Woldemar Voigt and a Swing-Wing

Skyraider’s 3D Aviation Art!

Who invented variable wing-sweep? Barnes Wallis? Maybe not, for Voigt’s Messerschmitt Me. P. 1101 prototype must be the basis, not just of a swept and variable wing idea, but also of a sharply swept, ducted engine, single-seat fighter design. The fact the American `copy’ that was the Bell X-5 seemed identical was of no accident, for the Me P. 1101 was also seized and shipped back to America. Intriguingly, much of Voigt’s Messerschmitt P. 1101 research fell into French hands, who, unlike the British, had no need, nor compunction, to hand it to the Americans, and refused to do so. The Me P. 1101 was not without problems, it was far too heavy for a glider designer like Willi Messerschmitt to countenance and the 40° wing sweep, with proposed variable or `swing-wing’ mechanism, defied solution in the ill-funded dog days of a war about to end. Yet, with its internally- mounted wing geometry gearing design, the P. 1101 would signal the successful 1960s use of such. So, the P. 1101 would be no last-ditch wonder weapon, and was not suited to rough-and-ready construction and short airframe life. Yet within the Me P. 1101 lay many future design trends; the P. 1101 still looks like a 1980s airframe.

Strangely, yet somewhat unsurprisingly, the Bell Aircraft Corporation’s chief designer, Robert Woods, just happened to find himself standing in a barn in Oberammergau, in early 1946, staring at the Me P. 1101. It was, of course, an expensive and difficult journey from the USA to the hills of southern Germany, but someone had to do it. The consequent Bell X-5 was, even to the most pro- American observer, an alleged blatant copy. Other 1950s American swept-wing fighters look like crosses between the Me P. 1101 and the Multhopp Ta 183. In doing so they would take on the MiG-15s that were also blatant copies of German design.

Although ultimately unsuccessful in terms of being directly copied, the effect of the Me P. 1101 would also lead to its designer, W. Voigt, finding himself at Wright Field, Dayton, Ohio, in 1946 – thence to a career in the US aerospace industry. And the P. 1101 was not to be Messerschmitt’s final fling in design terms either, because the ultimate route that Messerschmitt advanced design was to take, followed the all-wing path. From the P. 1101 came the P. 1102 as a tailless all-wing idea (with vertical fin) and a series of jet-powered all-wing airframe proposals designed to meet the Reich’s last final struggles for a weapon to strike fear into American hearts.

Messerschmitt had not been an avid follower of the all-wing and his thoughts on tailless design included a vertical fin or `tail’, but not a drag inducing horizontal stabiliser tail unit. Yet, as a glider designer prior to his powered-designs, Messerschmitt had kept a close eye on the Hortens and Lippisch. Ultimately, the P. 1111/12 design proposals of early 1945 were advanced all-wing ideas and again, looks like an early iteration of a later British idea, the DH 108, and the American Northrop X-4. Of significance, here too, in the P. 1112, we saw the annular, wing root/leading edge/engine air intake concept for the first time – later seen in the de Havilland Comet, Vickers V. 1000 and Valiant, and in production in the Handley Page Victor – as well as a host of American machines.

Of the world’s first swept-winged jet fighter Me 262 (and the even more aerodynamic Me 262 HG), we can say that this airframe taught others more about wings and high-speed flight than can be easily grasped. The Me 262s stepping stone was a monumental moment of learning for the Allies that seized it and its technology. Overnight, straight-winged jets from de Havilland, Gloster, Lockheed and others, were utterly redundant, thrown upon the dustbin of design. The Vampire might not have been rendered useless, but we can say it was of restricted ability no matter how much it was loved. De Havilland soon designed the DH 101 and the key DH 108 and then the DH 110 Vixen. Glosters, Lockheed, North American et al, all went swept-winged `overnight’. For the British, the Hawker P. 1067 Hunter became their swept-winged dream machine, despite its `borrowed’ technology.

Crescent-Shaped Planforms – The Often-Forgotten Advance

The idea of a swept-back, crescent-shaped wing was seen in the works of early pioneers, not least Weiss and Handley Page, but a reverse crescent- shaped planform wing – one where the sweep reduced towards the wingtips – was shaped in Germany and applied by the Arado company and its chief designer, Walter Blume, deputy Hans Rebeski, and the aerodynamicist Rudiger Kosin. Kosin had studied forward-sweep and varying back-sweep. Arado proposed a crescent- winged two, and then four-engined bomber with a sweepback angle of 37° on the inboard wing and two cranks to 29° and 25° towards the outboard wing section.

The benefits of the compromise of a crescent wing was the reduction in wing sweep near the wingtips and that it moved the load on the wingtips forwards of the axis of the wing and improved airflow near the tips, rather than degrading it. This also reduced unfavourable behaviour near the stall and at high Mach numbers, yet retained the advantages of sweep more generally. Tip-stalling and spinning risks at low speed were thus reduced and a better-handling machine created. The wing might have to be a bit stronger and the wingtips thinner to ensure good airflow, but the crescent wing would be lighter in construction than a delta-wing and did provide another solution to how long, thin, highly swept-wings could be made to work and to do so safely across the speed graph – not just at high velocity and high-altitude cruise. Of interest, the `kinks’ in the varying sweep of the crescent wing do not seem to produce significant localised airflow disturbances.

There is little surprise to be found in the claims by the British Handley Page company who built the superb Victor bomber with its crescent wing, that it says it started investigating the crescent wing in 1946. Yet it omits to mention that just a few months earlier, in April 1945, the British had scooped up many drawings and research data on crescent wing design from the Arado company and its aerodynamicist Kosin, in Berlin – when the Arado factory was seized by British troops and accompanying experts. By 1946, Handley Page were looking at that data, and by 1951 were proposing a crescent-winged bomber – which became the `Victor’ – also using a T-tail and wing-root buried engines.What of straighter, less swept, or even unswept-wings, surely they could not offer the aerodynamic advantages of the swept-wing? Science soon revealed that after the benefits of a swept-wing at supersonic speed, an (almost) unswept, short, low aspect ratio wing planform could, with very thin aerofoil (as thin as 3 or 4 per cent thickness/chord ratio), also offer lower supersonic drag. Such `stub’ wings stemmed in part from the short stub wing learning as applied to von Braun’s rockets. At Mach 1.5, the lowest drag came from a highly swept-wing, but the next lowest drag, could, said the experts, come from a small, unswept-wing that, instead of delaying compressibility, just `fought’ through it into the supersonic airflow advantage.

It was at approach and landing speeds that such highly swept and, also unswept but thin aerofoil section wings, became problematic – unless dangerously high, thrust and fuel-hungry landing speeds were to be used. All sorts of lift generating – yet ultimately drag and weight inducing – flaps and slats might be used. But surely the advantages of a moderately swept all-wing could solve all these conflicting themes?

In terms of the powerplant revolution, the likes of Flight, and Mr Keith-Lucas, also postulated on two themes of great note, given the date of 1952. The first was Keith-Lucas’ suggestion that swivelling engine thrust/exhaust might be used to assist landing and the second was what type of airframe might be able to house an atomic reactor powerplant? An atomic-powered aircraft would require a large deep receptacle to house the reactor – was the answer the deep-hulled flying boat with all its internal room for a massive atomic engine? Or was the more likely receptacle for an atomic powerplant the deep wing box of a massive all-wing machine?