Secret Projects of the Luftwaffe - Vol 1 - Jet Fighters 1939 -1945

By Dan Sharp

Germany’s air ministry was quick to grasp the potential of the jet engine as early as 1938 and by 1939 several German aircraft manufacturers were already working on fighter designs that would utilize this new form of propulsion. Rocket engines too were seen as the way of the future and companies were commissioned to design fighters around them.

As the Second World War began, the urgent need to bring these advanced new types into production saw a host of innovative aircraft designs being produced which would eventually result in Messerschmitt’s Me 262 jet fighter and the Me 163 rocket-propelled interceptor. And as the war progressed, efforts were increasingly made to find better ways of utilizing jet, rocket and latterly ramjet engines in fighter aircraft.

Aviation companies from across Germany set their finest minds to the task and produced some of the most radical aircraft designs the world had ever seen. They proposed rotating wing ramjet fighters, arrowhead-shaped rammers, rocket-firing bat-winged gun platforms, sleek speed machines, tailless flying wings, tiny mini fighters and a host of others ranging from deadly looking advanced fighters to downright dangerous vertical launch interceptors.

Secret Projects of the Luftwaffe Volume 1: Jet Fighters 1939-1945 by Dan Sharp, based on original research using German wartime documents, offers the most complete and authoritative account yet of these fascinating designs through previously unseen photographs, illustrations and period documentation from archives around the world.

• Language: English
• Publisher: Tempest
• Release date: Sep 22, 2020
• ISBN: 9781911658801

Dan Sharp

Dan Sharp studied history at the University of Liverpool before beginning a career in journalism. Having spent several years as the news editor of a regional daily newspaper, he switched to motorcycle magazines. His previously published works on aviation have covered subjects ranging from German Second World War projects to Concorde. He lives in Nottinghamshire with his wife and two children.

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Preface

German aircraft development during the Second World War has been endlessly studied – but usually only from the perspective of individual designs that were actually built and entered service in one form other another. The deeper story of the military requirements, technical specifications, manufacturer competitions and prototype construction which preceded the delivery of series production model airframes to the Luftwaffe has seldom been explored in any detail.

The result has been much confusion about the sometimes complex processes and discussions underpinning the development of front-line combat machines and the development of the aircraft intended to replace them.

From the beginning of the war to the very end, an ever-changing cast of decision-makers at the Reichsluftfahrtministerium (RLM – the German air ministry) and elsewhere agonised over the likely direction of the air war and attempted to provide the Luftwaffe with materiel which anticipated the enemy’s future capabilities – including the introduction of jet aircraft.

This book is an attempt to provide a clear timeline of Germany’s attempts to produce high-speed fighter aircraft using innovative new propulsion systems before the Allies could do so. Every effort has been made to base this timeline on surviving contemporary documents and those documents, and other sources, have been cited.

My interest in German Second World War ‘secret projects’ began in 1991 when film director George Lucas’s LucasFilm Games produced a videogame called Secret Weapons of the Luftwaffe for the PC. The image on the cover showed a pair of flying-wing aircraft the like of which I had never seen before. They were depicted in Luftwaffe markings attacking a formation of high-flying American bombers. At first I assumed that these aircraft must be fictional but the book accompanying the game included photographs of prototypes indicating that such aircraft were indeed built, albeit in prototype form.

Seven years later, my friend Alexander Power directed me to a website called Luft46.com and I was amazed to discover the vast and bewildering range of ‘secret projects’ apparently designed by German aircraft companies during the war.

While the RAF’s Spitfires and the Luftwaffe’s Bf 109s were engaged in a bitter battle to the death above war-torn Europe, Germany’s finest engineers had been busily creating outlandish flying wings, rammers, tiny bombers, parasite aircraft, tail-first designs, aircraft with forward-swept wings and aircraft where the wings spun around like the blades of a helicopter – a cornucopia of oddities.

The more I read about the ‘projects’ the clearer it became that there were discrepancies in the information presented about them. Some were plainly designed at the same time and for the same purpose but they were not linked together. Instead, the projects were grouped by manufacturer. I found this same approach in the few books that existed on the subject.

In the mainstream aviation press of the day, these designs were frequently written off as ‘freaks’ – products of designers motivated by basic intellectual curiosity, or fear, or boredom, or a toadying desire to please Adolf Hitler. Yet some designs seemed far ahead of their time and some authors of the late 1990s such as Walter Schick and Manfred Griehl were eager to point out similarities they saw between those designs and postwar jets built and flown by the Soviets and the Western Allies.

This idea fascinated me at the time; that the early Cold War jets on both sides had perhaps been based on captured German technology. Certainly, the Allies captured a huge quantity of German aviation industry documents in the immediate aftermath of the war and studied much of it in detail. But the links between specific German wartime projects and postwar aircraft seemed circumstantial in most cases. It was a hypothesis which went nowhere, the once-regular updates to Luft46.com dried up and my interest waned.

More than a decade later I found myself at a loose end and decided to revisit the subject. I discovered that books written about German ‘secret projects’ remained as confusing and contradictory as ever but this time I resolved to see whether I could discover why those wartime ‘oddities’ were created and how they might fit together on a straightforward timeline.

The result was Luftwaffe: Secret Jets of the Third Reich – published by Mortons in 2015. This was based on a couple of years’ research using primary source material and aimed to tell the story of jet aircraft development in wartime Germany with a particular emphasis on fighters. It was a shot in the dark for the company but it paid off and the publication sold out.

I followed up Secret Jets with Secret Bombers (2016), Secret Wings (2017), Secret Designs (2018) and Secret Projects (2019), all based on my ongoing primary source research. But the first title, Secret Jets, was never reprinted – despite repeated calls for Mortons to make it available again in hard copy format.

The opportunity finally arose to reprint Secret Jets as a book in 2019 but by now, after five more years of research, the timeline of jet fighter development in Second World War Germany had become a great deal clearer, as had errors in the original work. I could not allow that publication to be simply reissued. So I promised my publisher that I would completely rewrite Secret Jets – rebuilding it from the ground up, rechecking all the original sources and consulting many new ones, correcting errors and layering on a substantial amount of new detail.

This book is the result. Keen-eyed readers who own or have read the ‘Secret’ series to date will undoubtedly notice fragments of those works within it – but the overall focus on jet fighters has been tightened and the level of detail now offered is, I believe, unrivalled. I hope too that the inclusion of all sources used in the writing of this volume will allow readers to judge for themselves the accuracy of the account herein presented.

Dan Sharp

ACKNOWLEDGEMENTS AND THANKS

This book would not have been possible without the help of Stephen Walton at the Imperial War Museum and my friend and fellow research enthusiast Steve Coates. I am indebted to them both for their unwavering support and generosity. Elizabeth Borja and David Schwartz at the National Air and Space Museum’s archives section and Becky Jordan and Olivia Garrison at Iowa State University Library provided invaluable assistance for which I am most grateful.

Thanks are also due to Jenz Baganz, JC Carbonel, Chris Cocks, Zoltán Csombó, Calum Douglas, Chris Elwell, Paul Fincham, Ian Fisher, Simon Fowler, Chris Gall, TimHartley, Pauline Hawkins, Carlos Alberto Henriques, Luca Landino, Scott Lowther, Paul Malmassari, Paul Martell-Mead, Eddie Nielinger, Steve O’Hara, Ronnie Olsthoorn, Martin Pegg, Sean Phillips, Alexander Power, Stephen Ransom, Chris Sandham-Bailey, Dan Savage, Jonathan Schofield, Sven Schultze, J Richard Smith, Kay Stout, Oliver Thiele, Greg Twiner, Daniel Uhr, Gary Webster, Paul Williams and Tony Wilson.

Introduction

German Second World War jet fighter development

Germany gained an early lead in jet fighter development during the Second World War but failed to capitalise on it until it was far too late. The result is a tale of incredible technological advances punctuated by a litany of missed opportunities.

Development of the jet engine in Germany began and progressed in parallel with work on gas turbines taking place in Britain during the mid-1930s. By the end of the decade, however, the Germans had moved more decisively to realise the new powerplant’s potential.

The German government encouraged all of the country’s major engine manufacturers to begin work on jet engine designs and as a result, despite the technological challenges involved, BMW, Junkers and Heinkel-Hirth all made significant progress during the early part of the Second World War.

Just two aircraft manufacturers were initially entrusted with the task of building a single-seat fighter incorporating this new propulsion technology – Messerschmitt and Heinkel. When the initial specification was issued in January 1939, it called for a single-jet aircraft but both companies ended up building relatively large twin-engine aircraft instead. This was because early turbojets were too weak to power an aircraft loaded with military equipment on their own.

At the time, this detail did not seem to pose any significant problems since turbojet engines were lighter than piston engines and much cheaper and faster to build. A twin-jet fighter was therefore lighter than the equivalent fighter with two piston engines and only slightly more expensive than a fighter with a single piston engine. Messerschmitt designed the Me 262 and Heinkel the He 280. Each had its engines in wing-mounted nacelles allowing easy access for maintenance and negating any loss of thrust that might occur as a result of a long intake duct. In addition, early turbojets were fragile and notoriously unreliable. Having a second engine provided a useful backup in case the other failed.

It was a safe choice of configuration but it had a number of drawbacks. In economic terms, two jet engines meant that building a single Me 262 was still somewhat more expensive than building a single Bf 109 or Fw 190. A larger airframe meant a greater quantity of light metal was required for each Me 262 built.

GERMAN JET DEVELOPMENT TIMELINE

Display model of the Lippisch Delta VI photographed and set against a ‘sky scene’ for promotional purposes. The Delta VI was typical of advanced projects being dreamt up by Germany’s aircraft designers as the war neared its conclusion.

In development terms, positioning the turbojets under the wings restricted the size of engines that could easily be installed. The He 280 failed partially because its airframe had been designed for the Heinkel HeS 8 and it struggled to accommodate the larger Jumo 004 when required to do so. Furthermore, wings that needed to support engine nacelles had to be strong and therefore thick. It would prove difficult, later, to alter the wing design of the Me 262 without major structural revisions.

Thicker wings had a knock-on effect for performance, as did the use of drag-inducing external nacelles, and most fighter pilots were used to flying single-engine designs, requiring additional training to manage two engines in flight. Despite all this, the twin-jet designs offered the promise of performance beyond anything likely to be possible with piston engines.

The future viability of jet engines for fighter aircraft in general remained in doubt until July 18, 1942, when the Jumo 004-powered third Me 262 prototype was able to fly for 25 minutes without problems. After more than three years of development, it was now clear that turbojets could be made reliable enough for operational use. But it would be a further 22 months before the Me 262 finally began to enter front-line service with the Luftwaffe.

Much of German aircraft manufacturers’ design and development effort during 1944–45 was devoted to finding a way of combatting the increasingly effective USAAF daylight raids over Germany.

The rocket-propelled Messerschmitt Me 163 had a similarly tortuous development history – though its shortcomings were even clearer than those of the Me 262. The diminutive aircraft was the culmination of a long line of tailless aircraft experiments carried out by its maverick creator Alexander Lippisch and was intended as a technology demonstrator rather than as a front line fighter.

Its viability was conclusively proven more than nine months earlier than that of the Me 262, when the first prototype was flown at 1,000km/h on October 2, 1941, but rather than following Lippisch’s plan to build a much larger interceptor based on the now-established principle of rocket propulsion for a fighter, it was decided that an almost entirely new version of the Me 163 itself should be built – the Me 163 B. This would perform in a similar fashion to the prototype – with all the problems of a dollylaunched, skid-landing small-airframe prototype – but with sufficient room to carry cannon.

Designing, building and testing this new aircraft meant it took even longer to get the Me 163 B into service than it had taken the Me 262, with the Luftwaffe only able to begin limited operations with it in May 1944. And even then it proved to be more of a menace to its own pilots than the enemy – its volatile rocket fuel causing a number of fatal explosions and its unforgiving skid landing gear resulting in several serious back injuries. Operations were soon curtailed when Allied bombing raids knocked out the small number of chemicals factories capable of producing its fuel.

The third jet aircraft to see service with the Luftwaffe was the Arado Ar 234. Designed without advanced features as a simple reconnaissance platform, it perhaps represents the greatest missed opportunity of the three. Arado’s brief in 1940 was to create an airborne camera platform able to cover Britain all the way up to the naval base at Scapa Flow. There was no requirement for armament, no requirement for more than one crewman and no particular need for manoeuvrability. The design that emerged was therefore all about achieving a particular range – to the extent that even a wheeled undercarriage was initially sacrificed to keep weight down and provide more room for fuel tanks.

The Ar 234 V1 made its first flight on July 30, 1943, and although Arado had already drawn up various proposals to repurpose the aircraft as a light bomber or even as a fighter, the lack of space within its slender fuselage and its unsophisticated layout made it largely unsuitable for anything other than the task for which it had been created. Its first operational sorties were carried out in August 1944.

With the introduction of the de Havilland Mosquito, the Allies had a means of overflying Germany with nearimpunity to take reconnaissance photos. Developing an interceptor that could catch the powerful and high-flying British aircraft was a high priority in 1944.

It is worth noting that the first two developments were begun when Germany was still at peace and neither the resources of the Reichsluftfahrtministerium (RLM – the German air ministry) nor those of the aircraft manufacturers were being taxed by the demands of developing and supplying aircraft for front-line combat. Furthermore, all three developments were begun when the much-maligned Ernst Udet was, as Generalluftzeugmeister, in charge of providing the Luftwaffe’s equipment.

After D-Day, the Luftwaffe had yet another problem – how to combat powerful and heavily armed Allied fighterbombers at low level.

The Messerschmitt Me 262 had an incredible turn of speed and awesome firepower but it could not be built fast enough and was unsuitable for combatting low-level enemy fighter-bombers.

When the Second World War began in September 1939, resources that had been available for experimental development were reallocated to more directly supporting the war effort. At Messerschmitt, this meant intensive efforts to upgrade and improve the Bf 109 and Bf 110. Following the suicide of Udet and the appointment of Erhard Milch as Generalluftzeugmeister in November 1941, there was an even tighter focus on existing types to the detriment of all experimental designs.

Milch also proved far less willing than Udet to gamble on unproven technology and his office prioritised the development of new piston-engine aircraft to the extent that between November 1941 and June 1944 – when he left office – there were no new requirements for fighters with turbojet or rocket propulsion. He had, in December 1942, ordered the ‘Vulkan’ programme into effect which was supposed to give top priority to the development of the Me 163, Me 262, He 280, Me 328 and Ar 234 but this seems to have made little difference to any of them.

The aircraft companies themselves had continued, of their own volition, to half-heartedly work on a handful of new jet and rocket designs, eventually approaching Milch and the RLM in May 1943 with the idea of building lightweight single-jet fighters based largely on existing fighter airframes.

This initiative seems to have been greeted with some enthusiasm at first but that soon tailed off as attention focused once more on the next generation of piston-engine fighters – the Me 209 and Ta 153 as potential replacements for the Bf 109 and Fw 190. With the benefit of hindsight, the development of a lightweight single-jet single-seat fighter based on the Jumo 004 appears to have been one of the greatest missed opportunities of the war.

Had the Me 262 been cancelled as soon as the Jumo 004 had proven reliable in July 1942, and every effort diverted towards the design and series production of something similar to the He 162, Germany might have had a fleet of cheap high-performance single-jet fighters ready for action by the end of 1943. This might conceivably have altered the course of the war – but as it was the opportunity slipped past unnoticed.

Udet’s time in office as Generalluftzeugmeister had been characterised by an explosion in aircraft development – with a huge number of types being commissioned as prototypes either as competitors for a particular requirement or as experiments to study a particular concept. However, where the RLM under Udet had had some success in ruthlessly cancelling projects which failed to meet requirements or which failed to live up to expectations (with a few notable exceptions, such as the Me 210), Milch inherited a large number of aircraft types and projects which, objectively, were surplus to requirements and merely allowed them to continue in the hope that they could somehow be improved.

Even by May 1944, the German aircraft industry was still producing 32 different aircraft types¹ (this having been pared back from some 53 types at one point during 1943),² many of them obsolete types that had soldiered on because plans to replace them had come to nothing or which represented the remnants of failed lines of development.

To make matters worse, Germany was facing a critical shortage of all aircraft types at the beginning of the year, with Allied bombing having repeatedly targeted the large factories where they were built. Efforts to resolve this problem resulted in the formation of the Jägerstab or ‘Fighter Staff’ on March 1, 1944. This new organisation, formed by Albert Speer’s Reichsministerium für Rüstung und Kriegsproduktion, had relieved the RLM of its responsibility to oversee aircraft production and set about dispersing it to dozens of small factories and workshops across Germany.

This Junkers-produced slide from December 1944 shows the cost of a twin-jet Me 262 – RM 150,000 – compared to that of a single piston-engine Focke-Wulf Ta 152, RM 144,000 and a single-jet He 162 at just RM 75,000.The economic and production benefits of a single-jet design are clear.

However, it was not until May 25, 1944, that Reichsmarschall Hermann Göring himself outlined plans to reduce the 32 types down to just 16, thereby freeing up vital production capacity. Among the aircraft axed immediately or scheduled for expiry over the next 18 months were the Bf 108, Bf 110, Me 210, Me 323, Me 410, Ju 52, Ju 352, Ju 188, Ju 288, Ju 290 and Ju 390. The remaining types included the Ar 234, Do 335, Fw 190/Ta 152, Ta 154, Ju 287, Ju 388, He 277, He 111, Bf 109, Me 163 and Me 262.

Wind tunnel testing of the Junkers Ju 287 fast bomber. The proliferation of wind tunnels in Germany enabled a huge number of different designs to be tested quickly and rapidly advanced designers’ knowledge of aerodynamics. Conversely, it has been argued that the opportunity to test so many designs resulted in too much data – making it difficult and time-consuming to decide which forms and features worked best.

Göring explicitly stated that he expected Me 262 production to be substantially increased, that the aircraft should be a fighter (even though, as Milch reminded everyone during the meeting, Adolf Hitler had declared that it should be a bomber) and that units operating the Me 262 should be strategically located to defend important industrial targets.

It had taken years to reach this point and even if the Me 262 had been built as a bomber it would not have been available in time to fly missions over the Normandy beaches when the long-anticipated invasion finally happened on June 6, 1944 – the role Hitler had envisioned for it. Neither was it suitable for combating the low-flying fighter-bombers that would begin ranging across occupied Europe in the wake of D-Day.

Where Germany had been quick to recognise the potential of turbojet propulsion at the end of the 1930s, it had been fatally slow to realise that potential. It was now almost too late to put any completely new jet or rocket-propelled aircraft into production. And it was certainly too late for any such aircraft to have an impact on the remainder of the war. But even in mid-1944, no one involved in aircraft development knew the full extent of Germany’s increasingly dire war situation on the ground and no one was planning for defeat.

ADVANCED PROJECTS

With the departure of Milch on June 20, 1944, responsibility for the commissioning and development of new aircraft seems to have briefly entered a period of limbo where no one was directly in charge of development. It was therefore left to Oberstleutnant Siegfried Knemeyer of the RLM’s Techniches Amt to tentatively begin working up specifications for a new generation of jet- and rocketpropelled aircraft.

This period of uncertainty came to an end on August 1, 1944, when Speer’s ministry assumed full responsibility for Germany’s technical air defence and the RLM’s Technisches Amt was replaced by a new organisational structure – the Chef der Technischen Luftrüstung (Chef TLR for short) under Oberst Ulrich Diesing. This effectively gave Knemeyer, on behalf of the Oberkommando der Luftwaffe (OKL – Luftwaffe high command), and with the blessing of Speer’s deputy Hauptdienstleiter Karl-Otto Saur, carte blanche to draft ambitious specifications which drew on the full range of technological advances made in Germany since the beginning of the war. Because although Milch had scarcely utilised it, a huge amount of groundbreaking aviation research had been carried out during his time in office.

Diagram showing the high speed wind tunnel at the Luftfahrtforschungsanstalt Hermann Göring, BraunschweigVölkenrode. By the summer of 1943 Germany had access to more modern wind tunnel testing facilities than any other country in the world – having invested huge sums of money in constructing them.

By the summer of 1943 there were no fewer than 58 German wind tunnel facilities in operation – 10 shared between the Aerodynamische Versuchsanstalt (AVA) and Kaiser-Wilhelm Institut (KWI) at Göttingen, five at the Deutsche Versuchsanstalt für Luftfahrt (DVL) in Berlin, one at the Deutsche Forschungsanstalt für Segelflug (DFS) at Darmstadt, seven at the Luftfahrtforschungsanstalt Hermann Göring (LFA) at Braunschweig, six at the Forschungsanstant Graf Zeppelin (FGZ) in Stuttgart, 19 at various technical schools, one at Blohm & Voss in Hamburg, one at Dornier in Friedrichshafen, one at FockeAchgelis in Laupheim, one at Focke-Wulf in Kirchorsten, two at Heinkel in Marienehe, three at Junkers in Dessau and one at Messerschmitt in Augsburg. Fifteen of these generated an airflow fast enough for transsonic or supersonic research.³

Far from embracing jet types as the future, the RLM under Generalfeldmarschall Erhard Milch tended to prioritise the development of high-performance piston engine types such as the Focke-Wulf Ta 152.

There were even another 13 in occupied countries to which the German firms had access (even though, as the Allies broke through their encirclement on the French coast and drove east, and the Soviets pushed ever westwards, they were about to lose it) – two in Czechoslovakia, four in Poland, two in Holland and five in France – though none of these could be regarded as ‘high-speed’. And yet more wind tunnels were built in the Reich itself during the last two years of the war at great expense, such as the 100,000hp Ötztal wind tunnel in Austria which was 70% complete when the war ended and which American investigators later valued at between $60 and $70 million.

Across the industry, the number of personnel involved in development work increased from 7,000 in 1943 to 8,000 by 1945. In addition, the budget for aviation research and development soared from 340 million Reichsmarks in 1943 to RM 500 million in 1945.⁴

InJuly, Knemeyer had given specifications to Messerschmitt, Heinkel and Focke-Wulf for a new jet fighter to replace the Me 262 and presented Blohm & Voss, Dornier and Focke-Wulf with specifications for ‘Hochleistungsjäger’ –a high performance piston-engined fighter with a pusher-prop configuration. In August he commissioned former Fieseler technical director Erich Bachem, Messerschmitt and Heinkel to begin work on new rocket-propelled interceptors.