We went through a lot of pain, trying to get the “External” view in our aircraft correct. There’s actually a documentation bug here, and some unexpected behavior.
The docs state that a “CHASE_PLANE” camera in cameras.cfg controls the External camera. This is actually incorrect, cameras.cfg doesn’t have any effect on the external camera.
The only parameter which controls it is wing_span in flight_model.cfg, which determines the camera radius.