modesto2
Topic Author
Posts: 2714
Joined: Sun Jul 16, 2000 3:44 am

APU Intake

Wed Oct 18, 2000 2:28 pm

Could someone please explain how the APU intake functions? Thanks.
 
NKP S2
Posts: 1665
Joined: Mon Dec 20, 1999 3:16 am

RE: APU Intake

Wed Oct 18, 2000 2:54 pm

It let's air into it.   Seriously though, the air intake door is opened and closed by an electric actuator. APU start sequences are controlled automatically once initiated, and nothing happens unless the previous event takes place -- Once a start or off command is made a chain of sequenced events take place, inlet door opening or closing among them. Feedback from an open limit switch in the actuator tells the APU control unit that it's ready to energize the electric starter and continue further the start sequence...oil pressure...ignition...fuel...starter cut-out...ready to load speed and arming of the low oil pressure switch. I gave very general info due to the fact there are many variations of APU's and aircraft --- It would not be practical to list them all now.

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