9. Ram Air Exhaust Louvers
A. Louvers are installed at the ram air outlet to restrict airflow through the ram air system during flight. The louvers are installed parallel to each other and are supported at either end by a support angle. Individual arms are splined to mate with the outboard end of each louver and are linked together at the other end of the arm to obtain simultaneous movement of each. The forward arm mates with a torque shaft that extends from the arm to the ram air actuator located in the ram air duct cavity. As the actuator moves, the louvers rotate to reduce or increase the exhaust area. Since the torque shaft is connected to the crank that operates the ram air inlet modulation panel control cables, movement of the exhaust louvers and the inlet modulation panel is obtained at the same time. The exhaust louvers are the primary restrictions to ram airflow while the inlet panel reduces the possibility of aerodynamic resonance in the ram air ducts.
10. Inspection Doors
A. Two inspection doors in each ram air system permit visually checking for foreign material in the ram air ducts or heat exchangers. One inspection door is located on the bottom of the ram air duct just outboard of the secondary heat exchanger. The other door is located on the bottom of the duct outboard of the primary heat exchanger. Open the ram air duct access door to gain access to either inspection door.
11. Operation
A. Ram Air Modulation Control (See figure 2).
(1)
General
(a)
Ram air modulation provides maximum airflow through the ram air system during ground operation. During flight, however, maximum airflow is seldom required. Ram sir modulation permits a reduction in airflow at this time which, in turn, results in substantial drag reduction. The modulation system automatically adjusts airflow according to air conditioning requirements.
(b)
The ram air modulation system consists of adjustable inlet and exhaust opening, a ram air actuator, a cable system with mechanical linkage to the modulation panel, exhaust louvers, and deflector, a ram air control, a ram air temperature sensor, and the interrelated circuitry.
(c)
There are three different steps of ram air modulation as determined by three airplane positions. Fixed positions are obtained when the airplane is on the ground and on the takeoff. During flight the openings vary according to airplane requirements.
(2)
Ground Operation
(a) When the airplane is on the ground the landing gear safety relay and the air-ground relay complete a circuit to the open side of the actuator and open all circuits to the close side. If the modulation panel and exhaust louvers are not already full open they will drive full open and the actuator position switches will move to the positions shown in Fig. 2. The deflector is mechanically linked to the inlet modulation panel and will be fully extended at this time. At the same time another position switch (switch 3) in the actuator completes a circuit for the RAM DOOR FULL OPEN light.
(3)
Flight Operation
(a)
When the airplane breaks ground on takeoff the air-ground relay becomes de-energized but the turbofan control relay stays energized because the flaps are down. This completes a circuit to the close side of the actuator through another position switch (switch 2) and the actuator moves to position 2. At actuator position 2 the inlet modulation panel and exhaust louvers have moved to a slightly closed position, but not one which will appreciably affect ram airflow. Refer to Fig. 2. At this position, however, the deflector door will have moved to the faired position. Any additional movement of the inlet panel will not affect the position of the deflector because the mechanism is against its stop. A cam link and torsion spring permits further movement of the panel.
(b)
After takeoff, when the flaps are raised, the turbofan control relay becomes de-energized, the turbofan valve drives closed, and a circuit is completed to the ram air control. This circuit continues to drive the actuator toward close until actuator 3 is reached. At position 3 the actuator position switch (switch 3) closes. From this point on, as long as the flaps are up the ram air control will position the actuator somewhere between position 3 and 4. The positioning of the actuator depends on the temperature of the air at the air cycle machine compressor discharge. A ram air control sensor, located in the air cycle machine compressor discharge duct, provides a signal to the ram air control which positions the ram air exhaust louvers and inlet modulation panel. The ram air control sends either an extend or retract signal to ram air actuator as required to control air flow through ram air ducts and hold air cycle machine compressor discharge temperature to as near 230°F as possible. On cold days it may not be possible to attain the 230°F temperature. If this be the case, the actuator will drive to position 4, (full extend) and remain there until the temperature rises or flaps are lowered for landing. During approach and landing the ram air modulation system reverses the sequence noted for on-the-ground and takeoff conditions.
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本文链接地址：737 AMM 飞机维护手册 AIR CONDITIONING 空调(84)
