Hi there. I remember a web site, must have been a flight-sim web site, that has sound files that you can download of virtually every engine sound possible.
I don't do flight-sim so maybe someone here who does can point you in the right directon.
Once you have downloaded the sound file it will need converting to a MP3. Once it is an MP3 file you can save it on your desktop then connect you phone and transfer the file to your phone.
Once that is done I guess you find the file on your phone then select that as the ringtone. I don't have a Blackberry but I reckon most phones would have that option.