Unity Camera and transform?

Hi All

I Have my plane script, a plane and multiple cameras with in my scene. What I am looking to do is when "V" is pressed it changes to the second camera and so on. I have the camera change working properly but when it disables the main chase camera it stops the plane from moving forward. My Plane script is in C# and the camera change script is in Java.

Plane script

 using UnityEngine;
 using System.Collections;
 
 public class PlanePilot : MonoBehaviour {
 
     public float turnSpeed = 50.0f;
     public float speed = 80.0f;
     public GameObject explosion;
 
     void Start () {
         Debug.Log("Plane Pilot script added to: " + gameObject.name);
     }
 
     // Update is called once per frame
     void Update () {
         
         Vector3 moveCamTo = transform.position - transform.forward * 15.0f + Vector3.up * 5.0f;
         float bias = 0.96f;
         Camera.main.transform.position = Camera.main.transform.position * bias +
             moveCamTo * (1.0f-bias);
         Camera.main.transform.LookAt (transform.position + transform.forward * 20.0f );
 
 
         transform.position += transform.forward * Time.deltaTime * speed; 
 
         speed -= transform.forward.y * Time.deltaTime * 50.0f;
 
         if (speed < 35.0f) {
             speed = 35.0f;
         }
         if (speed > 90.0f) {
             speed = 90.0f;
         }
 
         transform.Rotate( Input.GetAxis("Vertical"), 0.0f, -Input.GetAxis("Horizontal") );
 
         if(Input.GetKey(KeyCode.PageUp))
             transform.Rotate(Vector3.up, -turnSpeed * Time.deltaTime);
 
         if(Input.GetKey(KeyCode.PageDown))
             transform.Rotate(Vector3.up, turnSpeed * Time.deltaTime);
 
         if(Input.GetKey(KeyCode.Q))
             transform.Rotate(Vector3.up, -turnSpeed * Time.deltaTime);
 
         if(Input.GetKey(KeyCode.E))
             transform.Rotate(Vector3.up, turnSpeed * Time.deltaTime);
 
 
         float terrainHightWhereWeAre = Terrain.activeTerrain.SampleHeight (transform.position);
 
         if (terrainHightWhereWeAre > transform.position.y) 
         { 
             Instantiate(explosion,transform.position,transform.rotation);
             Destroy(gameObject);
         }
     }
 }

Cam script

 var cam1: Camera;
  var cam2: Camera;
  var cam3: Camera;
  
  function Start() {
      cam1.enabled = true;
      cam2.enabled = false;
      cam3.enabled = false;
 
 Void update ()
  if (Input.GetKeyDown(KeyCode.V) && (cam1.enabled == true)) {
  cam1.enabled = false;
  cam2.enabled = true;
  cam3.enabled = false;
  }
  else if (Input.GetKeyDown(KeyCode.V) && (cam2.enabled == true)) {
  cam1.enabled = false;
  cam2.enabled = false;
  cam3.enabled = true;
  }
  else if (Input.GetKeyDown(KeyCode.V) && (cam2.enabled == true)) {
  cam1.enabled = true;
  cam2.enabled = false;
  cam3.enabled = false;
  }

Thanks