It's no possible to take off UAV if pre-placed by editor near tent hangars.
Once you take control the engine start, but if you press the 'Q' key to accellerate the UAV stuck on the same place.
If you use the UAV terminal and create a waypoint far from UAV, the UAV dont move a meter!
Also, if you press the 'A' or 'D' keys, you don't will notice any movement of ailerons.

This happen only on Stratis Island.
On landing runway UAV work as expected.