B.
Angle Gearboxes
(1)
The angle gearboxes are mounted on the aft side of the landing gear beam forward of the ground spoiler panels. The torque tubes attaching to the angle gearbox provide the flap drive between the inboard flap tranmissions.
C.
Right Angle Gearboxes
(1)
The right angle gearboxes are mounted on the wheel well aft bulkhead aft of the inboard flap inboard transmissions. The gearboxes provide a 90-degree change in torque tube direction in the flap drive between the flap power unit and inboard flap inboard transmissions. The right angle gearbox in the right wheel well is a reversing gearbox which reverses torque tube rotation for the right wing.
12. Flap Transmission Assembly__________________________
A. The flap transmission assembly converts flap torque tube rotation into linear motion to extend or retract the trailing edge flaps. Each transmission assembly consists of a transmission gearbox, a universal joint, and a ball nut and screw actuator (Fig. 6).
B. The transmission assemblies are mounted on the flap tracks just aft of the landing gear support beam and the wing rear spar (Fig. 1). Each transmission assembly is enclosed in a flap track fairing. Flap drive system torque tubes attach to the input shafts on the transmission gearbox.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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737-300/400/500MAINTENANCE MANUAL
C. The transmission gearbox contains mating bevel gears and a torque limiter. The inboard transmission assembly on each flap incorporates a no-back friction brake. The torque limiter consists of two springs wound together, an internal shaft with two bevel gears, an output shaft, and a housing. If a flap jams, excessive torque on the screw actuator will cause the springs to expand and bind against the torque limiter housing. The torque limiter is designed to operate in either direction of flap travel. Excessive torque is absorbed by the torque limiter until the flap hydraulic motor stalls. At extended flap positions, the no-back friction brake prevents flap retraction due to airloads. The brake consists of a brake disk, ratchet wheel, and two pawls. At extended flap positions, uploads transmitted to the jackscrew force the brake disk against the ratchet wheel resulting in a braking action. The brake action does not oppose flap extension since the pawls do not engage the ratchet wheel in this direction of rotation. The brake ratchets oppose retraction and in order to retract the flaps it is necessary to slip the no-back friction brake from the upstream side. The transmission gearbox is a sealed unit filled with MIL-H-5606 hydraulic oil.
D. The ball nut and screw actuator consists of a jackscrew, a downstop nut, and recirculating ball bearing nut. The universal joint attaches the jackscrew to the transmission gearbox. The universal joint allows angular deflection of the jackscrew during flap operation. The ball bearing nut is attached to the midflap through a gimbal assembly. During flap operation, the ball bearing nut is restrained from turning and travels fore and aft on the rotating screw to extend and retract the flaps. Total jackscrew travel is restricted by upstops and downstops on the ball nut and screw actuator. Upstop lugs on the ball bearing nut and on the universal joint limit flap travel when the flaps are retracted. Downstop lugs on the ball bearing nut and on the downstop nut limit flap travel when the flaps are extended. The ball bearing nut has drilled passages and externally mounted tubes that allow recirculation of the steel balls. Scrapers and wipers are incorporated at each end of the ball nut to remove foreign material from the jackscrew. An oil reservoir in the ball bearing nut provides lubrication of the nut and screw actuator.
13. Flap Alternate Drive Unit_________________________
A. The flap alternate drive unit uses electric power to drive the flap system if a failure prevents normal hydraulic operation of the flap system. The unit is mounted on the flap power unit located on the aft bulkhead in the right wheel well. The alternate drive unit is energized by actuating the alternate flaps arm switch and the control switch located on the overhead panel. A 115/200-volt ac motor and a gearbox are the primary alternate drive unit components. The gearbox incorporates a double planetary reduction gear train and a disconnect and overload clutch.
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