APU bug on B737/B738

I think I found a bug on the mentioned airplanes. After switching off the APU, the sound is still there in the HUD/cockpit view. Restarting the app or device doesn’t seem to help.

The app version is 21.8 (1879) and the device is a Samsung SM-P610.


I think it has something to do with the engine sound since it got a little fix on in the 21.8 update


Also, as in general, the electricity won’t go immediately as soon as you turn off the APU.
When you turn on the battery switch you will have some electricity until you turn on the APU as well. But in infinite flight APU is misused… (Also, the APU consume a little bit of fuel, in infinite flight it doesn’t consume any fuel at all)

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Thanks for your reply but I don’t think this is the issue as other aircrafts like the T7 and A333 don’t have this problem. When I turn off the APU on these planes the sound will turn off.

Hi there! I tried to recreate the issue, but I was unable to. Is it still happening to you? As others have mentioned the APU sound stays for a little bit and then cuts off after once the APU is turned off. If you are talking about engine start, the specific sound stays as I believe it is also associated with the engines running, however shutting them off (for me) results in the sound going away after a few seconds. I tried each scenario multiple times on both the B737 and B738, including the engine starts. Were your engines running when you had this issue? If you still believe that you have a unique issue, do you mind sharing your replay via Share My Infinite Flight. You said you noticed it in the HUD/cockpit view so it is unlikely that it was airport ambient noise. I hope this helps.

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I’ve not tried it today but yesterday I even had it inflight when I turned off both engines to check. In a few hours I will make a replay and upload it so you can see what I mean.

The replay should be here: Share My Infinite Flight

I downloaded the replay, but I did not have the same issue that you reported here. As soon as your APU turned off, the sound went away on my end. Is it possible you heard the ambient noise?

I am pretty sure the sound of the APU is still there after starting the engines. I even re-installed the app and it makes no difference. It is really annoying hearing the APU when the engines are idling.

Oh wait you are only talking about starting the engines. I’m pretty sure that that is just the sound of the fans in the cockpit that you hear. 3rd person view may reveal that the APU sound is actually off. I do not think that noise is specific to the APU, just to the electronics (whether they are powered by the APU or the engine gens). Wow, it took me a sec! I’m not 100% sure about this conclusion but it seems to make sense to me.

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Hahaha maybe I"ve not explained the issue very well 🤣

I’m not sure if this sound is about the cooling fans blowing. On other planes with a APU (like the T7 and the A330) I don’t hear it. With those planes the sound of the APU dissapears when the engines are on idle and the APU is switched off. So I think it is an issue with the B737/B738 and maybe some others planes as well.
Let’s wait and see if somebody of the development team can explain if this is a bug or something else.

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