What happened
On 02 March 2021, an Airbus Helicopters EC120B, registration F-HPIC, was performing a yaw take-off from the Marnaz Helicopter Landing Site (HLS) in Haute-Savoie, France. The pilot, intending to fly over the Mont Blanc massif, initiated a north-facing yaw take-off to avoid trees bordering the landing site.
As the aircraft transitioned into horizontal flight, the pilot observed on the First Limit Indicator (FLI) that engine power was rapidly approaching the Maximum Take-Off Power (MTOP) limit. Fearing insufficient power to clear the obstacles, the pilot decided to abort the take-ob. To avoid the trees in the initial flight path, the pilot executed a 90-degree right turn to target an emergency landing on a nearby road. During this maneuver, the helicopter struck a power line and a billboard before colliding with the ground and rolling onto its right side. The pilot and four passengers evacuated the aircraft unharmed.
The investigation
The BEA examined the wreckage alongside manufacturers Airbus Helicopters and Safran Helicopter Engines. The investigation confirmed that the engine was producing power at the time of impact and found no technical malfunctions contributing to the accident. However, the wreckage showed significant damage, including a failure of the tail boom and substantial damage to the main rotor blades.
Investigators analyzed flight data from the Helisafe onboard computer and video footage recorded by a passenger. The data revealed that the helicopter was not in a stabilized hover before beginning the take-off maneuver. Furthermore, while the engine was functioning, a discrepancy was noted regarding the Fuel Control Unit (FCU); the maximum gas generator speed (NG) physically achievable by the unit was lower than the values specified in the flight manual.
Regarding weight and balance, the investigation found that the pilot's pre-flight calculations were slightly inaccurate. The pilot had omitted the weight of the landing skids (4 kg) and relied on passenger-declared weights, which introduced uncertainty into the total weight calculation. The aircraft was operating close to its maximum permissible weight.
Findings
- The pilot attempted a complex yaw take-off in a restricted environment with a low power reserve due to the aircraft being near its maximum weight.
- The lack of a stabilized hover prevented the pilot from performing essential checks, such as verifying the center of gravity, assessing available power, and monitoring obstacle clearance.
- The pilot's relatively limited experience with this specific aircraft type and the technical demands of a yaw take-off contributed to the difficulty of managing the aborted maneuver.
- The decision to turn right toward the road, while intended to avoid trees, placed the aircraft in the path of the power lines and billboard.