R **ON A/C 106-149, 151-199, 204-299, 301-399, 401-499,
In an emergency the Blue auxiliary system supplies hydraulic power to the aircraft. Electrical power can also be supplied through the Blue auxiliary system by the constant speed motor generator (CSMG). The system supplies hydraulic power in less than 4.5 seconds from the time it gets the electrical command to extend the RAT. The hydraulic power available from the RAT is sufficient to supply the flight controls and the CSMG (for electrical power). The RAT is available and will operate through the entire flight envelope. The RAT has a stall protection device which prevents a RAT stall below the governed speed range. The stall protection device limits the maximum power the pump can take from the turbine. When the stall protection device is in operation, the pump displacement is adjusted to get a constant RAT speed not related to the aircraft speed. The RAT has a de-icing device which is installed in the nose of the turbine hub. The de-icing device produces heat which keeps the nose temperature to 3 deg.C (37.40 deg.F) minimum. This temperature prevents icing conditions at the turbine hub when the RAT is in operation. The de-icing device does not use external power sources. The heat is produced by the eddy current heating device. The heating device has two basic components, an electrically conductive aluminium plate and an even number of samarium cobalt magnets. The magnets are cicumferrentially mounted on a stationary magnetic plate. When relative rotation take place, the flux field, when it passes through the aluminium plate, produces a current. As aluminium has an electrical resistance, power is generated which is than dissipated in the form of heat. The main components of the Blue auxiliary system are:
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the RAT,
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the leg assembly with its pivot,
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the hydraulic pump,
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the ejection jack,
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the RAT control panel and
R 1EFF : 062-099, 106-149, 151-199, 204-299, 1 29-22-00Page 12 1301-399, 401-499, 1Config-1 Aug 01/05 1 1 1CES 1 -selector switches to extend the RAT from the flight compartment.
All the components are in the left belly fairing. This does not include the RAT control panel and the selector switches. The RAT control panel is part of the ground-service panel of the Blue hydraulic system, and the selector switches are in the flight compartment.
The drain port of the RAT gearbox has a leakage drain line which transfers hydraulic fluid from the internal reservoir of the RAT pump to an external drain tank. The location of the drain tank is behind a cover plate on the left side of the RAT bay.
A pushbutton switch (2805GE) is installed on the hydraulic control panel 40VU in the cockpit. This switch permits the pilot to manually select the deployment of the RAT.
When it is on stand-by, the RAT (2GE) stays retracted in its stow compartment. In an emergency, the RAT is deployed (automatically or manually) to supply hydraulic power to the Blue main hydraulic system.
R **ON A/C 062-099, 106-149, 151-199, 204-299, 301-399, 401-499,
The turbine is a constant-speed variable-pitch unit with two blades. The mechanical governor and the pitch-change mechanism are installed in the hub. The turbine is attached to the lower end of the leg assembly and operates the gearbox which drives the hydraulic pump. The hydraulic pump has a stall protection which makes sure that the power demand from the pump does not exceed the power available from the turbine.
An index mechanism installed on the front of the leg assembly locks the turbine hub assembly in the correct position. The turbine hub has markings which allows easy alignment between the turbine hub and the index mechanism. This then permits the RAT to be stowed.
During the deployment of the RAT, the index mechanism disengages from the turbine hub when the leg is not more than 10 deg. before full extension. The RAT retracts hydraulically with the hydraulic supply from the Blue electric pump or from a ground supply. The retraction of the RAT is operated by the RAT control panel (3GE). The RAT can retract only if the turbine is in the correct position and the index mechanism is engaged. If the index mechanism is not engaged, it is necessary to turn the turbine manually until the index mechanism engages. The RAT will also not retract if the ground test tool is still attached.
The ejection jack is attached to the top end of the leg assembly and the RAT mounting frame. The ejection jack extends the RAT into the airflow with the
R 1EFF : 062-099, 106-149, 151-199, 204-299, 1 29-22-00Page 13 1301-399, 401-499, 1Config-1 Aug 01/05 1 1 1CES 1 force of a spring. Therefore no hydraulic power is necessary to extend the RAT. Hydraulic power is required to retract the RAT. You can retract the RAT only when the aircraft is on the ground.
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