Motorcycling, 'Tilly’s orifice' and RAF Spitfires (Merlin engine)

Unlike the German Messerschmitt Bf 109E, Merlin engines in Spitfires had a habit of stalling when put into a steep forward dive:

Complaints from the pilots led to a concentrated search for a solution. Engine manufacturers Rolls-Royce produced an improved carburettor, but this failed in testing. It was Beatrice 'Tilly' Shilling, a woman engineer working at the Royal Aircraft Establishment at Farnborough, who came up with a simple device which could be fitted without taking the aircraft out of service. She designed a thimble-shaped brass flow restrictor (later further refined to a flat washer) with very precisely-calculated dimensions to allow the flow of just enough fuel for the engine to develop maximum engine power. It came in two versions, one for 12 psi manifold pressure and another for the 15 psi achieved by supercharged units.

While not completely solving the problem, the restrictor, along with modifications to the needle valve, permitted pilots to perform quick negative G manoeuvres without loss of engine power. This improvement removed the annoying drawback the RAF's Rolls-Royce Merlin-powered fighters had had in comparison to the German Messerschmitt Bf 109E machine, whose Daimler-Benz DB 601 inverted V12 power plant had had fuel injection since 1937. Miss Shilling travelled with a small team around the countryside to one RAF base after another in early 1941 fitting the restrictors, giving priority to front-line units. By March 1941 the device had been installed throughout RAF Fighter Command. Officially named the 'R.A.E. restrictor', the device was immensely popular with pilots, who affectionately named it 'Miss Shilling's orifice' or simply the 'Tilly orifice'.

http://camillajessop.blogspot.co.uk/2012/01/miss-tilly-and-her-orifice.html

http://camillajessop.blogspot.co.uk/2012/01/miss-tilly-and-her-orifice.html

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Bernhard,
Great stuff, Thanks.

+1
Good write up on her in Wikipedia which includes this line about her incentive for improving her future husband's lap times : "According to anecdote, she refused to marry him until he also had been awarded the Brooklands Gold Star for lapping the circuit at over 100 mph"

Apparently the 'stalling' was due to an increase in fuel level in the carburettor when the plane was pushed into a dive, often when chasing a fuel injected Messerschmidt. The Spitfire would shove out a cloud of black smoke while the Messerschmidt simply dived away. I've often wondered about fuel injection on motorcycles. My friend owns Motec and was in the UK for a while. He fitted injector nozzles into the bell mouths of a road-race Honda and immediately cut a full second off lap times on one race circuit.