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 (12.1 US gal/min).
 Temperature :

 - Fluid temperature during use is between -40 deg.C to +107 deg.C (-40 deg.F to 224.6 deg.F)

 - The temperature of equipment is between -54 deg.C to +121 deg.C

 (-65.2 deg.F to +249.8 deg.F) during the operating phase.
 The HCU has the following functions :

 - supply pressure to the hydraulic system (pressurizing valve)

 - regulate blocker doors stow speed (flow limiter)

 - supply latches (directional valve solenoid)

 - supply actuators (directional valve).
 Electrical characteristics :
 Pressurizing valve solenoid and directional valve solenoid :
 Each ECU channel interfaces with the thrust reverser valve solenoids.
 Each solenoid contains two electrically independent coils, one
 dedicated to channel A and the other to channel B. Each of these
 windings conforms to the following characteristics :

 - actuation current : 300 mA min from ECU

 - actuation voltage : 16VDC max at 300 mA

 - max steady state voltage 31.5VDC

 - DC resistance : 18 ohms min.

 - reactance (below 300 Hz) 500 millihenries nominal

 - update time capability 50 milliseconds min.
 Each solenoid winding will be connected to the ECU via a two wire
 cable.
 The resistance of the wiring in series with each winding as measured
 at the connection to the ECU will be less than 55 ohms.

 NOTE : Pressurizing valve solenoid :
____
 - energized: pressurizing valve open

 - deenergized: pressurizing valve closed Directional valve solenoid :

 - energized: thrust reverser deploy

 - deenergized: thrust reverser stow

 (2) Component description
 (a) Pressurizing valve and mechanical inhibition (Ref. Fig. 020, 021) The pressurizing valve is a two position valve which is solenoid actuated to the open position. The valve is spring loaded to the closed position (solenoid de-energized).
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 Pressurizing Valve and Mechanical Inhibition
 Figure 020
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 Thrust Reverser HCU Pressuring Valve Inhibition
 Figure 021
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 E E The pressurizing valve can also be manually closed and pinned (inhibited) to prevent inadvertent actuation of the thrust reverser during maintenance work. Energizing the valve solenoid opens a port (B) allowing the displacement of the piston valve (2). Then the hydraulic pressure

 (A) is supplied to the stow side of the actuators and to the directional valve (in C).
 (b) Directional valve (Ref. Fig. 022) The directional valve is a three port, two position, valve. Energizing the valve solenoid opens a port (B) allowing hydraulic pressure for the door latches (the HCU pressurizing valve must be open). When the last latch is supplied the hydraulic pressure return (C') moves a piston valve (13) to the deploy position. Then hydraulic pressure is ported to the deploy side of the actuator piston (B'). De-energizing the solenoid closes a port and allows spring (12) and hydraulic pressure to move the piston valve to the stow position. In normal operation, the hydraulic pressure will move the piston valve to the stow position if the spring breaks.

 (c) Flow limiter (Ref. Fig. 023) The flow limiter regulates the hydraulic fluid flow returning to the HCU from the actuator piston head in order to control/limit the blocker door stowing rate under varying conditions. Flow entering the flow limiter from the actuators goes through an orifice which creates a pressure drop. The pressure in the flow limiter chamber then acts on a spring loaded piston. As pressure is increased, the piston (1) moves down and compresses the spring (2). As the piston moves down, it begins closing the chamber exit (F), therefore restricting the flow rate from the actuator. The maximum flow obtained is 40 l/min (10.57 US gal/min).

 (d) Bleed valve (Ref. Fig. 023) The bleed valve is provided as a means to ensure air is purged from the thrust reverser actuation system. While the system is self-purging by means of cycling the doors prescribed the thrust reverser actuation system is connected to hydraulic supply, the application of a procedure using the HCU bleed valve following removal/replacement of hydraulic components will assist removal of trapped air that could affect proper operation of clogging indicator.
　
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