Short 'Sunderland'

The Short S.25 Sunderland was a British flying boat patrol bomber developed for the Royal Air Force (RAF) by Short Brothers. Based in part upon the S.23 'Empire' flying boat, the flagship of Imperial Airways, the S.25 was extensively re-engineered for military service. It was one of the most powerful and widely used flying boats throughout the Second World War, and was involved in countering the threat posed by German U-boats in the Battle of the Atlantic. RAF Sunderlands also saw service throughout the Korean War and continued in service until 1959.

In 1934, Imperial Airways announced a competition to design and produce 28 flying boats, each weighing 18 long tons (18 t) and having a range of 700 mi (1,100 km) with a capacity for 24 passengers. The contract went to Short Brothers of Rochester and while the first example of the new type, the S.23 Empire was under development, the British Air Ministry was taking actions that would result in a military version. The 1933 Air Ministry Specification R.2/33 called for a next-generation flying boat for ocean reconnaissance. The new aircraft had to have four engines but could be either a monoplane or biplane design, although Specification R.2/33 was roughly in parallel with the Imperial Airways requirement. Short however, continued to develop the S.23 'Empire', while it also worked on a response to R.2/33 at a lower priority. Short developed the S.25 Sunderland from their S.23 or 'C-class' flying boat, the flagship of Imperial Airways. The S.25 first flew on 16 October 1937. The prototype was damaged during high-speed taxiing on the Solent river, however, an order was placed for 11 Mk.I Sunderlands (with R.A.F. serial nos. L2158-L2168). They were delivered between April and August 1938 with the first operational Sunderland, no. L2158, making its first flight on 21 April 1938. They were followed by another 53 Mk.I'he cockpit section placed backwards to make room for a nose gun turret installation. A second turret was placed in the tail. On the dorsal part of the fuselage there were two removable small hatches providing room for two additional board guns. The S.25 shared much in common with the S.23 but it had a deeper hull profile. As with the S.23, the Sunderland's fuselage contained two decks with six bunks on the lower one, a galley with a twin kerosene pressure stove, a yacht-style porcelain flush toilet, an anchoring winch, and a small machine shop for inflight repairs. The crew was originally intended to be seven but increased in later versions to 11 crew members or more. It was of all-metal, mainly flush-riveted construction except for the control surfaces, which were of fabric-covered metal frame construction and the thick wings carried the four nacelle-mounted Pegasus engines and accommodated six drum fuel tanks with a total capacity of 9,200 litres (2,025 Imperial gallons, 2,430 U.S. gallons). As with all water-based aircraft, there was a need to be able to navigate on water and to control the craft up to and at a mooring. The Sunderland could be moored to a buoy by a pendant that attached to the keel under the forward fuselage. When the craft was off the buoy, the forward end of the pendant was attached to the front of the hull just below the bomb aimer's window. For anchoring, there was a demountable bollard that fixed to the forward fuselage from where the front turret was retracted to allow an airman to man the position and pick up the buoy cage or to toss out the anchor.

By the start of World War Two in September 1939 three squadrons had been equipped with the Sunderlands. Sunderlands quickly proved useful in the rescue of the crews from torpedoed ships. On 21 September 1939, two Sunderlands rescued the entire 34-man crew of the torpedoed merchantman Kensington Court from the North Sea. The Sunderland was not designed to land to pick up survivors in open ocean as it could land and take-off only from sheltered coastal waters. From 1942 onwards, landings in open sea were expressly forbidden, except in special circumstances and with permission. U-boat patrols, carrying eight depth charges, were an important task of the Sunderlands. They patrolled the approaches, or flew convoy protection missions. The two were often combined, with the Sunderlands meeting the convoys at some distance in the ocean. When a U-boat was sighted, the Sunderlands tried to attack it before it submerged. Development in surface radar during the war allowed the Sunderland to carry these with some Mk. III's being fitted with an A.S.V. Mk. II (Air-to Surface-Vessel) radar equipment for U-boat detection. These Sunderlands all carried the characteristic 4-mast array at the rear of the top fuselage. Many Mk. III's were later converted to Mk. V standard including an engine change to the R-1830 Twin Wasp.
During the war the Sunderland was employed by the air forces of Australia, Britain, and Canada. It was used principally to escort merchant convoys and hunt enemy submarines in the Atlantic Ocean, and destroyed over 60 U-boats. Sunderlands also served in the Mediterranean, South-East Asian, and Pacific theatres, and as well as their maritime patrol role they were employed as long-range transport aircraft. It was in this latter capacity that 40 Squadron RAAF operated Sunderlands around northern Australia and New Guinea in 1944 and 1945. The German gave it the nickname of 'Fliegendes Stachelschwein' (Flying Porcupine), although this could also be attributed to the large array of radar antennas fitted to many Sunderlands.

In Europe it was removed from service relatively quickly but in the Far East, where well developed runways were less common and large land based maritime patrol aircraft could not be used so easily, there was still a need for it, and it remained in service with the RAF Far East Air Force at Singapore until 1959, and with the Royal New Zealand Air Force's No. 5 Squadron RNZAF until 1967 and the Sunderland being retired from Australian service in 1947. The French Navy Escadrille 7FE, which received Sunderlands when it was formed in 1943 as No. 343 Squadron RAF, continued to operate them until December 1960. During the Berlin Airlift (June 1948 - August 1949) 10 Sunderlands and two transport variants (known as 'Hythes') were used to transport goods from Finkenwerder on the Elbe near Hamburg to the isolated city, landing on the Havel river beside RAF Gatow until it iced over. RAF Sunderlands also saw service during the Korean War initially with No. 88 Squadron but shortly followed by Nos. 205 and 209 Squadrons. The three squadrons shared the operational task equally with rotational detachments of three or four aircraft and crews based at Iwakuni, Japan. Missions lasting 10 to 13 hours were flown daily throughout the war.
With the end of the war, large contracts for the Sunderland were cancelled and the last of these flying boats was delivered in June 1946, with a total production of 777 aircraft completed.