Tilly Shilling and the Spitfire carburetor

Beatrice “Tilly” Shilling was an aeronautical engineer, motorcycle racer, and one of the unsung heroes of the Second World War. Her simple fix to a dangerous flaw in the engines of Britain’s fighter planes gave RAF pilots back a crucial edge in combat. Below are some slides I prepared for Ram Seshadri’s group ‘culture moment’ (March 2026).

In 1940, Spitfires and Hurricanes relied on the Rolls-Royce Merlin engine, which was fed by a carburetor. A carburetor uses a narrowing in the air intake, called a venturi, to create low pressure that draws fuel into the airflow. It works well in level flight, but when a pilot pushed the nose down sharply, the negative G sent fuel surging into the carburetor. The mixture became too rich and the engine cut out. German Messerschmitts used direct fuel injection and had no such problem, so their pilots could escape simply by diving.

Negative G flooded the Merlin engine's carburetor, cutting power at the worst possible moment.

Tilly’s solution was remarkably simple: a small brass restrictor fitted into the fuel line that limited the flow to just what the engine needed at full power. It could be installed without taking aircraft out of service, and in 1941 she travelled between RAF bases fitting them herself. It was an elegant piece of engineering from someone who, despite her talent, faced discrimination and received little credit in a male-dominated world.

Tilly's brass flow restrictor, and the engineer and motorcycle racer who designed it.

You can read more about her remarkable life here, or in Negative Gravity by Matthew Freudenberg.