What happened
On 11 April 2015, a Robin ATL, registration G-GFRO, was performing a private ferry flight from Nympsfield gliding site in Gloucestershire. The flight was being conducted to assist a new owner of the aircraft. Following an initial aborted takeoff attempt due to poor acceleration, the pilot attempted a second takeoff with the carburettor heat applied.
While climbing through approximately 100 ft agl, the engine experienced an abrupt drop in RPM. The pilot identified a suitable field for a forced landing and performed various emergency procedures, including switching fuel tanks and activating the fuel pump. Although the engine briefly appeared to recover, power levels fluctuated significantly between 2,200 and 2,700 RPM, preventing a sustained climb.
As the pilot prepared to land, radio communications warned of a glider occupying the primary landing area. To avoid a conflict, the pilot opted to land further down the field. During the landing roll, the engine power dropped to a sub-idle state and ceased entirely upon touchdown. As the aircraft travelled over uneven terrain, the nosewheel detached and the nose landing gear leg collapsed. There were no fatalities and no injuries to the two occupants.
The investigation
The AAIB examined the engine, specifically inspecting the spark plugs and leads, but found no identifiable anomalies. Analysis of the fuel showed no evidence of contamination. The investigation focused on the engine's performance fluctuations and the environmental conditions at the time of the accident.
Findings
- The aircraft was operating from a grass airfield with high moisture levels due to damp grass.
- The engine experienced intermittent power loss and RPM fluctuations.
- Carburettor icing is suspected to have been the primary cause of the power loss.