A Royal Air Force Service Inquiry has concluded that debris which had been present inside the carburettor of a Battle of Britain Memorial Flight Spitfire for decades was very likely to have caused the loss of engine power that resulted in the fatal crash near RAF Coningsby on 25 May 2024.
The report, published by the Ministry of Defence on 1st of October 2026, examines the circumstances surrounding the death of Squadron Leader Mark Long, who was flying Spitfire MK356 when the aircraft crashed shortly after taking off from RAF Coningsby in Lincolnshire.
Squadron Leader Long, 43, was the sole occupant of the aircraft and was killed in the accident.
The Service Inquiry was convened to establish the circumstances of the accident and identify lessons and recommendations aimed at improving safety. It is intended to support learning within Defence rather than apportion blame.
According to the report, MK356 was taking off at approximately 13:16 on 25th of May 2024 as Squadron Leader Long began a planned sortie involving a series of flypasts and an aerial display.
During the early part of the flight, the aircraft experienced a significant reduction in engine performance. Evidence examined by the inquiry, including engine performance information and witness accounts, was consistent with the aircraft experiencing fuel starvation.
The inquiry examined the Merlin engine and its carburettor in detail. It found that debris within the carburettor had partially obstructed the lean metering jet, restricting the amount of fuel reaching the engine.
The resulting mixture was too lean for the engine to produce the required power. The inquiry concluded that the debris was very likely to have been the causal factor that prevented the engine from producing sufficient thrust to maintain flight.
Importantly, chemical analysis of the material found inside the carburettor indicated that it had been present for decades.
The inquiry also examined the maintenance information associated with the carburettor. It identified inconsistencies between different maintenance publications, which created some uncertainty over the extent to which the component should be dismantled, inspected and cleaned.
The report says this ambiguity very likely reduced the opportunity for the material within the carburettor to be identified.
The findings do not suggest that the accident can be attributed to a single action or individual. Instead, the inquiry examined a number of technical, procedural and operational factors and made recommendations intended to reduce the likelihood of a similar occurrence.
The report contains 26 safety recommendations. These include measures relating to maintenance documentation and records, inspection and maintenance procedures, pilot training and the management of emergencies involving historic aircraft.
The inquiry also considered the survivability of the pilot following the impact. It found that the aircraft’s restraint system was critical to pilot survivability, while also concluding that aspects of the system and cockpit design were likely to have aggravated the consequences of the accident.
The report recommends consideration of changes to improve pilot protection. However, the inquiry also recognises the particular challenges associated with modifying historic aircraft, including the potential implications for their authenticity and airworthiness.
The Service Inquiry’s findings therefore extend beyond the immediate loss of engine power, looking at how historic aircraft can be maintained and operated safely while preserving their important heritage.
The accident resulted in the loss of both Squadron Leader Long and Spitfire MK356, but the report’s purpose is focused on learning from the circumstances and improving safety for future operations.
Squadron Leader Long had been an experienced RAF pilot and was serving with the Battle of Britain Memorial Flight at the time of the accident. He had previously flown the Tucano, Hawk and Harrier GR7/9 before joining the Typhoon Force at RAF Coningsby.
He had served as the RAF Typhoon display pilot and also undertaken Quick Reaction Alert and overseas air-policing duties. At the time of his death, he was in his fourth season flying with the BBMF.
Following the accident, the RAF said that Squadron Leader Long was a highly regarded pilot and colleague who had been passionate about aviation and the Battle of Britain Memorial Flight.
The publication of the Service Inquiry now provides the formal findings into an accident that had remained under investigation for more than two years.
The Ministry of Defence said the final report has been published to inform the military Chain of Command and the public of the inquiry’s findings and its recommendations to improve defence safety.