503 Ram Air System Component Location
Aug 15/67 Figure 1 21-52-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
5. Ram Air Inlet Modulation Panel Cable and Linkage System
A. The ram air inlet modulation panel and the deflector door are mechanically linked together and are operated by the ram air actuator through a cable system. The ram air actuator rod connects to a crank on the ram air modulation torque shaft quadrant assembly to drive the cable system.
B. Two cables extend forward from the torque shaft quadrant along the inboard side of the ram air duct cavity to the forward end of the cavity. The cables then pass through the forward end of the cavity and are secured to the ram air inlet modulation panel quadrant. The ram air inlet modulation panel quadrant drives the inlet modulation panel shaft, which moves the inlet panels.
C. The deflector door is also driven by the ram air inlet modulation panel quadrant. An arm assembly, which drives the deflector linkage, is mounted beside the inlet modulating panel quadrant on the inlet modulating panel shaft. A lug on the shoulder of the arm assembly fits into a cutout in the shoulder of the quadrant. A cam link and torsion spring allows additional movement of the quadrant for modulating the inlet panel after the deflector has retracted. An extension link assembly in the deflector linkage permits continued movement of the quadrant to the full extend position should the deflector fail to extend.
D. The ram air modulation torque shaft quadrant assembly and control cables may be reached by opening the ram air duct access door. Access to the deflector linkage and the ram air inlet modulation panel quadrant requires removing the air conditioning fairing panel below the ram air inlet. A grease fitting and bushing are located on the arm assembly, which drives the ram air inlet deflector (Ref Chapter 12, Air Conditioning Ram Air Inlet Modulation Shaft Assembly Lubrication).
6. Ram Air Control
A. The ram air control electrically controls the ram air actuator to position the inlet modulation panel and the exhaust louvers during flight when flaps are up. The control unit is installed on the inboard side of the keel beam downstream of the turbofan. A ram air temperature sensor is installed in the air cycle machine compressor discharge duct. See cooling air and ram air equipment location illustration, 21-50-0.
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21-52-0 Page 4 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. May 01/74
7. Turbofan
A. The turbofan is a turbine-powered fan located between sections of the ram air exhaust ducts. Air from the pneumatic system is directed through the turbofan case to a small two-stage turbine centrally located inside the case. A larger diameter fan is located forward of the turbine and is shaft-connected to the turbine. As the fan turns, air is blown from the exhaust ducts creating a low-pressure upstream f the turbofan. As a result outside air is drawn through the ram air ducts. The turbofan normally operates only during ground air conditioning operation or in flight when the flaps are not up. Operation is controlled by a turbofan valve. During flight when flaps are up the turbofan windmills as ram air passes through the ducts.
8. Turbofan Valve
A. The turbofan valve is a solenoid-actuated shutoff and regulation valve requiring 28-volt dc current and is spring-loaded to the closed position. The valve remains closed after current is applied to the opening coil of the solenoid until the upstream pressure reaches approximately 8 psi. At any upstream pressure above 30 psi the valve will move toward close enough to hold downstream pressure to approximately 30 psi. The valve closes when current is applied to the solenoid-closing coil. A closed limit switch in the valve completes a circuit to the ram air control when the valve is closed. Refer to Ram Air Modulation Control paragraph 12.A. A manual control rod permits opening or closing the valve manually. Two test ports are provided for checking valve operation under pressure. The left turbofan valve is located in the left equipment bay inboard of the turbofan. The right turbofan valve is located in the right equipment bay at the forward end where the valve duct connects to the right pack cold air supply duct.
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