What happened
On June 8, 2004, an AS 350 BA helicopter, registration 3A-MIK, was performing a scheduled passenger flight from Nice to Monaco. After departing from the Nice helipad, the aircraft followed its established maritime route at an altitude between 300 and 500 feet.
While cruising near Cap Ferrat, the helicopter experienced a sudden and total engine failure. The aircraft continued in level flight briefly as the main rotor speed decreased, before entering a steep descent. The helicopter struck the sea surface with significant force and sank rapidly to a depth of 285 meters. One passenger was ejected during the impact, while the pilot and the remaining three passengers were found still restrained within the wreckage.
The investigation
The investigation focused on the mechanical integrity of the engine and the pilot's response to the emergency. Technical examinations of the Turbomeca Arriel 1B engine revealed that the centrifugal compressor had suffered a structural failure. Specifically, investigators found pre-existing fatigue cracks on the first blade of the inlet guide vane and on at least two light strips of the compressor cover.
Investigators also reviewed the pilot's recent flight history. Although the pilot held all necessary licenses and had recently completed type training for the AS 350 BA, he had a significant gap in helicopter flight experience, having not flown since 1999. Furthermore, his recent training had not included sufficient practice for emergency procedures, such as autorotation, outside of his initial type rating course.
Findings
- The primary cause of the engine failure was the rupture of the centrifugal compressor due to pre-existing fatigue cracks.
- The pilot's ability to manage the emergency was compromised by a delayed identification of the engine failure.
- The pilot's lack of recent helicopter experience and limited practice with emergency maneuvers contributed to the inability to react effectively to the power loss.
- The aircraft was operating within its weight and balance limits and was fully compliant with maintenance requirements at the time of the accident.