History of Flight
On February 24, 2022, about 1656 eastern standard time, a Beech 35-C33, registration N6129V, was destroyed when it was involved in an accident near Hilltown Township, Pennsylvania. The flight instructor and the pilot receiving instruction were fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The pilot receiving instruction owned the airplane and had successfully completed the commercial pilot written examination. The purpose of the accident flight was to prepare him for the commercial pilot practical examination.
Review of Automatic Dependent Surveillance-Broadcast (ADS-B) data revealed that the airplane departed Doylestown Airport (DYL), Doylestown, Pennsylvania, about 1626. The data also showed that the airplane, while maneuvering at an altitude of about 2,000 ft mean sea level (about 1,600 ft above ground level), began to descend.
A witness, a licensed private pilot, reported hearing a single-engine airplane overhead and thought the engine was loud and the airspeed was slow, indicating a steep climb to practice a stall. When he looked up, he saw the airplane “diving, almost straight down” and “twisting toward the ground.” The airplane descended behind a tree line, and the witness then saw “a black ball of smoke.”
The airplane impacted a residential street. During the impact, a propeller blade separated and landed in a residence. The wreckage came to rest upright, oriented about 125° magnetic, and no debris path was observed. A postimpact fire consumed most of the wreckage.
Personnel Information
The pilot receiving instruction’s logbook was not recovered. On an application for his commercial pilot certificate, dated February 15, 2022, he reported a total flight experience of 733 hours. During a previous insurance renewal quote for the accident airplane, he reported 385 hours of flight experience in the make and model airplane. The flight instructor’s logbook indicated he had a total flight experience of approximately 11,500 hours, of which 8,000 hours were providing flight instruction.
Wreckage and Impact Information
The wreckage came to rest upright on a magnetic heading of about 125°, and no debris path was observed. The cockpit and cabin were mostly consumed by fire. Both wings separated from the airplane, but their respective flaps and ailerons remained attached. The empennage remained intact with the rudder and elevator still attached. The flaps and landing gear were retracted. Flight control continuity was confirmed from all flight control surfaces to the cockpit area. Measurement of the two elevator trim actuators corresponded to a 5° trim-tab-down (nose-up) position.
The engine came to rest upright separate from the airframe. The three propeller blades separated from the hub. One blade was consumed by fire about 12 inches outboard of the root. Another blade exhibited fire damage, s-bending, chordwise scratching, and leading-edge gouging. The other propeller blade exhibited s-bending, chordwise scratching, and leading-edge gouging.
Additional Information
A video study conducted by the National Transportation Safety Board (NTSB) estimated the engine speed based on a video recorded by a camera on a residential building. The 65-second video included sound. The study found that the engine was operating erratically near its expected operating speed—about 2,600 rpm. The last 11 seconds before ground impact included a 3-second period during which there was likely no combustion or the engine was idling. The airplane’s rapid descent toward the ground started about the same time as this 3-second period.
An NTSB performance study using ADS-B data showed that the airplane’s altitude varied between 1,400 and 4,000 ft mean sea level and that the calibrated airspeed varied between 50 and 150 knots. The study found that the airplane’s maneuvers during the final portion of flight were below its flaps-up, idle power stall speed and were twice briefly below the flaps-down stall speed. The performance study also used images from the video to correlate with flightpath data. During the final 30 seconds of flight, the airplane rolled left when engine noise was reduced.
Medical and Pathological Information
The Bucks County Coroner’s Office performed autopsies for both pilots. Their cause of death was multiple blunt force injuries. The flight instructor had a heart attack about 3 weeks before the accident. The autopsy examination of his heart was limited by the extent of his injuries.
Toxicology testing by the FAA Forensic Sciences Laboratory was negative for the pilot receiving instruction. For the flight instructor, testing identified ethanol in liver tissue but not in muscle tissue. Ethanol can be produced by body tissues after death. Testing also identified metoprolol in both tissues. Metoprolol is a beta-blocking drug used to treat high blood pressure, control heart rate, and prevent recurrent heart attacks, and is generally considered not to be impairing.