Hilltown Township, PA, USA
N6129V
BEECH 35
The flight instructor and the pilot receiving instruction were conducting a flight in an airplane that the pilot receiving instruction owned, and the purpose of the accident flight was to prepare him for the commercial pilot practical examination. About 30 minutes after takeoff, the airplane was maneuvering at an altitude of about 1,600 ft above ground level. The airplane then entered a left spin and descended toward the ground, impacting a residential street. A witness stated that he heard a single engine airplane overhead and thought the airplane’s loud engine sound did not match its slow airspeed, which meant to him that the airplane was most likely in a steep climb to practice a stall. The witness looked up again and saw the airplane diving almost straight down and twisting toward the ground. Examination of the wreckage revealed no preimpact mechanical malfunctions. Review of automatic dependent surveillance-broadcast (ADS-B) data revealed that the airplane’s maneuvers during the final portion of flight were conducted below its flaps-up, idle power stall speed and were twice briefly below the flaps-down stall speed. During the final 30 seconds of flight, the airplane rolled rapidly to the left when engine noise was reduced. The airplane’s rapid left roll and loss of altitude were consistent with an aerodynamic stall. Thus, the pilot who was flying (which could not be determined based on the available evidence) allowed the airplane’s critical angle of attack to be exceeded, resulting in a loss of airplane control. Toxicological testing detected ethanol and metoprolol in the flight instructor’s specimens. The most likely source of the ethanol was postmortem production; therefore, the identified ethanol did not contribute to the circumstances of the accident. Although direct effects from the flight instructor’s use of metoprolol likely did not contribute to the events, the available evidence precluded a determination of whether effects from the flight instructor’s recent heart attack and underlying heart disease contributed to the circumstances of the accident. In addition, if the flight instructor had experienced a medical event during the flight, should have been reasonable able to control the airplane.
HISTORY OF FLIGHTOn February 24, 2022, about 1656 eastern standard time, a Beech 35-C33, 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), the airplane began to descend. A witness to the accident was a licensed private pilot who tended to look up at the sky as small airplanes flew over. When the witness was standing in his neighbor’s driveway, he heard a single-engine airplane overhead and thought the airplane’s engine was loud and the airspeed was slow, which indicated to him that the airplane was most likely in a steep climb to practice a stall. By the time that he looked up at the sky again, he saw the airplane “diving, almost straight down” and “twisting toward the ground.” The airplane was out of the witness’ view after it descended behind a tree line. 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 INFORMATIONThe pilot’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. Review of the flight instructor’s logbook revealed that he had a total flight experience of approximately 11,500 hours; of which, 8,000 hours were providing flight instruction. WRECKAGE AND IMPACT INFORMATIONThe 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 INFORMATIONVideo Study The National Transportation Safety Board (NTSB) conducted a video study to estimate the speed of the airplane’s engine based on a video recorded by a camera installed on a residential building. The video was 65 seconds long and 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. Aircraft Performance Study The NTSB also conducted a performance study for the accident flight. 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 toward the end of the flight from the video recording to correlate the video data with the flightpath data. The study found that, during the final 30 seconds of flight, the airplane rolled left when engine noise was reduced. MEDICAL AND PATHOLOGICAL INFORMATIONThe Bucks County Coroner’s Office, Warminster, Pennsylvania, performed autopsies for both the pilot receiving instruction and the flight instructor by. 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 was performed on the pilot receiving instruction and flight instructor by the FAA Forensic Sciences Laboratory. The testing was negative for the pilot receiving instruction. The testing for the flight instructor identified ethanol in liver tissue but not in his muscle tissue. The testing also identified metoprolol in both tissues. Ethanol is primarily a social drug found in beer, wine, and liquor and is a central nervous system depressant. Ethanol can also be produced by body tissues after death. Metoprolol is a beta-blocking drug used to treat high blood pressure, control heart rate, and prevent recurrent heart attacks. The drug is generally considered not to be impairing.
The pilots’ exceedance of the airplane’s critical angle of attack while practicing maneuvers during an instructional flight, which resulted in an aerodynamic stall and and a loss of airplane control.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
