What happened
On May 26, 2019, a Robinson R44 Raven II, registration F-HNAF, was conducting a local instructional flight from Annecy Meythet. The flight involved an instructor and a student pilot performing hovering exercises in a nearby field. After an initial period of flight and a brief rest, the instructor assigned a specific exercise where the student controlled the pedals and collective pitch, while the instructor maintained control of the cyclic.
During the attempt to establish a hover, the helicopter suddenly began to rotate around its yaw axis, appearing to swing to the right. The instructor attempted to intervene by taking control of the pedals, but was unable to stop the rotation. In an effort to mitigate the situation, the instructor lowered the collective pitch. This resulted in a hard impact with the ground, causing the helicopter to tilt onto its left side. Following the collision, a fire broke out in the cabin, prompting both occupants to evacuate the aircraft.
The investigation
The investigation focused on the sequence of controls and the environmental conditions at the time of the accident. Investigators noted that the training site used for the exercise was not on the approved list of locations established by the flight training organization, as the instructor had chosen a closer field to accommodate the student's preference.
Examination of the Robinson R44 Raven II was partially limited due to fire damage; however, the tail boom and anti-torque rotor remained intact. Analysis indicated that the engine was delivering power at the time of the impact. The post-crash fire was likely caused by fuel spilling onto hot engine components during the violent impact and subsequent rollover. The investigation also reviewed the student's training progress, noting that while the student had experienced different instructors, they had recently been marked as proficient in hovering maneuvers.
Findings
- The primary cause of the accident was an insufficient coordination between the pedals and the collective pitch by the student pilot during the hover attempt.
- The instructor's decision to allow the student more autonomy over the controls—following a request from the student—likely led to a delayed reaction when the yaw rotation began.
- It is probable that the student was applying resistance to the pedals, which reduced the effectiveness of the instructor's corrective pedal inputs.
- The choice of an unauthorized landing site for training exercises contributed to the context of the event.