Unity Avion Script

var speed=0;
var Torque=10;
var Gravity=100.0;
var acceleration=2;
var maxspeed=1200;
var minspeed=0;
private var SavedGravity=0;
SavedGravity=Gravity;
function Update(){
if(speed >= maxspeed)speed=maxspeed;
if(speed<=minspeed)speed=minspeed;
if(Input.Getkey(KeyCode.W))speed=speed+1*acceleration;
if(Input.GetKey(KeyCode.S))speed=speed-1*acceleration;
ConstantForce.RelativeTorque.y=Input.GetAxis("Yaw")*Torque*2*Time.deltaTime;
ConstantForce.RelativeTorque.x=Input.GetAxis("Vertical")*Torque*Time.deltatime;
ConstantForce.RelativeTorque.z=-Input.GetAxis("Horizontal")*Torque*Time.deltatime;
Gravity=SavedGravity-speed;
ConstantForce.Force.y=-Gravity/100;
if(Gravity<=0)Gravity=0;
}