History of Flight
On July 29, 2023, at 0905 central daylight time, a North American AT-6D airplane, registration N49961, was destroyed when it crashed into Lake Winnebago near Oshkosh, Wisconsin. The pilot and passenger sustained fatal injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
The airplane had been at the annual Experimental Aircraft Association AirVenture fly-in at Wittman Regional Airport (OSH). According to ADS-B data, it departed runway 27 at OSH at 0857, turned right toward the north, and flew about 3 miles before turning east-northeast over Lake Winnebago, outside OSH Class D airspace. The airplane climbed to a peak altitude of 3,900 ft mean sea level, then descended rapidly into the lake at 0905.
Performance calculations based on ADS-B and winds aloft data indicated that during the final portion of flight, the airplane leveled at 3,900 ft and executed a right turn followed by a left turn before the rapid descent. After leveling, calibrated airspeed (CAS) was about 110 mph. During the turns, speed decreased to a minimum of 87 mph CAS just before the descent. The calculated load factor reached about 1.8 g during the second turn. The published 1g stall speed (wings level, landing gear and flaps retracted) was 67 mph at a loaded weight of 5,500 lbs. Based on the load factor, the accelerated stall speed at that weight would have been about 89 mph.
A witness on the lake reported seeing the airplane about 1 to 1.5 miles away and 30° above the horizon. He described the airplane as in a flat spin to the right and heard no noise. The airplane continued spinning until impact with the water. The airplane broke into pieces and came to rest on the lake bottom in about 20 ft of water.
Personnel Information
According to the pilot's flight logbook, at the time of the accident she had logged 687.8 total hours of flight experience, including 33 hours in the accident airplane make and model. A logbook entry dated May 26, 2023, for a 1.0-hour flight was noted as a checkout flight for the AT-6D, but the maneuvers performed were not specified.
Wreckage and Impact Information
A postaccident examination was conducted after the airplane was recovered from the lake. The fuselage was broken into two main pieces at the aft end of the rear-seat cockpit. The forward steel tube fuselage structure and aft aluminum structure were separated. The steel tube cage from the firewall to the rear of the aft cockpit was mainly intact, but significant crush damage was present in the front cockpit area.
The horizontal and vertical stabilizers remained attached and were mostly undamaged. Elevators and elevator trim tabs were attached; the left inboard elevator and right elevator had impact damage. Both elevator trim tabs were deflected downward (up elevator trim) but inconsistently: right tab about 30°, left about 23°. The torque shaft connecting the elevator halves was twisted and broken adjacent to the right elevator. The rudder was separated from the vertical stabilizer but partially attached via control cables; the rudder trim tab was neutral.
The right wing separated from the fuselage at the wing joint; the outboard panel was intact but impact damaged. The left wing remained attached and bent downward just outboard of the wing joint. Leading edges on both wings were crushed. Split flaps remained attached; ailerons were separated. The wing center section remained attached to the fuselage cage; the right portion was separated consistent with impact damage, and the left side was heavily damaged at the leading edge.
The left landing gear was attached and extended; the right landing gear was attached to a portion of the center section spar but separated from the wing. The landing gear was in the extended position during examination.
Examination of primary flight controls (aileron, elevator, rudder) revealed breaks consistent with impact damage. The propeller remained attached to the engine; one blade was bent rearward, the other relatively straight. The bent blade prevented engine rotation and was cut off for examination. The engine was rotated by hand after removing spark plugs; compression and suction could not be verified on all cylinders due to bent forward-mounted pushrods. Rocker covers on several cylinders were removed to verify valve action and valve train continuity.
No airframe, control system, or engine anomalies were found that would have precluded normal operation.
Medical and Pathological Information
The Walworth County Medical Examiner performed the pilot's autopsy, listing cause of death as multiple blunt force injuries. Toxicology testing by the FAA Forensic Sciences Laboratory did not identify any impairing substances in the pilot's specimens.