Miss Shilling's orifice

Miss Shilling's orifice was a very simple technical device created to counter engine cut-outs experienced during negative G manoeuvres in early Spitfire and Hurricane fighter aeroplanes during the Battle of Britain.

Since this float controlled the needle valve that regulated fuel intake, the carburettor would flood and drown the supercharger with an over-rich mixture.

German pilots could exploit this by pitching steeply forward while opening the throttle, a manoeuvre that pursuing British aircraft would be unable to emulate.

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.

During early 1941, Shilling travelled with a small team to fit the restrictors in one RAF base after another, giving priority to front-line units.