What happened
On August 9, 2021, a Diamond DA42-L360, registration N906ER, was involved in an accident near Hiddenite, North Carolina, during a multiengine instructional flight. The flight, operated by Academy of Aviation, involved a flight instructor and a private pilot performing various maneuvers and simulated emergency procedures.
Following a simulated single-engine approach and landing at Wilkes County Airport (UKF), the instructor attempted to simulate a right-engine failure during the takeoff roll. While the engine briefly lost power, it was restarted and functioned normally for the subsequent takeoff and climb. Upon reaching 5,000 feet mean sea level, the student performed an emergency descent maneuver while simulating a left-engine fire, which involved shutting down the left engine.
During this descent, the Attitude and Heading Reference System (AHRS) failed. As the aircraft descended, the instructor noted that the airspeed increased beyond 100 knots and the altitude dropped to approximately 3,000 feet. The student reported an inability to pitch the aircraft up, and the remaining right engine began to sputter. The instructor took control and attempted to restore power to both engines, but reported that the engines did not seem to be producing normal power. Despite both occupants pulling back on the flight controls as hard as possible, they were unable to stop the descent.
The aircraft touched down in an open soybean field, impacted a ditch, and skidded to a stop. The impact caused the nose gear to collapse and the right main landing gear to partially collapse, resulting in substantial damage to the right wing. The flight instructor and student pilot were not injured.
The investigation
Post-accident examinations of the engines and airframe showed no evidence of mechanical failures prior to the impact. Investigators confirmed that flight control continuity was maintained and all surfaces moved through their full range of motion. The variable elevator stop system, which limits upward elevator travel based on engine and flap settings, was tested and found to be functioning normally.
An NTSB performance study using ADS-B data showed that a rapid descent began at 5,000 feet, with the aircraft pitching down 30 degrees and banking right 45 degrees, reaching a maximum descent rate of 6,000 feet per minute. The study indicated that the airspeed likely remained above the aerodynamic stall speed throughout the descent.
Investigators noted that the manual elevator trim was found in a slightly nose-down position, and neither pilot adjusted the trim wheel during the descent. Additionally, the autopilot circuit breaker had been pulled and collated, which deactivated the electric elevator trim.
Findings
- The flight instructor and student were unable to arrest the descent following a simulated engine fire and emergency descent.
- The elevator trim was not adjusted by the crew to relieve control pressure during the descent.
- The aircraft's pitch likely remained somewhat controllable throughout the descent, as evidenced by the lack of significant damage to the fuselage and empennage.