[Paulo Hirth]

The best way to do a sound is not using a genuine bad quality sound file, but see a real video and search and colect good quality sound files, mix correct to try result a sound near real plane or at last superior stock sound.
Months ago i use a eletric engine for simulate a eletric flaps sound with good results.
The important is the RESULT, the sound in game, if you dont like you can change, fixes this sound
and post here your work with engine sounds.