When these aeroplanes performed a negative G force manoeuvre (pitching the nose hard down), fuel was forced upwards to the top of the float chamber of the carburettor rather than into the engine, leading to loss of power. If the negative G
continued, the fuel would collect in the top of the float chamber, forcing the float to the floor of the chamber. Thiis would in turn open the needle valve to maximum, flooding the carburettor with fuel and drowning the supercharger with over-rich mixture. This would lead to a rich mixture cut-out, which would shut down the engine completely, a serious drawback in combat.