they both sound like a jackhammer / Generator or a helicopter to me.
it happens only once I administrate the airport tow truck.
I reduced it's sound by editing the WAV file themselves (reduced the amplifier) to have a softer quieter sound.
that way you can still hear it from the cockpit , but very softly as you would hear it in real life.
I will search for airport tow truck on youtube and capture the sound of it both from the cockpit and outside of the cockpit and create two replacement files.
that way it will be realistic.
ai_singleprop01.wav - Cockpit View
xai_singleprop01.wav - All the other views
