Waterlooville
Beatrice Shilling was born on 8 March 1909 in Waterlooville, Hampshire. Her father Henry was a butcher. Her mother Annie, known as Nancy, ran the household. It was not a family that produced engineers. But Tilly, as she was known from childhood, showed no interest in following expectations. She spent her pocket money on hand tools. She won a prize in a national Meccano contest. At 14, she bought a motorcycle, took the two-stroke engine apart, learned how it worked, and put it back together. She was not asking permission. She was not being encouraged. She was just doing it.
She joined the Women's Engineering Society as a teenager, which tells you something about how early she had decided what she was going to be. In 1926, aged 17, she was taken on as an apprentice by Margaret Partridge, a pioneering electrical engineer who ran a rural electrification business in Devon. A woman engineer taking on a girl apprentice, through the Women's Engineering Society network, in 1926. That alone is a story. Shilling spent three years with Partridge, installing wiring and generators across the Devon countryside. She co-authored articles for The Electrical Age magazine. She was once found running a power station alone at night, which broke the rules on women working night shifts. Very Tilly. Then she went to Manchester.
Manchester and Brooklands
Shilling enrolled at the Victoria University of Manchester to study electrical engineering. She graduated with her bachelor's degree in 1932, alongside Sheila McGuffie. She stayed for a master's in mechanical engineering, completing it in 1933. Manchester gave her the formal credentials to match the instinct she had always had. She understood engines. Now she could prove it on paper.
But the proof that mattered most to Tilly Shilling came on a racetrack. On 24 August 1934, she took a Norton M30 around the Brooklands circuit at over 100 miles per hour. She became only the second woman ever to lap Brooklands at that speed, following Florence Blenkiron earlier that same year. The British Motorcycle Racing Club awarded her their Gold Star, the mark of a 100 mph lap. She had earned it on a bike she had modified herself.
At a job interview around this time, a man looked at her racing credentials and said, "I suppose the men let you win." She got the job anyway. She always got the job. The men who said things like that tended to find that Tilly Shilling was faster, sharper, and more stubborn than any of them.
The Problem
In 1936, Shilling joined the Royal Aircraft Establishment at Farnborough as a scientific officer. She started in the technical publications department, writing manuals. She did not stay there long. She transferred to aircraft engine work, and by 1 November 1939, two months into the war, she was promoted to technical officer in charge of carburettor research and development.
The problem she inherited was killing pilots. The Rolls-Royce Merlin engine, which powered both the Spitfire and the Hurricane, used a float-type SU carburettor. It worked beautifully in level flight and in positive-G manoeuvres. But when a pilot pushed the nose down, into a dive or a negative-G bunt, the float-type mechanism failed. The fuel first surged away from the jet, causing a momentary lean cut, then the float dropped, the needle valve opened fully, and the chamber flooded with fuel, giving a rich cut that could stall the engine entirely. It happened at exactly the moment the pilot needed power most.
German fighters did not have this problem. The Daimler-Benz DB 601 engine in the Messerschmitt Bf 109 used direct fuel injection, which was unaffected by negative G. A Luftwaffe pilot being chased by a Spitfire could push the stick forward, go into a steep dive, and escape. The Spitfire pilot who followed would have his engine cut out. In the Battle of France and the Battle of Britain, this flaw cost lives. RAF pilots developed a workaround, rolling the aircraft inverted before diving to keep positive G on the carburettor, but it was slower, clumsier, and sometimes the half-second it took was the difference between a kill and a coffin.
Rolls-Royce and SU knew about the problem. A full solution, a pressure carburettor that would work regardless of G-forces, was in development. But it hadn't yet been solved. The pilots needed something now.
The Orifice
Tilly Shilling's solution was so simple it was almost insulting. She designed a small metal restrictor, a flat washer with a precisely calibrated hole, that could be fitted into the fuel line of the Merlin engine. It limited the maximum flow of fuel so that even under negative G, the carburettor could not flood. It did not require the engine to be removed. It did not require the aircraft to be taken out of service. A fitter could install it quickly, without pulling the engine.
By March 1941, Shilling was leading a small team touring RAF fighter stations to retrofit the devices. She travelled between bases on her old racing motorcycle. The pilots loved her. They loved the device even more. It worked. It was not a perfect solution. It slightly restricted fuel flow at maximum power, which meant a tiny reduction in top-end performance. But it stopped the engine cutting out in a dive, which was the thing that was getting people killed.
The pilots called it "Miss Shilling's Orifice." The nickname was coined by Sir Stanley Hooker, the brilliant Rolls-Royce engineer who was leading supercharger development on the Merlin. The official name was the RAE restrictor. Nobody called it that. It remained in service as a stopgap until 1943, when a pressure carburettor was finally introduced across the fleet, solving the problem permanently.
Shilling also designed her own version of a pressure carburettor, the RAE Hobson, though it was never put into production. The point had been made. She had identified the problem, designed a fix, delivered it personally, and kept pilots alive long enough for the full engineering solution to catch up. It was not glamorous work. It was not the kind of work that got you on the front page. But it was the kind of work that won wars.
"A flat washer with a hole in it. That was the fix. That was what stopped Spitfire engines dying in a dive. Sometimes the best engineering is the simplest."
The Rest of the Race
The war ended, but Tilly Shilling did not slow down. She stayed at the Royal Aircraft Establishment until her retirement in 1969, working on the Blue Streak missile programme and researching the effects of wet runways on aircraft braking. She even helped design and build a bobsled for the Royal Air Force's Olympic team. None of it was headline work. All of it was precise, practical, and quietly essential.
She and George raced cars together for years after the war. They drove a 1934 Lagonda Rapier, an Austin-Healey Sebring Sprite, and an Elva 200 Formula Junior. They raced at Goodwood and scored podium finishes. She was still competing, still modifying engines, still faster than people expected a woman in her fifties to be. George had been a bomber pilot with No. 625 Squadron during the war and had earned the Distinguished Flying Cross. He came home with tinnitus and health problems that never fully went away. They were a well-matched pair: both stubborn, both fast, both more interested in what an engine could do than in what anyone else thought about it.
Shilling was appointed OBE in 1949 by King George VI for her wartime work. She received an honorary doctorate from the University of Surrey in 1969. She was elected an Associate Member of the Institution of Mechanical Engineers in 1956, joining under her married name Naylor. She used the title Chartered Engineer. Despite all of it, she never reached the top rank at the RAE. Those promotions, by the conventions of the time, were only offered to men.
She died on 18 November 1990, aged 81. She had been an engineer for over sixty years. She had raced motorcycles and cars, designed weapons systems and carburettors, fixed Spitfires and Formula One cars, and outlasted every man who had ever told her she didn't belong. She was trained at Manchester, made her name at Farnborough, and her legacy is in every history of the Battle of Britain that bothers to tell the full story.
A butcher's daughter from Hampshire who bought a motorcycle at 14, earned her engineering degree at Manchester, and saved pilots' lives with a washer the size of a coin. That's a Manchester legend.