What happened
On 19 June 2022, a Pioneer 300, registration G-LEAH, was conducting a private flight from Ludham Airfield in Norfolk. Shortly after departing, at an altitude of approximately 300 feet, the Rotax 912 ULS engine began running roughly and experienced a significant reduction in power.
The pilot attempted to return to the airfield by turning left downwind. Despite adjustments to the throttle and the application of carburettor heat, the engine performance did not improve. While configuring the aircraft for landing by deploying the landing gear and the first stage of flaps, the pilot found the aircraft could not maintain the necessary altitude to complete the turn to final. Consequently, the aircraft landed in a field roughly 30 metres short of the runway threshold. The impact resulted in extensive damage to the engine mounting, propeller, landing gear, left wing, and wing box, though there were no injuries to the pilot or the passenger.
The investigation
The investigation focused on the cause of the engine power loss and the recent fueling of the aircraft. It was established that the aircraft had been refuelled one week prior with E10 Mogas, which had been purchased from a local petrol station. The Aircraft Flight Manual for this aircraft specifies the use of 100LL Avgas or unleaded Mogas with an octane rating of 981 or higher.
The investigation also examined the implications of using E10 fuel, which contains a higher ethanol concentration than the E5 variety. The Light Aircraft Association (LAA) does not approve E10 for use in their Permit to Fly aircraft due to risks such as ethanol-related corrosion of gaskets and fuel lines, as well as increased susceptibility to carburettor icing and vapour lock. The pilot noted that they had attempted to mitigate the risks of the E10 fuel by mixing it with Avgas.
Findings
- The engine experienced a loss of power and rough running shortly after takeoff.
- The aircraft was unable to maintain altitude to complete the approach to the runway.
- The use of E10 Mogas, which is not approved for this aircraft type, was a significant factor.
- The pilot had attempted to use E10 fuel by mixing it with Avgas to mitigate potential issues.