During the Battle of Britain, the Royal Air Force discovered a glaring problem with its Rolls-Royce Merlin-powered fighters—the Hawker Hurricane and the Supermarine Spitfire. See, that generation of Merlin was fitted with dual-choke, updraft carburetors built by the S.U. Carburettor Company Limited. These worked just like your regular updraft carb and were great in level flight. Problem was, you see, that fighter planes don't spend a lot of time in level flight.
Any negative-G maneuvers, such as pitching the nose down sharply in a dive, would cause the carbs to flood and the engine to cut out. Not exactly what you want in your badass, high-po, Nazi-killing fighter. RAF pilots figured out pretty quickly that they could perform a quick half-roll before diving in an attempt to counteract the flooding, but this only worked so well. It also introduced a delay in the RAF boys' maneuvers that provided ample opportunity for the fuel-injected Luftwaffe fighters—especially Willie Messerschmitt's legendary BF109—to either blow up the RAF planes or run for it as the situation allowed.
