random blobs of "turbulence" or whatever the hell it's supposed to be, engines (including turbine engines ((wtf))) can stall if you go to slow, helicopters randomly swerve around (dunno if this happens IRL or not), when rudders come off you can't control steering on the ground, etc.
i've never had a turbine engine stall on me when i fly too low, they only stall out if it has been damaged, which is probably the case for you. the helicopters could be better, i'll agree with you on that. turbulence is there to present a challenge, and i've only ever experienced it while flying very high or through the mountains (crosswinds), and i've never experience the rudder problem so I can't comment on that.
it's a game, not a simulator. it's not supposed to be realistic. the flying is great compared to most other open-world crime games that let you fly aircraft.