WPR18LA121

The owner lent the weight-shift-control aircraft to the pilot for a local flight. During that flight, the pilot noted that the aircraft's handling characteristics were different than other weight-shift-control aircraft he had flown, and that it was not as responsive to his control inputs. He asked the mechanic who had performed the most recent condition inspection whether these characteristics were normal, and the mechanic stated that it was typical for the aircraft make. On the day of the accident, the pilot again borrowed the aircraft for an early morning flight in light wind conditions. He noted during takeoff that the aircraft's roll tendency was more pronounced, and he completed a traffic pattern followed by a low pass over the runway. He again climbed the aircraft to pattern altitude and after leveling off, noticed that the roll tendency had become worse and he had limited control of the aircraft. On final approach, the aircraft's stability further decreased, and the aircraft entered a spiraling descent to ground contact. The aircraft's wing was replaced about two years before the accident and the required 5-hour flight testing period of the carriage and wing combination had not been completed. Examination of the aircraft revealed that the right outboard leading edge had fractured. The mechanic that examined the wreckage stated that the fracture surfaces and surrounding fabric indicated that the fracture occurred inflight, with the fractured edge of the tube rubbing the cloth to failure. He stated that this type of fracture in the leading edge was known to occur in this make and model, usually due to improper ground handling. Although review of maintenance records revealed no indication of previous damage to the wing assembly, the circumstances of the accident are consistent with a failure of the leading-edge structure, which subsequently resulted in an inflight loss of control.

On April 15, 2018 at 0620 mountain standard time, an Airborne Windsports Edge XT-912-L weight-shift-control aircraft, N107PW, was substantially damaged when it was involved in an accident near Peoria, Arizona. The sport pilot sustained minor injuries. The aircraft was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that his friend, who was a student pilot, recently purchased the weight-shift-control aircraft. A few days before the accident, after completing an annual inspection, the mechanic performed a maintenance test flight and stated that the aircraft operated normally. Shortly thereafter, the pilot performed several touch-and-go practice takeoff and landings. He noted during the flight that the aircraft's handling characteristics were different than other weight-shift-control aircraft he had flown, specifically that it was not as responsive in turns. He spoke to the mechanic after his flight, and asked him if such handling characteristics were normal, and the mechanic responded that it was typical for that make of weight-shift-control aircraft. On the day of the accident, the pilot borrowed the aircraft again, choosing to take an early morning flight because the wind was light (about 3 kts). The aircraft had not been flown since he had flown it after the maintenance flight. During the preflight inspection, he noted about 6.5 gallons of fuel remained and the aircraft's configuration had not changed. During takeoff, he felt that the aircraft's roll tendency was more pronounced, and he recalled that, upon reaching traffic pattern altitude, the aircraft seemed to be less stable. He could not determine if it was because of wind or his unfamiliarity with the make/model. He entered a right traffic pattern and performed a low pass over the runway about 15 ft above ground level (agl). The pilot again climbed to pattern altitude and after leveling off, noticed that the roll tendency had become even worse. While on the downwind leg of the traffic pattern, he decided that he needed to land because he was having difficulty maintaining control. As the pilot turned onto final approach, the aircraft's stability further decreased, and he pulled the bar back, continuing in a shallow descent. He reduced engine power while maintaining an airspeed of about 40 kts. He kept the bar inward and was at a slight crab angle, when the aircraft began to roll to the right. He recalled that it felt as if the aircraft had stalled but thought that the airspeed was too high for that to have occurred. The pilot continued to attempt to regain control by manipulating the control bar and adding additional engine power; however, about 250 feet agl, the aircraft began a descending, spiraling turn to the right. As he neared the ground, the roll began to correct, but the right wing impacted the ground. Upon impact, the engine was still running with full power and two witnesses ran toward the pilot, who was still in the cockpit. Neitherthe pilot nor witnesses could determine how to turn off the engine, and the engine ran until the fuel supply was exhausted. Examination of the aircraft revealed impact damage to the metal structure, with the 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 examined the wreckage and noted that the right outboard leading edge fracture surfaces were worn on the edges, consistent with being intact for a duration of time before completely fracturing. Additionally, the fractured edges had material embedded in their structure, consistent with a rubbing motion. The cloth at the fracture site of the right outboard leading edge appeared to be frayed rather than torn, consistent with the fractured edge of the tube rubbing the cloth to failure. The mechanic further stated that the leading edge comprises two tubes; the inboard tube is closer to the nose of the wing and is larger in diameter than the outboard tube. The smaller diameter outboard tube is inserted into the inboard tube to create the leading edge. If the aircraft is rotated back on the wingtips, as can occur if not properly secured while on the ground during a wind gust, a plastic deformation can occur at the junction of the outboard and inboard tubes. This deformation crystallizes the aluminum imperceptibly and in a location that is inaccessible during a preflight inspection. Thereafter, the tubes constantly bend and flex during flight and the deformation will evolve into a crack as the metal is work-hardened. Once this occurs, the outboard leading-edge separates, and the pilot will not be able to maintain control. According to maintenance records, the carriage had accrued 568 hours by June 2016, and in November 2016, received an Experimental Light-Sport (Weight-Shift-Control) Special Airworthiness Certificate, after a new wing was added. Compatibility between the wing and carriage were untested by the carriage manufacturer and was the responsibility of the owner during Phase 1 flight testing, which required 5 hours of flight. At the time of the accident, the aircraft had accrued 572.6 hours; a total of 4.6 hours since the installation of the new wing. Review of maintenance records revealed no indication of previous damage to the wing assembly.