Ten


OBERAMMERGAU

AFTER THE SCENES of devastation they had witnessed in the industrial regions in the north of Germany, particularly the horrors of Mittelwerk-Dora, it must have been with a sense of relief that members of the Fedden Mission travelled to Oberammergau in the picturesque Bavarian Alps on Friday 22 June 1945. The town is internationally famous for its passion plays which are presented in every year ending with a zero, although in 1940 the performance was cancelled because of the war. Otherwise this idyllic spot nestling in the hills seemed almost untouched by the war, which is exactly why Messerschmitt’s research and experimental division moved here in order to continue its work in secrecy unhampered by Allied bombing raids. In 1943 Messerschmitt took over the Hötzendorf Jäger Kaserne, a large army barracks, having been evacuated from Augsburg. There were extensive tunnels, up to 22 miles (37km) of them burrowing into the side of the neighbouring Laber mountain, to augment the factory space, and the local winter sports hotel was commandeered as accommodation for the executive staff. In all, Messerschmitt had a workforce of around 1,800 people at Oberammergau, including 500 in the design department alone.

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Aerial view of Hotzendorf Jäger Kaserne near Oberammergau, the extensive army barracks taken over by Messerschmitt in 1943.

The facility had been discovered by an American infantry unit on 29 April 1945, and it was almost two months later by the time Fedden’s group arrived by road on 22 June. Not surprisingly the Americans were in control and Fedden noted that a design team from the Bell Aircraft company had been working there for about five weeks on behalf of the USSTAF. But the Americans didn’t have the place entirely to themselves. Fedden also encountered a party from the British de Havilland aircraft company, which included de Havilland’s chief designer Mr Bishop. Immediately after the war de Havilland embarked on a series of experimental tail-less designs, commencing with the DH.108 which first flew in May 1946. These aircraft were used to investigate the behaviour of the swept wing in support of the DH.106 Comet and DH.100 Vampire programmes, though in the event the DH.100 featured straight tapered wings and distinctive twin-boom tail. After the war the Americans continued to occupy the Oberammergau site and, renamed as the Hawkins Barracks, it became the US Army School Europe until it was handed back to the Germans in 1974. It is now the primary training and educational centre for NATO.

Back in 1945 Oberammergau was an Aladdin’s cave stuffed with some of Germany’s most advanced aeronautical design and, unlike some of the cobbled-together short-term aircraft that had been thrown into the sky in the last-ditch defence of the Reich, here was a glimpse into the future. The Messerschmitt designers had been honing the shape of things to come.

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Members of the Fedden Mission at Messerschmitt’s experimental department, Oberammergau.

At Oberammergau Fedden was fortunate in being able to interview several members of the design staff, most notably Waldemar Voigt the chief designer, but also Hans Hornung and Joseph Helmschrott. At this time the company founder Willy Messerschmitt was being held in London for interrogation and pending possible charges relating to the company’s use of slave labour. Fedden firmly believed that he was able to obtain a far better picture of developments at Messerschmitt by going to Germany and into the works in order to talk directly with the engineers. In particular he singled out Voigt, describing him as ‘an extremely progressive engineer and most enthusiastic’. Fedden commented:

    He [Voigt] said that the recent work at Göttingen and Völkenrode had put an entirely new picture on interceptor fighters. He was strongly in favour of swept-back wings and of the opinion that the swept-back wing and the jet would accelerate the extensive use of tail-less type of aircraft in the near future.

Voigt took Fedden’s team down to a workshop where they were shown the familiar shark-like Me 262. He talked at some length about the aircraft’s flight characteristics and operational shortcomings, stating that because of inexperience among the pilots and stalling of the Jumo 004’s compressors, there had been a number of accidents during flight development. There had also been instances of the engines catching fire, due to the incomplete combustion of the fuel in the combustion chamber. As far as he was aware there had been fifteen fatal accidents, but this was no higher than on other interceptor aircraft. This comment struck Fedden as rather contradictory unless, as he put it, ‘the Germans accepted an appreciably higher accident rate than we do.’ In Voigt’s opinion automatic control of the jet engine was essential, but with a little more experience the Me 262 would have had an even greater potential as a fighter aircraft, capable of achieving speeds of up to 550mph (885km/h).

THE P.1101

The mission team saw a number of projects that were still in the developmental stage, in particular the P.1101, which Fedden refers to as the Me 1101. This was the prototype for a single-seater fighter produced in response to the 15 July 1944 Emergency Fighter Programme to create a second generation of jet fighters. Originally, the Messerschmitt people had produced a design featuring a wide fuselage, like an elongated egg, with a rounded air intake on either side at the wing roots and tapering off to a high slender tail clearing the jet exhaust and ending in a ‘V’ tail. The cockpit was right at the nose, flush to match the curved profile of the fuselage. The forward-mounted wings, shown in the original design drawings, had a compound sweep starting at 45° near the fuselage and changing to a shallower 26° towards the wing tips.

By August 1944 this design had changed, with a far sleeker extended nose, plus straight swept-back wings – borrowed from the Me 262’s outer wings – mounted mid-fuselage. Other variations came in quick succession, including consideration of a pulsejet and rocket booster combination known as the P.1101L. Following wind tunnel testing a finalised design was submitted to the Construction Bureau of the RLM in early December 1944. On 28 February 1945 the RLM announced that it had chosen the competing Focke-Wulf Ta 183 as the winner of the Emergency Fighter order. The Ta 183, which was known as the Huckebein (‘hunchback’), also featured a single turbojet within the short fuselage, cockpit above the engine and a high T-tail at the back. Work on the Ta 183s had commenced but none was completed by the time British troops overran the Focke-Wulf works on 8 April 1945. The Messerschmitt team, meanwhile, had continued with the development of the P.1101, but owing to the urgency of Germany’s worsening situation they went straight to full-scale prototype while the detailed design for the production version was still being finalised.

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Messerschmitt’s P.1101 prototype which the mission examined at Oberammergau.

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The prototype P.1101 V1, which Voigt showed to Fedden at Oberammergau, featured a single turbojet within the main fuselage. There was an open-mouth intake at the front and the pressurised cockpit with bubble canopy was positioned above the engine near the nose. The aircraft had swept-back wings and at the rear the fuselage tapered to a conventional tail but high enough to provide clearance for the exhaust. As part of the accelerated testing and parallel design programme the wings could be adjusted from between 35° to 45° before flight to assess the advantages of differing angles of sweep. This was a purely investigative measure and was never intended as an operational swing-wing feature. The fuel tanks were within the fuselage behind the cockpit, while the radio and oxygen equipment were in the rear section. There was a tricycle undercarriage with the main gear retracting towards the front. Armaments were to consist of either two or four MK108 30mm cannon, and/or under-wing mounted X-4 air-to-air missiles. This prototype had a Jumo 109-004B turbojet fitted for initial trials as the intended and more powerful Heinkel-Hirth HeS 011A was not ready in time, although the engine had been mounted in such a way that the two types were readily interchangeable.

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Messerschmitt’s drawing of the P.1101 published in the Fedden Mission report along with this photograph, below, showing the single turbojet.

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An artist’s impression of the P.1101 in flight.

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Bell X-5, clearly inspired by Messerschmitt’s P.1101 prototype. (Nasa)

Maximum speed was estimated as being around 612mph (980km/h), the equivalent of Mach 0.8 at 23,000ft (7,000m) altitude, and according to Voigt the prototype would have been flying by June of 1945. When the Americans discovered the Oberammergau facilities on 29 April 1945, the airframe – still without wings – had been hidden away in the nearby tunnels. At first there were suggestions that it could be completed but by this time some of the construction drawings had been removed by the French, and instead it was taken back to the USA – first to the Wright Patterson Air Force Base in Ohio and then, in 1948, to the works of the Bell Aircraft company in Buffalo, New York. It was fitted with an Allison J-35 engine but by then the aircraft had been damaged by rough handling in transit to such a degree that it could no longer be flown. Nonetheless, the unfinished German jet became the basis of the two Bell X-5 experimental aircraft which first flew in June 1951 and which bear more than a passing resemblance, in appearance at least, to their forebear, the Messerschmitt P.1101.

Some components of the German prototype were utilised for static testing, but the airframe was scrapped sometime in the 1950s. As we will see in the next chapter on captured and returned German aircraft, in the decades immediately after the war there was very little sentimentality or consideration given to preserving them for historical reasons and many unique aircraft were either dumped or scrapped.

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Messerschmitt’s drawing for the P.1110 high-altitude fighter-interceptor published in the mission report.

Me P.1110

Fedden also saw design drawings for the next high-altitude fighter-interceptor, the Messerschmitt P.1110. These revealed an aircraft of incredibly modern design and shape (not unlike the British Hawker Hunter which first flew in 1951 and was derived from the earlier Hawker P.1052 of 1948). With the P.1110 it was as if aeronautical evolution had skipped a step and jumped a generation in one go. Instead of a single air intake into the fuselage, it was to have twin annular intakes ahead of each wing root. The result was a much more slender fuselage with the low-profile cockpit located between the intakes ahead of the Heinkel-Hirth HeS 109-011A engine. Voigt explained that although a central intake might give 4 per cent more air than the twin-intakes, this new layout saved 15 per cent on drag. Suction fans driven by the turbojet would draw the boundary layer air in through slotted ducts, and the exhaust was at the rear just below the swept tailplane – the next version was to have a butterfly V-tail. The wings were similar to the P.1101’s with a 40° sweep. It was to be armed with three MK108 30mm cannon in the nose, with the possibility of another two cannon installed within the wings. Maximum speed was expected to be in the region of 630mph (1,015km/h).

To overcome the loss of ram air in the P.1110 design, together with the additional power consumption in sucking air from the boundary layer airflow, Voigt was investigating an alternative in which the two air intakes were located within the leading edge of the wing near the root. These intakes would join up behind the cockpit to feed air to the turbojet in the rear end of the fuselage. In January 1945 his design team had prepared designs for the P.1111 which had a sharply swept wing of 45° extending in a near delta-wing shape with just a vertical fin on the tail.

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Messerschmitt’s 1944 visualisation of the futuristic P.1108 Fernbomber project.

Me P.1112

One Messerschmitt design which had at least made it from the drawing board to initial mock-up stage was the P.1112. Started in February 1945, this was yet another swept-wing single-seat fighter/interceptor, but unlike the P.1111 it had the cockpit set well forward and streamlined into the fuselage with the pilot in a semi-inclined position. The indented air intakes for the Heinkel-Hirth HeS 109-011A turbojet were located roughly halfway along the sides of the fuselage, and at the rear there was a single vertical tail fin, although a V-tail had featured in earlier design drawings. Once again the aircraft had a very modern appearance, but although Voigt had predicted flight testing for the P.1112 by mid-1946, this design never got beyond a rudimentary wooden mock-up of the forward fuselage and cockpit area.

After the war, Voigt went to the USA where he contributed to the design of the Chance Vought F7U, a carrier-based fighter developed for the US Navy and known as the Cutlass, first flown in September 1948. While the profile of the Cutlass had the look of the P.1112, its most distinctive feature was the twin tail with a vertical fin located in the middle of each wing. The F7U proved to be a much-troubled aircraft. Under-powered, it was nicknamed the ‘Gutless Cutlass’ and suffered numerous technical and handling problems. Over a quarter of the 320 F7Us built were lost in accidents.

TAIL-LESS AIRCRAFT

The final design Fedden’s group saw at Oberammergau was what the report mission refers to as the PL.08, although he may have been muddling the PL.08.01 with the similar designation numbers of the P.1108/II judging from his description, which includes four Heinkel-Hirth HeS 109-011 turbojets.

The PL.08.01, designed in 1941 by Dr Wurster who had worked closely with Alexander Lippisch, was a proposed long-range bomber which featured a compound swept wing and was to be powered by four Daimler-Benz DB 615 piston engines mounted within the trailing edge and driving pusher props at the rear, whereas the P.1108/II, another long-range bomber designed by the Lippisch team, was to have been jet-powered. (The P.1101/I design featured a conventional fuselage with swept wings and engines mounted in nacelles.) Although the P.1108/II project was still very much in the early design stage Fedden states that, ‘the data available gives a good indication of the possibilities of large jet aircraft and the lines along which German design staffs were planning.’ Clearly those lines were of the fast and tail-less sort:

    The aircraft was a four-jet long range bomber, with an all-up weight of about 30 tons and a bomb load of 4 tons. It was stated to have been designed to have a range of 7,000km [4,350 miles] at a cruising speed of 800 to 850km/h [495 to 530mph] at 9 to 12km [30,000 to 40,000ft] altitude. These figures are quoted as given to the Mission without any definite proof, and were described as only approximate, since all the data on this project has been removed by the French. The intended position of the four Heinkel 001 jet units on this aircraft were interesting. If the machine was made tail-less, the jet units would have been placed on the chord line at the trailing edge, near the wing root, with an influx pipe passing through the wing from the leading edge, or from a scoop on the upper surface of the wing. With a normal type of aircraft they would still have positioned the jet near the trailing edge, but with its axis somewhat below the chord line. The air intake would then be from the air flow beneath the wing, using a modified trailing edge in the region of the engines. The firm stated that these positions had been shown to be the best from the standpoint of minimum drag, and they did not contemplate any trouble from far aft position, as this would be compensated for by the heavily swept-back wings as far as the centre of gravity was concerned.

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The P.1108 Fernbomber would probably have been fitted with four Heinkel turbojets.

The design of the P.1108/II was well on the way to being what we would now term as a flying wing, although strictly speaking a full flying wing has no tail fin at all. If the P.1110 had represented a leap in design it is hard to be sure whether that of the P.1108/II was a leap into the future or the past. Much has been written about the advent of the truly tail-less aircraft, the flying wing, but it should be remembered that they had been a recurring theme in the aeronautical and popular science press of the 1930s which regularly featured designs for tail-less, or rather all-wing, aircraft. These were invariably depicted as futuristic airliners with lavish passenger accommodation contained within the deep leading edge of the wing. It is interesting to note that in his paper, ‘The Future of Civil Aviation’, which Fedden delivered at the Royal Aeronautical Society in the summer of 1944, and long before the wartime developments in Germany had come to light, he had given some prominence to the potential of the tail-less aircraft:

    The construction of larger machines might become feasible in ten years’ time, using the tail-less design with improved materials and constructional techniques.

The paper was illustrated with drawings for three sizes of tail-less craft, ranging from an eighteen-seater with a compound sweep to its wing and four air-cooled piston engines buried within the wing to drive pusher propellers, to a thirty-two seater with a straight sweep, and even a small ‘jet-propelled mail carrier’. The bigger versions were intended for long-distance travel, mainly transatlantic, and featured conventional rounded fuselages to accommodate the passengers. They bore a striking resemblance to the designs for the Messerschmitt P.08.01.

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Design for a thirty-two seater tail-less airliner – in other words a flying wing – published in Fedden’s 1944 paper The Future of Civil Aviation.

In fact, the concept of the flying wing was nothing new, even in the 1930s. It can be traced back to the dawn of heavier-than-air flight and a time when the pioneers were unfettered by any rulebooks of aeronautical convention. (In many ways this situation was replicated in the spirit of aeronautical experimentation found in Germany during the Second World War.) Several of the early European aviators took an all-wing approach to their designs, primarily with gliders, and some of these were moderately successful. However, complications arose when adding engine power to the inherent difficulties in controlling a craft without a tail. In September 1906 the Danish aviator Jacob Christian Ellehammer managed to get off the ground in a form of tail-less craft which resembled a biplane made up of two kites, the lower one fixed and the upper one flexible like a hang-glider, powered by an 18hp engine. This achievement is sometimes credited as the first powered heavier-than-air flight in Europe as it pre-dates Albert Santos-Dumont’s flight some two months later, but Ellehammer’s craft was tethered by wire to a pole and only managed a few circuits around a circular track without any directional stability or control.

The first free flight with a tail-less aircraft occurred in England. John William Dunne had also begun experiments with un-powered tail-less gliders and in conditions of great secrecy, because of the interest shown by the British Army’s embryonic aviation department at South Farnborough, in the spring of 1907 he managed some brief hops with the distinctive V-shaped D.1-A glider. His experiments continued with a series of gliders which, in December 1910, resulted in the flight of the powered D.5 biplane. Further models followed, but ironically the great stability of Dunne’s designs made them incompatible with the handling characteristics required in a more manoeuvrable military aircraft.

It was only after the First World War and the advent of thicker-winged monoplanes that designs for a true wingless aircraft, with engines, cockpit, passengers and so on housed within the wing itself were to emerge. In 1910 Hugo Junkers patented designs for a thick-wing aircraft and in the early 1920s the Junkers company produced conceptual designs for several large passenger aircraft. These were widely publicised, especially the J-1000 which was a colossal machine with a wingspan of 203ft (62m) intended for long-distance passenger services – possibly transatlantic – with twenty-six cabins accommodating up to 100 passengers, plus a crew of ten.

However, this all-wing design did feature an additional canard-style wing mounted on twin booms at the front, plus a pair of vertical fins on the trailing edge of the main wing. The J-1000 never made it off the drawing board, partly because of the limitations on permitted aircraft sizes imposed upon Germany in the terms of the Treaty of Versailles. Consequently the nearest a Junkers flying wing came to realisation was the 1931 G-38 Grossflugzeug; a four-engined airliner with three eleven-seater cabins, plus smoker cabins and wash rooms all contained within the thick leading edge and nose. The wing was very large, 6ft (1.8m) thick at the root and with a maximum chord – the measurement from the centre of the leading edge to the trailing edge – of 33ft (10m), but the G-38 still had a central fuselage and tail. Only two were built, the largest aircraft in the world at the time, and the prototype registered D-2000 first flew in November 1929.

The G-38s established several world records and the second aircraft, D-APIS, continued in service for Lufthansa until the outbreak of war. It was destroyed on the ground during an RAF bombing raid on Athens in May 1942. However, these aircraft did not lead on to further development of the wingless configuration. There was some interest in other countries, including from Jack Northrop and Charles Eshelman in the USA, as well as in the Soviet Union, while in Germany the main impetus remained in hands of three aeronautical designers; Alexander Lippisch and the Horten brothers, Walter and Reimar. (A third Horten brother, Wolfram, was killed flying a Luftwaffe bomber at Dunkirk.)

During the First World War Lippisch had flown as an aerial photographer and mapper, and when peace came he went to work for the Zeppelin company. It was during this time that he developed an interest in the aerodynamics of tail-less aircraft and during the 1920s and ‘30s this led to the design of a series of gliders. These included the Ente (‘duck’), which in 1928 became the first aircraft to fly under rocket power and, as described in the previous chapter, Lippisch’s designs led directly to the development of the Messerschmitt Me 163B rocket powered interceptor. While Lippisch was to steer more towards the delta-wing configuration, his innovative glider designs caught the imagination of the young Horten brothers. Enthusiastic sports flyers, they constructed their own glider which competed at the Ninth Glider Competitions in 1933. The H1 tail-less glider had a very simple wing form, tapered towards the tips but without sweep. Subsequent designs saw the refinement of the wing shape and by 1937 it had evolved into the Ho VII, a powered aircraft with twin 240hp Argus 10C engines on the trailing edge driving pusher propellers.

The great advantage of the slick wing configuration was a drastic reduction in drag which, in turn gave the potential for savings in fuel consumption and far greater range; characteristics that caught Hermann Göring’s eye. In 1943 he issued a request for designs to produce a bomber that could meet his ‘3 x 1,000’ requirements: Carrying a 1,000kg load over a distance of 1,000km at a speed of 1,000km/h. In other words he wanted an effective long-range bomber that was fast enough to be impervious to Britain’s fighter defences. In response, the Hortens came up with an innovative design for a flying wing to be powered by two turbojets, the H.IX (later known as the Ho 229).

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Horton 229 V3, a prototype jet-powered flying wing, handed over to Northrop after the war and now in storage with the Smithsonian.

This design consisted of a central pod made up from welded steel tubing, with the wing spars built of wood. The wings, or rather wing, swept to an angle of 32° and with rounded tips, were covered with thin plywood panels glued together with a charcoal and sawdust mixture. There were control surfaces along the entire trailing edge. The cockpit was set well forward for maximum visibility past the wing, and the aircraft rode on a retractable tricycle undercarriage, with the front wheel on the first two prototypes sourced from a Heinkel He 177. Steering on the ground was via a small brake flap on each wing tip, and a drogue parachute slowed the aircraft upon landing. It was intended to install two BMW 109-003 jet engines, but as these were not available in time the ubiquitous Jumo 109-004 was used instead.

Given its official RLM designation as the Ho 229, the V1 prototype began testing as a glider in March 1944, and despite a mishap on landing it performed well. The second prototype achieved speeds up to 500mph (800km/h) but was wrecked after an engine failure. However, it had shown sufficient promise for the RLM to continue with the programme, although further design and development was handed over to the aircraft’s builder, Gothaer Waggonfabrik, at Friedrichsrode, in Thuringia to the south-west of Nordhausen. Consequently the aircraft is sometimes referred to as the Go 229. The third prototype, V3, had a wingspan of 55ft (16.76m) and was fitted with the more powerful Jumo 109-004C turbojets, but had yet to fly when the US Army captured the works. The V4 and V5 prototypes intended for a night-fighter role were also under construction at the time. In addition, preliminary design work had commenced on a single-engine fighter version, fitted with the more powerful Heinkel-Hirth 109-011A and known as the Ho X. A test version of this aircraft fitted with a single piston engine was under construction at Hersfeld, near Kassel.

The legacy of the Hortens’ flying wing has been much debated. After the war the Ho 229 V3 prototype was placed in the hands of the Northrop Corporation because of Jack Northrop’s existing interest in the concept. Since 1941 Northrop had been working on the XB-35, a long-range flying wing capable of flying from US airfields to carry out bombing raids on Nazi-occupied Europe in the event that Britain had been overrun – a reverse take on Germany’s Amerikabomber programme. It was to have a wingspan of 172ft (52.4m) – roughly three times bigger than the Ho 229 – and would be driven by four Pratt & Witney R-4360 radial engines, giving a maximum speed of only 393mph (632km/h) but a range estimated at over 8,000 miles (12,875km).

A one-third scale piston-engined prototype, dubbed the N-9M, first flew in December 1942. This test aircraft was used to gather flight data for the big XB-35 which was in the design stage. The war had already ended when the first of the YB-35s – the designation for the test model versions of the XB-35 – made its maiden flight in July 1946. By then the emergence of the jet-powered aircraft from Germany at the end of the war convinced the USAF that a piston-powered XB-35 would be obsolete before it became operational. Prior to the YB-35’s maiden flight the decision had already been made to replace the engines on two of the test aircraft with Allison J35 turbojets and these jet-powered flying wings became known as the YB-49 model. The first of these flew on 21 October 1947, but by 1951 the programme had been terminated following the loss of one aircraft and a succession of technical difficulties.

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The YB-49, a jet-powered version of Northrop’s flying wing, first flew on 21 October 1947. (USAF)

This was not the end of the flying wing, however. The Horten brothers had rightly surmised that its slim cross-section made a flying wing harder to detect by radar. They had even tried to enhance this characteristic by adding charcoal dust to the wood glue to absorb electromagnetic waves. What they didn’t appreciate was that its flatter shape and the absence of radar reflecting vertical surfaces were the key factor in what we now term as stealth technology. In the 1980s engineers from the Northrop-Grumman Corporation made several visits to the Smithsonian Museum’s facility at Silver Hill, Maryland, where the captured Ho 229 V3 prototype was still in storage. Their research led to the Northrop B-2 stealth bomber where the aerodynamic qualities of the flying wing are secondary to its low radar signature. The flying wing concept is also being reviewed and re-branded as the Blended Wing Body (BWB) with a flattened and more aerofoil-like shape to deliver lower drag and high-lift. The Boeing Phantom Works in association with Nasa’s Langley Research Centre commenced flight testing with the remotely piloted X-48B in July 2007.

DELTA WINGS

The delta wing, named after the Greek character Delta which is represented by the D symbol, is so closely related to the flying wing that it can be regarded as a variation on the same theme. The main proponent of the delta wing in Germany was Alexander Lippisch of Messerschmitt Me 163 fame, although that aircraft wasn’t a pure delta as the wings didn’t extend to a full triangle. But such was the success of the Me 163 in terms of its aerodynamic qualities, bearing in mind that it always returned to the ground in glider mode, that Lippisch went on to experiment further with the design. This wartime work culminated in the Lippisch DM-1, or Darmstadt-München 1, a glider intended as a development model to test low-speed handling for a proposed super-fast ramjet-powered interceptor known as the Lippisch LP-13a. Eugene Sanger had already conducted flight tests with extremely powerful Lorin-type ramjets carried on the back of a Dornier Do 217E, and for the P.13a a ramjet that might be fuelled by coal dust had been proposed, possibly combined with rocket motors.

Development of the test glider was started by the Flugtechnische Fachgruppe (FFG) – an association of students and aircraft designers at the Darmstadt and München (Munich) universities – in August of 1944, but after the facilities were bombed they moved the work to Prien in Bavaria. The DM-1 featured a distinctive pure delta of 60° sweep, resulting in a triangular plan shape, mirrored by another triangle to form the high dorsal fin. In theory the compression shock at Mach 1 would occur on both the leading edge of the wings and fin at the same time. This single-seater, just 20ft 8in (6.32m) long, was constructed of steel tubing frame with a plywood skin, with the cockpit crammed into the space at the junction of the three triangular elements. In the final operational version the circular intake for the ramjet would have extended to the nose. The intention was to launch the DM-1 by piggy-back. Film footage exists of what appears to be a scale model of the DM-1 in flight, as the prototype aircraft was not ready by the time American troops arrived on the scene in May 1945. Work continued on the DM-1 under the guidance of the US military and in November 1945 Dr Lippisch and the completed glider were shipped to the USA. The model was scrutinised in the Langley Aeronautical Laboratory’s wind tunnel and the data obtained from these studies led to the design of the Convair XP-92. Just as with the P.13a this aircraft was to have been powered by a combination of rocket and ramjet, but in the event a single test aircraft, the XF-92A, flew on 18 September 1948 fitted with an Allison J33-A-21 turbojet. The success of the XP-92 led Convair to feature the delta wing on a number of designs including the F-102 Delta Dagger, F-106 Delta Dart, B-58 Hustler, the F2Y Sea Dart produced for the US Navy, and the experimental FY Pogo VTOL aircraft.

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Lippisch DM-1 delta-wing with triangular dorsal fin. (SDASM)

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Convair’s XF-92A delta-wing test aircraft first flew in 1948. (USAF)

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Dornier Do 217E test-bed for the ramjet engine.

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