Turning on APU cuts everything off

I know this isn’t the thread for it, but if anyone can provide me with one? I tried searching but didn’t get far. Seems like a new bug is out there. If I turn the APU on during my final approach or until descent, etc. it cuts everything off on the airliner, including avionics. It’ll boot back up on its own but it’s definitely strange.

Hi @Tommy7471,
I’ve moved your post out of the topic you posted in.

What aircraft are you using?

Hi @Hester40MT - I have experienced this in both the aftermarket 737 Max and default A320N. Thank you for moving it!

Haven’t tried yet, but why would you want to start the APU on final or during the descent?

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I tried this in the FBW A320 on the PC and it works… Are you on XBox? If you’re on PC, get the FBW A320 and don’t look back.

Yeah APU is turned on after touchdown when clear of runway from every IRL landing video I’ve ever watched. Granted, I’m not a real pilot by any stretch of the imagination, but this is my understanding of what the process is having watched it many times. If I’m wrong someone please, smack me silly.

I don’t suppose it should really matter though. Why it would cut off avionics seems strange.


This depends if e.g. a GPU is available at your parking stand.

But this wasn’t my question.

Just do it out of habit so I don’t forget, but still happens even if I’m on the ground or not unfortunately. On Xbox here. Couldn’t justify a PC for the sole purpose of this sim. I hear great things on the FBW and hope it comes to us eventually

Its not standard, usually after landing or not at all. In any case it should not cut the power of course, if you need start-up the APU in flight because of an engine or generator problem you want it to work. I don’t know what the logic is on the Airbus but usually engine driven generator has priority over APU generator so there shouldn’t be any power transfer happening, and even when transferring does occur to or from APU generator, this should not lead to a power interruption.

As for the minute trivia question why anyone would want to start the APU on approach: Requiring two electrical power sources for a Cat II or Cat III landing and having a generator out would be a reason on some aircraft…

Or dual engine failure :slight_smile:

Hah, yes indeed! I seem to recall that it was noted that Sully threw on his APU out of checklist sequence almost immediately after realising both engines were compromised, and this rapid, instinctive action ensured he retained flight controls all of the way to the “ground”.


Yes or to fly ETOPS on some aircraft.

Not really. The RAT extends automatically and provides sufficient hydraulic pressure to power the flight controls.

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APU is started with a single engine failure already to restore redundancy by having dual generators. At least on the aircraft I’m familiar with.

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Same on Embraer, the batteries would power essential aircraft systems while the RAT deploys (takes around 7 seconds), the FBW has its own back-up battery on top of that should there be any power interruption. The hydraulics are pressurized by an accumulator during the 7 second period, when the RAT is fully spooled up it powers essential electronics and electrical hydraulic pump. I don’t believe an aircraft would be certified under CS-25 should it lose flight controls in case of dual generator / engine failure.

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