Hi Team! I need help with a twin motor tailsitter I am designing and testing. It is a plank foam wing, with an SLS nylon printed fuselage. CG is at 18-20% back from LE for dynamic stability. wing profile is a NACA 25115 reflex wing, with carbon plate wing fences/vertical stabilizer/landing gear on the wing tips. The aircraft has very large control surfaces, about 1/4 to 1/3 of the wing area, similar to an aerobatic plane. It hovers pretty well, but I have been having consistent handoff issues as soon as the transition to forward FW is done, and it occurs within milliseconds of the hand off to the FW controller. It is a violent pitch discontinuity that occurs immediately after handoff, and the aircraft becomes unrecoverable. I have been reducing gains a bit to prevent a massive pitch oscillation that had been happening before this latest flight, again right after transition was done. There is a big change in the elevon trim right at handoff. Transition itself is beautiful. The latest flight log is attached. Can someone please take a look and see what I am missing? Is it just FW trims that need to be adjusted? Thanks so much in advance!
I think its just a matter of turning the FW gains. You might find it easier with a lower Q_TAILSIT_ANGLE so the FW controller switch happens sooner and you don’t have so far to recover back to VTOL if it goes wrong.