Aviation of World War II

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S.25 Sunderland

Flying Boat


Short S.25 Sunderland

The Short S.25 Sunderlad was a four-engined general-purpose flying-boat designed during 1933/34 in response to Specification R.2/33, which spelt out the needs of Operational Requirement 8 as a replacement for the biplane 'boats then in service. Designed under direction of Arthur Gouge, S.25 retained overall configuration and geometry of Scion Senior, and was in many respects the military counterpart of S.23 Empire Boat, which was the first to fly. A single prototype S.25 ordered in 1934 for competitive evaluation against Saro A. 33. Powered by four 950 hp Bristol Pegasus X engines, prototype K4774 first flew on October 16, 1937. After four flights, sweepback of 4.5 deg introduced on the mainplanes, and 1,010 hp Pegasus XXIIs fitted; testing in this form resumed on March 7, 1938.

Short Sunderland I: Initial production version of S.25. Total of Short Sunderland Is built to 74 by Shorts at Rochester and 15 by Blackburn at Dumbarton. First of development batch flew on April 21, 1938 and 42 Short Sunderland Is flying by September 1939; first by Blackburn flew late - 1941. Short Sunderland I was powered by four 1,010 hp Pegasus XXII engines and carried a crew of 9-10.

Armament comprised a single (later, two) guns in FN 11 nose turret, four guns in FN13 tail turret and (later aircraft) two Vickers 'K' guns in dorsal hatches, all of 0.303-in (7.7-mm) calibre'. A 2,000 Ib (908 kg) bomb-load was carried.

Short Sunderland II: Operationally-improved Mk I with 815 hp Pegasus XVIII engines and two-speed superchargers, FN7 two-gun dorsal turret in place of open 'K'-gun mounts, and FN4A tail turret with double rpg. Most Mk Us also fitted with ASV Mk II radar, indicated by aerial masts and transmitter loops on rear fuselage, and central and underwing Yagi homing aerials. Prototype conversion of (first Blackburn-built) Mk I, T9083, followed by 23 by Shorts at Rochester, five by Blackburn and five by Short & Harland in Belfast (where first flew on April 24, 1942). Served alongside Mk Is in four squadrons and as initial equipment of four more.

Short Sunderland III: Principal war-time production and service version, featuring impoved low-drag hull design and faired main step. Other features as Mk II. Prototype (Mk I conversion) T9042 flown at Rochester on June 28, 1941, and first production Mk III, also at Rochester, on December 15, 1941. Production totals, 186 from Rochester, 71 from Belfast, 170 from Blackburn Dumbarton and 35 from Short-operated factory on Lake Windermere in the English Lake District. The Windermere factory also did some conversion work upgrading Mark III Sunderlands to Mark Vs (thanks John Evans, Pembroke Dock, Wales).

Early in 1943, centimetric ASV Mk III replaced ASV Mk II; later, ASV Mk VIC, with fairings for underwing scanners, was fitted in Short Sunderland IIIAs. From late 1943, Mk Ills fitted with four additional forward-firing machine guns in the nose, and a further modification provided pairs of 0.50-in (12.7-mm) guns to fire through beam hatches aft of dorsal turret, bringing the total to 18 machine guns.

Short Sunderland IV: See separate entry for S.45 Seaford.

Short Sunderland V: As Mk III but fitted with 1,200 hp Pratt & Whitney R-1830-90 engines. Prototype conversions of Mk Ills by Shorts at Rochester (ML765) and by No 10 Sqn (RAAF) at Mount Batten (ML839), flown in March and May 1944 respectively. Existing Mk III contracts switched to Mk Vs, with deliveries starting late-1944, all with ASV Mk VIC and full 18-gun armament. Short built 47 at Rochester where the last one flew on September 27, 1945; Short and Harland built 47 at Belfast, completed June 1946; and Blackburn built 60 at Dumbarton, where last Mk V flew on November 8, 1945. Entered service February 1945 and used (mostly post-war) by nine RAF squadrons.

MK. I Mk. V
Crew 9-10 10-13
Wingspan 34.34 m (112 ft 8 in) 34.34 m (112 ft 8 in)
Height 10,52 m (34 ft 6 in) 10,52 m (34 ft 6 in)
Length 26.11 m (85 ft 8 in) 26.11 m (85 ft 8 in)
Wing area 138.14 m² (1,487 ft²) 138.14 m² (1,487 ft²)
Engine Bristol Pegasus XXII Pratt & Whitney R-1830-90B
Power 4x (1,010 hp) each 4x (1,200 hp)
Empty weight 12,832kg (28,290 lb) 16,783 kg (37,000 lb)
Loaded weight 20,730kg (45,700 lb) 27,216 kg (60,000 lb)
Maximum speed 338km/h (210 ml/h) 343km/h (213 ml/h)
Rate of climb 6.1 m/sec (1,200 ft/min) 4.27 m/sec (840 ft/min)
Service range 4,686 km (2,910 mis) endurance*, over 15 hours
Service ceiling 6,248 m (20,500 ft) 5,455 m (17,900 ft)

* - at cruising speed

Photo Description
Drawing Short Sunderland Mk II

Drawing Short Sunderland Mk II

Sunderland Mk.I in flight at 1941

Short Sunderland Mk.I at 1941


  • "Encyclopedia of military engineering" /Aerospace Publising/
  • "British warplanes of World War II" /under cor. Daniel March/