AIR -ENGINE EXTERNAL ACCESSORY COOLING -GENERAL DESCRIPTION
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AIR -ENGINE EXTERNAL ACCESSORY COOLING -NACELLE ZONE VENTILATION
Purpose
The nacelle zone ventilation system supplies fan air to cool the area around the outside of the high pressure compressor and diffuser cases.
Location
The nacelle zone ventilation shutoff valve and duct are on the left thrust reverser half inner wall at 11:00.
General Description
The nacelle zone ventilation shutoff valve is a butterfly type valve. A spring holds it open. PS3 servo air pressure closes the valve.
The EEC controls the shutoff valve as a function of altitude. The EEC also sends fault data to the AIMS.
When the airplane is below 30,000 feet, the spring keeps the valve open. Fan air flows through the valve. The nacelle zone ventilation duct holes distribute the airflow into the nacelle area.
When the airplane is above 30,000 feet, the EEC supplies an electrical ground for the shutoff valve solenoid to energize. Pneumatic pressure then closes the valve.
Training Information Point
If the valve fails in the closed position, it can be manually locked open. You can turn the manual lockout hex in the counterclockwise direction to move the valve to the open position. You install the threaded manual lockout bolt after the valve is open.
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AIR -ENGINE EXTERNAL ACCESSORY COOLING -NACELLE ZONE VENTILATION
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
AIR -TURBINE CASE COOLING (TCC) SYSTEM -GENERAL DESCRIPTION
Purpose
The turbine case cooling (TCC) system controls the fan air that cools and decreases the size of the HPT and LPT cases. This increases the fuel efficiency and the life of the turbine cases.
General Description
The TCC system has these five parts:
*
Actuator
*
Control cables
*
Valves
*
Collectors
*
Manifolds.
The TCC system operates automatically. The EEC controls the system as a function of altitude and HPC rotor speed (N2). The servo fuel changes the position of the actuator pistons to modulate the HPT or LPT TCC air valve. This increases or decreases the flow of fan air to the turbine case.
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