Leg Assembly, RAT Actuator and Hydraulic Pump
Figure 008
R 1EFF : 001-049, 051-061, 101-105, 201-203, 1 29-22-00Page 23 1 1 Config-1 May 01/05 1 1 1CES 1
Leg Assembly and Components
Figure 008A
R 1EFF : 062-099, 106-149, 151-199, 204-299, 1 29-22-00Page 24 1301-399, 401-499, 1Config-1 Aug 01/05 1 1 1CES 1 The front of the leg assembly has a blade index mechanism. The mechanism locks the turbine so that it does not turn when it is retracted or not fully extended. The blades are locked in position in line with the leg assembly. Thus the blades cannot cause damage to the aircraft skin when the RAT is extended. The index lock mechanism is automatically disengaged when the RAT is approximately 5 degrees from full extension.
R **ON A/C 062-099, 106-149, 151-199, 204-299, 301-399, 401-499,
The leg assembly is the mechanical and hydraulic connection between the pump assembly and the aircraft.
The main part of the leg assembly is a one-piece forging which includes attachments for other components. At the bottom end, the leg assembly holds the turbine. The top of the leg assembly has a pivot where it is attached to the aircraft structure. The pivot includes swivel connections for the hydraulic supply to and from the pump. The stationary part of the hydraulic system is connected to the movable part by a swivel joint (pivot).The swivel joint has a check valve in the pump discharge line and a device which gives a warm-up flow to the actuator only in the RAT stow condition.
The cascade-type orifice for the warm-up flow is protected by self-cleaning filters.
**ON A/C 001-049, 051-061, 101-105, 201-203,
The blade index mechanism has sufficient strength to hold the turbine under all conditions. This includes the condition where the pump operates as a motor and tries to turn the turbine. Such a condition can occur if there is a failure of the GCM and system pressure is supplied to the pump. The index mechanism includes a position switch which prevents the retraction of the RAT if the lock is not correctly engaged. If the turbine is not in the correct position for the index to engage, the RAT will not retract. It is thus necessary to turn the turbine manually to the correct position before it will retract.
The lower end of the leg assembly between the turbine and pump contains a gerotor (gear-type) pump and a frequency wheel/pulse generator. The main drive shaft of the turbine drives the pump and the generator directly. The gerotor pump supplies the pitch change mechanism with servo pressure. The frequency wheel/pulse generator supplies turbine speed data during ground test. The data is sent to the ground test connection in the RAT control panel. The RAT ground test box uses the data during test of the RAT.
The pivot includes two microswitches. One microswitch monitors the turbine index position and will stop the retraction of the RAT if the turbine blades are not in the correct position (this switch only operates until the leg assembly is 11 degrees from its extended position). The other microswitch monitors the position of the leg assembly. It completes the circuit when the leg assembly is more than 10.5 degrees from its extended position.
Also on the leg assembly are attachment lugs for the RAT actuator and for the aircraft door links. Rods connect the doors to the leg assembly. The doors open automatically when the RAT extends.
C. Hydraulic Pump (Ref. Fig. 008)
The hydraulic pump is installed on the bottom of the RAT leg assembly at the rear. A drive shaft which is connected directly to the turbine turns it. The pump is a variable-displacement, piston-type pump with a movable swash plate. The flow of hydraulic fluid goes to and from the aircraft through two rigid pipes which are connected to the leg assembly. The pump case drain goes directly into the priming chamber of the servo pump. An external case drain is thus not necessary.
During a ground test of the RAT system the pump operates as a motor.
D. RAT Actuator 2454GE
The RAT actuator is installed between the aircraft structure and the RAT leg assembly. It extends the RAT into the airflow and locks it in position. It also retracts the RAT when the aircraft is on the ground. The actuator is of the spring-loaded type. Spring pressure extends it, hydraulic power retracts it. Installed on the actuator are two solenoids and a limit switch.
The two solenoids control the extension. Any one of the solenoids can cause the actuator to extend. The ground retraction module controls the retraction of the actuator. The actuator is mechanically locked in both the extended and retracted positions. Both locks are internal. The solenoids release the retract lock and hydraulic pressure releases the extend lock. The actuator is made so that the return fluid flow decreases in the last part of its travel to give a damping effect.
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：A320飞机维护手册 AMM HYDRAULIC POWER 液压5(98)
