Short Sperrin

infobox Aircraft
name=SA.4 Sperrin
type=Experimental aircraft
manufacturer= Short Brothers and Harland, Belfast


caption=
designer=
first flight=First prototype: 10 August 1951
Second prototype: 12 August 1952
introduced=
retired=First prototype: 1958
Second prototype: 1957
status=
primary user=Royal Air Force (intended)
more users=
produced=
number built=2
unit cost=
variants with their own articles=The Short SA.4 "Sperrin" (named after the Sperrin Mountains, a range of hills in Northern Ireland) was a British jet bomber design of the early 1950s built by Short Brothers and Harland of Belfast, popularly abbreviated "Shorts". It first flew in 1951. Although it was not put into production because swept-wing designs such as the Vickers Valiant were by then available, the Sperrin prototypes were valuable for research data on large jet aircraft.

Design and development

In the post-Second World War war period, the British authorities felt there was a need for an independent strategic bombing capability—in other words that they should not be reliant upon the American Strategic Air Command. In late 1948, the Air Ministry issued their specification B.14/46 [ Gunston 1980, p. 341.] for an advanced jet bomber that should be the equal of anything that either the Soviet Union or the Americans would have. The exact requirements included a weight of convert|140000|lb|abbr=on, the ability to fly to a target convert|1500|nmi|km distant at convert|500|kn|km/h from altitudes of 45,000-50,000 ft and be simple enough to maintain at overseas bases. A further stipulation that a "special" in RAF jargon, a nuclear bomb, weighing convert|10000|lb|abbr=on and measuring 30 ft (length) and ten ft (diameter) could be accommodated.

There had already been specification "B.35/46" the previous year for a "medium-range bomber landplane" that could carry a "10,000 pound [4,500 kilogram] bomb to a target 1,500 nautical miles [2,780 kilometers] from a base which may be anywhere in the world." [Wood 1975, p. 130.]

The 1947 request anticipated that the fully laden weight would be under 100,000 lb (45 tonnes), the bomber have a cruising speed of convert|500|kn|km/h and that the service ceiling would be 50,000 feet (15,200 m). This request would be the foundation of the V-bombers.

However the Air Ministry accepted that the request might prove to be beyond the reach of Britain's aircraft manufacturers and prepared for a fall-back position in the form of an earlier specification B.14/46 which was more conservative in its demands and under this they placed a contract for two flying prototypes and a static test machine with Shorts.

The design known initially as SA.4 and later as the "Sperrin" had more in common with the Second World War designs than the new jet age. It was straight winged, although the leading edge was slightly swept. The engines were mounted in nacelles mid-wing; two engines per wing with one engine stacked above the other. The airframe was built largely of aluminium alloys with tricycle undercarriage, the nose gear retracting backward and the main gear in the wings towards the fuselage.

The SA.4 was designed for a crew of five: pilot, copilot, bombardier, navigator and radio operator, though only the pilot had an ejection seat.

Testing

The first prototype ("VX158"), powered by four Rolls-Royce Avon RA.2 engines of convert|6000|lbf|kN|abbr=on of thrust and piloted by Tom Brooke-Smith, had its maiden flight on 10 August 1951. By this time the decision had been taken to order the Vickers Valiant instead of the Sperrin and the project was cancelled, although the Ministry of Supply determined that the Sperrin would serve as a research aircraft. Work on the two prototypes was continued, with the second prototype ("XV161") flying on 12 August 1952 with Sqn Ldr "Wally" Runciman [Sqn Ldr W.J. Runciman, A.F.C, D.F.M] at the controls, accompanied by Flight Test Development Engineer Malcolm Wild. It was fitted with more powerful Avon RA.3s of 6,500 lbf (28.1 kN) thrust.

The two Sperrins were used in a variety of research trials through the 1950s, including engine tests using "VX158" as a testbed for the de Havilland Gyron turbojet - a large engine delivering 15,000 lbf (66.7 kN) thrust. The Gyron Gy1 replaced the lower Avon in the port nacelle (see image). For the first flight with this engine configuration on 7 July 1955., "VX158" was piloted by Jock Eassie and Chris Beaumont. Testing with this asymmetric engine configuration continued until March 1956, when the single Gyron Gy1 was removed and two Gyron Gy2 engines, each providing convert|20000|lbf|kN|abbr=on thrust, were fitted, one in each engine nacelle below the original Avon RA.2s.

The first flight of "VX158" with the new engine configuration took place on 26 June 1956, again with "Jock" Eassie and Chris Beaumont at the controls. During this flight the port outer undercarriage cover fell off; "VX161" was flown over from Farnborough and its corresponding cover was used to repair "VX158". "VX161" never flew again and was scrapped at Sydenham in 1957Barnes and James 1989, p. 429.] . "VX158" was flown at the Farnborough Airshow in 1956 with two Avons and two Gyrons fitted but "six months later the Gyron programme was discontinued and "VX158" was scrapped at Hatfield in 1958"Barnes and James 1989, p. 429.] .

A photograph of "VX158" with both Gyrons fitted can be seen in C.H. Barnes' and D.N. James' definitive work "Shorts Aircraft since 1900" [Barnes and James 1989, p. 431.] .

Among other test work, "VX161" (which had a fully operational weapons bay) was involved in trials relating to bomb shapes with concrete mock-ups of the Blue Danube nuclear bomb and the Blue Boar missile. Neither project was continued.

pecifications first prototype ("VX158")

aircraft specifications
plane or copter?=plane
jet or prop?=jet
crew=Five (pilot, co-pilot, bombardier, navigator and radio operator)
capacity=
length main=102 ft 2 in
length alt=31.14 m
span main=109 ft
span alt=33.2 m
height main=28 ft 6 in
height alt=8.69 m
area main=1,897 ft²
area alt=176.2 m²
empty weight main=72,000 lb
empty weight alt=33,000 kg
loaded weight main=
loaded weight alt=
max takeoff weight main=115,000 lb
max takeoff weight alt=52,200 kg
engine (jet)=Rolls-Royce Avon
type of jet=turbojet
number of jets=4
thrust main=6,000 lbf
thrust alt=27 kN
max speed main=567 mph
max speed alt=493 knots, 912 km/h
range main=3,200 mi
range alt=2,800 nm, 5,150 km
ceiling main=45,000 ft
ceiling alt=13,700 m
climb rate main=
climb rate alt=
loading main=
loading alt=
power/mass main=
power/mass alt=

The Sperrin had four different engine configurations
# Four Rolls-Royce Avon RA.2 turbojets of 26.6 kN (6,000 lbf) thrust each ("VX158")
# Four Rolls-Royce Avon RA.3 turbojets of 28.1 kN (6,500 lbf) thrust each ( ("VX161"))
# Three Rolls-Royce Avon RA. turbojets of 26.6 kN (6,000 lbf) thrust each (two on the starboard wing, one in the upper part of the port engine nacelle) and one de Havilland Gyron Gy1 turbojet of 66.7 kN (15,000 lbf) thrust in the lower part of the port engine nacelle ( ("VX158")) (see image above)
# Two Rolls-Royce Avon RA.2 turbojets combined with two de Havilland Gyron Gy2 turbojets of 100 kN (20,000 lbf) thrust each ( ("VX158"))

ee also

aircontent
related=
similar aircraft=*
* Convair XB-46
* English Electric Canberra
* Ilyushin Il-28
* Martin XB-48
* North American B-45
* Tupolev Tu-14
lists=
* List of bomber aircraft
see also=

References

Notes

Bibliography

* Barnes, C.H. with revisions by James, Derek N. "Shorts Aircraft since 1900". London: Putnam, 1989 (revised). ISBN 0-85177-819-4.
* Gunston, Bill. "Short's Stop-Gap Bomber." "Aeroplane Monthly", Vol. 8, no. 7, July 1980. p. 340-346.
* Wood, Derek. "Project Cancelled". Indianapolis: The Bobbs-Merrill Company Inc., 1975. ISBN 0-672-52166-0.

External links

* [http://www.faqs.org/docs/air/avval.html The Vickers Valiant "v1.1.0 /1 April 2003/ Greg Goebel/public domain" article]
* [http://prototypes.free.fr/sperrin/sperrin-3.htm Excellent photos of both Sperrins, including VX158 with two Gyrons fitted]