27-41-00
ALL ú ú 03 Page 7 ú Mar 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500
MAINTENANCE MANUAL
ELECTRO
MAGNETIC
CLUTCH JACKSCREW
MOTOR SAFETY AUXILIARY
ROD BRAKE
ASSEMBLY
SEE A
BRAKE
UNLOCK
GEAR
DRIVE RATCHET
GEAR PAWL
CLUTCH
REDUCTION DRIVE
GEAR GEAR
TORQUE LIMITER PRIMARY BRAKES
CLUTCH
AUTOPILOT
TRIM SERVO
TRIM SERVO UPPER CLUTCH INPUT GEAR
INPUT GEAR MEMBER
LOWER CLUTCH
MEMBER
RELEASE CAM AND
ROLLER ASSEMBLY
(4 LOCATIONS)
CLUTCH SPRING
CABLE DRUM
UNLOCK RING
RATCHET RING
UNLOCK ROLLER
(4 LOCATIONS)
PAWL
(4 LOCATIONS)
JACKSCREW
AUXILIARY BRAKE
(TOP VIEW)
A
Stabilizer Jackscrew and Gearbox Assembly
Figure 4
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27-41-00
ALL ú ú 01 Page 8 ú Nov 15/97
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
B. The primary brake system in the stabilizer trim gearbox prevents any aerodynamic loads on the stabilizer from rotating the jackscrew when the control system is not being operated. When the jackscrew shaft is driven by the jackscrew gearbox in a direction which increases the airloads on the stabilizer, a brake plate rotates through a ratchet producing a clicking sound in the assembly.
C. The auxiliary brake system is provided in case of primary brake system failure. When the jackscrew is turned by the jackscrew gearbox, the auxiliary brake system is released through a gear driven by the gearbox. If the primary brake system fails, the jackscrew shaft rotation applies the auxiliary brake to prevent any additional shaft rotation.
7. Primary Stabilizer Trim Actuator (Fig. 1)________________________________
A. The primary stabilizer trim actuator provides power to actuate the stabilizer during normal operation. The actuator consists of a two speed,three phase induction motor, two electromagnetic clutches, a speed change relay and a torque limiting clutch. The trim motor is powered by 115 volt, three phase, 400 cycle power and is capable of emergency operation on two phase power supply. Electromagnetic clutches control the direction of rotation of the output shaft and are powered by 28 volts dc. The speed change relay, is also powered by 28 volts dc, determines output shaft speed as a function of flap position. High speed (with flaps extended beyond zero degrees) is three times faster than low speed (for flaps retracted). A mechanical clutch on the output shaft limits the maximum output torque to protect components in jackscrew gearbox.
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