The M.39B Libellula (from

Libellulidae The chasers, darters, skimmers, and perchers and their relatives form the Libellulidae, the largest family of dragonflies. It is sometimes considered to contain the Corduliidae as the subfamily Corduliinae and the Macromiidae as the subfamily M ...

, a taxonomic family of

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of dragonflies are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...

) was a

Second World War World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

tandem wing QAC Quickie Q2 A tandem wing is a wing configuration in which a flying craft or animal has two or more sets of wings set one behind another. All the wings contribute to lift. The tandem wing is distinct from the biplane in which the wings are ...

experimental aircraft built by

Miles Aircraft Miles was the name used for aircraft and associated businesses of British engineer Frederick George Miles, who, with his wife – aviator and draughtswoman Maxine Blossom Miles, Maxine "Blossom" Miles (née Forbes-Robertson) – and his brother ...

. A scale version of the M.39 design was proposed by Miles to meet Air Ministry specification B.11/41 for a fast bomber. The M.39B was used by Miles to generate data from which the M.39 design was improved, but the M.39 project was cancelled and the M.39B broken up.

Design and development

M.39

Though it had some problems, the earlier M.35 proved sufficient to show the idea had merits, and the larger M.39 was drawn up as a twin-engined design prepared to meet Specification B.11/41 which had been issued by the Air Ministry for a high speed bomber. The specification had been written for the P.1005 proposal by Hawker, powered by two

Napier Sabre The Napier Sabre is a British H engine, H-24-cylinder, coolant, liquid-cooled, sleeve valve, piston aircraft engine, aero engine, designed by Frank Halford, Major Frank Halford and built by D. Napier & Son during World War II. The engine evolv ...

engines, estimated to achieve 400+ mph at 25,000 ft and deliver a 2,000 lb bomb load over 1,600 miles. The P.1005 was cancelled after several delays on behalf of the Air Ministry and before Miles submitted his design to the Ministry in July. In November 1943 a full-size prototype (to use the serial ''RR910'') was ordered, but not built.Buttler p87 Until the intended (three)

Power Jets Power Jets was a British company set up by Frank Whittle for the purpose of designing and manufacturing jet engines. The company was nationalised in 1944, and evolved into the National Gas Turbine Establishment. History The origins of Powe ...

W.2/500 turbojets were available the M.39 would have had two

Rolls-Royce Merlin The Rolls-Royce Merlin is a British Coolant#Liquids, liquid-cooled V12 engine, V-12 Reciprocating engine, piston aero engine of 27-litre (1,650 cu in) Engine displacement, capacity. Rolls-Royce Limited, Rolls-Royce designed the engine an ...

60 inline or

Bristol Hercules The Bristol Hercules is a 14-cylinder two-row radial aircraft engine designed by Sir Roy Fedden and produced by the Bristol Engine Company starting in 1939. It was the most numerous of their single sleeve valve ( Burt-McCollum, or Argyll, ty ...

VIII radial piston engines. The M.39 would have a crew of three in a pressurized cabin. As well as the bomb-bay amidships, the M.39 was intended to carry two fixed

20 mm cannon 20 mm caliber is a specific size of popular autocannon ammunition. The dividing line between smaller-caliber weapons, commonly called "guns", from larger-caliber "cannons" (e.g. machine gun vs. autocannon), is conventionally taken to be the 20 m ...

s in the roots of the forward wings.

M.39B

To prove the concept Miles designed and built a 5/8th scale version, the M.39B, which flew on 22 July 1943, showing no "undesirable handling" characteristics. It coincided with interest by the authorities in unorthodox designs for large aircraft. The rear wing was mounted higher than the forward one to avoid downwash and give ground clearance for the propellers. The M39 design had inboard flaps and outboard ailerons on the rear wing and the front wing had an auxiliary aerofoil/flap/elevator device, which could vary the wing area without changing

lift coefficient In fluid dynamics, the lift coefficient () is a dimensionless quantity that relates the lift generated by a lifting body to the fluid density around the body, the fluid velocity and an associated reference area. A lifting body is a foil or a co ...

.Buttler p86-87 The

Ministry of Aircraft Production Ministry may refer to: Government * Ministry (collective executive), the complete body of government ministers under the leadership of a prime minister * Ministry (government department), a department of a government Religion * Christian mi ...

agreed to a development contract and purchase of the M.39B. Miles continued testing, generating more flight data and submitted an improved M.39 design in early 1944. Meanwhile, the sole M.39B passed to the

Royal Aircraft Establishment The Royal Aircraft Establishment (RAE) was a British research establishment, known by several different names during its history, that eventually came under the aegis of the Ministry of Defence (United Kingdom), UK Ministry of Defence (MoD), bef ...

at Farnborough in 1944, where it carried the serial ''SR392'', being damaged and repaired after two accidents, only to be broken up with the full-sized bomber project's cancellation.

Specifications (M.39B Mockup)

Notes

Bibliography

* * Brown, Don Lambert. ''Miles Aircraft Since 1925''. London: Putnam & Company Ltd., 1970. . * Buttler, Tony. ''British Secret Projects Fighters & Bombers, 1935–1950''. Hinckley: Midland Publications, 2004. .

External links

* * *
Miles Tandem Monoplanes
Flight 1944

– Flight 1944 {{Miles aircraft 1940s British experimental aircraft Cancelled military aircraft projects of the United Kingdom

Libellula ''Libellula'' is a genus of dragonflies, called chasers (in English) or skimmers (in American), in the family Libellulidae. They are distributed throughout the temperate zone of the Northern Hemisphere. Many have showy wing patterns. Overvie ...

Tandem-wing aircraft Aircraft first flown in 1943 Twin piston-engined tractor aircraft Aircraft with retractable tricycle landing gear