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 solved the drawback of the RAF's Rolls-Royce Merlin-powered fighters versus the German Messerschmitt Bf 109E machine. The Daimler-Benz DB 601 inverted V12 powerplant had utilised fuel injection since 1937. 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. 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, adopting the affectionate nickname 'Miss Shilling's orifice' (or simply the 'Tilly orifice'), given to the restrictor by Sir Stanley Hooker, the engineer who led supercharger development at Rolls-Royce.
