CEN17LA307

The sport pilot (who was not an instructor) and the student-pilot-rated passenger were making a local personal flight in the weight-shift-control (WSC) aircraft. The pilot was seated in the front seat, and the passenger was seated in the rear seat. A flight instructor observed the WSC aircraft make several stable visual approaches to a grass runway. The last approach was unstable, which the flight instructor attributed to the passenger attempting to fly the approach. A go-around was initiated, which transitioned to a diving left turn that continued to impact with a river. Postaccident examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The aircraft's two "training bars," which were designed for use by a flight instructor flying from the rear seat, were each deformed to the left, consistent with the passenger gripping them as the aircraft impacted the river. The passenger had recently accomplished a solo flight in a fixed-wing airplane, which has reverse control inputs from a WSC aircraft. The passenger likely made incorrect control inputs during the go-around, due to negative transfer of learning from his fixed-wing airplane training. Because of the position of the training bars, the front-seat pilot would have been unable to see the inputs being made by the person in the rear seat. Although toxicological testing indicated that the pilot had used diphenhydramine at some point before the accident, the blood levels of this drug can change postmortem, and the pilot's blood levels at the time of the accident may have been significantly lower than the therapeutic range. Based on the accident scenario and available information, the pilot's use of diphenhydramine most likely did not contribute to the accident.

The single-engine, propeller-driven, pusher-configured, two-seat tandem WSC aircraft was manufactured by P&M Aviation in 2007 and purchased by the pilot in 2009. Powered by a Rotax 912 four-stroke engine and equipped with a three-bladed composite propeller, the aircraft had a pilot-passenger "pod" suspended by a triangular frame, hinged below the wing, which permitted weight shift control of pitch and roll. The pilot and passenger each had a headset to allow for in-flight communications. Aircraft control inputs for pitch and roll were made via a control bar and were the reverse of a fixed wing airplane. For example, pushing right on the control bar of a WSC aircraft resulted in a turn to the left, and pushing forward on the control bar resulted in an increased pitch attitude. Extension "training" bars were installed to allow for control inputs from the rear seat. These bars, which were designed for use by a flight instructor flying from the rear seat, were behind the front seat pilot's field of view. On August 8, 2017, about 2005 central daylight time, a Pegasus Quantum Q-2 weight-shift-control (WSC) aircraft, N56092, impacted a river during a go-around at the Fort Atkinson Municipal Airport (61C), Fort Atkinson, Wisconsin. The sport pilot and the pilot-rated passenger were fatally injured, and the aircraft was substantially damaged. The aircraft was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91 as a personal flight. Day visual meteorological conditions prevailed for the local flight, which departed 61C about 1930. According to a flight instructor located on the ramp at 61C, the pilot made a solo landing in the aircraft about 1915. After the passenger was loaded in the rear seat, the aircraft departed from runway 21 and subsequently made several stable low approaches to a parallel grass runway. The aircraft then made an "unstable approach," which the flight instructor attributed to the passenger possibly flying the approach. He heard the engine power increase and saw the aircraft bank to the left. The left bank steepened, and the aircraft descended rapidly until it impacted a river and submerged. The Milwaukee County Medical Examiner, Milwaukee, Wisconsin, performed an autopsy on the pilot and determined that the cause of death was blunt force injuries. No significant natural disease was identified. The FAA's Bioaeronautical Sciences Research Laboratory, Oklahoma City, Oklahoma, performed toxicology testing and identified diphenhydramine in urine (unquantified) and at 0.049 µg/ml in cavity blood. Diphenhydramine is a sedating antihistamine used to treat allergy symptoms and as a sleep aid. It is available over the counter under the names Benadryl and Unisom. Diphenhydramine carries the following warning: "may impair mental and/or physical ability required for the performance of potentially hazardous tasks (e.g., driving, operating heavy machinery)." Compared to other antihistamines,diphenhydramine causes marked sedation; it is also classed as a central nervous system depressant. Altered mood and impaired cognitive and psychomotor performance may also be observed. The therapeutic range or the range of blood levels where psychoactive effects would be routinely expected is between 0.0250 and 0.1120 µg/ml. It is possible for diphenhydramine levels to either increase or decrease postmortem. The Milwaukee County Medical Examiner performed an autopsy on the passenger and determined that the cause of death was multiple blunt force injuries. No significant natural disease was identified. The FAA's Bioaeronautical Sciences Research Laboratory performed toxicology testing and did not identify any tested-for substances. The 51-year-old pilot held a Federal Aviation Administration (FAA) sport pilot certificate for WSC aircraft and a repairman certificate for light sport aircraft in the WSC category. The pilot had never applied for a medical certificate nor was he required to do so. The 16-year-old passenger held a student pilot certificate and had recently accomplished a solo flight in a fixed-wing airplane. The accident flight was the student pilot's first flight in a WSC aircraft. A postaccident examination revealed that both wing tip straps were intact. All of the battens and luff lines were in place and attached. All flying wires were intact, except for a rear starboard wire, which had fractured and was wrapped around the propeller hub. The fracture surface of the rear starboard wire had a broomstraw appearance. The trailing edge of the wing contained one damaged area where the propeller was protruding from the wing. A manufacturer-recommended Bettsometer testing device was used to measure the strength of the aircraft's fabric surfaces. All areas tested above the recommended 1,360 grams of force in both chord-wise and span-wise directions, except for a section of the starboard wing, which tested at 1,100 grams of force. The starboard wing's fabric was not torn. The engine was hand rotated and mechanical continuity was confirmed. The spark plugs exhibited a normal condition. The oil tank was at the full level, and the fuel tank contained about 11 gallons of fuel. The aircraft's two "training" bars were each bent to the left. The most significant bending occurred near the bottom of the bars, where they connected to the base tube. Examination of the airframe and engine revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.