Enemy Avoid Terrain

you can try doing raycast so he's above the grownd so that helicopter tries to add transform.position up if length of raycast is too low

I'm not expert of rays tho but my thinking is in that way

the otherway would be figuering out the terrain height and adding on that 2 distances

you'll need to do a bit of math for that as terrain heights don't have meters

this is how I find at what possition I'm on terrain and I'm lowering that point a bit

 using UnityEngine;
 using System.Collections;
 [System.Serializable]
 
 public class Terraform : $$anonymous$$onoBehaviour {
     public Terrain terrain ;
     public TerrainData tData;
      
     public int xRes ;
     public int yRes ;
     
     public float[,] heights;
     
     
     public int PlayerXi ;
     public int PlayerZi ;
 
     
     private GameObject Player ;
     void Start () {
         Player = GameObject.Find("Camera") ;
 
         
         tData = terrain.terrainData;
         
         xRes = tData.heightmapWidth;
         yRes = tData.heightmapHeight;
         
         //terrain.activeTerrain.heightmap$$anonymous$$aximumLOD = 0;
     }
     
     
     void On$$anonymous$$ouseDown() {
         
         PlayerXi = (int) Player.transform.position.x;
         PlayerZi = (int) Player.transform.position.z;
         
         heights = tData.GetHeights(0, 0, xRes, yRes);
         
         // Z is X //// X is Y
         heights[PlayerZi,PlayerXi] -= 0.004f ;
 
         tData.SetHeights(0, 0, heights);
     }
 }