Investigation Summary
The accident occurred at a private helicopter landing site (HLS) that had been selected by the pilot and passenger the previous day. The site was heavily restricted by surrounding vegetation, necessitating a vertical takeoff profile. Investigators found that the specific area chosen for the maneuver provided very narrow safety margins. On the day of the accident, the tree branches were in shade, creating a low-contrast environment that likely hindered the pilot's ability to accurately judge the distance between the rotor blades and the obstacles. Technical examination of the wreckage revealed that the impact with the trees caused a catastrophic failure of the tail boom, with 90% of its rivets shearing off. The resulting overtorque on the main rotor hub was so severe that it ripped the front passenger seats from their mountings. Although an artificial horizon indicator had been reported as inoperative two days prior to the flight, this was not considered a contributing factor to the visual-reference takeoff accident.
Final Conclusions
The BEA concluded that the accident was caused by the pilot's choice of a takeoff area that restricted safe maneuvering options. This decision led to a vertical takeoff with insufficient safety margins relative to nearby trees. Contributing to the collision was the difficulty in assessing obstacle distance due to the shady environment and low light contrast. The investigation also highlighted the potential impact of physiological aging on visual performance, specifically contrast sensitivity.
Photographic Evidence (1)
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Systems & Failure Modes
Main Rotor
The primary lift and control system which struck tree branches at 19 meters, leading to catastrophic structural failure.
Tail Boom
The rear structural section of the helicopter which separated completely upon rotor impact with the trees.
Artificial Horizon
A flight instrument reported as inoperative two days prior, though not required for the VFR takeoff maneuver performed.
Interesting Facts
- 01The aircraft was operated by Dolijet, a company chaired by the passenger, Olivier Dassault.
- 02The highest tree at the takeoff site was 23 meters tall.
- 03The impact caused an overtorque that ripped the front passenger seats away from the floor.
- 04The tail boom separation involved the shearing of 90% of its rivets.
- 05The pilot was 74 years old at the time of the accident.
- 06The aircraft, MSN 1424, was manufactured in 1981.
Safety Actions & Advisories
Confined Area Training
The BEA recommended that EASA publish a guide for training organizations indicating distance-to-obstacle reference values for confined area operations, adapted for pilot experience levels.
Visual Aging Awareness
The BEA recommended that EASA include awareness modules for Aero-Medical Examiners (AMEs) to address the physiological consequences of aging, specifically using contrast sensitivity tests.