The Short S.23, C Class Empire flying boat was designed for long-range passenger and mail transport on British Empire routes operated by Imperial Airways. Powered by four 900 hp Bristol Pegasus XC radial engines and designed to carry a 3.5-ton payload (including 24 passengers), it was first flown July 3, 1936. By December 1937, a total of 25 had been built for Imperial Airways and a further six for Qantas; however eight of these 31 aircraft were lost prior to WWII.
The remainder were used principally by Imperial Airways' successor BOAC (retaining British civil registrations) throughout the war on segments of Empire routes, from Durban to India and Australia. Two ex-Imperial Airways machines were impressed by RAAF in September 1939 (replaced by two exchange craft from Qantas). In July 1940 two more ex-Qantas machines were impressed. All four aircraft were fitted with underwing bomb racks and guns, and were used by No 11 Squadron, RAAF, for coastal patrols and transport duty. Later these served with No 33 Squadron as transports. Three were lost in 1942, and the fourth returned to Qantas in July 1943, only to be lost in January 1944.
In 1940 the RAF impressed two Short S.23s (ex-BOAC); these were fitted with dorsal and tail turrets and ASV radar and delivered to No 119 Squadron in 1941. One was lost in August 1941 and other was returned to BOAC in December 1941 after brief service with No 413 (RCAF) Squadron. Of the remaining S.23s, seven were lost and ten survived the war.
The S.23 design was used as the basis for the successful Short S.25 Sunderland flying boat operated by the RAF and RAAF during and after the Second World War. No.10 Squadron RAAF were in the UK converting to the Sunderland when the war began in 1939 and became the first Australian unit to serve in a combat role during the conflict.
Max speed, 200 mph (322 kmlh). Service ceiling, 20,000 ft (6,100 m). Range, 760 miles (1,245 km). Empty weight, 23,500 Ib (10,670 kg). Gross weight, 40,500 Ib (18,380 kg). Span, 114 ft 0 in (34.7 m). Length, 88 ft 0 in (26.8 m). Wing area, 1,500 sq ft (139.5 m2).