MCDANIEL RV-6-CH — Scio, OR

What happened

The purpose of the flight was for the pilot-rated passenger to show the owner/pilot how to perform rolls in the experimental kit-built airplane. A witness reported observing the airplane in level flight about 1,000 feet above ground level before it entered a steeply banked turn. The airplane was halfway through the turn when the right wing folded up over the fuselage. The wing departed the airframe, and the airplane rapidly descended to the ground. The right wing was located about 1,090 feet from the main wreckage.

The owner/pilot was not the builder of the airplane, and he had no record of aerobatic flight experience. The pilot-rated passenger's logbook indicated that he had made a single 0.5-hour flight in another RV-6 that included performance of rolls and wing-overs.

The operating limitations document for the airplane noted that aerobatic flight was prohibited unless such flights were satisfactorily accomplished and recorded in the aircraft logbook during its flight test period. No entries were found in the logbook that would satisfy this requirement.

Postaccident examination of the separated right wing determined that the upper and lower spar-caps had failed in buckle and overload. Although the airplane was registered with the Federal Aviation Administration by the builder as an RV-6-CH model, the design of its spar caps was found to be substantially different from the kit manufacturer's design for the RV-6 model airplane, a model which can be approved for aerobatic maneuvers. Rather the design was similar to the wing cap spar design for the older RV-3 model airplane, a design which was found to be susceptible to failure in buckle when exposed to aerobatic flight. Following a number of inflight wing failures in RV-3 airplanes during aerobatic flight, the kit manufacturer recommended that no aerobatic maneuvers be performed in RV-3 model airplanes until wing spar modifications that increase the spar's stiffness and resistance to buckling have been accomplished. Because the purpose of the flight was performance of an aerobatic maneuver (rolls) and because the airplane's wing spar cap design was not suitable for aerobatic flight, it is likely that at some point during the flight, an aerobatic maneuver was performed that weakened the wing, and the final steep turn was then sufficient to overload the wing.

Toxicology results showed that the owner/pilot had therapeutic levels of diphenhydramine, a sedating antihistamine, in his system; however, it could not be determined if he was flying at the time of the accident or if this impairment contributed to the accident.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.