What happened
On 2/24/2019, an LH212 Delta2 microlight helicopter, registration 83AQG, was performing left-hand aerodrome circuits at Montélimar-Ancône aerodrome. During the downwind leg of the circuit, one of the tail rotor blades failed at its attachment point. This failure caused the tail rotor to break away from the aircraft, leading to a total loss of control. The helicopter subsequently collided with the ground, resulting in two fatalities (the student pilot and the instructor) and the destruction of the aircraft.
The investigation
The BEA examined the wreckage and identified that the helicopter had struck the ground with high energy, nearly vertically. Investigators found several components scattered along the downwind leg, including a broken tail rotor blade and the end section of the tail boom.
Detailed microscopic examination of the failed blade (marked "19") revealed two distinct zones: a smooth, shiny region indicating progressive fatigue cracking, and a textured region indicating a sudden overload failure. The investigation also compared the wreckage to a previous accident involving an identical aircraft type (07-QL) operated by the same company, which had experienced a similar tail rotor blade separation in 2018. Furthermore, the BEA examined various other tail rotor blades from the LH212 fleet and noted geometric differences in the blade roots between different production standards.
Findings
- The primary cause of the accident was the failure of a tail rotor blade due to progressive fatigue damage at the root.
- The fatigue crack was located in a position that made it nearly impossible to detect using conventional workshop inspection methods, as the crack was hidden beneath a crimped ball-bearing bushing.
- A design modification to the blade root, which deviated from the original Dragonfly helicopter design, may have introduced stress concentrations that reduced the fatigue life of the components.
- The operator had recently installed a tail rotor from another aircraft (85AKR) onto 83AQG following a recent overhaul, though vibration checks performed prior to the flight were within acceptable limits.
- The lack of a formal continuing airworthiness system and the cessation of the manufacturer's (LCA) operations meant that technical updates and service bulletins may not have been effectively communicated to all users.