Short S.23 Empire
The Short S.23 Empire was a four-engined British flying boat airliner, built by Short Brothers at Rochester for the Empire Air Mail Scheme and flown by Imperial Airways — later BOAC — Qantas Empire Airways and Tasman Empire Airways. First flown in July 1936, the C-class boats carried passengers and mail between Britain, Africa, India, Australia and New Zealand; production totalled 42 aircraft: 31 S.23s and the developed S.30 and S.33 variants. The war brought the Horseshoe Route, RAAF service and heavy losses in 1942. The last boats were retired and scrapped in the later 1940s, and no example survives.
Why It Mattered
The Empire boats were built for the Empire Air Mail Scheme, the plan to carry all first-class mail between Britain and its dominions by air, with no surcharge on the sender. Imperial Airways ordered twenty-eight of them before the design existed or any example had flown. The network they opened linked England with Africa, India, the Far East, Australia and New Zealand, and every boat carried a name beginning with C, from Canopus onward. The South Australian Aviation Museum rates the boat, for its size, as technically well ahead of every other British aircraft of its day. The design also fed directly into the military line: the RAF Museum describes the Sunderland as a military development of the C-class Empire flying boat.
Design Notes
Arthur Gouge, the company's chief designer, centred the design on a deep fuselage carried up into the wing, which cut drag and allowed a cantilever wing that was lighter and stronger. His narrower planing bottom reduced water drag on take-off for an eighteen-ton boat, and his patented flaps gave thirty per cent more lift and a 12 mph lower speed with no trim change. The structure was all metal except for the fabric-covered tail and control surfaces. Four Bristol Pegasus Xc radial engines of 920 hp gave a maximum speed of 200 mph and a cruising speed of 165 mph. Inside, the flight crew and radio operator worked on an upper control deck with a large mail compartment behind them, while twenty-four passengers sat in four cabins on the lower deck. The boats were among the first British commercial aircraft to fly with an automatic pilot. Development produced the S.30, which changed to Bristol Perseus engines, and two S.33s similar to the S.23s except for strengthened hulls.
Operational History
The first boat, Canopus, lifted off briefly during taxi trials on 3 July 1936 and made its official first flight the next day; production ran at about one aircraft a month. Commercial operations, including the air mail scheme, began in early February 1937 with a Mediterranean service between Southampton and Alexandria. That July, Caledonia flew an experimental Atlantic crossing from Shannon in Ireland to Botwood in Newfoundland. A year later the one-off Mayo Composite used a carrier aircraft based on the S.23 to launch the small S.20 Mercury floatplane in mid-air off the west coast of Ireland. The Australia route was completed in July 1938: the Singapore-to-Sydney extension opened, and Qantas Empire Airways' Cooee left Rose Bay on 5 July on the first through flight to Southampton. Tasman Empire Airways began its Auckland-to-Sydney service with S.30s on 30 April 1940. Italy's entry into the war in June 1940 closed the Mediterranean to mail flights, and the boats were rerouted onto the Horseshoe Route, running from Auckland and Sydney via Cairo to Durban. While that route stayed open, Qantas worked the Sydney-to-Karachi section and BOAC the rest. Japan's entry into the war closed the route in December 1941; within weeks Corio had been shot down near Koepang, on 30 January 1942, and Circe between Java and Western Australia, on 28 February. Five boats were taken over by the RAAF, which used them for coastal reconnaissance and general transport.
Afterlife
The survivors came off the routes soon after the war, and several were scrapped at Hythe in 1947. Coriolanus, which had transferred to Qantas in September 1942, remained in service until it was broken up at Rose Bay in 1948. TEAL's S.30s held the Tasman crossing until 1947, completing 442 crossings by 29 October that year. One of them, ZK-AMA, spent its retirement as a coffee bar at Mechanics Bay, Auckland, lasting into the late 1950s before it too was scrapped. No example of the Short C-class survives.