Short Empire

Origins During the 1930s, demand for air travel was rapidly growing. The British national flag airline Imperial Airways sought to fully expand air service across the British Empire. Imperial Airways' technical adviser, planned a specification for a new type of aircraft to serve passenger and freight requirements throughout the world. This required an aircraft to carry 24 passengers in comfort, as well as airmail or freight while having a cruising speed of , a normal range of at least and the capability for an extended range of to cross the North Atlantic. Shorts developed its own machinery to produce the necessary T-shaped Hiduminium alloy lengths that comprised the main spar. A specialised and patented flap, known as Gouge flaps after its creator, caused only a small increase in drag, while the wing's lift coefficient was increased by 30 percent, the landing speed reduced by 12 per cent, and no trim changes were needed. Early flights were relatively trouble-free, and Parker was satisfied with its performance and handling. On 17 September 1936, G-ADHL first flew for Imperial Airways, with the final proving flight to Marseille, France took place on 22 October 1936. The first series of the Short Empires, the S.23, could carry five crew, 17 passengers, and of cargo at a maximum speed of and was powered by four Bristol Pegasus Xc radial engines. The second Empire and the first of the long-range models, registered G-ADHM, named Caledonia, made its first flight on 15 September 1936 and was delivered to Imperial Airways on 4 December 1936. In late 1937, Imperial Airways placed a follow-on order for another 11 Empires. When combined with the original order of 28, this had the distinction of being the largest order by a single customer placed for a British civil aircraft at that time. While the first three aircraft of the additional order were of the typical S.23 class, intended for Qantas Empire Airways, the rest had a number of detail changes and were designated the S.30. Short's Rochester factory produced all 43 Empires built. Further development The S.30 series was fitted with four Bristol Perseus XIIc sleeve valve engines in the place of the Pegasus engines. the Perseus engines were each lighter and 17.3% more fuel efficient, but developed less power. It was roughly 15 percent larger, as well as using the much more powerful Bristol Hercules radial engine and a further improved hull design. It was intended to be used on the north Atlantic route. ==Design==

, Suffolk, England, September 1936 The Short Empire flying boat was a clean high-wing monoplane, initially powered by four wing-mounted Bristol Pegasus Xc radial engines which drove de Havilland-built variable-pitch propellers. The engines were each enclosed within NACA cowls and mounted ahead of the leading edge of the wings. This allowed portions of the leading edge adjacent to the engines to be hinged forward to be used as platforms to maintain the engines. The Pegasus Xc engines each produced on takeoff, decreasing to at an altitude of . Its useful load included of fuel (weighing ), of oil, assorted equipment (weighing ), along with the payload and five crew (weighing ). To simplify manufacturing and to maximize usable internal volume, only a simple single curvature on the hull was employed that didn't require the use of a press for most of the airframe. On previous Shorts' flying boats, a more complex S-shaped curvature and a sudden reduction in beam just above the chines had been employed instead. The cabins could be fitted with seating or sleeper bunks. Near the rear of the aircraft, an additional freight and mail compartment extended into the rear fuselage. The radio operator had Marconi shock-proof radio sets for transmitting and receiving while the retractable direction-finding loop antenna could be rotated for visual or aural homing. While designed as civil aircraft, examples of the type would not only see military service but were specifically refitted for this purpose. In 1941, two Empire flying boats – Clio and Cordelia were modified at Shorts' Belfast facility with gun turrets in dorsal and tail positions, bomb racks extending out of slots cut in the fuselage sides as on the Sunderland, and air to surface vessel (ASV) radar equipment installed on the top and sides of the fuselage. They were used by Coastal Command. More extensive military use was made of the Empire's military counterpart, the Short Sunderland. ==Operational history==

s in the Townsville Harbour, Queensland, December 1938 On 8 February 1937, an Empire flying boat, Castor, completed the first scheduled flight, from Calshot, Hampshire, England to Alexandria, Egypt. This flight covered a distance of roughly non-stop. On 18 February 1937, Caledonia, the first of the Empires built, flew the same Calshot-Alexandria route; it was able to traverse the route non-stop at an average speed of 170 mph. Using the S.21 design (based on the S.23) as the carrier, a smaller four-engined floatplane, the Short S.20, was mounted upon its back; the most obvious difference between the S.21 and regular S.23 aeroplanes was the additional superstructure to carry the floatplane. In further flights, the Empire-Mercury combination went on to set a number of long-distance records; one such flight was conducted on 6 October 1938, flying from Dundee, Scotland to Orange River, South Africa, covering in 42 hrs 5 min. However, in spite of the demonstrated merits and workability of the concept, the outbreak of the Second World War resulted in the effective termination of all development work. During wartime, there was interest in the concept using alternative land-based aircraft to deliver Hawker Hurricane fighter aircraft for aerial protection over the mid-Atlantic. After Italy entered the Second World War in June 1940, it became impossible for mail to be safely flown between Britain and Egypt (and thus onto Australia) via the Mediterranean. Accordingly, a new "Horseshoe Route" was established that ran from Auckland/Sydney via Cairo (following the old "Eastern Route") to Durban, South Africa, and thence by sea to Britain. This was restricted after the loss of Singapore in February 1942 to being between Durban and Calcutta, India. Wartime experience in operating the type at overload weights resulted in the realisation that the Empires could take off at considerably higher weights than the conservative maxima provided by Shorts and, although the last Empire crossings to America were made in 1940 (by Clare and Clyde), many more flights were made on the long, demanding and vital over-water Lisbon-Bathurst flights. ==Variants==

42 "C Class" Short Empire flying boats were built, including 31 S.23s, nine S.30s and two S.33s. • S.23 Mk I : powered by four Bristol Pegasus Xc poppet valve radial engines. 27 built. • S.23 Mk II Bermuda : powered by four Bristol Pegasus Xc poppet valve radial engines. 2 built. • S.23 Mk III Atlantic : powered by four Bristol Pegasus Xc poppet valve radial engines. two built. • S.23M : two converted from impressed S.23 Mk I, with an ASV radar, armed with two Boulton Paul gun turrets and depth charges. • S.30 Mk I : powered by four Bristol Perseus XIIc sleeve valve radial engines. One built. • S.30 Mk I (Cathay) : powered by four Bristol Pegasus Xc poppet valve radial engines. One built. • S.30 Mk II New Zealand : powered by four Bristol Perseus XIIc sleeve valve radial engines. One built. • S.30 Mk III Atlantic : powered by four Bristol Perseus XIIc sleeve valve radial engines. Four built. • S.30 Mk IV New Zealand : powered by four Bristol Perseus XIIc sleeve valve radial engines. Two built. • S.30M : two converted from impressed S.30 Mk III Atlantic for ASV trials and transport duties. • S.33 : powered by four Bristol Pegasus Xc poppet valve radial engines. Two completed, third example scrapped when 75% complete. Many S.23, S.30 & S.33 were re-engined during the war with Bristol Pegasus XXII poppet valve radial engines. ==Accidents and incidents==

Most accidents involving the aircraft occurred during landing and were generally attributed to pilot error. For pilots trained on smaller less sophisticated aircraft judgement of height was difficult due to the high cockpit of the Empire, as well as the concept of using flaps to manage speed. With time improved familiarity reduced the accident rate. Once in service the structure was found to be weak in places, especially on the planing bottoms, which led to later models employing thicker gauge skins on the hull and wings. ;27 November 1938:G-AETV Calpurnia of Imperial Airways crashed on landing on Lake Habbaniya, Iraq with the loss of four lives. ;21 January 1939:G-ADUU Cavalier of Imperial Airways ditched in the Atlantic Ocean due to carburettor icing affecting all four engines. The aircraft subsequently sank with the loss of three lives. Ten survivors were rescued by the American tanker . ;14 March 1939: G-ADVB Corsair (under Capt E.S. Alcock, brother of John Alcock) foundered during a forced landing on the Dungu River. After 10 months' salvage work, and one failed take-off attempt, it was flown off the river on 6 January 1940. ;1 May 1939: G-ADVD Challenger of Imperial Airways crashed on landing in Mozambique Harbour with the loss of two lives. ;February 1941:G-AFCX Clyde of BOAC was wrecked in a gale at Lisbon, Portugal. ;29 December 1941:G-ADUX Cassiopeia of BOAC crashed after striking debris on takeoff from Sabang, Indonesia, killing four. ;30 January 1942:G-AEUH Corio of BOAC was shot down by seven Japanese fighter aircraft and crashed off West Timor, killing 13 of the 18 people on board. The aircraft was owned by BOAC, but was operated by Qantas. ;28 February 1942: G-AETZ Circe of Qantas was shot down south of Java by Mitsubishi G4M "Betty" aircraft of the Imperial Japanese Navy with the loss of all on board. ;22 April 1943:G-AEUB (VH-ADU) crashed off Port Moresby, with 18 survivors. ==List of aircraft==

, South Africa, circa 1942 , India at Rod El Farag flying boat base, Cairo ==Operators==

, as G-AFBL aircraft, ZK-AMC, named Awarua, circa 1940 Civil operators ; • Qantas ; • TEAL ; • Imperial Airways • BOAC Military operators ; • Royal Australian Air Force • No. 11 Squadron RAAF • No. 13 Squadron RAAF • No. 20 Squadron RAAF • No. 33 Squadron RAAF • No. 41 Squadron RAAF ; • Royal Air Force • No. 119 Squadron RAF ==Specifications (Short S.23)==