Loading screen with LoadLevelAsync

Hello Everyone,

I'm trying to implement a simple loading screen, but can't seem to get the loading screen to actually display. Instead I just get a black screen when the level is loading. Sometimes the black screen is only for a fraction of the second and other times it's nearly a full second.

Heres the code I've got so far. Does anyone have any ideas on how to get this to work? Perhaps I'm using coroutines and yields wrong?

 using UnityEngine;
 using System.Collections;
 
 public class LevelManager : MonoBehaviour {
     static GameObject screen;
 
     void Awake()
     {
         screen = gameObject;
         DontDestroyOnLoad(screen);
         screen.SetActive(false);
     }
 
     public static void Load(string name)
     {
         screen.SetActive(true);
         LevelManager instance = screen.GetComponent<LevelManager>();
         instance.StartCoroutine(instance.InnerLoad(name));
     }
 
     IEnumerator InnerLoad(string name)
     {
         AsyncOperation async = Application.LoadLevelAsync(name);
         while (!async.isDone)
         {
             screen.SetActive(false);
             yield return null;
         }
     }
 }