By the mid-twenties the RAF was desperate to replace their First World War vintage Felixstowe flying boats and had almost given up the search when R J Mitchell's development of his civilian Swan design was offered. It proved an immediate success and established not only the name of the designer but that of the company in military circles.
The first eighteen Southamptons delivered were Mk Is with wooden hulls. However a lengthy marine research programme had convinced the Royal Air Force of the superior qualities of metal over wood and so the final forty-eight were delivered as Southampton MkIIs with metal hulls and powered by two 335kW Napier Lion V engines. In a programme begun in 1929 all surviving wooden-hulled Southamptons were re-built with metal hulls.
Southamptons first entered service in August 1925 and quickly became famous for long-distance formation flights, 'showing the flag' in many parts of the world. The most notable was a 43500km (27000 mile) cruise of the Far East Flight's four Southamptons from Felixstowe to Singapore via the Mediterranean and India in 1927 and 1928.
The Southampton flying-boat was one of the most successful ever used by the Royal Air Force. With a reputation for reliability, its service life of eleven years was surpassed only by that of the Sunderland.
Southampton Mk II
Engines: 2 x Napier Lion VA W-12, 373kW
Max take-off weight: 6895 kg / 15201 lb
Empty weight: 4082 kg / 8999 lb
Wingspan: 22.86 m / 75 ft 0 in
Length: 15.58 m / 51 ft 1 in
Height: 6.82 m / 22 ft 5 in
Wing area: 134.61 sq.m / 1448.93 sq ft
Max. speed: 174 km/h / 108 mph
Ceiling: 4265 m / 14000 ft
Range: 1500 km / 932 miles
Armament: 3 x 7.7mm machine-guns