In 1940, British fighter pilots began noticing something deeply frightening about their aircraft. Push a Spitfire or Hurricane into a sharp dive, and the engine could suddenly splutter, lose its strength, or stop altogether. German pilots already understood the advantage. Their fuel-injected Messerschmitt Bf 109s could dive aggressively without suffering the same problem. British Merlin engines relied on carburetors, and when the aircraft experienced negative G forces, fuel rushed through the carburetor in the wrong way, leaving the engine without the mixture it needed. In a fight for your life, even a few seconds could mean everything. Then Beatrice Shilling stepped in. Shilling was an aeronautical engineer at the Royal Aircraft Establishment, but she was far from the quiet, conventional engineer people might have expected. Before the war, she raced motorcycles at Brooklands, one of Britain’s most dangerous racing circuits. She became one of the few women to earn its prestigious Gold Star after completing a lap at more than 100 mph. She knew machines. Rather than attempting to rebuild the entire carburetor, Shilling found a remarkably simple answer: a tiny metal restrictor placed in the fuel system to control the sudden rush of fuel during negative-G maneuvers. From 1941 onward, Shilling and a small team traveled from RAF station to RAF station, fitting the modification directly onto fighter aircraft. The pilots soon gave the little device a nickname that would follow it into history. “Miss Shilling’s orifice.” It was not a perfect solution. Later carburetor technology eventually dealt with the problem more completely. But that little piece of metal gave RAF pilots something precious when they needed it most: an engine that was far less likely to betray them during combat, without having to wait for an entirely new engine design. And perhaps the best part of the story is the woman behind it. Before Beatrice Shilling helped keep British fighters alive in the sky, she had already been spending her weekends pushing motorcycle engines beyond 100 miles per hour on a dangerous racing circuit. When war placed a dangerous engine problem in front of her, she did what she knew best. She understood the machine.