 She designed a thimble-shaped brass flow restrictor (later refined to a flat washer) with precisely calculated dimensions to allow just enough fuel flow for 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.