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3. DESCRIPTION
A. Electrohydraulic generator
The electrohydraulic generator consists of an electric motor with a double way of rotation, which drives a gear pump. The reservoir is integrated to the generator. The pressures are regulated by two pressure relief valves. Control is ensured by a lever on the configuration and control box, located on the L.H. strip. The electrohydraulic generator is secured to the L.H. side of frame C3, under the rear bench seatpan.
A circuit-breaker protects the pump system. It is supplied by the BUS 3 of the aircraft and is located on the L.H. circuit-breaker panel.
Opt. or Std Post-MOD. 151 (28 Volts)
A testable amber indicator light, located on M6 advisory panel, indicates to the pilot, via a relay, the operation of the electrohydraulic generator.
This relay, of the ILS type, is secured to frame C3, on the right of the landing gear relay support.
B. Distribution plate
The distribution plate is located under the electrohydraulic generator. It consists of a body equipped with a shuttle valve and a return spring.
C. Landing gear emergency valve
The landing gear emergency valve consists of a body, a piston equipped with seals moving inside the body thanks to a control lever. The piston makes the landing gear "extended" and "retracted" systems communicate in order to allow the landing gear emergency extension. In order to maneuver the control lever, press the central knob and pull the control rearwards.
It is located under the L.H. instrument panel behind the L.H. strip. 4. OPERATION
The electrohydraulic generator provides, in the landing gear hydraulic system, a pressure which allows the landing gear "retraction" or "extension" maneuvers. Two relays located close to the generator control it. The pressurized fluid routes in the system up to the actuator "retracted" or "extended" chamber. The provided pressure pushes the actuator piston in order to maneuver the landing gear up to the selected position.
A pressure switch, located close to the generator, cuts the system when the generator is correctly pressurized, which allows the landing gears to remain "up". The system pressure is kept by the return valve in the hydraulic generation unit.
The pressure switch operates as follows :
1) At the opening, when the system reaches the required pressure for a value of 1400 psi ± 70 psi (96.55 bars ± 4.85 bars) that is between 1330 psi (91.7 bars) and 1470 psi (101.4 bars).
2) At the closing, when the pressure decreases in the system and when the landing gear is "UP", approximately 20 % below the nominal value 1400 psi (96.55 bars).
The closing value is generally about 360 psi (25 bars) below the opening value.
Hydraulic generation - Location of components
Figure 1
ABAB
Validity : Electrohydraulic generator "L.H.C." 32-35-00 Page 3
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本文链接地址：TB20 MAINTENANCE MANUAL 32 起落架 TB20飞机维护手册(74)
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