Flight Controls -System Description 737 Operations Manual
Yaw Damper
The yaw damper system prevents unwanted (Dutch) roll and provides turn coordination. The yaw damper coupler receives inputs from the yaw rate gyro and the air data computer. It then provides inputs to the rudder through 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 uses hydraulic system B pressure only. If hydraulic system 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. Then the YAW DAMPER switch disengages and the amber YAW DAMPER light illuminates and the YAW DAMPER cannot be reengaged.
Flight Controls -System Description
B
A
Copyright . The Boeing Company. See title page for details.
9.20.14 December 5, 2003
Flight Controls -System Description 737 Operations Manual
Speed Brakes
The speed brakes consist of flight spoilers and ground spoilers. Hydraulic system A powers all six ground spoilers, three on the upper surface of each wing. The SPEED BRAKE lever controls the spoilers. When the SPEED BRAKE lever is actuated all the spoilers extend when the airplane is on the ground, and only the flight spoilers extend when the airplane is in the air.
In Flight Operation
Operating the SPEED BRAKE lever in flight causes all flight spoiler panels to rise symmetrically to act as speed brakes. Caution should be exercised when deploying flight spoilers during a turn, as they greatly increase roll rate. When the speed brakes are in an intermediate position roll rates increase significantly. Moving the SPEED BRAKE lever past the FLIGHT detent causes buffeting and is not recommended in flight.
Ground Operation
During landing, the auto speed brake system operates when these conditions occur:
.
SPEED BRAKE lever is in the ARMED position
.
SPEED BRAKE ARMED light is illuminated
.
both thrust levers are retarded to IDLE
.
main landing gear wheels spin–up (more than 60 kts) – SPEED BRAKE
lever automatically moves to the UP position, and the flight spoilers
deploy
.
right main landing gear strut compresses on touchdown, causing the
mechanical linkage to open the ground spoiler bypass valve, and the
ground spoilers deploy
If a wheel spin–up signal is not detected, when the air/ground system senses ground mode, the SPEED BRAKE lever moves to the UP position, and all spoiler panels deploy automatically.
During a rejected takeoff (RTO), the auto speed brake system operates when these conditions occur:
.
main landing gear wheels spin–up (more than 60 kts)
.
takeoff is rejected, both thrust levers are retarded to IDLE and the reverse
thrust levers are positioned for reverse thrust – SPEED BRAKE lever
automatically moves to the UP position and all spoilers deploy.
After a RTO or landing, if either thrust lever is advanced, the SPEED BRAKE lever automatically moves to the DOWN detent and all spoiler panels retract. The spoiler panels may also be retracted by manually moving the SPEED BRAKE lever to the DOWN detent.
Flight Controls -System Description
Speed Brakes Schematic
UP
RIGHT MAIN LANDING GEAR
As installed
Flaps and Slats
The flaps and slats are high lift devices that increase wing lift and decrease stall
speed during takeoff, low speed maneuvering and landing. LE devices consist of four flaps and six slats: two flaps inboard and three slats outboard of each engine. Slats extend to form a sealed or slotted leading edge depending on the TE flap setting. The TE devices consist of triple slotted flaps inboard and outboard of each engine.
Copyright . The Boeing Company. See title page for details.
9.20.16 December 5, 2003
Flight Controls -System Description
737 Operations Manual
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. To prevent excessive structural loads from increased Mach at higher altitude, flap extension above 20,000 feet should not be attempted.
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