Start animation with different game object

Hi, I have this aeroplane model with animation of rudder, and I want to activate it through another game object..

( Because i had assigned a box collider in the aeroplane as a trigger for aileron animation, so no choice i have to use another gameobject's collider as a new trigger for rudder... Unless there is a way to use script to control different collider; such as: box collider, sphere collider etc, which i really no idea.. )

This is a script of my aeroplane :

 public class landinggear : MonoBehaviour {
     private Animator anim;
     private GameObject player;
     private activateRudder rud;
 
 void Start () {
 
         anim = GetComponent <Animator> ();
         rud = GameObject.Find ("stair").GetComponent<"name of script in stair"> ();
     }
 void Update () {
     
         if (rud.... 

Here onwards I dont know how to let unity go and check whether my character got enter collider of the stair.

Script of stair :

 public class activateRudder : MonoBehaviour {
 
      
     private Animator ani;
     private GameObject player;
 
     
     void OnTriggerStay(Collider other){...

Not really know what to do with this script..cause basically is just to enter a collider..

So my intention is If i enter collider of stairs.. the aeroplane bool will activate to true... I really stuck in this part, anyone who know how to solve this really much appreciate your help... Thanks