What happened
On September 21, 2005, a Robinson R22 Mariner helicopter, registration F-GRIB, was conducting a flight test for a student pilot's private license. The flight originated from Issy-les-Moulineaux, with a scheduled stop at Pontoise for maneuvers before proceeding toward Dreux.
During the flight, the examiner initiated a simulated engine failure by reducing power to practice an autorotation. Shortly after the power reduction, the crew lost control of the aircraft. Witnesses observed the helicopter pitch up, flip onto its back, and descend vertically. The aircraft struck the ground in a plowed field, resulting in two fatalities and the total destruction of the helicopter.
The investigation
The investigation focused on the aircraft's configuration and the flight dynamics during the autorotation maneuver. Investigators examined the wreckage and found that the main rotor blades were intact but not rotating at the time of impact. The tail boom had been severed in several sections, with damage patterns matching contact with the main rotor blades.
Technical analysis of the engine and fuel systems revealed no mechanical failures or fuel starvation. The investigation also noted that the aircraft was equipped with floats, which alters the helicopter's handling characteristics. The examiner's experience and the student's recent training history were also reviewed, alongside the specific aerodynamic risks associated with the R22 Mariner's semi-rigid rotor system during low load factors.
Findings
- The primary cause of the accident was the inappropriate execution of an autorotation maneuver during a simulated engine failure.
- The student pilot, who was more accustomed to standard landing gear configurations, likely applied imprecise or incorrect control inputs following the power reduction.
- The presence of floats on the Robinson R22 Mariner significantly altered the aircraft's flight qualities, making longitudinal attitude and yaw control more difficult during autorotation.
- The examiner's reaction to the developing instability was likely delayed, possibly due to an intention to avoid failing the student during the examination.