Spitfire crash caused by carburettor debris restricting fuel, inquiry finds

UK military investigators have concluded that debris lodged in the carburettor of a Supermarine Spitfire Mk IX cut fuel to the engine, causing a loss of thrust and a fatal descent into a field shortly after take-off.

The aircraft belonged to the Battle of Britain Memorial Flight. It left RAF Coningsby on 25 May 2024, followed by a Hawker Hurricane. The two aircraft were due to give separate solo displays at different locations that day.

According to the Defence Safety Authority, the Packard Merlin 266 lost about 150rpm for seven seconds as the Spitfire accelerated along runway 07, then recovered. The aircraft became airborne at roughly 90kt, but almost at once the engine speed fell again, by 200rpm over two seconds, just before the gear was retracted.

Data showed the climb rate and airspeed dropping after the second reduction. The authority said this pointed to a fall in thrust tied to the engine speed loss. Some 37 seconds after lifting off, the pilot radioed air traffic control to say he was turning downwind and would land immediately back on runway 07. The inquiry said the Spitfire was then 300ft above the ground, climbing at about 150ft/min, much lower and slower than it should have been.

A modular signal recorder on board showed engine speed continuing to fall through the turn, which the inquiry described as signs of rough running. At 91kt the aircraft was well below its usual 120kt minimum manoeuvring speed. Even a shallow turn added drag and, with the slight climb, slowed it further. The manoeuvre also pushed the stall speed up toward the speed the aircraft was actually flying. At about 83kt it rolled to 60° to the right.