steering Indicator::LEFT –LEFT –Indicates nose wheel steering displacement left of Indicates nose wheel steering displacement left of center position.center position.

CENTER –CENTER –Normal straight ahead position.Normal straight ahead position.

RIGHT –RIGHT –Indicates nose wheel steering displacement right Indicates nose wheel steering displacement right of center position.of center position.

This concludes the review of the Landing Gear controls and indicators. This concludes the review of the Landing Gear controls and indicators. The next section will discuss the system in greater detail.The next section will discuss the system in greater detail.

Click Click NextNext to continue. to continue.


Landing Gear OperationLanding Gear Operation

The aircraft has two main landing gear and single nose gear. Each gear is equipped The aircraft has two main landing gear and single nose gear. Each gear is equipped with two tire and wheel assemblies. Each main gear wheel is fitted with disc-type with two tire and wheel assemblies. Each main gear wheel is fitted with disc-type hydraulic brakes which are modulated by the antiskid system. To absorb the impact hydraulic brakes which are modulated by the antiskid system. To absorb the impact on landing, air-oil type shock struts are installed on all three gear. “A” system on landing, air-oil type shock struts are installed on all three gear. “A” system hydraulics supplies power for normal retraction, extension, and nose wheel steering. hydraulics supplies power for normal retraction, extension, and nose wheel steering.


737-300/400 Hydraulic Schematic (specific to landing gear)

“A” system hydraulics

supplies power for normal retraction,

extension, and nose wheel

steering.

“A” system hydraulics

supplies power for normal retraction,

extension, and nose wheel

steering.

“B” system pressure

“A” system pressure

Supply

Standby system pressure

Case drain return

Electric pump

Motor

Hydraulic shutoff

Engine driven pump

“A” system

reservoir

Return

No. 1fuel tank

To reservoir Hydraulic heat exchanger

Nose wheel steering

Landing gear transfer unit

Landing gear


737-300/400 Hydraulic Schematic (specific to landing gear

transfer unit)

A landing gear transfer unit is installed in the main gear wheel well. When all of the following conditions exist, “B” system hydraulics will retract the landing gear via the landing gear transfer unit:• Airborne• No. 1 engine drops below 56% N2 • LANDING GEAR handle in the UP position• Landing gear not up

When this becomes especially useful is during a loss of the No. 1 engine immediately after takeoff. With the No. 1 engine inoperative, the “A” system engine driven pump is also inoperative. Even though the “A” system electric pump is operating normally, the volume output of the pump is not great enough to raise the gear at a rate which is required during single engine operations. As the No. 1 engine N2 gauge drops below 56%, the landing gear transfer unit will connect “B” system hydraulics to the landing gear. “B” system will now raise the gear at a normal retraction rate.

A landing gear transfer unit is installed in the main gear wheel well. When all of the following conditions exist, “B” system hydraulics will retract the landing gear via the landing gear transfer unit:• Airborne• No. 1 engine drops below 56% N2 • LANDING GEAR handle in the UP position• Landing gear not up

When this becomes especially useful is during a loss of the No. 1 engine immediately after takeoff. With the No. 1 engine inoperative, the “A” system engine driven pump is also inoperative. Even though the “A” system electric pump is operating normally, the volume output of the pump is not great enough to raise the gear at a rate which is required during single engine operations. As the No. 1 engine N2 gauge drops below 56%, the landing gear transfer unit will connect “B” system hydraulics to the landing gear. “B” system will now raise the gear at a normal retraction rate.



Supply


Case drain return

Motor

Electric pump

Engine driven pump

Hydraulic shutoff

“B” system

reservoirReturn

No. 2fuel tank

To reservoirHydraulic heat exchanger

Electric pump

Motor

Hydraulic shutoff

Engine driven pump

“A” system

reservoir

Return

No. 1fuel tank


Nose wheel steering

Landing gear transfer unit

Landing gear



The main gear is locked in the “down” position by a folding lock strut, and held in the The main gear is locked in the “down” position by a folding lock strut, and held in the “up” position by an uplock hook and uplock roller. When the LANDING GEAR lever is “up” position by an uplock hook and uplock roller. When the LANDING GEAR lever is moved to the UP position, the main gear retracts inboard into the main gear wheel moved to the UP position, the main gear retracts inboard into the main gear wheel well. During retraction, main gear wheel rotation is stopped by “A” system hydraulics well. During retraction, main gear wheel rotation is stopped by “A” system hydraulics via the alternate brake metering valves. When the main gear is fully retracted, the via the alternate brake metering valves. When the main gear is fully retracted, the doors are faired with the fuselage. Rubber blade-type seals and oversized hubcaps doors are faired with the fuselage. Rubber blade-type seals and oversized hubcaps complete the fairing of the outboard wheels.complete the fairing of the outboard wheels.

See picture ofSee picture ofuplock hook and uplock hook and

uplock rolleruplock roller



The nose gear is locked in the “up” and “down” position by a folding lock strut. When The nose gear is locked in the “up” and “down” position by a folding lock strut. When the LANDING GEAR lever is moved to the UP position, the nose gear retracts forward into the LANDING GEAR lever is moved to the UP position, the nose gear retracts forward into the nose gear wheel well. As the gear retracts, nose gear wheel rotation is stopped by the nose gear wheel well. As the gear retracts, nose gear wheel rotation is stopped by tire contact with the snubbers. The snubbers are installed on the ceiling of the nose gear tire contact with the snubbers. The snubbers are installed on the ceiling of the nose gear wheel well. The nose gear doors are mechanically linked to the nose gear and will fair wheel well. The nose gear doors are mechanically linked to the nose gear and will fair with the fuselage when the gear is fully retracted.with the fuselage when the gear is fully retracted.

See picture ofSee picture ofsnubberssnubbers


Brake SystemBrake System

The brake system includes a normal brake system, an alternate brake system, one brake The brake system includes a normal brake system, an alternate brake system, one brake accumulator, an autobrake system, antiskid protection, and a parking brake. Each main gear accumulator, an autobrake system, antiskid protection, and a parking brake. Each main gear wheel has a multi-disc hydraulic powered brake. Four brake wear indicator pins are provided wheel has a multi-disc hydraulic powered brake. Four brake wear indicator pins are provided on each main gear to indicate when the brakes need to be replaced. on each main gear to indicate when the brakes need to be replaced.

See picture of See picture of one brakeone brake

wear indicator pin.wear indicator pin.


Brake SystemBrake System

Each brake is provided with pistons which actuate the brake when hydraulic pressure is Each brake is provided with pistons which actuate the brake when hydraulic pressure is applied. The brake system is manually controlled by the the Captain’s or First Officer’s brake applied. The brake system is manually controlled by the the Captain’s or First Officer’s brake pedals thru linkage and cables to the brake metering valve for each main gear. The intensity of pedals thru linkage and cables to the brake metering valve for each main gear. The intensity of pressure established in the brakes varies directly with the amount of pedal force maintained. pressure established in the brakes varies directly with the amount of pedal force maintained. The nose gear wheels do not incorporate any type of braking system.The nose gear wheels do not incorporate any type of braking system.


737-300/400 Hydraulic Schematic (specific to the normal

brake system)

“B” system hydraulics

supplies power to the normal

braking system for each main gear wheel.

“B” system hydraulics

supplies power to the normal

braking system for each main gear wheel.



Supply


Case drain return

Motor

Electric pump

Engine driven pump

Hydraulic shutoff

“B” system

reservoirReturn

No. 2fuel tank


Normal brakes


737-300/400 Hydraulic Schematic (specific to the alternate

brake system)

If “B” hydraulic system loses

pressure, separate hydraulic lines are

utilized to automatically

supply “A” hydraulic system pressure to each main gear wheel. This is known as alternate brakes

If “B” hydraulic system loses

pressure, separate hydraulic lines are

utilized to automatically

supply “A” hydraulic system pressure to each main gear wheel. This is known as alternate brakes



Supply


Case drain return

Motor

Electric pump

Engine driven pump

Hydraulic shutoff

“B” system

reservoirReturn

No. 2fuel tank


Accumulator isolation valve

Electric pump

Motor

Hydraulic shutoff

Engine driven pump

“A” system

reservoir

Return

No. 1fuel tank


Normal brakes

Alternate Brakes Selector Valve

Alternate brakes


737-300/400 Hydraulic Schematic (specific to the

accumulator braking)

If “A” and “B” hydraulic system pressure is lost,

the brake accumulator will supply trapped

hydraulic fluid to each main gear wheel. Enough

pressure exists in the accumulator

for approximately six brake

applications. Note:

Antiskid protection is available during

accumulator braking.

If “A” and “B” hydraulic system pressure is lost,

the brake accumulator will supply trapped

hydraulic fluid to each main gear wheel. Enough

pressure exists in the accumulator

for approximately six brake

applications. Note:

Antiskid protection is available during

accumulator braking.



Supply


Case drain return

Motor

Electric pump

Engine driven pump

Hydraulic shutoff

“B” system

reservoirReturn

No. 2fuel tank


Accumulator isolation valve

Electric pump

Motor

Hydraulic shutoff

Engine driven pump

“A” system

reservoir

Return

No. 1fuel tank


Alternate brakes

Normal brakes

Alternate Brakes Selector Valve

P

Hydraulic brake pressure accumulator

See picture of See picture of brake accumulatorbrake accumulator


Autobrake SystemAutobrake System

The autobrake system provides automatic braking upon landing when a pre-selected The autobrake system provides automatic braking upon landing when a pre-selected deceleration rate (1, 2, 3 or MAX) is chosen. It also provides automatic braking in the deceleration rate (1, 2, 3 or MAX) is chosen. It also provides automatic braking in the case of a rejected takeoff (RTO) after a wheel speed of 90 knots is attained. The case of a rejected takeoff (RTO) after a wheel speed of 90 knots is attained. The autobrake system operates utilizing “B” system hydraulics only. If the “B” hydraulic autobrake system operates utilizing “B” system hydraulics only. If the “B” hydraulic system is inoperative, the autobrake system is also inoperative. Antiskid protection is system is inoperative, the autobrake system is also inoperative. Antiskid protection is available during autobrake operation.available during autobrake operation.



If automatic braking is desired upon landing, a deceleration rate must be selected while If automatic braking is desired upon landing, a deceleration rate must be selected while still airborne. When a rate is selected, a self-test is initiated and the AUTOBRAKE DISARM still airborne. When a rate is selected, a self-test is initiated and the AUTOBRAKE DISARM light will not illuminate unless the system has detected a fault. After landing, autobrake light will not illuminate unless the system has detected a fault. After landing, autobrake application begins when both forward thrust levers are retarded to idle and wheel speed of application begins when both forward thrust levers are retarded to idle and wheel speed of at least one wheel on each main gear is greater than 60 knots. Autobrake pressure will at least one wheel on each main gear is greater than 60 knots. Autobrake pressure will gradually increase during the first three seconds after touchdown. The system will then gradually increase during the first three seconds after touchdown. The system will then maintain a constant deceleration rate and, if allowed, will bring the aircraft to a complete maintain a constant deceleration rate and, if allowed, will bring the aircraft to a complete stop unless braking is terminated by the pilot or a system fault is detected. stop unless braking is terminated by the pilot or a system fault is detected.



To maintain the selected deceleration rate, pressure from the autobrake system is To maintain the selected deceleration rate, pressure from the autobrake system is reduced as additional drag (thrust reversers, spoilers) contributes to the total reduced as additional drag (thrust reversers, spoilers) contributes to the total deceleration.deceleration.

The following deceleration rates are provided:The following deceleration rates are provided:““1” – 4 feet/second1” – 4 feet/second22

““2” – 5 feet/second2” – 5 feet/second22

““3” – 7.2 feet/second3” – 7.2 feet/second22

““MAX” – 14 feet/secondMAX” – 14 feet/second22



If automatic braking is desired during a rejected takeoff, the AUTO BRAKE select If automatic braking is desired during a rejected takeoff, the AUTO BRAKE select switch must be positioned to RTO. After selecting RTO, the AUTO BRAKE DISARM switch must be positioned to RTO. After selecting RTO, the AUTO BRAKE DISARM light will illuminate while the braking system performs a self-test. One to two seconds light will illuminate while the braking system performs a self-test. One to two seconds later, the light will extinguish if the self-test was successful.later, the light will extinguish if the self-test was successful.



To arm the RTO mode prior to takeoff, the following conditions must exist:To arm the RTO mode prior to takeoff, the following conditions must exist:• AUTO BRAKE select switch must be in the RTO position.AUTO BRAKE select switch must be in the RTO position.• Aircraft must be on the ground.Aircraft must be on the ground.• Autobrake and antiskid circuits must be operational.Autobrake and antiskid circuits must be operational.• Both forward thrust levers must be positioned to idle.Both forward thrust levers must be positioned to idle.• Wheel speed must be less than 60 knots.Wheel speed must be less than 60 knots.

After a successful test, the autobrake system is now in an unarmed “waiting-mode.”After a successful test, the autobrake system is now in an unarmed “waiting-mode.”



When wheel speed is greater than 60 knots, RTO mode is now in a “semi-armed” mode. When wheel speed is greater than 60 knots, RTO mode is now in a “semi-armed” mode. However, if the takeoff is rejected with a wheel speed between 60 and 90 knots, automatic However, if the takeoff is rejected with a wheel speed between 60 and 90 knots, automatic braking is not applied and the AUTO BRAKE DISARM light illuminates.braking is not applied and the AUTO BRAKE DISARM light illuminates.

Once wheel speed is greater than 90 knots, the autobrake system is “fully-armed.” If the Once wheel speed is greater than 90 knots, the autobrake system is “fully-armed.” If the takeoff is rejected and the forward thrust levers are retarded to idle, maximum braking takeoff is rejected and the forward thrust levers are retarded to idle, maximum braking (3,000 psi) is (3,000 psi) is immediatelyimmediately applied to all four wheels. The system will bring the aircraft to a applied to all four wheels. The system will bring the aircraft to a complete stop unless braking is terminated by the pilot or a system fault is detected.complete stop unless braking is terminated by the pilot or a system fault is detected.



If the takeoff was normal and an RTO was not initiated, the RTO mode is automatically If the takeoff was normal and an RTO was not initiated, the RTO mode is automatically disarmed when the right main gear strut extends (air/ground sensing system in “air-mode”). disarmed when the right main gear strut extends (air/ground sensing system in “air-mode”). When this occurs, the AUTO BRAKE DISARM light will not illuminate and the select switch When this occurs, the AUTO BRAKE DISARM light will not illuminate and the select switch must manually be positioned to OFF. However, if a landing is made with the select switch must manually be positioned to OFF. However, if a landing is made with the select switch still in RTO, automatic braking will not occur and the AUTO BRAKE DISARM light will still in RTO, automatic braking will not occur and the AUTO BRAKE DISARM light will illuminate two minutes after touchdown.illuminate two minutes after touchdown.


Antiskid ProtectionAntiskid Protection

Antiskid protection is provided in the normal and alternate brake systems. The types Antiskid protection is provided in the normal and alternate brake systems. The types of antiskid protection available include normal, touchdown, and locked wheel. When of antiskid protection available include normal, touchdown, and locked wheel. When the pilot depresses the brake pedals, the brake metering valves open and hydraulic the pilot depresses the brake pedals, the brake metering valves open and hydraulic fluid is directed to the brakes via the antiskid valves. fluid is directed to the brakes via the antiskid valves.



Normal brakes (“B” system hydraulics) provide Normal brakes (“B” system hydraulics) provide each main gear wheeleach main gear wheel with individual with individual antiskid protection. Therefore, each individual wheel has its own normal antiskid antiskid protection. Therefore, each individual wheel has its own normal antiskid valve. When the normal antiskid system detects a skid, the associated antiskid valve valve. When the normal antiskid system detects a skid, the associated antiskid valve for the affected wheel(s) reduces brake pressure until the skidding stops. Once the for the affected wheel(s) reduces brake pressure until the skidding stops. Once the skidding has stopped, brake pressure is increased via the associated antiskid valve.skidding has stopped, brake pressure is increased via the associated antiskid valve.



Alternate brakes (“A” system hydraulics) provide Alternate brakes (“A” system hydraulics) provide each main gear wheel each main gear wheel pairspairs, instead of , instead of individual wheels, with antiskid protection. Therefore, each wheel pair has its own individual wheels, with antiskid protection. Therefore, each wheel pair has its own alternate antiskid valve. The mated pairs are left and right inboard wheels, and left and alternate antiskid valve. The mated pairs are left and right inboard wheels, and left and right outboard wheels. When the alternate antiskid system detects a skid, the right outboard wheels. When the alternate antiskid system detects a skid, the associated antiskid valve for the affected pair reduces brake pressure until the skidding associated antiskid valve for the affected pair reduces brake pressure until the skidding stops. Once the skidding has stopped, brake pressure is increased via the associated stops. Once the skidding has stopped, brake pressure is increased via the associated antiskid valve.antiskid valve.



Normal, touchdown and locked wheel antiskid protection are all available from the Normal, touchdown and locked wheel antiskid protection are all available from the normal antiskid system. However, touchdown and locked wheel protection are not normal antiskid system. However, touchdown and locked wheel protection are not available from the alternate antiskid system.available from the alternate antiskid system.


Air/Ground SenseAir/Ground Sense

Certain systems require electrical control depending upon the condition of the aircraft Certain systems require electrical control depending upon the condition of the aircraft (airborne or on the ground). The condition of the aircraft is sensed by the landing gear (airborne or on the ground). The condition of the aircraft is sensed by the landing gear air/ground sensors. There are two air/ground sensors installed on the aircraft. The air/ground sensors. There are two air/ground sensors installed on the aircraft. The main gear sensor is located in the main gear wheel well and is connected to the right main gear sensor is located in the main gear wheel well and is connected to the right main gear via a teleflex cable. The nose gear sensor is located on the steering collar main gear via a teleflex cable. The nose gear sensor is located on the steering collar of the nose gear shock strut. The picture above indicates where the air/ground of the nose gear shock strut. The picture above indicates where the air/ground sensors are located.sensors are located.

Teleflex cable Teleflex cable for main gear for main gear

air/ground air/ground sensorsensor

Nose gear Nose gear air/ground air/ground

sensorsensor

See picture of See picture of teleflex cable for mainteleflex cable for maingear air/ground sensegear air/ground sense

See picture ofSee picture ofnose gearnose gear

air/ground sensorair/ground sensor



The parking brake is set by depressing either the Captain’s or First Officer’s brake The parking brake is set by depressing either the Captain’s or First Officer’s brake pedals fully while simultaneously pulling the PARKING BRAKE lever aft. This pedals fully while simultaneously pulling the PARKING BRAKE lever aft. This mechanically latches the brake pedals in the depressed position and commands the mechanically latches the brake pedals in the depressed position and commands the parking brake valve to close. The PARK BRAKE LIGHT will illuminate indicating the parking brake valve to close. The PARK BRAKE LIGHT will illuminate indicating the parking brake is set. The parking brake is released by depressing either the Captain’s or parking brake is set. The parking brake is released by depressing either the Captain’s or First Officer’s brake pedals until the PARKING BRAKE lever releases.First Officer’s brake pedals until the PARKING BRAKE lever releases.


Nose Wheel Steering Nose Wheel Steering Depressurization ValveDepressurization Valve

To depressurize the steering system, a lockout pin may be installed in the nose wheel To depressurize the steering system, a lockout pin may be installed in the nose wheel steering depressurization valve. This is useful if an aircraft is being towed while the “A” steering depressurization valve. This is useful if an aircraft is being towed while the “A” hydraulic system is pressurized. Some airline operators may use the depressurization hydraulic system is pressurized. Some airline operators may use the depressurization valve during push-back from their boarding gate to ensure the safety of the ground valve during push-back from their boarding gate to ensure the safety of the ground personnel.personnel.

737-300/400 landing gear

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