Originally Posted by
MD83FO
What are the consequences of having the APU master ON before takeoff, and back OFF sometime after?
Perplexing idea, but I flown under rules that mandated APU on for LVP and similar. 🤷🏼 (now imagine if such idea came from the NAA perhaps you'd be pressed to reinvent the wheel a little).
1) The flap will be open. Looking at the MEL items where the APU is left running, there may be no performance penalty. Hm, actually it would not be thrusting nor sucking even a little, with the open inlet in this scenario causing net parasitic drag - so perhaps check with CDL and the OEM is needed to formally tick all the boxes.
2) Some less insightful people might think it is actually a good idea. 🤔
3) Something happens in the electric system with Master SW on (cue emerg elec proc), so worthwhile researching if that is relevant and with consequences or not.
4) the wear of the switch push-button and system contractors is increased.
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recorded in order of appearance).