What happened
On 6 June 2015, a Bell 206B Jet Ranger II, registration G-RAMY, departed from a private landing site near Creg-ny-Baa, Isle of Man, for a short flight. After disembarking passengers, the pilot restarted the engine and lifted off into challenging weather conditions characterized by strong, gusty winds. Witnesses observed the helicopter flying at a low altitude, between 100 and 300 feet, before the aircraft began to oscillate heavily in roll. The fuselage was seen to rotate in yaw beneath the rotor disc multiple times. Suddenly, the nose of the helicopter pitched up into the rotor disc, causing the aircraft to break apart in flight. The fuselage, rotors, and various fragments fell separately to the ground. The impact of the fuselage was fatal for the pilot.
The investigation
Investigators examined the wreckage and recovered the technical log, which showed no recent mechanical defects. Analysis of the main rotor assembly revealed that the rotor mast had failed due to a bending overload. There was clear evidence that the teeter stops had made violent contact with the mast, a phenomenon known as mast bumping. The investigation also reviewed meteorological data, which showed wind gusts of up to 46 knots in the area at the time of the accident. Witnesses described the aircraft's erratic motion as being consistent with a pilot attempting to maintain control during severe turbulence. Furthermore, the investigation noted that the pilot had not received specific training in mountain flying techniques, which are essential for managing the complex airflows found in such terrain.
Findings
- The primary cause of the accident was the catastrophic failure of the main rotor mast resulting from heavy mast bumping.
- Extreme wind conditions and turbulence in the mountainous terrain likely prompted large, abrupt control inputs by the pilot.
- The pilot's attempts to stabilize the aircraft in gusty winds contributed to the mast-bumping event.
- The pilot lacked specialized training in mountain flying techniques to mitigate the risks of such environments.