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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
D. During retraction, the return flow from the actuator head end bypasses the lock piston through a check valve, and the preload spring holds the lock piston in the locked position. The spring bias of the preload spring also prevents pressure surges from inadvertently unlocking the serrated disks while the thrust reverser is stowed. The pivot arm for the lock lever follows the motion of the nonrotating disk and is spring biased by the torsion spring toward the extend direction. This spring bias is necessary to make sure that the actuator lock proximity sensor, whose target is installed on the lock lever, correctly shows the lock condition. The spring bias also makes sure that the locking disks stay apart when engagement is not intended.
E. As the center hydraulic actuator nears the stowed position during retraction, the helical lock spring becomes compressed which moves the splined, nonrotating disk against the rotating disk. This causes the two disks to ratchet until the actuator piston is against the bottom. The center hydraulic actuator is locked against extension by serration engagement which prevents acme screw rotation and hence piston movement.
11. Synchronous Shaft Locks (Sync Locks)
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A. The lower non-locking actuator on each sleeve is equipped with a sync lock. This sync lock is attached to the threaded end of the actuator where the manual drive mechanism was previously attached. The sync lock is equipped with a 0.25 inch square drive that is inserted into the worm gear and flex shaft mechanism of the actuator. A rotor and pin lock inside the sync lock holds the flex shaft in the locked position unless the sync lock is energized. When energized, the solenoid inside the sync lock pulls an armature which, in turn, pulls the two lock pins away from the teeth of a rotor, allowing it and its connected square drive to rotate. Due to the electrical command architecture, the sync lock will unlock prior to hydraulic fluid becoming available to the system.
12. Rotary Flexible Drive Shafts (Flexshafts) and Tubing (Fig. 10)
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A. Rotary flexshafts are used to synchronize non-locking hydraulic actuators and the locking hydraulic actuator on each thrust reverser half. The flexshafts are connected to worm gears of the hydraulic actuator through a 0.25 inch square drive fitting. The flexshaft goes through the extend hydraulic tubing which connects the hydraulic actuators. Hydraulic fluid flows from locking hydraulic actuator through the extend tubing to upper and lower non-locking hydraulic actuators. The flexshaft will make the hydraulic actuators drive or retard each other and thereby keep synchronization.
13. Thrust Reverser Opening System (Fig. 11)
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A. Safety requires the use of a hold-open rod before getting below an open thrust reverser. The hold-open rod engages a fitting on each side of the engine fan case. This permits the thrust reverser to be opened to the 45 degree position.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
A
THRUST REVERSER UPPER HYDRAULIC
TORQUE BOX ACTUATOR (NON-LOCKING)
ROTARY FLEXSHAFTS
AND TUBING
CENTER HYDRAULIC ACTUATOR (LOCKING)
LOWER HYDRAULIC ACTUATOR (NON-LOCKING)
WORM WHEEL
OIL PASSAGE
TUBENUT
SLIP JOINT
WORM GEAR HYDRAULIC ACTUATOR NON-LOCKING FLEXSHAFT TUBING HYDRAULIC
A-A
Figure 10 Rotary Flexshafts and Tubing
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