The Hawker Audax was a Hart variant, designed for army cooperation, seeing much service in the British Empire. The first Audax flew in late 1931 and over 700 Audaxes were produced. The Audax was similar to the Hart, though it had some modifications, including a hook to pick up messages. The Audax was armed with a single .303 in (7.7 mm) Lewis light machine gun and a .303 in (7.7 mm) Vickers machine gun. The Audax was powered by a version of the Kestrel engine and had a maximum speed of 170 mph (274 km/h). A number of variants of the Audax were produced. The Audax saw limited service during the Second World War, ending its service by 1945. Harold Skaarup web pages