What happened
On 24 July 2011, a Robinson R44 II helicopter, registration G-ROTG, was on a private flight from Aldwick to Padstow. As the flight progressed through Devon, the weather conditions deteriorated. While flying near Okehampton, the pilot unintentionally entered instrument meteorological conditions (IMC).
During the flight, the pilot contacted air traffic control to report being "lost in cloud" and requested assistance. Radar data showed that the aircraft performed a 180-degree turn, attempting to climb to approximately 3,800 ft amsl. However, during this maneuver, the aircraft entered a rapid descent. In the final seconds of the flight, the helicopter's vertical speed increased to approximately 14,000 ft/min. The aircraft struck a field near Marhamchurch, near Bude, resulting in a post-impact fire. The pilot sustained 1 fatal injury.
The investigation
The AAIB examined the wreckage, engine, and transmission components. The investigation included an analysis of radar and GPS track logs, radio telephony recordings, and a review of the pilot's training and experience. Investigators also analyzed the aircraft's fuel supply and the storage facilities at the pilot's private site.
Technical examinations of the engine and rotor systems showed no evidence of mechanical failure or in-flight breakup. The engine was found to be delivering significant power at the time of impact. Additionally, the investigation reviewed the weather forecasts for the area, which had predicted low cloud and potential hill fog.
Findings
- The pilot encountered deteriorating visual environments (DVE) and likely became spatially disorientated after entering cloud.
- The aircraft's high rate of descent was not caused by any mechanical fault.
- The fuel supply contained contaminants, including a kerosene-type product and a phthalate ester, likely due to the use of non-aviation approved storage and dispensing equipment.
- The pilot's training included instrument appreciation, but the extreme nature of the descent left insufficient capacity for recovery.
Safety action
- The Civil Aviation Authority is recommended to publish guidance for General Aviation pilots regarding the quality and storage of fuel for use in aircraft.