What happened
On February 16, 2021, a Dynali H3 Sport microlight helicopter, registration 60ACX, was engaged in a cross-country pleasure flight. The pilot had been performing handling exercises near a private landing site and the Mouy aerodrome before proceeding toward Persan-Beaumont aerodrome. At approximately 15:30, the pilot placed a telephone call to an instructor to provide his intentions.
Roughly twelve seconds after concluding the call, the pilot initiated a left turn at an altitude of approximately 600 feet. During this maneuver, the aircraft entered an unusual attitude, characterized by rapid and extreme changes in bank and pitch. The helicopter subsequently struck trees and the ground, resulting in the fatal injury of the pilot and the destruction of the aircraft.
The investigation
Investigators examined the wreckage and analyzed data retrieved from the aircraft's Electronic Flight Instrument System (EFIS) and Engine Monitoring System (EMS). Witnesses at the scene reported hearing an engine backfire and observing the helicopter yaw and pitch down before falling vertically. One witness noted that parts appeared to separate from the aircraft during the descent.
Physical examination of the wreckage revealed that the rotor blades had struck the tail boom and the vertical stabilizer, causing significant damage. The investigation also identified a rupture in the flexible coupling between the tail rotor drive shaft and the engine drive shaft; however, laboratory testing suggested this rupture was a consequence of the structural loads caused by the rotor-to-tail-boom impact, rather than the cause of the accident. Data from the engine monitoring system allowed investigators to rule out any engine malfunction prior to the loss of control.
Findings
- The aircraft entered a steep left bank of 52 degrees, which was significantly steeper than the bank angles recorded during previous turns in the same flight.
- The pilot made rapid, large-amplitude inputs on the collective pitch control during the maneuver.
- The loss of control may have been caused by the pilot overreacting to the steep bank angle during the turn.
- While not definitively proven to be a factor, the use of a telephone during flight may have served as a distraction, potentially impacting flight management during the critical phase of the turn.