The limit switch has two functions. It stops the supply of electrical power to the RAT retraction module when the RAT is fully retracted. It also sends a signal to the electronic centralized aircraft monitoring (ECAM) system when the RAT is extended.
R **ON A/C 062-099, 106-149, 151-199, 204-299, 301-399, 401-499,
C. Hydraulic Pump
(Ref. Fig. 008A)
The hydraulic pump is a standard axial piston-type pump. The pump has a cylinder barrel with nine pistons. An external power supply drives the barrel. The pistons turn against a face cam and are held by a hold-down plate. When the cylinder barrel turns, the pistons slide in and out of their cylinders. Movement of the pistons causes hydraulic fluid to move in and out through the pump ports. The change in the position angle of the face cam controls the volume of hydraulic fluid from the hydraulic pump.
The angle position of the face cam is changed by a stroking piston. The stroking piston is controlled by a pressure compensator valve. The changes to the angle of the face cam make the pump output fulfil the flow-demand of the aircraft hydraulic system.
The hydraulic pump also includes an anti-stall system. The anti-stall system makes sure that the pump holds the fluid pressure on the primary aircraft hydraulic system at the start-up of the turbine, when the flow-demand is more than the available flow, and maintains the hydraulic power related to the available airflow as the airspeed decreases on approach for landing.
The anti-stall valve permits the turbine to get to the operational speed in less time. This is because the piston pump is constrained to a minimum output until the pump gets to the preset speed. When the aircraft approaches for landing, the anti-stall valve holds the pump output in balance to the airspeed at the turbine.
The output of the gerotor pump is applied to the anti-stall valve. The compensator valve can not operate fast enough to fulfil the demand when the turbine RPM is less than the governed operation range. When the pressure drops across an orifice in the pump, it causes the piston in the anti-stall valve to move. Thus it applies case drain pressure to the stroking piston. The stroking piston then moves the face cam to the maximum output position. As the output changes, the compensating valve takes control of the stroking piston and adjusts the output to fulfil the demand.
D. Ejection Jack (1GE) (Ref. Fig. 009) Hydraulic power is not necessary to extend the RAT. A spring forces the RAT to extend. In the stow position, the spring is compressed and an internal uplock segment keeps the actuator cylinder in the retracted position.
Two solenoids operate the lock release mechanism for the deployment of the ejection jack. If one solenoid has a malfunction, this will not prevent the deployment of the ejection jack. One solenoid is enough to deploy the RAT. The two solenoids for the ejection release are attached externally to the upper end of the ejection jack.
A stowed switch gives a signal to tell you if the RAT is in the correct stow position or not.
**ON A/C 001-049, 051-061, 101-105, 201-203,
E. RAT Ground Retraction Module (2455GE)
The RAT ground retraction module is installed in the RAT compartment in the left belly fairing. It is a two-position, three-way, solenoid-operated valve. The RAT control panel controls it. It is used to retract the RAT.
When selected, the solenoid moves a pilot valve which causes high-pressure fluid to go to the retract side of the actuator. The actuator then retracts the RAT to its usual flight position. At the same time, a pressure switch in the RAT ground retraction module operates. This makes the warning light on the RAT ground control panel come on. The pressure switch also sends a signal to the ECAM system and the RAT FAULT light comes on.
When the RAT is locked in its retracted position, the supply of electrical power to the pilot valve solenoid stops. The high-pressure hydraulic supply also stops, the contacts of the pressure switch open, and the warning light goes off.
If, during the retraction of the RAT, the electrical power supply to the solenoid of the pilot valve is removed, the high-pressure supply stops. The RAT then returns to its extended position because of actuator spring pressure.
R 1EFF : ALL 1 29-22-00Page 28 1 1 Config-1 Aug 01/05 1 1 1CES 1
Ejection Jack
Figure 009
R 1EFF : 062-099, 106-149, 151-199, 204-299, 1 29-22-00Page 29 1301-399, 401-499, 1Config-1 Aug 01/05 1 1 1CES 1
F. RAT Ground Check Module (2027GE) (Ref. Fig. 010) The RAT ground check module is installed in the RAT compartment in the left belly fairing. Its main use is to isolate the RAT from the high-pressure system of the aircraft when the RAT is retracted. It also makes it possible for the RAT to supply the aircraft system when necessary. A third function is to supply fluid from the high-pressure system to the RAT pump for ground test.
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