CM,
Yes, sorry if I wasn't clear, I was answering Coff's question abou the lift fan door operation, and excluded the thrust control aspect.
You're right. Lift fan thrust is controlled by operation of the lift fan inlet guide vanes. The lift fan exhaust vane box is also used to help control thrust (by varying nozzle exit area), as well as vectoring the lift fan thrust angle.
The door scheduling does two things. First, it reduces door drag, so reducing power requirements and also door loading (so less weight of structure required). Secondly, and just as importantly, it improves the lift fan intake 'capture efficiency' - at higher forward speeds, the air doesn't really want to turn 90 degrees and go down the fan - having the door at 30 degrees makes it do that. (That was one of the shortcomings with the X-35 'bi-fold' design - it didn't work as well at higher forward speeds).
Hope this helps
Engines