(e)
Hydraulic fluid is prevented from entering the extend cavity of the two lock actuators by a rotary pressure seal, until the spring loading of the lock valve is overcome by hydraulic pressure. Movement of the lock valve opens a passage to the extend cavity and operates a lock lever to disengage the locking sleeve.
(f)
As the actuator piston extends, the acme nut in the piston head rotates the acme screw shaft and worm gear to drive the flexible shafts for synchronized operation. The actuator piston pushes the translating cowl rearward, exposing the cascades. The blocker doors are pulled inward by the blocker door drag links to block the fan duct downstream and direct the gas flow through the cascades.
(g)
The feedback actuators, attached to the translating cowl,
extend as the cowl moves rearward. The spiral shaft rotates
the feedback arm and the movement is relayed through the
feedback cable to the balk mechanism in the control linkage.
(h)
As the translating cowl departs from the stowed position, electrical circuits between the restow sensors and the auto restow logic card are de-energized. The logic card, through an AND logic gate, de-energizes the stow relay causing the stow relay contacts to close. The electrical supply is re-routed through the closed stow relay contacts, by-passing the air/ground relay and selector switch, thus maintaining the supply to the isolation valve solenoid throughout the retract cycle when the selector switch contacts are open.
(2) Retraction
(a) Forward thrust is selected by moving the reverse thrust lever forward to reverse idle and downward to cancel reverse thrust. The balk mechanism retains the forward thrust lever at idle until the system has moved through approximately 62 per cent of its travel. Engine power can then be increased progressively, relative to the position of the reverser system, until full forward thrust is attained.
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78-31-00
ALL ú ú C03 Page 8 ú Mar 15/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
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CFM56 ENGINES
737-300/400/500/ /MAINTENANCE MANUAL ////////////////////////
(b)
Cancelling reverse thrust opens the selector switch contacts. The isolation valve solenoid, however, remains energized through the closed contacts of the stow relay. The reverse lever repositions the directional control valve, which vents the extend side of the sytem through the hydraulic return line while maintaining pressure on the retract side.
(c)
Pressure difference across the actuator piston head causes the piston to move to the retract position. System synchronization is maintained through the acme nuts, screw and the flexible drive shafts.
(d)
The translating cowl moves forward as the actuator pistons retract. The feedback actuators rotate the feedback arms and the movement is relayed through the feedback cable to the baulk mechanism.
(e)
As the translating cowl reaches the stowed position, the electrical circuit to the auto restow logic card is energized through the restow sensors. The electrical signals energize the AND logic gate causing the relay contacts to close with a 10 second time delay. This action energizes the stow relay, resulting in the relay contacts opening and de-energizing the thrust reverser isolation valve.
(f)
As pressure decays in the extend side of the system, the lock valve in each of the lock actuators closes and blocks the fluid inlet port. A non-return valve opens to allow fluid in the extend cavity to escape. The piston of the lock actuator, nearing the end of the retract stroke, pushes the locking sleeve into engagement with the serrations on the lock. The sleeve will then ratchet until the piston bottoms in the fully retracted position.
(g)
When you move the reverse thrust lever to the stow position, power is sent through the switch to a two minute time delay relay. The two minute time delay permits the thrust reverser to retract which provides time for the indicating system to detect failures that prevent the locking actuator from locking the thrust reverser sleeve in the retracted position. After two minutes, power is sent through the time delay relay to unlatch the latch relay, which then de-energizes the sync lock solenoid. This permits the sync lock to mechanically lock the rotary flex shaft system.
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