Fauvel AV 36 flying wing breaks up in aerobatics from hidden spar damage

The pilot of a Fauvel AV 36 flying wing was seriously injured when the wooden glider broke up in flight during an aerobatic display near Haiterbach; his automatic parachute saved him. After a tow to about 1,000 m for looping figures, the wing failed and the right wing separated at the fuselage. Investigators found no overload: the break-up began with long-hidden degradation of an auxiliary spar deep in the rear structure, weakened over years by poor gluing, moisture, wood-destroying fungus and a German-variant hinge modification. When it failed, side loads passed to the main spar, which was not built for them and broke.

1. Aerobatic display, wooden flying wing: A Fauvel AV 36 flying wing was towed to about 1,000 m at an airshow and flew a program of about eight or nine looping figures.
2. Hidden pre-damage in an auxiliary spar: An auxiliary spar in the rear structure had long-standing defects — poor gluing, moisture, wood-destroying fungus, a German-variant hinge modification and corrosion — in an area too enclosed to inspect.
3. Auxiliary spar fails in level flight: Approaching the field in near-horizontal flight, the weakened auxiliary spar gave way.
4. Loads transfer to the main spar: The fore-and-aft loads it had carried passed to the main spar, which is built for vertical bending and broke; the right wing separated at the fuselage.
5. Break-up; pilot parachutes down: The glider came apart in the air; the pilot's automatic parachute deployed and he came down in woodland, seriously injured.