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Miles M52

Written by George Colclough

Introduction:

For aviation scholars and enthusiasts, the tragedy and decline of the United Kingdom’s postwar aerospace industry is all too familiar. The briefest of surveys reveal countless examples of promising and potentially world changing prototypes, snuffed out by pessimistic politicians and decorated generals with chests full of medals from past wars, and ideas that belonged in past wars.

Today we bring you the story of one such aeroplane; a trailblazing supersonic research aircraft, that had all the potential to see the United Kingdom be the first nation to achieve level supersonic flight, before it was mysteriously cancelled and grounded just as it sat on the apex of greatness.

This is the story of the Miles M.52.

https://commons.wikimedia.org/wiki/File:Miles_M.52_3-view.svg

Background and Specifications:

Miles themselves are a company often overlooked by popular historiography, and while the company certainly lacked the grand resume of other British aircraft manufacturers such as Avro, whos mighty Lancaster rained hellfire down upon the reich, and Supermarine, whos sprightly Spitfire kept the might of the Luftwaffe at bay during the Battle of Britain, Miles was nonetheless a valuable part of Britain’s wartime aerospace industry.

The company, founded in 1928, made a name for itself throughout the 1930’s by producing a range of low-tech and affordable, but nonetheless innovative light aircraft. Their products such as the Miles Master, of which 3,249 were purchased by the Royal Airforce were highly valued, as the need for dependable, but low cost trainers for both raw and veteran pilots was insatiable during the rapidly evolving world of interwar aviation.

In addition to providing good products at a great price the company also built up significant brownie points with the Ministry of Supply in 1942, when an administrative error led to the Miles Company falsely believing it had been awarded a sizeable contract, and it accordingly began investing in property and tooling that the RAF had no intention of exploiting. When this error came to light Frederick George Miles, the company’s founder, while certainly not exactly frilled about his wasted investment, sought no damages or compensation from the incident, not wishing to be a burden on Britain’s already stretched wartime resources.

Consequently when Air Ministry Specification E.24/43, a specification for an incredibly advanced, high speed research aircraft was issued in October of 1943 the modest Miles Company, with its humble but nonetheless stellar reputation found itself invited to submit a proposal along with the big boys of Avro, Vickers Armstrong, Handley Page, and Short. Much to everyone’s shock, including Miles themselves, they were awarded the contract.

E.24/43 itself 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 (able to) climb to 36,000 feet (11,000 m) in 1.5 minutes.”

If you’re thinking E.24.43 was quite a lofty set of demands for the aerospace industry of the time, you are absolutely correct. In fact the specifications themselves weren’t exactly grounded in reality. The specifications were intended to match what the British then believed Germany’s advanced high speed aircraft, such as the ME163 and ME 262 to be capable of. This belief however, was completely flawed and incorrect, and stemmed from a misunderstanding of an intercepted German communication discussing the aforementioned aircrafts’ performance. The Germans were discussing the performance in metric KPH, the British radio operator, whose brain was tuned to Great British Imperial MPH never thought to convert the figures and subsequently passed the wrong information up the chain, where they found their way into specification E.24.43.

Messerschmitt Me 163 B Komet https://flic.kr/p/dknU5r

Design:

The British were no strangers to Wallace and Gromiting their way out of tricky situations however, and accordingly the team at Miles set about their herculean task with complete enthusiasm and gusto, seeing the specification as little more than a lengthy series of hurdles that stood between them and a phenomenal aircraft.

The two main problems were drag and speed; you can have the most powerful engine ever manufactured, and it’ll come to naught if your aircraft has the drag coefficient of a brick. Likewise, you can have the most slippery airframe ever drafted, and it’ll similarly come to naught if it doesn’t have the power to actually push it up to speed.

An enormous number of highly advanced innovations and features were incorporated into the aircraft, which was dubbed the M.52, short for Miles: Model 52 early in its development life. Miles were pioneers in this period, as they had minimal amounts of previous data or research to build upon, and often had to innovate from scratch, or incorporate research from other fields of design, and figure out how to apply it to aviation. For example, an RAF study in 1943 had extensively tested the high speed performance of the Supermarine Spitfire, and proven that thick and flat surfaces such as curved noses, thick wings, and hinged control surfaces caused a detrimental amount of drag, but how to replace these features? That was unknown.

The design team looked to bullets, a technology which had long been happily breaking the sound barrier for inspiration. In particular they looked at pointed spitzer bullets, a 19th century technology which was both significantly faster and more stable than its flat headed forerunners. Looking at the sharp pointed front, and cylindrical shape of the Miles M.52, it is quite apparent to see exactly how this revelation was incorporated into the M.52.

Miles M52 https://flic.kr/p/haxwQZ

The pointed front of the Miles M.52 was also discovered to be useful as it allowed a shock wave to form on its apex and be directed to the lip of the intake; this ensured decent airflow to the engine and helped supersonic performance. This pointed shape in front of the intake, which would later be dubbed an ‘inlet cone’ is not unique to this aircraft, and despite the failure of the project would later go on to be implemented on many other high speed jets, such as the SR-71, Mig-21, and English Electric Lightning. Its implementation on the M.52 however does have one unique feature, which, as far as I am aware, is unique to the M.52 – in that the cockpit was built into this inlet cone in order to maintain the smooth, aerodynamic shape of the fuselage.

Given the experimental, unproven nature of the M.52 the entire cockpit was built to be detachable. In the event of an emergency the pilot could fire explosive bolts, at which point air pressure would separate the cockpit from the rest of the airframe, and a parachute would deploy to slow the cockpit upon its descent, at which point the pilot could bale from the cockpit after descending to a lower altitude.

So the fuselage was sorted, but what about the wings? How could they be constructed to generate maximum lift, but minimum drag.

To solve the wing problem the Miles team turned to the Swiss aeronautical engineer Jakob Ackeret. Ackeret had previously proposed a biconvex wing design that he theorised would produce a very thin, yet strong wing, which would produce minimal drag. Coach built mockups were put through extensive wind tunnel testing, and soon a perfect shape was discovered, and incorporated into the M.52 design. The resulting shape was so thin, that they came to be casually known as ‘Gillete’ wings – after the famous manufacturer of razors. The wings were also sharply angled at their tips after wind tunnel testing revealed that the now pointed nose of the aircraft created a shock wave that interfered with airflow over traditionally shaped wing tips.

The evolving wing design created another problem, without nice thick wings, where would they put the fuel tanks? This was a comparatively straightforward fix, the diameter of the fuselage was dictated largely by the initial low pressure fan and compressor, and the turbine exhaust casing, which were significantly broader than the later high pressure compressor and combustion chamber. This created a nice empty space around the middle of the engine that fuel tanks could be crammed in – easy!

The next problem was how to actually control the thing, as wind tunnel testing, along with pilot experience in production aircraft showed that traditional hinged tail planes became ineffective at even transonic speeds, nevermind supersonic. In a nutshell, this is because the forces exerted on the control surfaces by fast moving air generate a greater force than that which can be exerted by the pilot who is connected to the control surface by a simple mechanical actuator. Not only that, the Miles team also had to overcome the phenomenon of control-reversal, an umbrella term for a series of physical and psychological phenomena which cause controls to behave incorrectly, or at least be perceived to behave incorrectly in high speed flight.

The solution here proved straightforward enough, thanks to an innovation Miles dubbed the all-moving tail, in a nutshell – adding a motor to the control surfaces’ actuators to augment the force that can be exerted upon the control surface by the pilot.

Power was to come from a modified Power Jets W.2. The W.2 was the latest engine to come from legendary jet propulsion pioneer Frank Whittle, itself a derivative and expansion of the Power Jets W.1, the first British jet engine to fly. Although certainly dated in comparison to modern engines, the W.2 was a trailblazer for its time, and would later go on to be refined further still into the Rolls Royce Derwent engine, that powered the British Gloster Meteor, and the Soviet Tupolev 78.

Venerable though it proved to be, the Miles team were not ignorant to the limitations of the W.2 engine, and were aware that this new, unrefined, and in many ways still fully untested technology would need serious refinement to be able to satisfy the lofty expectations put upon the Miles M.52.

https://flic.kr/p/2kmS7WY Power Jets W.2/700 centifugal turbojet – Midland Air Museum

They did the maths, and predicted that the W.2 in its off the shelf form would happily take the M.52 upto transonic speeds, but the projects limited resources had to be rationed, so immediate focus was simply upon getting the engine fitted and the airframe flight worthy, with concerns about generating the extra power necessary for supersonic flight being added to the to-do list once the project had progressed further.

This rationing of priorities in the face of limited resources and tight time schedules should not be mistaken for the Miles team not having a plan however, quite the opposite, as they fully intended to incorporate a reheater, or afterburner for our American viewers into the engine at a later date.

A reheater exploits the fact that a jet engine combusts with a surplus of air, not all of which is used during combustion. Put simply, a reheater mixes fuel with excess oxygen downstream of the turbine proper, which in turn combust and increase the overall thrust being produced by the engine.

Reheating was not invented by the Miles team, as the technology was first implemented on the Italian Caproni Campini C.C.2 in 1941, but they did however innovate with the use of an augmentor fan driven from the engines shaft to efficiently draw air in to support the secondary combustion of the reheater.

The modified engines were tested on a Gloster Meteor in late 1944, and showed very promising results. Both period engineers, and Eric Brown, the definitive historian of the Miles M.52 saw no reason why this modified engine shouldn’t have been able to take the M.52 up to one thousand miles per hour.

This synopsis of the M.52’s development may make the aircraft’s development seem like it was quite the straightforward breezy process. Sadly, this was not the case, and the design of the M.52 underwent many changes during development, owing to the uncertain nature of the task at hand, and meddling from various opposing factions of designers and engineers.

For example, the team in charge of designing the M.52’s biconvex wings were often at loggerheads with the engine team. The former were concerned about the ability of such thin wings to generate drag, and wanted a more traditional thicker and stronger wing design. In turn the latter were concerned about the extra weight and drag a thicker wing would create, and stressed that their engine was already being pushed to its limits.

Numerous suggestions were floated in an attempt to make these two parties reach an accord. Rocket assistance for both take off, and the level supersonic run were proposed, aswell as launching the M.52 from a high altitude Avro Lancaster bomber, the cancellation of the project preventing this dilemma from ever being settled.

Another concern was the predicted high landing speed of the M.52. Estimates placed the aircraft’s landing speed at anywhere from 160-200 miles per hour. This is normal for modern high performance jets, but was alarmingly high for the time, with the prop powered Supermarine Spitfire landing at speeds of around 110-120 miles per hour, and the jet powered Gloster Meteor landing at around 130 miles per hour. This problem was also further compounded by the thin landing gear profile of the M.52, which was predicted to make the aircraft very top heavy and upstable during landing.

Sadly, this problem was unable to be solved due to the M.52’s very nature as a cutting edge high speed research aircraft, which demanded a small airframe with thin wings, and therefore left no space in the wings for the landing gear, which would have widened the landing gear profile and stabilised the aircraft. No workaround was found to be viable, and they simply had to accept it.

Despite the locking of horns at Miles, and the herculean engineering hurdles that had to be jumped, the M.52 project progressed well, and eventually reached the stage where some preliminary testing could begin.

A Miles M.3B Falcon Six was modified with a full scale recreation of the M.52’s proposed wings and undercarriage – dubbed the Gillette Falcon due to its razor thin wings. This testbed first flew on the 11th of August 1944, and during testing the wing design appeared to live up to its lofty expectations: the wing area was reduced by 12% and provided decent lift during both low and high altitude flight. All was not perfect however, as the landing speed of the Gillette Falcon increased significantly from 40 miles per hour to 61 miles per hour, and it was also incredibly unstable during landing owing to its new undercarriage.

These results were deemed promising enough to continue onto high speed testing however, and to that end a Supermarine Spitfire, the fastest aircraft then available to Miles, was fitted with the M.52’s proposed all-flying tail. High speed testing was conducted from October to November 1944, and consisted of the Spitfire making repeated high altitude, high speed dives in order to test the responsiveness of the tails control surfaces at transonic speed. These tests peaked at a speed of Mach 0.86, and were deemed an overwhelming success, with no control issues being reported during any test.

https://flic.kr/p/7zSfP4

All appeared rosy for the M.52 by the close of 1944. The aircraft’s innovative features appeared to be perfectly viable, and just before the close that year, with design work roughly 90% complete the Air Ministry gave the go ahead for the construction of three fully functional, flying prototypes of the M.52. Sadly, this is where today’s post stops being positive and uplifting – the prototypes would never be finished, never fly, and all the blood, sweat, tears, and money poured into the project would come to absolutely naught.

Cancellation, and Conspiracy?:

The project was cancelled in February 1946, by then director of Scientific Research, Sir Ben Lockspeiser. Officially, this cancellation was due to concerns about pilot safety, cost overruns, budget cuts, and recently surfaced German research that pointed to swept wings being optimal for supersonic flight.

Additional potential explanations have surfaced in the years following the project’s cancellation, with one predominant theory claiming the cancellation was caused by American pressure, as they wanted their Bell X-1 to be the first plane to go supersonic in level flight, and another theory suggesting the project was sabotaged by Barnes Wallis, of bouncing bomb fame.

https://picryl.com/media/x-1-1-in-flight

On the matter of Barnes Wallis’ role in the project downfall, the theory goes that Barnes Wallis, on behalf of his employer Vickers, firmly believed the future of supersonic aviation to be in rockets, and that the age of the aeroplane as a viable weapons platform and military tool was coming to an end in the face of this new technology. This was by no means a settled debate however, with the future of aviation becoming an incredibly hot button and partisan issue immediately after world war two.

Proponents of this theory state that Barnes Wallis leveraged his fame and influence as the lauded inventor of the Grand Slam and bouncing bombs to kill the M.52 project and secure further funding for his own vision.

There is evidence for this theory for sure, but it remains circumstantial, as while Wallis was certainly allocated more funding for unmanned rocket testing following the M.52’s cancellation, damning evidence that points to machination on Wallis’ part hasn’t surfaced, and instead it appears he was simply in the right place at the right time to receive further funding as the M.52 project fell out of vogue with the British government.

On the matter of the Bell X-1, it is often compared to the Miles M.52, and particularly in British circles you will regularly encounter the claim that the X-1 was nothing but a cheap knock off of the M.52, that had rocket engines crammed in it so that America could beat its trans-atlantic rival in claiming the supersonic mantle, but is this true? Let us review the evidence.

We know for sure that in late 1944 the British government signed an agreement with its American counterpart to exchange high speed research data, and that Britain sent significantly more documents than it received. But since Britain was a pioneer of high-speed aviation, this is surely to be expected, and isn’t necessarily indicative of foul play on America’s part?

But we also know that development of the Bell X-1 started after an American delegation visited the Miles team. None of this delegation were directly employed in the construction of the X-1, but maybe some files and thoughts were passed along?

We also know that early in Bell’s development of the X-1, the company was struggling greatly with developing a tail that would work at high speed, with wind tunnel testing teaching Bell the hard lessons learned earlier by Miles. We have no surviving documentation to prove how Bell got the idea, but they arrived at exactly the same solution as Miles after the aforementioned technology transfer… But this also isn’t damning, and could just be a coincidence, after all, how many ways can you really design high speed control surfaces?

As previously mentioned, we ultimately don’t know if any industrial espionage was involved in the development of the X-1, but my personal hunch, given the track record of American interference in Britain’s defence industry in this period, such as the fiasco of the EM2 rifle’s cancellation, TSR2’s sabotage, the expulsion of British scientists from the Manhattan Project in 1946, and the peculiarities in Blue Streak and Skybolt’s joint cancellation… one has to be open to the idea that industrial espionage, or something more sinister was involved. 

What we do know is that at the point of cancellation, the first M.52 prototype was 82% completed, and no more than a few months away from taking flight, and had a proposed test programme that would see the M.52 go for Mach 1 by the end of 1946, after a series of subsonic test flights.

The M.52’s cancellation also killed the Miles Aircraft Company, which in the face of drying up demand for trainer aircraft following the end of World War II, had bet all on black and pumped all its resources into attempting to become a pioneer of future high speed aircraft design. Following the end of government funding for the M.52, Miles was unable to find any other buyers for their technology either domestically or internationally, and subsequently the company entered receivership in 1947. Its assets were then bought and amalgamated into Handley Page.

Closing Remarks:

In conclusion, there is no clear story behind the downfall of the M.52, and as previously hinted at, the historiography tends to be split along national lines, with British commentators generally taking an incredibly anti American stance, which prescribes the collapse of the project to borderline national sabotage, and American commentators generally prescribing the appearance of a remarkably similar aircraft of their own down to coincidence. Ultimately, we don’t know the full story of the M.52’s eventual cancellation, so we are left to come up with our own theories and head canon from the available evidence.

In the end, for all the blood, sweat, tears, and money poured into its development, and regardless of any machinations that may have contributed to its downfall, the Miles M.52 ultimately became little more than an interesting footnote in the history of British aviation. In that way it really is representative of the story of post war British aviation: full of promise and revolutionary potential, that came to naught as the Britain aviation industry entered terminal decline and became a hollowed out husk of something that was once great.

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