What happened
On 4 January 2019, a Eurofox 912(S), registration G-CHUP, was being prepared for a private flight at Nympsfield Airfield in Gloucestershire. The pilot attempted to start the Rotax 912ULS/EP915ECi engine following the standard procedure, which involves keeping the brakes applied, the control column held back, and the throttle positioned slightly open.
After several failed attempts to ignite the engine, the pilot began pumping the throttle while simultaneously turning the starter key. The engine eventually started, but it immediately surged to high power. This sudden increase in thrust caused the aircraft to pitch forward onto its nose, resulting in severe damage to the propeller.
The investigation
The investigation, prompted by the pilot's report, examined the engine starting sequence and the pilot's experience with the specific engine type. The pilot, who held a Light Aircraft Pilot License and had 746 total flying hours, noted that he was more accustomed to operating carburetted engines. In those engines, pumping the throttle is a common method for priming the engine during start-up. However, the engine manual for this fuel-injected unit recommends a specific throttle setting of only 1 to 2 cm open during the starting process.
Findings
- The primary cause of the incident was the incorrect use of the throttle during the engine start sequence.
- The pilot's action of pumping the throttle while engaging the starter caused an excessive amount of fuel to be present, leading to the high-power surge.
- The pilot's familiarity with carburetted engine procedures influenced the error, as the fuel-injection system requires different handling.
- As a result of the incident, the pilot has updated his engine start checklist to clearly highlight the required throttle position.