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Miles M.20 Low-Cost Monoplane Fighter Prototype


The Miles M.20 lightweight fighter was intended to be mass-produced as an emergency measure - only two prototypes were completed before the end.

 Updated: 7/21/2015; Authored By Staff Writer; Content ¬©www.MilitaryFactory.com

Victory for Britain in the early stages of World War 2 (1939-1945) was not assured and this led the nation to invest in many programs to meet emerging wartime requirements. One issue at hand was the shortage of capable frontline fighters of modern design, the current stable made up of prewar Hawker Hurricanes and Supermarine Spitfires which were capable aircraft but there was no guarantee of their availability if war material or production was disrupted by German bombers.

Back in 1938, Frederick George Miles, technical lead at Phillips & Powis Aircraft Ltd (to become Miles Aircraft in 1943), penciled out a low-cost, wooden single-seat, single-engine monoplane fighter on his Miles "Master" - a low-wing monoplane trainer of which some 3,250 were ultimately built for the Royal Air Force and foreign customers. The gull-wing planform was retained in the new design and power would be served from a Rolls-Royce "Peregrine I" series inline engine fitted at front. Work continued on the design, which now carried the company model designation of "M.20" and a mockup was constructed in an effort to sell the type to the British government who gearing up for war. The aircraft was looked over during late June of 1939, prior to Britain's entry into World War 2, but interest was low and the design ultimately passed on.

Everything changed in September when Germany crossed into Poland and forced Britain and France into a new World War in Europe. When France fell to the German onslaught, all of the pressure fell, in turn, to Britain which ultimately led to the "Battle of Britain" - the grand air war which saved the Empire and sent German warplanners an uncharacteristic defeat.

The Miles company had continued work on the M.20 and, in June of 1940, delivered its revised M.20/2. Air Ministry interest was now piqued and this led to an important meeting in July to forward the M.20 project some. A window of three months was assigned to the design team and a contract was given for a single flyable prototype to be completed. There were also restrictions to further challenge the group and this included use of an existing engine (the Rolls-Royce Merlin XX became the front-runner) and other fighter aircraft related components. The aircraft would have to feature a fixed wheeled undercarriage to simplify operation, rely heavily on wood in its construction (metal was a fast becoming a rare available material), and there would have to be a complete lack of complex hydraulics to simplify construction.

Beyond all this, the Air Ministry also was looking for an aircraft with very modern fighter-like performance. Required speeds were in the 350 mile-per-hour-range and a service ceiling of 32,000 feet was envisioned. For armament, it was requested that the fighter carry four 0.303 machine guns in each wing for a total of eight guns.

The specification written to cover the new design became F.19/40.

Miles engineers returned with an admirable design considering the restrictions heaped upon the project and the limited timeline. A well-streamlined wooden fuselage was developed with the engine fitted to the front using the original Bristol Beaufighter engine mounting. A useful bubble-style canopy covered the single-seat cockpit which sat near midships and offered excellent vision save for over the nose. The wing mainplanes were slightly ahead of midships and given elegant lines that included curved tips. The tail unit was conventional overall and sat a single vertical fin between two low-mounted tailplane units. The fixed undercarriage was spatted at the two main legs for aerodynamic efficiency and a tail wheel supported the rear section of the aircraft when on the ground. A large spinner was fitted at the nose as part of the three-bladed propeller with an air scoop showcased under the nose.




The company had produced the fighter in short order - it was flying even before the imposed Air Ministry deadline as it recorded a first flight on September 15th, 1940, just nine weeks after the beginning of the design phase! Because of the drag incurred by the fixed undercarriage care was taken at the fuselage and wings to streamline these elements as much as possible. The wooden wings were also thicker than more modern metal ones and this only served to add additional drag when cutting through the air. However, Miles personnel instituted all manner of engineering to remedy these issues as best they could.

During testing the aircraft exhibited good controlling on the whole and performance was sound. It was found that the compact aircraft did require quite a bit of runway to get airborne. Diving characteristics were ultimately proven and spin/stall recovery was as expected. A slight issue with the rudder forced a cut-off rear section of fuselage to be fitted and the vertical tailfin moved further aft. During a test flight in February of 1941, the prototype's brakes locked up and this led to a crash of the aircraft upon landing - though the pilot managed to survive. In any event the first prototype was lost and its remains ultimately scrapped (after the war).

The accident did no favors to the M.20 project and the British victory in the Battle of Britain began to guarantee availability of Spitfires and Hurricanes for the foreseeable future. The Royal Air Force interest in the Miles low-cost fighter waned until it was completely lost to other attention being given elsewhere in the war effort.

One last attempt at keeping the M.20 program going was made to deliver the aircraft as a "disposable" fighter aboard merchant and navy elements for the Fleet Air Arm (FAA) service. The fighter could be launched via catapult, conduct its mission as normal and then the pilot would abandon his aircraft into the sea - he then recovered by boat to fight another day. Specification N.1/41 was written to cover this requirement in July of 1941.

Miles engineers developed this concept through the follow-up M.20/4 prototype which featured some slight alterations to the original design. The undercarriage spats were lightened some and a more aerodynamic spinner fitted to the propeller unit. Arrestor gear would be a standard fit on production models. Air Ministry specifications were accordingly reduced for this over-water fighter requirement, the top speed being just 300 miles per hour.

Trials of this M.20 form began in April of 1941 and controls were found to be heavy while the engine brought troubles all its own. It was realized that the large faired-over main landing gear legs could really put the pilot at risk should a wave peak be prematurely caught before the pilot had vacated his aircraft. Despite these reservations the program was allowed to endure to the point that armament trials were beginning in July. For a brief period in February-to-March of 1942, the aircraft was finally in the hands of No.24 Squadron but was quickly passed back to the Miles company where it found no further military interest- a modified form of the Hawker Hurricane, the "Hurricat" was selected over the M.20 instead.

This marked the end for the Miles wooden "budget fighter" as it lay in storage until taken apart in November of 1943.



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Miles M.20 Technical Specifications



Service Year: 1940
Type: Low-Cost Monoplane Fighter Prototype
National Origin: United Kingdom
Manufacturer(s): Miles Aircraft - UK
Production Total: 2


Structural (Crew Space, Dimensions and Weights)



Operating Crew (Typical): 1
Overall Length: 30.68 feet (9.35 meters)
Overall Width: 34.58 feet (10.54 meters)
Overall Height: 12.50 feet (3.81 meters)

Weight (Empty): 5,919 lb (2,685 kg)
Weight (MTOW): 8,001 lb (3,629 kg)

Installed Power and Standard Day Performance



Propulsion: 1 x Rolls-Royce Merlin XX V12 liquid-cooled inline piston engine developing 1,260 horsepower.

Maximum Speed: 333 mph (536 kph; 289 knots)
Maximum Range: 920 miles (1,481 km)
Service Ceiling: 32,808 feet (10,000 meters; 6.21 miles)
Rate-of-Climb: 2,222 feet-per-minute (677 m/min)

Armament / Mission Payload



STANDARD:
8 x 7.7mm Browning machine guns (four to a wing)

OPTIONAL:
Centerline fuel drop tank (proposed).

Global Operators / Customers



United Kingdom (cancelled)

Model Variants (Including Prototypes)



M.20 - Base Series Designation; original design of 1939
M/20/2 - Revised M.20 form for RAF service; single example completed and flown.
M.20/4 - Disposable convoy protection fighter; single prototype completed and flown.