I need your help please.
Today I tested a recently built fixed wing frame, the Skywalker 1900 build for a course in Argentina to teach people about UAVs and make them fly legal. I am using an APM 2.5 with GPS and no airspeed sensor (yet).
The first flight was good for trimming and then executed the AUTOTUNE flight mode. After doing all the manouvers I tried a loiter command without problems... then I tried a RTL and the plane went into an aggresive dive with full power. I was quick to change it to manual BUT the wings detached from the airframe and crashed. I had VERY BIG LUCK that the plane smashed some branch from the trees and had almost nothing brocken.
Since I dont have too much experiencie with first flights tuning I want to know what went wrong. The Loiter was made successfully. Also when I was flying the plane away from me before the RTL manual test, it entered in RTL because of a RC failsafe and tried to come back, change it to FWBA and when I triggered the RTL had this mess. I dont have an idea of what was the cause of the aggressive dive, maybe heavy vibrations on the APM? Can you help me to analyze the tlog that I have since I dont know what to look for?
I attach a link to download the log (wetransfer) and also by here in this post. The critical moment is at 98% of the log, just at the final.
VERY thank you in advance.