-
the RAT position switches
-
the ground check module.
There is also a 28 V DC supply from the RAT control panel to the ground test box when it is connected.
**ON A/C ALL
5. Component Description
_____________________
A. Ram Air Turbine (RAT)
**ON A/C 001-049, 051-061, 101-105, 201-203,
(Ref. Fig. 007)
R **ON A/C 062-099, 106-149, 151-199, 204-299, 301-399, 401-499,
(Ref. Fig. 007A)
Ram Air Turbine (RAT)
Figure 007
R 1EFF : 001-049, 051-061, 101-105, 201-203, 1 29-22-00Page 19 1 1 Config-1 May 01/05 1 1 1CES 1
Ram Air Turbine (RAT)
Figure 007A
R 1EFF : 062-099, 106-149, 151-199, 204-299, 1 29-22-00Page 20 1301-399, 401-499, 1Config-1 Aug 01/05 1 1 1CES 1
**ON A/C 001-049, 051-061, 101-105, 201-203,
The RAT is a constant-speed unit with two variable-pitch blades which have a disc diameter of 27.5 in. (69.8 cm). The pitch change mechanism is hydraulically operated and contained in the hub together with the speed control governor. A gerotor pump in the leg assembly supplies hydraulic servo power to the pitch change mechanism. When the RAT is stopped and there is no servo pressure, the blades are held in the fully coarse position. This makes sure that the turbine does not turn too fast on start-up when the RAT is extended. Also contained in the hub of the RAT are centrifugally-operated overspeed valves and a control pressure-relief valve.
When the RAT is fully extended into the airflow, the turbine index lock is released and the blades start to turn. The gerotor pump supplies hydraulic servo pressure and the blade pitch changes to a finer angle. The governor flyweights move the governor valve spool against the governor spring. The position of the governor valve spool controls the flow of hydraulic fluid to the pitch change piston. The pitch change piston, which is connected directly to the blade roots, moves against the coarse pitch spring and thus sets the blade pitch.
If the speed of the turbine changes, the flyweights change their position and the valve spool moves. This makes the position of the pitch change piston change which changes the blade pitch. The blades move until they are at the correct pitch to give the governed turbine speed. At that speed, the governor flyweight and spring hold the governor valve spool in place. The blade pitch is then constant until the speed changes again.
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 hub size and shape of the turbine is designed to avoid icing problems on the RAT.
The diameter of the hub assembly with the two turbine blades has an overall diameter of 1003 mm (39.4882 in.). The rotation speed of the turbine is kept between 4.800 and 6.540 revolutions per minute (RPM) because of the blade pitch angle adjustment. A governor mixes the blade counterweight, the governor, the spring and the aerodynamic forces to adjust the blade pitch angle.
An index mechanism locks the rotary assembly (turbine blade and hub) in the stowed position and during extension. During extension the rotary assembly is locked until not more than 10 deg. before full extension. A
R 1EFF : ALL 1 29-22-00Page 21 1 1 Config-1 Aug 01/05 1 1 1CES 1 clearance of 19 mm (0.7480 in.) between the RAT doors and turbine blades is given.
The hub has markings to make sure that the index mechanism and the hub align easily for the retraction of the RAT. It is not possible to retract the RAT more than 10 deg. if the rotary assembly is not correctly locked or if the ground tool is installed. The index mechanism therefore prevents damage to the RAT, the RAT doors and the aircraft structure.
The gearbox drain port has a leakage drain line which transfers hydraulic fluid from the internal reservoir of the RAT pump to an external drain tank.
**ON A/C ALL
B. Leg Assembly
**ON A/C 001-049, 051-061, 101-105, 201-203,
(Ref. Fig. 008)
R **ON A/C 062-099, 106-149, 151-199, 204-299, 301-399, 401-499,
(Ref. Fig. 008A)
**ON A/C 001-049, 051-061, 101-105, 201-203,
The leg assembly is the mechanical and hydraulic connection between the turbine/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 at the front and the hydraulic pump at the rear. 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 leg assembly is drilled to make high-pressure and low-pressure galleries between the pivot and the rigid pipes. The rigid pipes are at the lower end of the leg assembly and connect the leg galleries to the pump connections.
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