What happened
On March 6, 2024, a Hélicoptères Guimbal Cabri G2 departed from Egelsbach for a training flight focused on emergency procedures. The flight, involving an instructor and a student pilot, proceeded toward the south over Eberstadt and Pfungstadt. Upon reaching an area near Groß-Rohrheim, the crew initiated an instructional autorotation.
An initial attempt at the maneuver was aborted after the student pilot initiated the flare too early and too high. Following a period of repositioning, a second autorotation attempt was commenced at approximately 1,000 ft AGL. During this second attempt, the crew performed an initial flare and a subsequent second flare to reduce airspeed. The instructor had increased engine power via the throttle prior to the first flare to prepare for the transition back to powered flight. However, at approximately 13:00, the helicopter experienced an unplanned hard landing.
The investigation
The BFU examined the wreckage and the flight sequence. The investigation found that the helicopter's tail boom had separated from the fuselage at the connection point to the cabin. Fragments of the tail boom, including the fin and the Fenestron, were scattered in the field. The tail rotor driveshaft was also broken.
Technical inspections of the controls, rotor system, and drive train revealed no evidence of any pre-existing mechanical failure or malfunction. The investigation also reviewed the aircraft's maintenance history and the flight school's training syllabus. No injuries were reported among the two occupants.
Findings
- The accident was caused by non-optimal coordination between the instructor and the student pilot.
- The helicopter experienced a hard landing characterized by low rotor RPM.
- The structural failure of the tail boom was caused by a combination of low rotor RPM, a high load factor, an abrupt lowering of the collective pitch, and a neutral-to-rear cyclic pitch, which allowed the main rotor blades to strike the tail boom.