What happened
On 29 March 2017, an Airbus Helicopters AS3/55F1 Ecureuil II, registration G-OHCP, was conducting a private flight from a base near Cranfield towards a destination near Dublin. The flight was being conducted under Visual Flight Rules (VFR), which requires the pilot to remain clear of clouds and maintain visual contact with the ground.
As the flight progressed through the Snowdonia region, weather conditions significantly deteriorated due to an approaching weather front. While the aircraft was initially flying at approximately 3,000 feet, it began a descent. A witness observed the helicopter passing overhead at 2,500 feet before it disappeared into low cloud cover. Shortly thereafter, the aircraft struck the eastern face of Rhinog Fawr mountain at an elevation of 2,060 feet. The impact, which occurred at approximately cruise speed, resulted in 5 fatalities (the pilot and four passengers) and the total destruction of the aircraft.
The investigation
Investigators from the AAIB examined the wreckage and the aircraft's systems to determine the sequence of events. The examination of the autopilot system confirmed that the aircraft was in a controlled descent using heading, turn coordination, and vertical speed modes at the time of impact. The flight instruments, including the artificial horizon, were found to be operational during the accident.
Analysis of the engines showed no evidence of mechanical failure prior to the crash; both the left and right engines were functioning normally, and the rotor systems were under power at the moment of impact. The investigation also reviewed the pilot's use of an iPad equipped with flight planning applications. While the device provided weather and navigation data, the Garmin GNS430 GPS unit installed in the helicopter lacked the specific modification required to provide terrain warnings.
Findings
- The aircraft entered Instrument Meteorological Conditions (IMC) after flying into cloud cover while in a descent.
- The pilot did not initiate a turn to avoid the rising terrain or to return to visual conditions.
- The lack of a terrain warning function on the GPS unit meant the pilot had no automated alert regarding the approaching mountain.
- The pilot was flying towards deteriorating weather, and while the aircraft was within its weight and balance limits, the transition from VMC to IMC left the pilot without visual references to the ground.