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Air inlet plenum flange seal

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Air inlet door

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Air inlet door actuator

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Air inlet door position switch

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Air inlet door seal.

Location
The air inlet components are above the APU. The air inlet door is on the upper right side of the tailcone.
Interface
The electrical load management system (ELMS) controls the air inlet door. The APUC receives door position data for control and fault indications.
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777 AIRCRAFT MAINTENANCE MANUAL

APU POWER PLANT -AIR INLET -INTRODUCTION

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APU POWER PLANT -AIR INLET -AIR INLET DUCT AND PLENUM FLANGE SEAL

Air Inlet Duct
The air inlet duct connects the APU door to the APU plenum. The duct supplies air to the APU by the shortest, most direct path. The duct is made of composite material.
The duct vent supplies air to the APU compartment for compartment and oil cooling.
APU Air Inlet Plenum Flange Seal
The air inlet plenum flange seal closes and seals the air inlet duct where it connects with the APU plenum. The flange seal is made of a flexible fiberglass/NOMEX/silicone material. The seal also helps to isolate APU vibration from the duct.
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APU POWER PLANT -AIR INLET -AIR INLET DUCT AND PLENUM FLANGE SEAL

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APU POWER PLANT -APU AIR INLET -AIR INLET DOOR COMPONENTS

Air Inlet Door
The air inlet door opens to let air into the engine and load compressor plenum.
The air inlet door is on the right, upper surface of the tail cone immediately aft of the rudder trailing edge. This position decreases the possibility of water or slush ingestion during ground and flight operations.
Air Inlet Door Seal
The air inlet door seal keeps fluids and contaminants out of the inlet duct when the door is closed. The seal is a bulb-type seal made of silicone rubber.
Air Inlet Door Actuator
The air inlet door actuator is an electric actuator that opens and closes the air inlet door.
The inlet door actuator is in a canister assembly on the upper forward section of the air inlet duct. The canister assembly supports the actuator and seals the operating rod slot in the duct.
Air Inlet Door Position Switch
The air inlet door position switch supplies a door open or door not open signal to the ELMS and to the APUC. The switch is on the aft side of the air inlet duct.
Training Information Point
You can manually operate the air inlet door with the manual drive socket on the inlet door actuator assembly.
You must remove a cover (not shown) on the canister assembly to get access to the transfer cover and the manual drive sockets.
You turn the transfer cover socket to select the manual mode. This does these things:
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Uncovers the manual drive socket

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Disengages the electrical drive mechanism

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Engages the manual drive mechanism.

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APU POWER PLANT -APU AIR INLET -AIR INLET DOOR COMPONENTS

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APU POWER PLANT -APU AIR INLET -FUNCTIONAL DESCRIPTION

General
The APU air inlet door opens for APU start and run operation and closes when the APU is not running. The ELMS contains the control logic for the APU air inlet door.
APU Start
When the APU is OFF, the air inlet door is closed and sealed. When the APU selector is in the ON or START position, the ELMS energizes the control relay to open the air inlet door.
The air inlet door position switch sends a signal to the APUC and to the ELMS when the air inlet door gets to the open position. The door takes 30-40 seconds to open fully.
Normal Operation
During normal operation, an APU running signal from the APUC to the ELMS keeps the door open.
APU Shutdown
On shutdown, the ELMS energizes the control relay to close the air inlet door when the speed of the APU engine goes below 15 percent RPM. The door takes 30-40 seconds to close fully.
The APU fire switch (P5) or fire shutdown switch (P40) operation cause the air inlet door to close immediately.
Door Position Disagreement
If door position disagrees with the commanded position, the ELMS sends a signal to the AIMS to show the APU DOOR status message.
　
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