After shutting down the APU with the GPU connected, the APU intake door never closes. Why? It stays open inflight even.

Forgive me if I'm wrong but the APU inlet on a 737 isn't a door, it's a bicycle seat-shaped indent below the tail section so it can't close.

You are correct but there is a little cover thing that I called a door that is constantly sticking out from the APU inlet.

Isn't that just a vortex generator? Not sure it moves. Might be wrong though B)

There is a vortex generator there. I believe the door is internal (inside the NACA inlet).

 

It's not an external door like the 777.

There is a vortex generator there. I believe the door is internal (inside the NACA inlet).

 

 

 

The vortex generator is attached to the door.  The entire assemply moves in and out when the door opens and closes.  It does not move very much.  On the real plane it's not terribly obvious if the door is open or closed when you look at it from the outside.

 

It's better described as an inlet plug than a door.  If you zoom in on the external model and watch closely you can see the door moving when you move the APU switch to the ON position.

The vortex generator is attached to the door.  The entire assemply moves in and out when the door opens and closes.  It does not move very much.  On the real plane it's not terribly obvious if the door is open or closed when you look at it from the outside.

 

It's better described as an inlet plug than a door.  If you zoom in on the external model and watch closely you can see the door moving when you move the APU switch to the ON position.

 

Great info - thanks Joe!

 

It's better described as an inlet plug than a door.  If you zoom in on the external model and watch closely you can see the door moving when you move the APU switch to the ON position.

 

Jeez PMDG modelling is just outrageously good.