Transform.position not working ???

 public class PlaneScript : MonoBehaviour
 {
     Vector3 velocidad = Vector3.zero;
     public float Gravedad;
     public float VelocidadSalto;
     bool Salto = false, IsAlive = true;
     public float velMax;
     void Update ()
     {
         if (IsAlive && Input.GetKeyDown(KeyCode.Space))
         {
             Salto = true;
         }
         else if(IsAlive && Input.touchCount >= 1)
         {
             Touch myT = Input.GetTouch(0);
             if(myT.phase == TouchPhase.Began)
             {
                 Salto = true;
             }
         }
     }
     void FixedUpdate()
     {
         //Gravity
         velocidad.y += Gravedad * Time.deltaTime;
         //JumpVelocity
         if (Salto)
         {
             Salto = false;
             //if(transform.position.y < 1.5f)
             //{
                 velocidad.y = VelocidadSalto;
             //}
         }
         //SetTheVelocity
         transform.position += velocidad * Time.deltaTime;
     }
 }