The Short Seaford was originally developed as the Sunderland Mk IV, and was an attempt to use the Bristol Hercules engines of the Short Stirling on the Sunderland. Only two prototypes and eight production aircraft were built, and the type never saw combat.
Work on the Sunderland IV began late in 1941. It was hoped that the Hercules engines would increase the speed and range of the Sunderland, making it more suitable for use in the Pacific. Perhaps as a result of the dramatic Japanese victories, which quickly pushed the British back to the Indian border and away from the areas where flying boats were most useful, work on the Sunderland IV progressed very slowly.
The prototype of the Sunderland IV did not make its maiden flight until 30 August 1944. The new aircraft was longer than the standard Sunderland, with a wider fuselage. Early tests proved that it needed a bigger tail, and the new tail plane was given a distinct dihedral to keep the horizontal tail plane clear of spray. Performance was somewhat disappointing – the Mk IV was the faster version of the Sunderland by 29mph, but had a lower ceiling and shorter range than any other version. By the time the prototype made its first flight the Mk V, with its Pratt & Whitney engines, had solved most of the power problems of the Sunderland, and there was no need for the Mk. IV.
The Mk IV would have been very heavily armed. It was to have carried two 20mm cannon in the dorsal turret, two 0.5in guns in the nose and tail turrets and beam positions and two fixed 0.303in guns in the nose. Payload would have been the standard 2,000lb of all versions of the Sunderland.
Eight of the forty aircraft ordered were completed, and were given the new name Short S.45 Seaford. They were given short service trials with No.201 Squadron, and were then converted into Short Solent airlines for civil use.
Engine: Bristol Hercules XIX
Span: 112ft 9in
Length: 88ft 7in
Height: 34ft 6in
Max speed: 242mph
Loaded Weight: 75,000lb
Armament: Two 0.5in guns in nose and tail turrets and two in beam positions, two fixed forward firing 0.303in guns and two 20mm cannon in dorsal turret
Bomb load: 2,000lb on retractable racks