What happened
On 16 October 2004, a Piper PA-15 Vagabond, registration G-BOVB, was preparing for a short flight from a farm strip at Whitefield's Farm, near South Molton, Devon. The pilot, accompanied by one passenger, intended to fly to Eaglescott Airfield. The takeoff was planned to the east, utilizing a strip that featured a slight uphill section followed by a notable downslope.
During the takeoff roll, the pilot noted satisfactory acceleration, reaching 50 mph. However, shortly after becoming airborne, the aircraft failed to establish a climb. Instead, the rate of climb diminished, and the aircraft entered a gradual descent, flying parallel to the sloping terrain. The pilot attempted to steer toward a larger field for a forced landing, but the aircraft struck a hedge at the end of the strip with its main wheels. The impact caused the aircraft to pitch forward, striking the propeller on the ground and eventually inverting. Both the pilot and passenger sustained minor injuries.
The investigation
The investigation examined the engine, fuel, and environmental conditions. The engine showed no signs of internal mechanical failure, and the throttle remained in the fully open position. Fuel samples taken before and after the event were clear, ruling out contamination. The aircraft's weight and balance were confirmed to be within limits.
Investigators also looked at the meteorological conditions. While a slight tailwind was possible due to local wind effects from nearby trees, it was not deemed significant enough to compromise performance. However, the investigation focused on the risk of carburettor icing due to the high humidity and the specific fuel mixture used.
Findings
- The aircraft was using a fuel mixture of AVGAS and MOGAS; the higher volatility and water content of MOGAS can increase the risk of icing.
- The combination of temperature and dew point indicated a serious risk of icing at all power settings.
- The aircraft had been idling in a damp area of the field, which likely contributed to ice formation.
- It is possible that the application of carburettor heat prior to takeoff was insufficient to clear any ice that had formed.