The (S.A.1) Sturgeon began life as a high-performance torpedo bomber during the Second World War with a bomb bay that could accommodate six 500 lb bombs or any of the current standard aerial torpedoes, operating from Audacious and Centaur-class aircraft carriers. The torpedo requirement was dropped when the Second World War ended and plans for large aircraft carriers were abandoned.
Specification S.11/43 for a naval reconnaissance aircraft called for the design and construction of a twin-engine plane for visual and photographic reconnaissance and shadowing, by day or night. The specification included a maximum all-up weight of 24,000 lb, height (stowed) of 17 ft, length of 45 ft and a wingspan of 60 ft (spread) / 20 ft (folded). Powered wing-folding was also required.
The contract went to Short Brothers for their revised S.38 Sturgeon designated the PR Mk 1 on 12 February 1944 for three prototypes, with military serials RK787, RK791 and RK794 assigned. The first Short S.A.1 Sturgeon I RK787 flew at Rochester Airport on 7 June 1946, appearing at Farnborough in July. Deck landing trials were completed in 1947. The second, RK791, flew from Sydenham, Belfast on 18 May 1948.
The pilot's cockpit was a sub assembly bolted to the front of the spar, the navigator was behind the centre section of the wing and the radio operator — separated from the navigator by his equipment — behind him. The navigator and radio operator entered through a door, which acted as a ladder when opened, in the starboard side with their seats being offset to port. The cameras were installed in the fuselage behind the radio operator. One of the Sturgeon's unfortunate failings was in placement of controls. The fire extinguisher switch was located next to the cockpit switches required for firing the engine starter cartridges, resulting in some inadvertent mishaps and some unintended hilarity for ground crews. Armament would be two 0.5 inch machine guns with a 1,000 lb bomb or two 500 lb bombs (or depth charges).
The PR.1 competed in the Air League Challenge Cup Race of 1949 with an average speed of 295 mph.
The production series of 100 aircraft was cancelled but the design stayed alive with modifications to accommodate a target tug role as the S.39 (also known as S.A.2) Sturgeon. A third prototype, RK794, was modified to a Mk 2 standard with a new serial, VR363.
The TT Mk 2 was a large but clean-looking twin-engined, mid-wing cantilever monoplane design with a distinctive glazed nose in its target tug configuration. The all-metal monocoque fuselage was built in four sections ending at a cantilever tailplane with single fin and rudder. Rudder and tailplanes were fabric covered. The wing design featured a swept leading edge and taper on outboard sections, and wing folds outboard of the twin Rolls-Royce Merlin 140 engines driving contra-rotating propellers (which allowed shorter blades and the Merlins to be mounted closer to the centreline). The main wheels retracted rearwards into the engine nacelles while the tail wheel retracted forwards into the fuselage. Radiators were mounted in the leading edge between the nacelles and the fuselage.
The Sturgeon's postwar role began as a naval liaison and target tug aircraft with modifications to the nose, lengthened to provide a crew position forward of the propeller arcs and a winch system. The crew of two included a pilot in an enclosed cockpit, level with leading edge of wing. The all-purpose "observer" in the nose had to perform the functions of "navigator, wireless operator, target operator and camera operator. He moved between stations in the nose and rear fuselage." Five TT2s were further converted into the less-sophisticated TT3 variant.
The penultimate and last Sturgeons were redone as prototypes for a proposed anti-submarine aircraft, powered by two Armstrong Siddeley Mamba AS Ma3 turboprops of 1,147 hp (1,100 kW) driving two four-bladed propellers. The engine exhausts were directed downwards instead of to the rear. Another major modification was the grafting on of a gigantic bulbous nose that housed two radar operators in stations forward of the engines and the radar itself below. Acute problems arising from the resultant "schnoz" led to the demise of the project — "the efflux from the Mamba turboprops seriously destabilized the aircraft at some power settings and destroyed the good handling characteristics. It proved impossible to trim for safe flight on one engine which was a necessity for long endurance on anti-submarine patrols."
Two Sturgeon SB 3 prototypes were ordered with the first, WF632 flying on 8 December 1950 at Belfast. The design proved extremely difficult to trim when flying on one engine and so unstable that no effort was made to resolve these problems, consequently, the project was cancelled before the second prototype, WF636 flew. Both aircraft had very short lives, being scrapped in 1951.
General characteristics
- Crew: 2
- Length: 44 ft (13.70 m)
- Wingspan: 59 ft 11 in (18.26 m)
- Height: 13 ft 2½ in (40.39 m)
- Wing area: 518.4 ft² (48.16 m²)
- Airfoil: NACA 65,2—2.5 modified
- Empty weight: 16,967 lb (7,696 kg)
- Loaded weight: 18,126 lb (8,222 kg)
- Max takeoff weight: 21,700 lb (9,840 kg)
- Powerplant: 2 × Rolls-Royce Merlin 140 liquid-cooled V12 engines, 2,080 hp (1,550 kW) each
- Propellers: three-bladed contra-rotating Rotol propellers, 2 per engine
Performance
- Maximum speed: 318 knots (366 mph, 590 km/h) at 24,200 ft
- Cruise speed: 312 mph (502 km/h) at 15,000 ft
- Service ceiling: 35,200 ft (10,700 m)
