|The BOAC Short 'C' Class flying boat G-AFBL Cooee, at Rod El Farag, Egypt, c. 1946|
|Role||Flying boat mail and passenger carrier|
|First flight||3 July 1936|
|Introduction||Delivered 22 October 1936,
First revenue flight 6 February 1937
|Primary users||Imperial Airways/BOAC
Qantas Empire Airways
Royal Australian Air Force
Royal Air Force
|Variants||Short Mayo Composite|
The Short Empire was a medium range four engined monoplane passenger and mail carrying flying boat, of the 1930s and 1940s, that flew between Britain and the British colonies in Africa, Asia and Australia as well as providing service between Bermuda and New York City. It was manufactured by Short Brothers and was developed in parallel with the Short Sunderland patrol bomber of World War II and the piggy-back Short Mayo Composite .
Design and development
The Empire was officially known as the C-class by Imperial Airways and each aircraft operated by them was given a name beginning with C. The first aircraft, G-ADHL Canopus, was completed in June 1936 and launched on 3 July. A total of 42 Empires were built, all at Short's Rochester factory.
Imperial Airways (and its successor BOAC), Qantas and TEAL operated the Short Empire in commercial service, while the Royal Air Force, Royal Australian Air Force, Royal New Zealand Air Force and briefly the Royal Canadian Air Force used them on military operations during the Second World War, particularly for anti-submarine patrol and transport duties.
The first series of the Short Empires, the S.23, could carry 5 crew, 17 passengers, and 4,480 lb (2,035 kg) of cargo at a maximum speed of 174 knots (320 km/h) and were powered by four 920 horsepower (690 kW) Bristol Pegasus radials.
The Short Empire was designed to operate along the Imperial Airways routes to South Africa and Australia, where no leg was much over 500 miles (800 km). After the design was finalized and production was started it was realized, with some pressure from the United States, that it would be desirable to offer a similar service across the Atlantic. The range of the S.23 was less than that of the equivalent US Sikorsky "Clipper" flying boats and as such they could not provide a true trans-Atlantic service. Two boats (Caledonia and Cambria) were lightened and given long range tanks and experimented with in-flight refuelling so they could make the trip but that meant they could carry fewer passengers and cargo. In an attempt to manage the Atlantic crossing, a piggy-back approach was tried. Using the S.21 design (based on the S.23) as the carrier, with a smaller four-engined floatplane, the Short S.20, mounted on its back. Only a single example was built of the S.21 carrier aircraft, the Maia, and of the S.20 Mercury. Together they were known as the Short Mayo Composite. A successful mid-air launch of Mercury was made in 1938, and it was to set a number of long distance records however a launch aircraft was required for both sides of the Atlantic and the Mercury was limited to carrying mail, and no further development of this concept occurred in the UK.
The S.30 series were fitted with the more efficient, but lower power 890 horsepower (660 kW) Bristol Perseus sleeve valve engines and had a strengthened airframe allowing the take off weight to be increased to 46,000 pounds (21,000 kg), giving a range of 1,500 miles (2,400 km). Cabot, Caribou, Clyde and Connemara were fitted with in-flight refuelling equipment and extra fuel tanks so they could be used for a regular trans-atlantic airmail service. The idea was for the aircraft to take off and once airborne take on extra fuel to an all up weight of 53,000 pounds (24,000 kg) giving a range of over 2,500 miles (4,000 km). The extra fuel did reduce the payload to 4,270 pounds (1,940 kg) against the 6,250 pounds (2,830 kg) of the standard craft. The refuelling was by three converted Handley Page Harrow bombers, one operating out of Ireland and two out of Newfoundland. The S.33 was a further follow-on to the S.30 with the same Pegasus to what had been fitted to the S.23
Initially, they were designed for a 40,500 lb gross weight but by 1939 aircraft were strengthened for 53,000 lb (24,000 kg) 
Wartime experience in operating at overload resulted in the realization 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.
A completely new flying boat, the S.26 "G class" was produced for year-round use on the North Atlantic route (although it was used instead between the UK and West Africa. Of similar appearance to the C-class boats but about 15% larger in all dimensions with the more powerful Hercules engines and an improved hull design, they had a wing span of 134 feet (41 m) and a length of 101 feet (31 m).
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 920 hp (690 kW) Bristol Pegasus Xc poppet valve radial engines. 27 built.
- S.23 Mk II Bermuda : powered by four 920 horsepower (690 kW) Bristol Pegasus Xc poppet valve radial engines. 2 built.
- S.23 Mk III Atlantic : powered by four 920 hp (690 kW) 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 890 hp (660 kW) Bristol Perseus XIIc sleeve valve radial engines. One built.
- S.30 Mk I (Cathay) : powered by four 920 hp (690 kW) Bristol Pegasus Xc poppet valve radial engines. One built.
- S.30 Mk II New Zealand : powered by four 890 hp (660 kW) Bristol Perseus XIIc sleeve valve radial engines. One built.
- S.30 Mk III Atlantic : powered by four 890 hp (660 kW) Bristol Perseus XIIc sleeve valve radial engines. Four built.
- S.30 Mk IV New Zealand : powered by four 890 hp (660 kW) 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 920 hp (690 kW) 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 1,010 hp (750 kW) Bristol Pegasus XXII poppet valve radial engines.
In February 1937 Caledonia flew from Calshot to Alexandria, Egypt - some 2,500 miles (4,000 km) non-stop showing that Britain could move military materiel to its overseas bases. In 1937 Caledonia was flown experimentally from Foynes on the River Shannon west to Newfoundland while an American Sikorsky S-42 flew the opposite direction. Caledonia took just over 15 hours (including a period looking for landing spot) flying at an altitude of 1,500 to 5,000 ft (460 to 1,520 m) to cover 1,993 miles (3,207 km) - an average speed of about 130 mph (210 km/h). Several more survey flights of the Atlantic were made by Caledonia and Cambria. In August 1937, Cambria made the East-West flight in 14 hrs 24 min. In 1937 Cavalier was shipped to Bermuda and after assembly started a service to New York on 25 May 1937.
After Italy entered World War II in June 1940, it was impossible for mail to be flown between Britain and Egypt (and thus onto Australia) via the Mediterranean. 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.
List of aircraft
|G-ADHM||Caledonia||Imperial Airways, later BOAC|
|G-ADUT||Centaurus||Imperial Airways, to Royal Australian Air Force (RAAF) in 1939 (as serial A18-10)|
|G-ADUU||Cavalier||Imperial Airways, lost 21 January 1939 en route to Bermuda. 3 Fatalities, 10 Survivors.|
|G-ADUV||Cambria||Imperial Airways, later BOAC|
|G-ADUW||Castor||Imperial Airways, later BOAC|
|G-ADUX||Cassiopea||Imperial Airways, later BOAC|
|G-ADVB||Corsair||Imperial Airways, later BOAC|
|G-ADVD||Challenger||Imperial Airways, crashed on landing in Mozambique, 1 May 1939, and was written off.|
|G-AETV||Coriolanus||Imperial Airways, later BOAC, to QANTAS in 1942 (as registration VH-ABG)|
|G-AETW||Calpurnia||Imperial Airways. Crashed, sunk & wrecked, Lake Habbaniya, Iraq, 27 November 1938.|
|G-AETX||Ceres||Imperial Airways, later BOAC|
|G-AETY||Clio||Imperial Airways, later BOAC, to Royal Air Force (RAF) in 1940 (as AX659)|
|G-AETZ||Circe||Imperial Airways, later BOAC; shot down south of Java by Japanese Navy Mitsubishi G4M, 28 February 1942|
|G-AEUA||Calypso||Imperial Airways, to QANTAS in 1939 not used directly, to RAAF (as serial A18-11)|
|G-AEUB||Camilla||Imperial Airways, later BOAC - to QANTAS (as VH-ADU)|
|G-AEUC||Corinna||Imperial Airways, later BOAC|
|G-AEUD||Cordelia||Imperial Airways, later BOAC, to RAF in 1940 (as AX660), returned to BOAC in 1941 (as G-AEUD)|
|G-AEUE||Cameronian||Imperial Airways, later BOAC|
|G-AEUF||Corinthian||Imperial Airways, later BOAC|
|G-AEUG||Coogee||Imperial Airways, to QANTAS in 1938 (as VH-ABC), to RAAF in 1939 (as A18-12)|
|G-AEUH||Corio||Imperial Airways, to QANTAS in 1938 (as VH-ABD), to Imperial Airways in 1939 (as G-AEUH)|
|G-AEUI||Coorong||Imperial Airways, to QANTAS in 1938 (as VH-ABE), to Imperial Airways in 1939 (as G-AEUI)|
|G-AFBJ||Carpentaria||Imperial Airways not used, to QANTAS in 1937 (as VH-ABA), to BOAC in 1942 (as G-AFBJ)|
|G-AFBK||Coolangatta||Imperial Airways not used, to QANTAS in 1937 (as VH-ABB), to RAAF in 1939 (as A18-13)|
|G-AFBL||Cooee||Imperial Airways not used, to QANTAS in 1937 (as VH-ABF) to BOAC in 1942|
|G-AFCT||Champion||Imperial Airways, later BOAC|
|G-AFCU||Cabot||Imperial Airways, to RAF in 1939 (as V3137)|
|G-AFCV||Caribou||Imperial Airways, to RAF in 1939 (as V3138)|
|G-AFCX||Clyde||Imperial Airways, later BOAC|
|G-AFCY||Captain Cook||Imperial Airways, to TEAL in 1940 (as ZK-AMC Awarua)|
|G-AFCZ||Australia then Clare||Imperial Airways, later BOAC|
|G-AFDA||Aotearoa||Imperial Airways, to TEAL in 1940 (as ZK-AMA)|
|G-AFKZ||Cathay||Imperial Airways, later BOAC|
|G-AFPZ||Clifton||BOAC, to RAAF (as A18-14), to QANTAS in 1942 (as VH-ACD)|
|G-AFRA||Cleopatra||BOAC, 1st Service 5-6-40 Poole to Durban. Final Service ended 5-11-46 at Poole.|
- Royal Australian Air Force
Specifications (Shorts S.23)
Data from The Encyclopedia of World Aircraft
- Length: 88 ft (26.82m)
- Wingspan: 114 ft (34.75 m)
- Height: 31 ft 9¾ in (9.70 m)
- Wing area: 1,500 ft² (139.35 m²)
- Empty weight: 23,500 lb (10,659 kg)
- Max. takeoff weight: 40,500 lb (18,370 kg)
- Powerplant: 4 × Bristol Pegasus radial engines, 920 hp (696 kW) each
- Related development
- Aircraft of comparable role, configuration and era
- Boeing 314
- Dornier Do 26
- Kawanishi H6K
- Latécoère 611
- Martin China Clipper
- Potez-CAMS 141
- Sikorsky S-42
- Related lists
- Cassidy, Brian (1996). Flying Empires Short 'C' class Empire flying boats. Bath, UK: Queens Parade Press. pp. 21 & 54–55. ISBN 0-9529298-2-1.
- Robert Mayo – Short Aircraft Engineer's Concept
- "The Greatest Short" Flight 20 July 1939. page e
- Flight 15 February 1937
- Jackson 1974, p. 146
- Flight, 24 August 1939, p. 188.
- "Circe Mystery Solved after 72 Years". australianflying.com.au. Yaffa Publishing Group. 28 February 2014. Retrieved 16 April 2014.
- Donald, David(Editor) (1997). The Encyclopedia of World Aircraft. Aerospace Publishing. ISBN 1-85605-375-X.
- BOAC At War - Part 2 - Aeroplane Monthly - August 1975
- Sims, Phillip, Adventurous Empires. Airlife Publishing, 2000. ISBN 1-84037-130-7
- Vector site development of Sunderland through Empire boats
- Barnes, C.H.; James D.N. Shorts Aircraft since 1900. London (1989): Putnam. ISBN 0-85177-819-4.
- Jackson, A.J. (1974). British Civil Aircraft since 1919 Volume 3. London: Putnam. ISBN 0-370-10014-X.
- "The Construction of the Empire Boats" (PDF), Flight, 29 October 1936
|Wikimedia Commons has media related to Short Empire.|
- British Aircraft of WW2
- Century of Flight entry
- ATLANTIC ROUTINE Flight 1937 - contemporary article on Sikorksy S42 and Empire Caledonia operating across Atlantic
-  LIFE photos by Margaret Bourke-White of CAVALIER and its competitor the Bermuda Clipper New York area 1937
-  LIFE photos by Margaret Bourke-White of CALEDONIA with a Beech Staggerwing near Central Park New York City July 1937
-  LIFE colour photos by Dmitri Kessel of CLARE at the La Guardia Marine Terminal New York City, during a series of mail/courier flights it, and CLYDE, operated to New York via Newfoundland during the Battle of Britain, 1940