Accident Overview
On April 15, 2018, at 0620 mountain standard time, an Airborne Windsports Edge XT-912-L weight-shift-control aircraft, registered as N107PW, was substantially damaged in an accident near Peoria, Arizona. The sport pilot sustained minor injuries. The aircraft was being operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Pilot Account
The pilot reported that a friend, a student pilot, had recently purchased the aircraft. Several days before the accident, following an annual inspection, a mechanic conducted a maintenance test flight and reported normal operation. The pilot subsequently performed several touch-and-go practice takeoffs and landings. During that flight, he noticed the aircraft's handling characteristics differed from other weight-shift-control aircraft he had flown, particularly in turn responsiveness. He later asked the mechanic if this was normal and was told it was typical for that make.
On the accident day, the pilot borrowed the aircraft again, choosing an early morning flight due to light winds (about 3 knots). The aircraft had not been flown since his previous flight. During preflight inspection, he noted about 6.5 gallons of fuel remaining and the configuration unchanged. During takeoff, he felt the aircraft's roll tendency was more pronounced. At traffic pattern altitude, the aircraft seemed less stable. He could not determine if this was due to wind or unfamiliarity with the make and model. He entered a right traffic pattern and performed a low pass about 15 feet above ground level (AGL). After climbing back to pattern altitude, the roll tendency worsened. While on the downwind leg, he decided to land due to difficulty maintaining control.
As the pilot turned onto final approach, stability further decreased. He pulled the bar back, maintaining a shallow descent, reduced engine power, and held an airspeed of about 40 knots. He kept the bar inward with a slight crab angle when the aircraft began rolling to the right. He recalled it felt like a stall but believed the airspeed was too high. He attempted to regain control by manipulating the control bar and adding power, but about 250 feet AGL, the aircraft entered a descending, spiraling turn to the right. Nearing the ground, the roll began to correct, but the right wing impacted the ground. The engine was still running at full power after impact. Neither the pilot nor two witnesses could determine how to shut off the engine, which continued running until fuel was exhausted.
Post-Accident Examination
Examination revealed impact damage to the metal structure, with both outboard leading edges completely broken off the frame. The left outboard leading edge was fractured consistent with impact. A mechanic familiar with weight-shift-control aircraft noted that the right outboard leading edge fracture surfaces were worn on the edges, consistent with being intact for a duration before completely fracturing, and had material embedded in their structure from rubbing. The cloth at the fracture site of the right outboard leading edge appeared frayed rather than torn, consistent with the fractured tube edge rubbing the cloth to failure.
The mechanic further stated that the leading edge comprises two tubes: a larger-diameter inboard tube closer to the wing nose and a smaller-diameter outboard tube inserted into it. If the aircraft is rotated back on the wingtips—as can occur if not properly secured during a wind gust—a plastic deformation can develop at the junction, crystallizing the aluminum imperceptibly in a location inaccessible during preflight. During flight, the tubes constantly bend and flex, causing the deformation to evolve into a crack as the metal work-hardens. Once the outboard leading edge separates, the pilot cannot maintain control.
Maintenance History
According to maintenance records, the carriage had accrued 568 hours by June 2016. In November 2016, the aircraft received an Experimental Light-Sport (Weight-Shift-Control) Special Airworthiness Certificate after a new wing was added. Compatibility between the wing and carriage was untested by the carriage manufacturer and was the owner’s responsibility during Phase 1 flight testing, which required 5 hours. At the time of the accident, the aircraft had accrued 572.6 hours total, with 4.6 hours since the new wing installation. Review of maintenance records revealed no indication of previous damage to the wing assembly.