Spring RTS Engine

Trying to make a helicopter but it's acting weird, like it's on ice in the air. Once it starts flying it takes ~forever~ to stop or change direction.

What the hell?

Also, it bobs up and down super quick, like spasmatically so.

http://springrts.com/mantis/view.php?id=3896

http://springrts.com/mantis/view.php?id=3891

The 'bobbing up and down' is strange behaviour I've also seen with speeder bikes in SWIW.