External electric current and APU sounds

Hello again!

I am creating sounds for an aircraft in FS and I would like to create also external electric current and APU sounds (I have the files already).
The problem is that only an internal electric current sound is supported by the sound configuration in the section of [GYRO_SOUND].

The [GYRO_SOUND] section lets to play only internal sounds.
I know that I can use the [JET_WHINE] section for example, to create an external electric current sound,
but the problem is that it can be heard everytime also when everything is shut down.
That's what I did for now, the solution with the [JET_WHINE] section.
I set another [JET_WHINE] section to play the external electric current sound all the time from 0 RPM to MAXIMUM RPM, in a constant volume and in a constant pitch.
But of course it's better maybe have another way.
The same problem is with the external APU sound.
I tried to find the events of button clicks in the gauges folders that set what sounds to play but I didn't success.

If your a/c has less than 4 engines then one engine can be the APU
I don't understand it, the plane itself has 3 engines for flying like in the 727 for example with T form wing.
About the APU i don't know how many engines, but in the Simulator you see only one gauge for the APU. Does it mean that there is only one engine for the APU?
But about the A/C what you said, there are 4 switches for battery in the panel. Is that what you mean?


Resource contributor
What he means is that (since fs has a limit of 4 engines) you can add an extra engine as a psuedo-APU, using XML code to keep it at idle. Us your sound cfg to define the APU sounds to this engine.

Alternatively, you can use Doug's XML sound gauge and control sounds directly. The only caveat is that it will be heard in all views unless you know what you're doing.
3 engines and T-tail, 4 battery switches, APU, sounds like a TU-154 :D
For FS-X, the XML sound gauge can report view status (cockpit/outside..) . For FS-9, use "(P:ACTIVE VIEW MODE)" (1=cockpit view, 2=VC, 3=tower, 4=spot, 5=top down)
You can use engine #4 as APU. Also, it will burn fuel!! And/Or use it as GPU by cranking the starter and flicking on the generator, above 10% N2 it generates electricity so to feed its own starter effectively becoming an over-unity energy creator. Starter will happily reach 22% N2 so this always works for jets!