The turbine speed increases to its controlled value (5400 rpm) and the RAT pump supplies the Blue main system of the aircraft.
R **ON A/C 062-099, 106-149, 151-199, 204-299, 301-399, 401-499,
The extension of the RAT is controlled by the:
-
manual operation of the pushbutton switch OVRD HYD 2805GE on the HYD section of the overhead panel 40VU, or
-
manual operation of the pushbutton switch OVRD ELEC 24XE on the overhead panel 21VU, or
-automatic control in the event of a total failure of the AC busbars 1XP and 2XP.
When the RAT receives an automatic or manual command to extend, one of the two deploy solenoids operates and releases the internal lock. Spring pressure causes the ejection jack to extend, which extends the RAT into the airflow. The RAT compartment doors open with the extension of the RAT. When the RAT extends, the stowed switch operates and sends a signal to the ECAM system where the legend RAT OUT appears.
The index mechanism disengages automatically when the RAT is 8 degrees from its fully extended position. As the RAT is caught by the airstream, the actuator operates as a shock absorber which prevents high-shock loads on the RAT and aircraft structure. When the rod of the actuator is at its maximum extension, movement of the turbine assembly stops.
D. RAT Operation
As the turbine assembly extends into the airstream, a stationary stop on the pivot operates a control cable. The cable is attached to the index lock plunger. The index lock releases the turbine hub at approximately 8 degrees from the fully extended position of the turbine assembly. The airstream then causes the turbine blades to rotate. A bevel gear inside the gearbox assembly transmits the rotation of the turbine to drive the hydraulic pump.
R 1EFF : ALL 1 29-22-00Page 45 1 1 Config-1 Aug 01/05 1 1 1CES 1 When the turbine is released to spin, it accelerates without pump load. As the turbine speed gets to the operational range, the pitch cam changes the angle of the blades to intermediate or the coarse-pitch position. The rotation speed of the turbine is opposed to the force of the governor spring, the blade and the counterweight.
As the speed of the turbine increases, the blades move to the coarse-pitch position for more air load. When the blades move to coarse-pitch, the governor spring is compressed. As the air load on the turbine blades increases, the turbine speed decreases. The governor spring, which is compressed, expands and overcomes the torques of the blades and the counterweight. Then the pitch cam adjusts the blades to a finer pitch position and the speed of the turbine increases. Thus the turbine is kept at a constant speed in its operation range between 92 and 135 knots equivalent air speed (KEAS) by the governor.
When the airspeed is less than 92 KEAS, the turbine speed decreases less than the governor operation range of 4.750 RPM. When the RPM is between
3.800 and 4.200 RPM, the anti-stall system then keeps the output of the pump in balance to the airspeed at the turbine. As the airspeed and the turbine speed continue to decrease, the output pressure of the pump drops to zero.
The bevel gearset in the gearbox supplies power to the hydraulic pump through the turbine. Attached to the RAT hub is a directly-driven shaft. An internal spline is on the aft end of the drive shaft which drives the turbine and the pump during the ground test of the RAT system: To test the turbine, the transmission, the pump and the actuator, a ground test tool is attached to the back of the RAT.
**ON A/C 001-049, 051-061, 101-105, 201-203,
E. Retraction
(Ref. Fig. 013)
**ON A/C 001-049, 051-061, 101-105, 201-203,
Post SB 29-1111 For A/C 001-049,051-061,101-105,201-203,
(Ref. Fig. 013A)
R 1EFF : ALL 1 29-22-00Page 46 1 1 Config-1 Aug 01/05 1 1 1CES 1 **ON A/C 001-049, 051-061, 101-105, 201-203,
It is possible to retract the RAT only when the aircraft is on the ground. Retraction is controlled from the RAT control panel in the Blue system ground service panel. The system must be in this condition before retraction of the RAT is started
-Blue main system pressurized,
-28 V DC supply to the RAT control panel,
-the turbine in its index position
NOTE : The turbine is turned manually to the index position, which is
____ indicated by the alignment marks on the turbine and leg.
When the ARM switch is set to its 'ON' position, electrical power is supplied to the STOW selector switch. When the switch is set to the STOW position, electrical power is supplied to the solenoid in the RAT ground retraction module.
The solenoid operates the pilot valve and connects the high-pressure supply of the aircraft to the retract side of the RAT actuator. The high-pressure fluid operates the pressure switch of the ground retraction module and the warning light on the RAT control panel comes on. Thus there is an indication that the RAT retraction module is not in its flight position.
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