Flight History
On 13 October 2004, a private pilot flying a Robinson R22 Beta (registration G-BYTD) departed Sywel Aerodrome at approximately 0830 UTC for a solo flight. While leaving the air traffic zone, the pilot noted the carburettor temperature gauge indicating above the yellow avoid arc and applied additional carburettor heat. After about ten minutes of cruising at 2,000 feet amsl and 80 knots, the pilot began a descent to 1,500 feet amsl. As the aircraft reached 1,600 feet, the tail started to swing violently left and right. Attempts to correct the yaw worsened the situation, and altitude was quickly lost.
The pilot decided to perform a forced landing, turning into the wind and reducing speed while searching for a suitable site. At treetop height, he briefly straightened the aircraft but had to avoid a tree in a hedgerow. After clearing the hedgerow, he touched down in a cultivated field at an estimated 40 knots. The right skid contacted the ground first, followed by the left; the skids broke off. The rotor then struck the ground, and the aircraft rolled over, coming to rest on its right side approximately 15 meters beyond the skid impact marks. The canopy shattered. The pilot reported losing consciousness during the rollover and later regaining consciousness to find fuel leaking. He exited through the broken canopy and reached a roadside to summon help. The pilot sustained minor injuries; the aircraft was destroyed.
Carburettor Heating System
The Robinson R22 Beta was equipped with a manually selected carburettor heater and an additional carburettor heat assist device. An instrument panel gauge displayed carburettor temperature, with a yellow arc indicating the temperature range to be avoided. Below the gauge was a caution: "CAUTION BELOW 18 IN. MP, IGNORE GAGE & APPLY FULL CARB HEAT." The aircraft flight manual included instructions on carburettor heat usage. The Civil Aviation Authority issued supplementary instructions (Change Sheet No. 4 Issue 4) emphasizing that the Carb Heat Assist does not automatically apply the correct amount of heat; the pilot must monitor the gauge and manually apply heat as required. It also stated that before entering a descent or autorotation, full carburettor heat must be selected.
Weather Conditions
At the time of the flight, surface air temperature and dew point were about 12°C and 9°C, respectively, yielding a humidity of 82–87%. Meteorological reports indicated cloud cover at 1,200–1,500 feet amsl, suggesting higher humidity at that altitude. These conditions are conducive to serious carburettor icing if adequate heating is not applied.
Conclusion
The pilot applied some carburettor heat while airborne, but it is likely that insufficient heat was applied, particularly during the descent, leading to a build-up of carburettor ice. The pilot's relative inexperience (77 hours total, all on type) and the effects of the engine governor made it difficult for him to recognize the situation. The governor likely hunted, causing torque fluctuations and yaw. The pilot attempted a forced landing, but his inexperience contributed to a heavy, fast run-on landing that resulted in the destruction of the aircraft.