i would like to rotate an object from an other objects script

hey, Im trying to make a flight game that includes a verticcal takeoff and landing plane, for grafic and utility purpose i would like to have an engine rotate, the engine being a child of the plane, from the code of the plane it selffor some akward reason, the cube seems to rotate x, y, and z axis at the same time when i only need x, and extreemly fast. here is the code im using.

 #pragma strict
 
 var Speed = 0; 
 var Torque = 10;
 var Gravity = 100.0;
 var Acceleration = 2;
 var maxSpeed = 0;
 var minSpeed = 0;
 private var SavedGravity = 0;
 var engin : Transform;
 var engineOrient = 0.0;
 var engineRotSpeed = 10.0;
 SavedGravity = Gravity;
 
 function Start () {
 
 }
 
 function Update () {
 
 if (Speed >= maxSpeed)Speed = maxSpeed;
 if (Speed <= minSpeed)Speed = minSpeed;
 if (Input.GetKey(KeyCode.W))Speed += 1 * Acceleration;
 if (Input.GetKey(KeyCode.S))Speed -= 1 * Acceleration;
 if (Input.GetKey(KeyCode.Tab))engineOrient += 1 * engineRotSpeed/100; 
 if (Input.GetKey(KeyCode.LeftControl))engineOrient -= 1 * engineRotSpeed/100;
 
 constantForce.relativeTorque.y = Input.GetAxis("Yaw") * Torque * 2 * Time.deltaTime;
 constantForce.relativeTorque.x = Input.GetAxis("Pitch") * Torque * Time.deltaTime;
 constantForce.relativeTorque.z = Input.GetAxis("Roll") * Torque * Time.deltaTime;
 
 // set direction of engine
 engin.transform.rotation.x = engineOrient;
 
 Gravity = SavedGravity - Speed;
 if(Gravity <= 0)Gravity = 0;
 // note that the speed s not here because it will be set acording to the engines orientation

thank you all