 They were equipped with dust filters for desert operations and an additional 350 lb (159 kg) of armour plating was added to the radiator housing, cockpit and fuel tanks.The Mk IV was used in ground-attack missions in the European theatre until the early days of 1944, before being replaced by the more modern Hawker Typhoon.French ace Pierre Clostermann recalls in his book, "The Big Show", that RP-3-equipped Hurricanes were limited to 205 mph (330 km/h) top speed due to the rockets' drag, and that Hurricane casualty rates against the lethal German flak were extremely high.