History of Flight
The aircraft departed from Runway 26 at Caernarfon Airport for a post-engineering test flight, primarily to test the right engine starter motor. A radio transmission at 1314:50 UTC indicated the pilot requested a Frequency Information Service, stating an intention to climb to 4,000 feet and operate between 4,000 and 2,000 feet. No further radio communications were received. Radar data showed the aircraft climbing to approximately 4,840 feet before entering a descent at an average rate of 2,400 ft/min. Radar contact was lost at 3,040 feet at 1325:10 UTC, 1.7 nm south of Moel Hebog. Witnesses near Llyn Cwmystradllyn observed the aircraft in straight and level flight before it struck the mountain. The engine sounded normal with no change in noise before impact. The emergency services were notified at 1348:15 UTC.
Meteorological Conditions
The RAF Valley weather report at 1350 UTC recorded surface wind 190°/2 kt, visibility 15 km, no significant weather, cloud bases at 10,000 and 15,000 feet, temperature 22°C, and dew point 14°C. Local witnesses confirmed good visibility, little wind, and no low cloud.
Pilot Information
The pilot held a Basic Commercial Pilots Licence and served as the Airport Director at Caernarfon. He had 5,120 total flying hours, 67 on type, and began flight training in 1982. He was a former RAF Air Traffic Control Officer and Chief Flying Instructor. At age 56, he was medically fit.
Medical and Pathology
Post-mortem examination found no pre-existing medical condition. Toxicology detected no alcohol or common drugs. A 4% carbon monoxide saturation was considered insignificant.
Accident Site Examination
The aircraft impacted a rocky crag on Moel Hebog at about 1,850 feet amsl, with the wreckage concentrated in a small area. The empennage was found inverted, and the rest of the airframe was severely disrupted. Propeller damage indicated roughly cruise power at impact. The impact angle was approximately 90° to the mountain face, with slight right bank and level pitch. Impact speed was estimated over 160 kt.
Off-Site Examination
Examination of the wreckage at Farnborough revealed no anomalies with flying controls, structure, or engines. The Janitrol heater was not in operation and was considered unlikely to have caused carbon monoxide leakage. The carbon monoxide level in the pilot reinforced this conclusion.
Summary
The aircraft climbed above the intended 4,000 feet without a period of level flight, suggesting the proposed airtest was not performed. Secondary radar returns indicated electrical power was present. No distress calls were made. Witnesses observed the aircraft in level flight with constant engine noise until impact. No technical defects were found, and the Inquest recorded an open verdict due to insufficient evidence.