Fixed-Wing Test Aircraft — Independent Project

I designed and scratch-built a 600 mm wingspan fixed-wing RC aircraft from component level. The motor/ESC/battery combination came out of datasheet analysis rather than guesswork — the selected setup draws 20.53 A, which sits at 68% of the battery's 30 A continuous ceiling, leaving real headroom instead of running the pack at its limit.

The first motor burned out. The cause was a prop-size mismatch: I was running a drone motor outside its thermal envelope, because a fixed-wing operating range asks for sustained load in a way a quadcopter's duty cycle never does. Diagnosed it, corrected the pairing.

Then it kept breaking in flight, repeatedly, in the same way. I worked through three iterative test cycles to find out why. Frame-by-frame flight video analysis put the centre of gravity at roughly 60% MAC against a 25–33% safe range — badly aft, which makes the aircraft violently pitch-unstable. I corrected it to 22% MAC.

That was not the whole story. To find out whether the hand-launch technique was also contributing, I cross-referenced against a same-day ground-roll takeoff on the identical airframe that succeeded. Same aircraft, same conditions, different launch method, different outcome — which isolated hand-launch as an independent failure variable rather than a symptom of the CG problem.

I reached three consecutive controlled takeoffs (V1 complete) after redesigning the launch technique to counter a landing-gear geometry fault. Failure recurrence analysis identified polyfoam as the limiting structural material at the load joint, which is driving a PETG and carbon-rod structural revision for V2.