ANALYSIS
Flying wings: why everybody still talks about them | Part 1

Image : Airbus

VALIUS VENCKUNAS

In September 2020, Airbus presented their project ZEROe – three hydrogen-powered concept aircraft. A small conventional jet, a turboprop, and a blended-wing design, the trio quickly captured media’s attention, which, frankly, was their primary job.

Of all three designs, the spotlight was squarely taken by the blended-wing one. It stirred imaginations and produced headlines promising that this is what the airliner of the future looks like. Certainly, it was not the efficient engines or the new kind of fuel that resulted in such attention. It was an unusual form of the airplane.

It stood out from others because of its flying wing shape. And it marked nine decades of flying wings being the airliners of the very next generation, the one which is just around the corner.
What is a flying wing?

Those familiar with the matter will no doubt raise their eyebrows at the misuse of the term “flying wing”. The ZEROe concept actually does not belong to this category. It is simply a tailless blended-wing-body (BWB) design.

In the case of true flying wings, the aircraft does not have a fuselage at all, or alternatively – the entire fuselage is in the form of a wing. It may have slight protrusions for a cabin, engines, or stabilizers, but the idea is to have no definite “sections” of the aircraft's body.

In a BWB design, the fuselage exists, but its transition into wings is smooth, without a dividing line. In some cases, the fuselage itself acts as a wing too, providing some lift.

In theory, the flying wing and the BWB design are two different beasts.

In practice, they are constantly misidentified, thrown together, and largely constitute the same thing not only for the uneducated public but for aviation enthusiasts and professionals too. Part of it is the notoriety of the term “flying wing”, as the shape of short, vaguely triangular aircraft is automatically associated with it.

Part of the confusion comes from the practical standpoint, as both designs are an answer to the same problem: how to make an aircraft more efficient.

In any case, it is easy to miss a slight change in angle and thickness at the point where a fuselage ends and a wing begins. Lo and behold, the term “flying wing” gets attached to any tailless BWB design.

Slightly before the ZEROe, Airbus unveiled another futuristic project – the MAVERIC, an “airliner of the future” supposed to yet again revolutionize air travel. It was a clear BWB design. The main promotional image, used by the company, had “Flying wing demonstrator” written on it. If Airbus calls their tailless BWB designs flying wings, maybe there is no sin in being a bit imprecise.


(Image: Airbus)

The Renaissance of flying wings

MAVERIC and ZEROe stand on heaps of previous research, both by Airbus and its competitors.

Notably, in between them was the maiden flight of the Flying-V – KLM’s sub-scale technology demonstrator, a proper flying wing. In the future, it is supposed to compete with Airbus A350, having a similar range and passenger capacity, but much better fuel economy, mostly thanks to the hyper-efficient design.

A few years earlier, in 2017, COMAC tested the “Ling bird B” BWB demonstrator, produced by their enigmatic Dream Studio.

Before them, there was the X-48: NASA’s not-really-flying-wing BWB design, of which a couple of prototypes were tested between 2005 and 2013. It was initiated as a project by Boeing Phantom Works, with an intention to produce a military cargo aircraft at first and maybe use gained knowledge for an airliner design later.

NASA itself has conducted wind tunnel tests with tailless BWB designs at least since 2003. Even before that, Airbus was heading The VELA Project – a design study for (again) misnamed “flying wing” – Very Efficient Large Aircraft, conducted between 2002 and 2005, supported by the European Commission and joined by almost two dozens of research institutions and companies.

Quite bizarrely, two aerospace giants even had one joint project. In 2001 Russian Central Aerohydrodynamic Institute (TsAGI) was joined by both Airbus and Boeing for a study on the feasibility of large capacity flying wing aircraft, resulting in research papers.

By that time, Boeing had already purchased McDonnell Douglas, which was conducting intensive research of the potential of flying wing design for commercial air travel at least since 1990. By 1997 – right before the purchase – it was about to start constructing a large-scale model of BWB-1-1 – an airliner with a passenger capacity of 400 and an entry into service in the near future of 2005. It had three engines and was almost identical to what later became XB-48.

Further east, the Tupolev design bureau started working on the Tu-404 in 1991; of its two possible designs, the “flying wing” (again, a tailless BWB design) was considered as the most promising. Engineers at TsAGI were developing their own project - “Flying Wing-900”, which resulted in several designs and ended in the mid-90s.

Together, all of these attempts constitute what could be called the Renaissance of a flying wing. Several prototypes, a dozen of projects, and countless research papers on everything from aerodynamics to logistics of commercial tailless BWB aircraft were a result of a simple idea that flying wing-like airplanes are feasible for commercial operations. Why was that?

The Dark Age of flying wings

According to Russian scientists from TsAGI, the talks of applying flying wing configuration to passenger or transport airplanes first appeared in 1989.

McDonnell Douglas started their research at approximately the same time too. Between 1987 and 1989 NASA was conducting several preliminary studies into flying wings, including an ambitious (and secret) Mach-2 capable oblique flying wing transporter.

On one hand, it seems quite clear that the Renaissance took root in the late 80s. Which, undoubtedly, puts Northrop Grumman B-2 Spirit as at least one of its culprits.

Revealed in 1988 the B-2 quickly inserted itself into the mass consciousness as an image of the future, together with several F-117-inspired concepts of the supposed next-generation stealth fighter, which also featured tailless BWB design.

The B-2 is mentioned in almost every subsequent research paper on the matter. For civilian engineers, the success of flying wings in the military sphere meant that the design has potential. It works, and all we need is to import that concept into the civilian market. That was enough to drag the flying wing from the shadows where it had lurked through the whole Cold War.

Those shadows were cast mostly by the supersonic airliners. Their dawn seemed just around the corner for the most part of the second half of the 20th century and flying wings did not lend themselves for supersonic cruise very well. BWB designs – even tailless ones – were there, but mostly in the military sphere.

The attempts included the Spanloader project, managed by NASA in the 70s. It resulted in Boeing, Lockheed, and McDonnell Douglas presenting concepts for super-large transport aircraft with cargo bays inside their wings.

There was also the long-running and ultimately unsuccessful attempt by Aereon, which was developing its Dynairship ꟷ a family of flying wing-shaped airships ꟷ between the 60s and the 90s.

But otherwise, the civilian side of things was too preoccupied with supersonic airliners. Through the 50s flying wings still sometimes appeared on the covers of popular science magazines, but those instances were few, and they constituted just an echo of what came before them: the Golden Age of the flying wing.

This article was originally published on AeroTime News on January 7, 2021.

Flying wings: why they never succeeded, and probably never will | Part 2

Image : Wikipedia / Unknown author


The Golden Age of flying wings

The end of the Golden Age is much easier to pinpoint than the start. It was the 50s. The jet age preoccupied mass consciousness with sleekness, and flying wings are difficult to make sleek.

While the image of a flying wing as an airliner of the future may have subsided for that reason, militaries did not care about an image that much and experimented with the concept up until completely succumbing to the supersonic allure.

There were several American projects for nuclear-powered flying wings from the late 50s. There were several early Soviet supersonic fighter jet projects from the Cheranovsky bureau that never went beyond propaganda. Some even call British Armstrong Whitworth A.W. 52, de Havilland D.H. 108 and Avro Victor flying wings, despite all of them having quite a pronounced fuselage and maybe just a trace of BWB design.

In the commercial sector, the last breath of the Golden Age came in the form of late Northrop’s designs.

Jack Northrop was, quite likely, the world's most stubborn proponent of a flying wing. His YB-35 heavy bomber was almost accepted into service in the 40s, and its jet-powered upgrade, the YB-49, became a darling of aviation enthusiasts after bombing Martians in the 1953 version of The War of the Worlds.

It is not entirely clear whether the idea to turn the YB-49 into an airliner was considered seriously, but it was quite definitely popular with the press. Often called Northrop 6, the “Flying wing jet air-liner of the future” promised to be a fast and luxurious way to cross the Atlantic. In some renditions, it had a wide passenger compartment in the center and large lounges on both sides of it. In others, most of the internal space was filled with individual suites and a lounge traced the leading edge of the wing.

Such a layout was not accidental. It was a legacy of previous flying wings that took inspiration not from airplanes, but from ocean liners.

Bel Geddes Airliner Number 4 is, of course, the best known of them. A floatplane with a wingspan of 161 meters (528 ft), 9 decks and 26 engines, it would house a dining room, a bar, a gym, suites for 450 passengers, and an internal hangar for parasite aircraft.

It was not as much designed as dreamed up by Geddes with the help of engineer Otto A. Koller in the late 20s and early 30s. Despite assurances that the newest scientific advances would easily allow such an aircraft to be built, its unrealistic nature later became a joke in itself.

Although the Number 4 was the poster-child of the era, various kinds of flying wing-liners were almost omnipresent. From the covers of Tom Swift novels to glossy advertisements, to the very best art Popular Mechanics covers could offer, they enticed with the prospect of having an ocean cruise, but in the air.

Some German firms, such as Junkers and Rumpler, proposed several variants with a bit more realism than the Number 4 (still featuring suites and over-100-meters wingspan), while others allowed their ideas to just go to the Moon. In 1933, British newspaper The Sphere described (and spectacularly illustrated) a proposal for a seaplane capable of hauling 1500 passengers in its single 183 meter-spanning wing. Drawings depict a monstrosity whose floats alone could work as ocean liners.

We have approached the point where yet another discussion about what constitutes a flying wing has to take place. The designs from 20s and 30s, once again, seldom fit into the category. Many of them have protrusions that could be identified as fuselages. Some of them even have short, stubby tails with stabilizers. But people called them flying wings anyway.

The reason for that is, once again, purely practical. The wing in all those projects was the main fuselage, two most prominent elements of an aircraft combined into one for efficiency. All the additional elements were a deviation from the norm and that norm was a massive, mostly straight wing with glass-adorned viewing gallery in the leading edge.

There was this strive for a simpler form, even if it has to carry as much Art Deco décor as its underpowered engines can lift. Such was the image of an airliner of the future.

So where are they?

Every person writing the story of the development of flying wings is obliged to start it from their own country. For Americans, it is Northrop’s experiments in the 30s. For Russians, it is Cheranovsky’s gliders from the 20s. For Britons, it is early tailless airplanes built by John William Dunne in the 1910s. French go all the way back to the 1870s, when Alphonse Pénaud and Paul Gauchot patented something vaguely resembling flying wing aircraft.

It is easy to come up with arguments why one or another of them was not really a flying wing, but the reality is – if an aircraft is primarily composed of a wing housing a cabin, somebody will call it a flying wing. The utilitarian aspect of combining a wing with a fuselage is, possibly, the most defining feature of this nebulous category.

It is also the reason why flying wings exist.

The idea is to eliminate elements that create drag without creating lift. So, the fuselage has to go, or transform into something resembling a wing.

As a result, efficiency is the main selling point of flying wing aircraft. Various studies published between the 80s and the 2020s suggest that every flying wing design its authors came up with uses 15% to 30% less fuel than conventional jets. Here lies the allure to use flying wings for passenger service and the reason why most military designs that were adopted (or came close to adoption) were long-range bombers.

The efficiency comes with a caveat: the wing, or at least its center, has to be thick enough to accommodate the payload, be it bombs, cargo or passengers.

Bombs are the smallest of them, resulting in the B-2 and the YB-49’s relative sleekness. Cargo is a bit more difficult, which is why NASA Spanloader project resulted in some of the largest aircraft ever designed. Its documentation states that without immense size, the whole idea is just not worth it.

The same goes for airliners, which is why flying wings from the Renaissance of the 90s are rarely aimed at less than 300 passengers and sometimes go over 1000. The height of a cabin, together with ventilation systems above and cargo hold below, dictates the minimum thickness of the wing, which in turn defines the size of the aircraft (Russian double decker projects do not count, their logic is a bit special).

It also means that the cabin has to have a certain width, which is much, much greater than the width of even the largest real-world wide-body aircraft. McDonnell Douglas’ original airliner concept from the 90s features a ridiculous 43-abreast, 3-6-5-5-5-5-5-6-3 seating scheme. The idea was later carried over to Boeing and NASA X-48 and is prominently featured in its descriptions. A Popular Science issue from 1995 features a cutout of such a plane, where these rows and rows and rows and rows and rows of seats are full of happy, colorful people.



Seating scheme from early Mcdonnell Douglas designs (Image: NASA)

Problems such an arrangement brings are as plentiful as they are unsolvable with the 90s technology. First off, in the case of an emergency, all those happy people have to be evacuated and it has to be done quickly. The task is difficult enough with modern jumbo jets, but flying wings by design have much less exits. The issue of evacuation, as well as simply mind-boggling boarding time, come up time and time again as an argument not to build planes larger than the A380.

Then there is comfort. In flying wings from the 30s, passengers with their tailored suits and evening dresses stayed in personal suites and came out only to communal areas situated in the front or the back of the wing. Modern airlines do not work like that and most passengers would have to sit in a space which is virtually enclosed. Since the amount of windows per seat is almost non-existent, most designs feature internal compartments, or simply speaking – large windowless rooms with low ceiling. This flies in the face of the very basics of aircraft interior design, which rests on creating an illusion of open space.

Yet even this issue is small in comparison with another one. As most seats are situated quite far away from the center, a roll of an aircraft would subject some passengers to extreme vertical motion. Coupled with an enclosed space, the experience could very well amount to torture.

This is not even speaking of problems related to aeronautics and economics. Flying wings would require partial redesign of ground infrastructure. Everything from jet bridges to cargo containers would have to adapt to each specific design, as those compatible with KLM Flying-V would doubtfully fit the ZEROe.

Also, flying wings are difficult to pressurize in comparison with common tube-shaped fuselages. Some research suggests the increase in structural weight makes the advantage in efficiency negligible.

Then there is the problem with modifying the fuselage. Tubes can be shrunk and stretched without much fuss, creating variants of an airplane tailored to each carrier’s needs. Flying wings can not.

On top of that, they are notoriously difficult to control. Flying them would mean much more emphasis on automated systems. While it seems as an easy problem to solve nowadays, it does not help when piled up with all the other difficulties.
But why do people still talk about them?

On one hand, many problems can be dismissed.

Evacuation? Larger passageways and stricter procedures. Also, aviation safety improves all the time, and we might not need so many strict requirements in the future.

Comfort? Large screens, virtual reality goggles, even some good lighting can solve most of it. Some companies are even looking into building conventional planes without windows.

Torture while rolling? Well, turns do not have to be so sharp, an aircraft can roll slowly. Airliners are not fighter jets after all.

Advances in digital design, avionics and composite materials take care of the rest.

In the end, it is a question of investments. If airlines want to reap those 15% to 30% fuel savings, they will have to make the leap one day and many studies claim that every day of flying antiquated tube-and-wing airplanes just brings the revolution closer.

On the other hand, the research is far from conclusive. Massive cuts in fuel consumption were reached in recent decades by conventional means – better engines, better materials and more automation. There might be a limit to that in the future, but it is so far away yet that neither manufacturers nor airlines can see it.

Quite a lot of people who worked on early McDonnell Douglas design came out with their pessimism about the concept in later years. At the end of the X-48 program, Boeing concluded that it was simply not worth it. The latest generation of Airbus flying wings – the MAVERIC and the ZEROe – seem to be much smaller than its early attempts with VELA, which may solve the comfort problem, but put the efficiency into question. Russian aircraft manufacturers discarded their flying wing ideas long ago, and it is unclear if COMAC Ling bird B is even a real project.

KLM Flying-V seems to address most of the problems quite well and the airline has partnered with Airbus for its development. But there is no information in regards to when, or even if it is going to be produced. Airbus says their flying wings could fly by 2035, which is very optimistic, and it is a decidedly less ambitious project than the Flying-V.

Safe to say, even after manufacturers hit rock bottom with improvements to conventional designs, flying wings will take decades to appear. The current crisis, if anything, just pushed that date further away.

This does not mean that designs of the Renaissance are pointless. While they may be considered as a way to build up on the research that was started in the 80s and 90s, there is another, much clearer goal.

Another, much clearer goal

Bel Geddes Airliner Number 4 plays a central role in the Gernsback Continuum, a short story by an influential science fiction writer William Gibson. Almost a manifesto of the 80’s disillusionment with opulent techno-optimism of the genre, the story makes fun of the aircraft almost every time it mentions it.

For its main character, Airliner Number 4 is a semiotic phantom – an artifact of the future that was dreamed of, but never materialized. It became stuck in mass consciousness, put there by hopelessly naive engineers and designers of the 30s. Just like an UFO or a Bigfoot, it sometimes appears out of nowhere to haunt people living in a world where laws of physics work and there are no ballrooms in trans-Atlantic airliners.

Flying wings of the Golden Age will remain in the future that never came. Some early Renaissance designs are already there – the McDonnell Douglas BWB-450 and the Tupolev Tu-404 were supposed to enter into production in the early 2000s. There is a high chance they will be joined by Airbus flying wings in the 2030s.

That is because flying wings are destined for it. They are a symbol. A shortcut, which basically spells “innovation”, and companies do not shy from using it. It has been like that for almost a century and the trend is not going to stop any time soon. Airbus ZEROe program would not attract as much attention and would not look as innovative without a flying wing in it, and COMAC Dream Studio, a team of young engineers, would not be as cutting-edge and daring hadn’t they developed a flying wing-like airplane.

It does not mean that the design is not useful, or that there is no real future for flying wing airliners. It just means that for many – PR departments, investors, the media – its image is much more important than its practicality and there is no point in hiding from this simple fact.


This article was originally published on AeroTime News on January 10, 2021.