Miles M.52

Miles M.52

Picture - Artist's impression of the Miles M.52

Role: Experimental supersonic aircraft
National origin: United Kingdom
Manufacturer: Miles Aircraft
Designed by: Don L. Brown
Status: Cancelled
Number built: 1

The Miles M.52 was a turbojet powered supersonic research aircraft project designed in the United Kingdom in the mid 1940s. Design work was undertaken in secrecy between 1942 and 1945. In 1946 the Air Ministry prudently but controversially changed the project to a series of unmanned rocket powered scale aircraft, launched from a modified de Havilland Mosquito. In a successful test flight Mach 1.38 was achieved by a scale model in normally controllable transonic and supersonic level flight, a unique achievement at that time which validated the aerodynamics of the M.52. At that point the ministry cancelled that project and issued a new requirement which was to result in the English Electric Lightning. Work on the afterburning version of the Power Jets W.B.2/700 turbojet was also cancelled and the Power Jets company was incorporated into the National Gas Turbine Establishment.

Design and development

The British Miles Aircraft company had its beginnings in the mid 1920s, making its name in the 1930s with affordable ranges of innovative light aircraft. They became best known perhaps for the Miles Magister and Miles Master trainers, large numbers of which were used by the RAF for fighter pilot training. Although the company's products were relatively low-technology trainers and light aircraft, and did not include any jets, Miles had a good relationship with the Air Ministry and the Royal Aircraft Establishment (RAE), and had submitted several proposals for advanced aircraft in response to ministry specifications. In order to resolve a dispute about a contract mishandled by the Ministry of Aircraft Production, the company was invited to undertake a top-secret project to Air Ministry Specification E.24/43 for a jet-powered research plane to reach supersonic speeds. The contract, awarded in October 1943, called for an "aeroplane capable of flying over 1,000 mph (1,600 km/h) in level flight, over twice the existing speed record, and climb to 36,000 feet (11,000 m) in 1.5 minutes." The specification was intended only to match the supposed performance of a German aircraft: the 1,000 mph (supersonic) requirement resulted from the mistranslation of an intercepted communication stating that the maximum speed was 1,000 km/h (subsonic). This report dealt with the Me 163A and/or the Me 262.

Many early jet aircraft had round noses, thick wings and hinged elevators, giving them critical Mach numbers well below the speed of sound, and were less suitable for research into high subsonic speeds (in dives) than the Spitfire with its thinner wings. RAE tests with the Spitfire in 1943 had proved that drag was the main factor to be addressed in high speed aircraft.

A huge number of advanced features were incorporated into the resulting M.52 design, many of which hint at a detailed knowledge of supersonic aerodynamics. With no other sources of such information Miles had turned to design data for stabilising projectiles. In particular, the design featured a conical nose and sharp wing leading edges, as it was known that round-nosed projectiles could not be stabilised at supersonic speeds. The design used very thin wings of biconvex section proposed by Jakob Ackeret for low drag. The wing tips were "clipped" to keep them clear of the conical shock wave generated by the nose of the aircraft. The fuselage had the minimum cross-section allowable around the centrifugal engine with fuel tanks in a saddle over the top.

Another critical addition was the use of a stabilator, also known as the all-moving tail or flying tail, a key to supersonic flight control which contrasted with traditional hinged tailplane (horizontal stabilizer) designs. Conventional control surfaces became ineffective at the high subsonic speeds then being achieved by fighters in dives, due to the aerodynamic forces caused by the formation of shockwaves at the hinge.

Picture - One of the Vickers models undergoing supersonic wind-tunnel testing at the Royal Aircraft Establishment (RAE) c.1943

The design was to be powered by Frank Whittle's latest engine, the Power Jets W.2/700. It incorporated a reheat jetpipe - also known as an afterburner - to give extra power. The burning of extra fuel in the tailpipe avoided overheating the metal of the turbine blades and made use of the unused oxygen in the exhaust. In order to supply more air to the afterburner than could move through the fairly small engine, a fan, powered by the engine, was installed in front of the assembly to blow air around the engine in ducts, making the W.2/700 essentially an early turbofan.

Finally the design included another critical element, the use of a shock cone in the nose to slow the incoming air to the subsonic speeds needed by the engine.

The fuselage of the M.52 was cylindrical and, like the rest of the aircraft, was constructed of high tensile steel with alloy covering.

The pilot would have sat in a small cockpit inside the shock cone in the nose of the aircraft, and in an emergency the entire area would be separated from the aircraft using explosive bolts. Air pressure would force the capsule off the fuselage and a parachute would slow its descent. The pilot would then exit the capsule at a lower height and parachute to safety. The chances of the pilot exiting the capsule were of serious concern, since it was not stable on its own at supersonic speeds, and likely would have tumbled, possibly breaking up.

The M.52's design underwent many changes during development due to the uncertain nature of the task. The overseeing committee was concerned that the biconvex wing would not give sufficient altitude for testing the aircraft in a dive. The thin wing could have been made thicker if required, or a section added to increase the wing span. As the project progressed an increase in total weight led to concerns that power would be insufficient and rocket assistance or extra fuel tanks were considered, as was high altitude air-launching from a bomber.

The calculated landing speed of 160 mph to 170 mph (comparable with modern fighters but very high for that time) combined with the small undercarriage track was a concern, but had to be accepted.

Testing

A Miles M.3B Falcon Six light aircraft that had been used for wing tests by the RAE, was provided to Miles in 1943. A full size wooden model of the M.52 wing, test instrumentation, and a different undercarriage were fitted. Owing to the wing's thinness and sharp leading and trailing edges somewhat resembling a razor blade, the aircraft was nicknamed the "Gillette Falcon". It was first flown on 11 August 1944. Compared with a standard Falcon Six, wing area was reduced by about 12%, but landing speed was increased by over 50% from 40 mph to 61 mph.

For high speed testing, the flying tail was fitted to the fastest aircraft available, a Supermarine Spitfire. RAE test pilot Eric Brown stated that he tested this successfully during October and November 1944, attaining Mach 0.86 in a dive from high altitude. The flying tail was also fitted to the "Gillette Falcon", low speed tests being flown at the RAE in April 1945.

Operational history

Prototypes

In 1944, design work was considered 90% complete and Miles was told to go ahead with the construction of three prototype M.52s. Later that year, the Air Ministry signed an agreement with the United States to exchange high-speed research and data. Miles Chief Aerodynamicist Dennis Bancroft stated that the Bell Aircraft company was given access to the drawings and research on the M.52, but the U.S. reneged on the agreement and no data was forthcoming in return. Unknown to Miles, Bell had already started construction of a rocket-powered supersonic design of their own, but with a conventional tail were battling the problem of control. A variable-incidence tail appeared to be the most promising solution; the Miles and RAE tests supported this. Later, following conversion of the tail, pilot Chuck Yeager verified it experimentally, and all subsequent supersonic aircraft would either have an all-moving tailplane or a delta wing.

Cancellation

By February 1946, the new Labour government introduced dramatic budget cuts. The Director of Scientific Research, Sir Ben Lockspeiser subsequently cancelled the project. Other factors contributing to the cancellation included doubts about pilot safety, as well as some German research that seemed to point to swept wings being desirable at supersonic speeds.

At cancellation, the first of the three M.52s was 82% completed, with test flights planned to begin in a few months. The test programme involved the progressive testing and development of the M.52 by the RAE, initially without reheat installed, with the aim of achieving Mach 1.07 by the end of 1946.

Miles became bankrupt in 1947 and assets including the design data for the M.52 were acquired by Handley Page.

Subsequent work

Several thousand pounds would have been required to complete the first M.52. Instead, the government instituted a new programme involving expendable, pilotless, rocket-propelled missiles. The design was passed to Barnes Wallis at Vickers Armstrong, and the engine development took place at the RAE. The result was a 30% scale radio-controlled model of the original M.52 design, powered by an Armstrong Siddeley Beta rocket engine.

The first launch took place on 8 October 1947 at high altitude from a DH Mosquito, but the rocket exploded shortly after release. Only days later, the Bell X-1 broke the sound barrier. There was a flurry of denunciation of Labour's decision to cancel the project, with the Daily Express taking up the cause for the restoration of the M.52 programme, to no effect. On 10 October 1948, a second rocket was launched, and the speed of Mach 1.38 was obtained in stable level flight, a unique achievement at that time. Instead of diving into the sea as planned, the model failed to respond to radio commands and was last observed (on radar) heading out into the Atlantic. Following that successful supersonic test flight, further work on this project was cancelled, being followed up immediately by the issue of Ministry of Supply Experimental Requirement ER.103 (below).

Many important design principles incorporated in the M.52 did not reappear until the mid- to late 1950s, with the development of truly supersonic aircraft such as the Fairey Delta 2, and the English Electric P.1 which became the highly regarded English Electric Lightning. Both of those aircraft were developed in response (initially) to requirement ER.103 of 1947, informed by the knowledge gained from the M.52 aircraft and missile research projects together with German experimental data.

Specifications (M.52)

Data from

General characteristics

Crew: 1
Length: 28 ft (8.5 m)
Wingspan: 27 ft (8.2 m)
Height: ()
Wing area: 108.1 ft² (10.04 m²)
Loaded weight: 7,710 lb (3,500 kg)
Max takeoff weight: 8,200 lb (3,720 kg)
Powerplant: 1x— Power Jets W.2/700 turbojet (fitted with augmentor and afterburner), 4,000 lbf (17.8 kN)

Performance

Maximum speed: 1,000 mph at 36,000 ft (1,600 km/h at 11,000 m)
Stall speed: 170 mph (274 km/h)
Service ceiling: 36,000 ft (10,972 m)
Rate of climb: to 36,000 ft in 1.5 minutes ()
Wing loading: 58 lb/sq ft ()

Sound barrier

Comparable aircraft

Bell X-1
Silbervogel

Bibliography

Amos, Peter. Miles Aircraft - The Early Years: The Story of F G Miles and his Aeroplanes, 1925-1939. Tonbridge, Kent, UK: Air-Britain (Historians) Ltd, 2009. ISBN 978-0-85130-410-6.
Brown, Don Lambert. Miles Aircraft Since 1925. London: Putnam & Company Ltd., 1970. ISBN 0-37000-127-3.
Brown, Eric. "Miles M.52: The Supersonic Dream." Air Enthusiast Thirteen, August-November 1980. ISSN 01443-5450.
Brown, Eric. Wings on my Sleeve. London: Weidenfeld & Nicolson, 2006. ISBN 978-0297845652.
Faster than Sound. NOVA (PBS) documentary, first broadcast 14 October 1997.
McDonnell, Patrick. "Beaten to the Barrier." Aeroplane Monthly Volume 26, No. 1, Issue 297, January 1998.
Pisano, Dominick A., R. Robert van der Linden and Frank H. Winter. Chuck Yeager and the Bell X-1: Breaking the Sound Barrier. Washington, DC: Smithsonian National Air and Space Museum (in association with Abrams, New York), 2006. ISBN 0-8109-5535-0.
Temple, Julian C. Wings Over Woodley - The Story of Miles Aircraft and the Adwest Group. Bourne End, Bucks, UK: Aston Publications, 1987. ISBN 0-946627-12-6.
Wood, Derek. Project Cancelled. Indianapolis: The Bobbs-Merrill Company Inc., 1975. ISBN 0-672-52166-0.
Yeager, Chuck et al. The Quest for Mach One: A First-Person Account of Breaking the Sound Barrier. New York: Penguin Studio, 1997. ISBN 0-670-87460-4.

Miles M.52 Pictures and Miles M.52 for Sale.

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Source: WikiPedia