(b) Unlocking sequence At the beginning of the deploy sequence, the hydraulic pressure is applied to the differential section locking sleeve (1). Then the sleeve moves away and the claws (4) which maintain the actuator rod, are free. Under the action of the nut (3) the claws open and the actuator rod becomes free. The minimum hydraulic pressure for which the locking sleeve moves away and the claws become free is 40 bars (580 psi). 3.5 cc (0.12 USOZ) are necessary to release the claws.
(c) Speed slowing down system (Ref. Fig. 015) At 95% of the deploy stroke, the hole (T), which permits the communication between the central hose and the rod actuator chamber, is closed by the piston shoulder. Then the fluid must pass through the restrictor (R), the pressure pushes the cup on its seat, and the fluid passes through a calibrated hole which causes speed reduction (speed less than or equal to 50 mm/s or
1.97 in./s).
(d) Stow sequence (Ref. Fig. 016) The actuator is initially in reverse flow position. As soon as the stow order is given, high pressure is ported into chamber (B), while chamber (A), is connected to return. Inside the restrictor, the pressure moves the sliding cup, then the fluid passage is free allowing a high speed at the beginning of stowing. The return pressure is 15 bars (217.5 psi). The nominal pressure in chamber (B) is 206 bars (2987 psi). The stowing strength obtained is about 2305 daN (51.82 lbf).
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Slow Running System
Figure 015
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Blocker Door Actuator - Stow and Lock Phase
Figure 016
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(e) Locking sequence The nut (3) which is linked with the piston, arrives against the claws. As the shape of the claws is bevelled, the nut can displace the claws. While the actuator is not locked, the locking sleeve is maintained in unlocked position by the spring (5) and in the locking sequence by the open claws. When the nut is passed, the claws return to their initial position, and over the action of the spring (7), the locking ring fixes the claws. When the actuator is locked, the nut arrives in abutment against the actuator body, which permits a small over flushing of the doors. When the doors are locked, the chamber (B) is connected to return, the actuator takes a rest position. In this position the rod has a locking clearance of 3 mm (0.118 in.).
(f) Door latch failure If a door latch breakes, the nut comes against the claws which are fixed, and that prevents the door from moving more than 1/2 in. from the stowed position. This movement is sufficient to actuate the UNSTOW switch to provide cockpit indication of the failure. The ECU logic will also evaluate the unstow signal. If reverser deployment has not been selected, the HCU pressurizing valve will be commanded to open thus supplying stow pressure to the actuator.
E. Hydraulic Control Unit
(Ref. Fig. 017, 018, 019)
(1) General The hydraulic control unit controls hydraulic fluid flow to the thrust reverser latches and blocker door actuator. Control and feedback signals are exchanged with the engine ECU. The HCU is mounted on the upper forward face of the right hand thrust reverser forward frame. The HCU incorporates the following items :
- a pressurizing valve and a mechanical inhibition
- a directional valve
- a flow limiter
- a bleed valve
- a pressure switch
- a filter and clogging indicator
- a check valve restrictor
- a thermal blanket
The (yellow or green) hydraulic system is used as the supply source.
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Hydraulic Control Unit
Figure 017
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Hydraulic Control Unit with Thermal Blanket Installed
Figure 018
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Hydraulic Control Unit - Schematic
Figure 019
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E E Feb 01/98 E E ECES E Flow rate supply from aircraft does not exceed 34.45 l/min by thrust reverser. Flow rate return to hydraulic reservoir does not exceed 45.8 l/min
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