What happened
On the morning of October 1, 2011, a Robinson R44 II helicopter, registered OO-T (as per source), was conducting a private flight to Cerfontaine Airfield (EBCF) for the purpose of refuelling. Upon arrival, the pilot was instructed by the airfield commander to position the aircraft near the fuel pump station, specifically noting that the ground wire for the fuel pump was somewhat short.
While hovering approximately one meter above the concrete platform, the helicopter experienced a sudden instability, pitching rearward and then forward. This oscillation caused the main rotor blades to strike the metallic roof of the fuel pump shelter. The impact was violent, causing the rotor blades to strike the structure repeatedly. The force of these impacts was so significant that the tail boom separated from the fuselage. Debris from the rotor was projected across the airfield, striking a tower building and a parked Cessna Caravan.
The investigation
The AAIU(Be) investigation examined the aircraft's condition, the pilot's experience, and the airfield's infrastructure. The investigation found that the pilot, while qualified, had relatively low flight experience, having held a license for only a few months.
Investigators also analyzed the design of the refuelling area. They noted that while vertical obstacles like fuel containers are easy to judge, the horizontal roof of the fuel pump shelter is much harder to estimate visually. Furthermore, the investigation revealed that there were no written procedures at the airfield instructing pilots to maintain a safe distance from the installation, and the radio instructions provided that morning encouraged the pilot to fly close to the structure to accommodate the short ground wire.
Findings
- The primary cause of the accident was a limited loss of control while hovering at an unsafe distance from obstacles.
- The pilot's relatively low level of experience contributed to the difficulty in managing the aircraft's stability near the structure.
- The lack of formal airfield procedures regarding safe landing distances for refuelling contributed to the event.
- Verbal instructions regarding the short length of the ground wire influenced the pilot to position the aircraft too close to the fuel pump shed.
Safety action
Following the accident, the AAIU(Be) issued a recommendation to the EBCF airfield authority. The authority subsequently updated its standard procedures to require that pilots land at a safe distance from both the Avgas and Jet Fuel containers and move the aircraft manually toward the pumps using ground handling wheels. This recommendation has been implemented and is considered satisfied.