Saunders-Roe SR.53

Picture - The second SR.53 on display at the September 1957 Farnborough Air Show

Role: Interceptor
Manufacturer: Saunders-Roe
Designed by: Maurice Brennan
First flight: 16 May 1957
Status: Experimental
Primary user: United Kingdom
Number built: 2
Variants: Saunders-Roe SR.177

The Saunders-Roe SR.53 was a prototype interceptor aircraft of mixed jet and rocket propulsion developed for the Royal Air Force in the early 1950s. Although its performance was promising, the need for such an aircraft was soon overtaken by surface-to-air missile development, consequently the project was cancelled after 56 test flights.

Design and development

The Second World War demonstrated the importance of strategic bombing to modern warfare, and as the Cold War developed, devising effective air defence against large waves of enemy bomber aircraft became a priority for many nations. Nazi Germany had looked to rocket-powered aircraft to fill this niche, with machines like the Messerschmitt Me 163 and Bachem Ba 349, which were capable of unparalleled rates-of-climb, enabling them to (at least in theory) rise to meet and intercept enemy bombers before they reached their targets. German rocket technology was studied extensively by the Allies in the aftermath of the war, and in light of the threat of the growing Soviet strategic bomber fleet and that nation's newly-developed atomic weapons, the UK's Air Ministry drafted an Operational Requirement O.R. 301 in May 1951 for a rocket-powered interceptor that could reach an altitude of 60,000 ft (18,300 m) in just 2 minutes 30 seconds. This was circulated to the nation's aircraft manufacturers the following February.

The development of the de Havilland Sprite (5,000 lb thrust) and the Armstrong Siddeley Snarler (2,000 lb thrust) for RATO use led to the possibility of a more powerful rocket engine being developed as the planned powerplant for a "point defence" interceptor. The requirements of the O.R. 301 were considered onerous including a ramp launch and landing on a skid, and with the compliance of the companies approached to tender, the amended Specification G124T allowed for a mixed powerplant configuration and a conventional undercarriage.

Picture - Colour drawing of the first SR.53

Of the six companies that tendered proposals, two were selected for development contracts, A.V. Roe with their Avro 720 and Saunders-Roe with their SR.53. Further refinement of the concept led to the defined Specification O.R. 337. The SR.53 itself was a sleek aircraft with a sharply pointed nose, delta-like wing, and a T-tail. The Armstrong Siddeley Viper jet and de Havilland Spectre rocket engine and exhausts were mounted one atop the other in the tail.

By September 1953, the programme to develop these aircraft came under scrutiny due to cost cuts, and the Avro 720 was abandoned, although it seemed almost ready to fly at this point. One of the reasons for preferring the SR.53 was although the aircraft was developmentally behind, its use of hydrogen peroxide as an oxidiser was viewed as less problematic than the Avro 720's use of liquid oxygen. With an original contract to build three prototypes, the SR.53 was scheduled for a first flight in July 1954 with a service introduction date set for 1957. At the same time, Saunders-Roe began work on a derivative design, the SR.177, which was large enough to carry a useful radar, essential to interception at the high altitudes where the new fighter was meant to operate, despite the fact that the specification did not require it. The new, larger aircraft was developed into versions for maritime use by the Royal Navy and for West Germany as well as for the RAF.

Operational history

The complexity of the design caused a series of setbacks, notably an explosion during ground tests of the Spectre rocket engine. The SR.53's's first flight began to fall further and further behind schedule. On 16 May 1957, Squadron Leader John S. Booth DFC was at the controls of XD145 for the first test flight, following up with the maiden flight of the second prototype XD151, on 6 December 1957. Test results indicated "...an extremely docile and exceedingly pleasant aircraft to fly, with very well harmonized controls." Both prototypes flew a total of 56 test flights, with Mach 1.33 speeds being obtained.

While testing at RAE Boscombe Down, XD151 crashed on 5 June 1958 during an aborted takeoff on its 12th flight. Running off the runway, the aircraft struck a concrete approach light, exploding on impact and killing its pilot, Squadron Leader Booth. The remaining prototype continued to fly with Lt Cdr Peter Lamb taking over the flight test programme.

Cancellation

It was 1957 before the first SR.53 took to the air, just over a month after the infamous 1957 Defence White Paper had been published outlining the British government's policy to largely abandon piloted aircraft in favour of concentrating on missile development. At the same time, jet engine development had progressed a long way in the six years since the SR.53's initial design. Combined with the fact that improvements in radar had meant that any incoming bomber threat could be detected much earlier, the need for an aircraft like the SR.53 had disappeared, and the project was cancelled on 29 July 1960, with the third prototype (XD153) never built.

Aircraft on display

The first SR.53 prototype, XD145, is preserved at the Royal Air Force Museum Cosford near Wolverhampton.

Operators

United Kingdom

Ministry of Supply

Specifications

Data from The British Fighter since 1912

General characteristics

Crew: One, pilot
Length: 45 ft 0 in (13.72 m)
Wingspan: 25 ft 1½ in (7.66 m)
Height: 10 ft 10 in (3.30 m)
Wing area: 274 ft² (25.5 m²)
Airfoil: RAE102
Empty weight: 7,400 lb (3,360 kg)
Loaded weight: 18,400 lb (8,360 kg)
Powerplant:
1x— Armstrong Siddeley Viper 8 turbojet, 1,640 lb (7.3 kN)
1x— de Havilland Spectre rocket, 8,000 lbf (35.7 kN)

Performance

Maximum speed: Mach 2.2
Endurance: 7 minutes at full power
Service ceiling: 67,000 ft (20,420 m)
Rate of climb: 52,800 ft/min (270 m/s) : 2 min 12 sec from brakes to 50,000 ft
Wing loading: 67.2 lb/ft² (328 kg/m²)
Thrust/weight (jet): 0.52

Armament

Missiles: 2 x— de Havilland Firestreak infra-red guided missiles

Related development

Saunders-Roe SR.177

Comparable aircraft

Avro 720
Republic XF-91 Thunderceptor
SNCASO Trident
SNCASE SE-212 Durandal

Bibliography

Jones, Barry. "Saro's Mixed Power Saga". Aeroplane Monthly, November 1994, Vol 22 No 11 Issue 259. pp. 32-39. London:IPC. ISSN 0143-7240.
London, Pete. "Saunders-Roe's Rocket Fighters." Aircraft, Vol. 43, no. 7, July 2010.
Mason, Francis K. The British Fighter since 1912. London: Putnam, 1992. ISBN 1-55750-082-7.
Winchester, Jim. "TSR.2." Concept Aircraft: Prototypes, X-Planes and Experimental Aircraft. Kent, UK: Grange Books plc., 2005. ISBN 1-84013-309-2.
Wood, Derek. Project Cancelled: The Disaster of Britain's Abandoned Aircraft Projects. London, UK: Jane's, 2nd edition, 1986. ISBN 0-7106-0441-6.

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Source: WikiPedia