How to invert rover wheels/wings?

[PeggleFrank]

I've made a small ion-powered glider that uses the adjustable wings (can't remember their names) and some rover wheels (because rover wheels are so much lighter and nicer to build with) but when I press W it makes the wheels spin and the wings pull the glider into the ground, and when I press S it slows down and goes into the air, usually exploding when it hits the ground because I'm using really cheap wheels and because it's lost too much momentum to actually stay in the air.

I tried inverting the wheels, but that's only for the left and right. Is there any way to invert the forward/backward movement of the wheels?