The Supermarine Scapa was an improved version of the Southampton flying boat, developed after Supermarine was taken over by Vickers, and using technology developed for the Schneider races. Unlike most military aircraft of the period it was not developed to satisfy an existing Air Ministry specification, but as a private venture. Supermarine then offered to produce the prototype Scapa (then known as the Southampton IV) in place of the final Southampton II on order. After the successful trials of the prototype another fourteen production Scapas were ordered, before production switched to the larger Stranraer.
The Scapa was essentially a refined version of the Southampton II. It was powered by a pair of Rolls Royce Kestrel engines, which were mounted in streamlined nacelles that were positions below the upper wing. The wings themselves were of the same length as on the Southampton, but were of an improved design, and used less drag inducing struts and more wire bracing. The hull was a cleaner version of that on the Southampton II, and was of all-metal construction. The open tandem cockpits of the earlier aircraft were replaced by an enclosed side-by-side cockpit for the pilots, while the other crew positions remained the same. The Scapa used a twin rudder tail, similar in shape to the triple rudder tail of the Southampton.
The Scapa was much faster than the Southampton (141mph compared to 95mph) and had a better maximum range. It entered service with No.202 Squadron at Malta in May 1935, and was then taken on a series of long range cruises around the Mediterranean and African coasts. The Scapa was also used by Nos. 204 and 240 Squadrons in home waters. It remained in service until 1939, although had been replaced by the start of the Second World War.
Engine: Two Rolls-Royce Kestrel IIIMS engines
Power: 525hp each
Wing span: 75ft
Length: 53ft 0in
Height: 19ft 0in
Empty weight: 10,030lb
Loaded weight: 16,040lb
Top speed: 141mph
Range: 1,100 miles
Service ceiling: 15,480ft
Armament: Three 0.303in Lewis guns
Bomb load: 1,000lb