The Supermarine Scapa was a British general reconnaissance flying boat built by Supermarine that was used by the Royal Air Force between 1935 and 1939. It was developed from the Southampton and formed the basis of the Supermarine Stranraer.
After experimenting with a three-engine design of flying boat, the Nanok, Supermarine's chief designer R. J. Mitchell decided that the hydrodynamic design developed in the twin-engined Supermarine Southampton, would be suitable for the next aircraft.
A prototype, designated the Southampton IV, was built. It had a hull that exceeded expectations in tests. An Air Ministry Specification was received in November 1931. The test pilot Joseph "Mutt" Summers took first flew the prototype on 8 July, 1932, by which time the name of the type had been changed to Scapa.
After 15 Scapas were built, production was changed to a more powerful development, the Supermarine Stranraer.
The Scapa's hull was an all-metal structure, while the wing and tail surfaces had metal structure with fabric covering. The two Rolls-Royce Kestrel V12 engines were mounted in nacelles underslung from the upper wing, and there were two fins, each placed at the mid semi-span of the tailplane. Similar to the Southampton, there were three gun positions: one in the nose, and two staggered in the rear fuselage. Each provided with a single .303 British (7.7 mm) caliber Lewis Mk.I machine guns.