Miss Tilly’s Orifice

Today I think I’ll tell the story of Miss Shilling’s Orifice.

Back in the Second World War, during the Battle of Britain, the Spitfire fighters with their powerful Merlin engines and their elliptical, highly-maneuverable wings did marvellous things above the skies of England. Unfortunately, there was a wee problemette with those engines: they had old-fashioned carburettors instead of fuel injection, relying on gravity to pull fuel into the engine – so if you went into a steep dive, the fuel supply to the engine would briefly cut out. Not good. If you carried on in your chosen maneuver, the engine would then be flooded. Very not good.

Enter Beatrice ‘Tilly’ Shilling, a young engineer (and motorcyclist) who had the clever idea of popping a little metal disc with a hole in the middle into the carburettor, to restrict and regulate the fuel flow and stop the flooding. It worked like a charm, and those mustachioed fly-boys soon dubbed it ”Miss Shilling’s Orifice”. Or just the Tilly Orifice. It’s official name, incidentally, was Miss Tilly’s Diaphragm.


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