21-52-00
ALL ú ú 02 Page 1 ú Mar 12/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 737-300/400/500MAINTENANCE MANUAL
C. The deflector door is hinged at its forward end to airplane structure and is shaped to fit in the scoop when retracted to prevent interference with ram airflow into the ram air ducts. A mechanism connected to the modulation panel cable system causes the deflector door to be extended when the airplane is on the ground and then to fair on takeoff. The deflector door minimizes the possibility of foreign material entering the ram air system when the airplane is moving on the ground.
3. Ram Air Ducts
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A. The ram air ducts are contained in the ram air duct cavity and the equipment bay. A web between the two compartments helps support the heat exchangers and the inlet ducts. The ram air exit ducts connect to the inboard side of the heat exchangers then extend to an outlet just aft of the equipment bay doors. A turbofan is included between duct sections immediately forward of the outlet. Access to the entire ram air duct system is obtained by opening the ram air duct access door and the air conditioning equipment bay doors.
4. Ram Air Actuator
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A. AIRPLANES WITH RAM AIR EXHAUST LOUVERS (PRE-SB 21-1123); The ram air actuator is a 115-volt ac motor-operated linear actuator. It operates in either direction and may be stopped at any position between full extend and full retract. The actuator is used to modulate the ram air inlet modulation panel and the ram air exhaust louvers, and moves the deflector door.
B. AIRPLANES WITHOUT RAM AIR EXHAUST LOUVERS (POST-SB 21-1123); The ram air actuator is a 115-volt ac motor-operated linear actuator. It operates in either direction and may be stopped at any position between full extend and full retract. The actuator is used to modulate the ram air inlet modulation panels and move the deflector door.
C. AIRPLANES WITH RAM AIR EXHAUST LOUVERS (PRE-SB 21-1123); The ram air actuator is controlled by relays in the Air Conditioning Accessory Unit and the ram air controller. The control is automatic and depends on whether airplane is on the ground, inflight with flaps extended or inflight with flaps positioned full up. When airplane is inflight with flaps full up, temperature of the air in the air cycle machine compressor discharge is sensed by the ram air controller to govern actuator position. There are four position switches in the actuator which work with the control system to obtain proper positioning of the inlet panel and the exhaust louvers. The ram air actuator is mounted on the aft bulkhead of the ram air duct cavity.
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