 restrictor, it was referred to under various names, such as Miss Tilly's diaphragm or the Tilly orifice in reference to its inventor, Beatrice "Tilly" Shilling.Early versions of the Rolls-Royce Merlin engine came equipped with a SU carburettor.When an aeroplane equipped with such an engine performed a negative G force manoeuvre (pitching the nose hard down), fuel was forced up to the top of the carburettor's float chamber rather than down into the engine, leading to loss of power.