May 2010 ONE OF THE MORE persistent hoaxes drifting about on the Internet concerns an airplane called the Kalinin K-7. Built in the early 1930s, the K-7 was Russian, and big. Really big. Russian designers those days displayed a positive passion for sheer size; Igor Sikorsky’s Ilya Muromets, for example, which flew just 10 years after the Wrights’ first powered hop, had four engines and a wingspan of more than 100 feet. The British firm of Handley Page built something similar. But the K-7 dwarfed them all. Its wing was an immense ellipse with a span of 174 feet — just 20 feet shy of a 747’s — eight feet thick and 35 feet from leading to trailing edge at the center. In a civil version, 120 passengers were to be seated spanwise within the wing. Twin booms supported the smallish empennage, and six engines of 750 horsepower each stood side by side on its leading edge. One or two pusher engines — reports differ — were added when the gigantic monoplane, which was of steel construction, was found to be heavier than anticipated. Its reported all-up weight was 84,000 pounds.
The K-7’s landing gear was unusual, being carried in two pods resembling amphibious floats but about the size of motor homes. In the military version, these were equipped with machine gun turrets. They were connected to the main structure by a thicket of struts and by a couple of very large tubes that, I suppose, housed stairways for the gunners.
All this is extraordinary enough, considering the year, but, on the principle that nothing is so impressive that it cannot be improved by a little falsification, someone has produced several renderings of a sort of Megalopseudokalinin — it deserves a dinosaur-like name — and some fanciful text to accompany them. I’m not sure what kind of software is used to create this kind of thing — maybe something for game design, where fantastic structures are standard equipment — but the concoction has at least 18 engines and bristles with guns, including a couple of turrets that seem to have been borrowed from a battle cruiser.
Some people leave skepticism behind when they turn on their computers, and I have seen this bit of skillful fakery excitedly passed along as a genuine Russian airplane, claimed to have a wingspan comparable to the Empire State Building laid on its side — although I think the effort would be wasted, since the height of the Empire State Building is well-known. It is 1,250 feet, omitting the antenna, or nearly five times the wingspan of an A380.
Another fantasy monster that, unlike the actual K-7 but like the Megalopseudokalinin, never became a reality was the so-called Airliner No. 4 of a well-respected industrial designer, Norman Bel Geddes. Proposed in 1929, I suspect before the stock market crash, Airliner No. 4 was a gigantic thing with a wingspan of more than 500 feet, intended to carry 600 well-heeled passengers across the Atlantic at a stately 87 knots. Its amenities were steamship-like — staterooms, ballrooms, dining rooms, a main salon with a 35-foot ceiling — and arranged on several levels. For landing it had, not unlike the Megalopseudokalinin, two gigantic pontoons; an airport of sufficient size was unimaginable. It was to be propelled by 20 1,900 hp engines disposed along an auxiliary wing above the main one, and would carry six spare engines to be swapped in if needed during a two-day trip from Chicago to London.
Futurist fantasies are a good way for an industrial designer to get a little publicity during a slow spell, but the visionary Bel Geddes took the precaution of consulting with an airplane designer, one Otto Koller, who had reportedly worked for the old Pfalz Aircraft of World War I fame, to ensure that his dream could actually fly. A flying wing design of moderate sweep and aspect ratio, it was aerodynamically sound and quite good-looking in a Buck Rogers sort of way. Pfalz airplanes had always been well-streamlined, and the 4, like the Douglas DC-3 of which it was a contemporary, clearly took streamlining seriously. Whether it could have been equipped with all of the luxurious amenities envisioned for it, however, while remaining within the projected empty weight of 330 tons, is very doubtful.
It is often pointed out, in connection with the growth of animals, that the weight of things increases in proportion to the cube of their linear dimensions — the ones you would measure with a ruler, such as span or fuselage length — and that weight must therefore sooner or later outrun strength. It used to be claimed, I don’t know on what evidence, that what we then called a brontosaurus — it has since become an apatosaurus — must have spent its life semi-immersed in water, since it was too heavy to be supported by mere bones. The claim might have been bogus, but the principle was sound; an ever-expanding apatosaurus would eventually arrive at the point where it would have to be all leg.
The rule of cubic growth, however, applies only to solid objects. An airplane is not solid; it is for the most part a thin shell, and so the weight of the airframe is more nearly proportional to its surface area than to its volume. The palatial empty spaces within Bel Geddes’ Airliner No. 4 weighed nothing. Very roughly speaking, then, the weight would be proportional to the square of the linear dimensions, as would wing area, and so one could expect an enormous airplane to have roughly the same general proportions as a much smaller one. We observe this to be the case; an A380 is not markedly different in shape from an A310. Indeed, even the sizes of structural parts like spar caps and fuselage skins remain in proportion, since aerodynamic forces, like weight, are more closely related to surface area than to volume. As far as I can tell, there is no fundamental limit to the size of airplanes. The same is not true of birds; their muscles are solid even though their bones are largely hollow, and so there is a natural constraint upon their growth.
What strikes us today as most unrealistic about Airliner No. 4 was its use of space. It was probably not apparent in 1929 that airliners would soon attain speeds of several hundred miles an hour, so that the durations of most flights would not justify installing, say, a barber shop or a ping-pong table aboard every airplane. Furthermore, since the financial return from operating an airliner depends on how many people can be crammed into it, thinly populated interior spaces do not make economic sense if they compromise performance, as opulently furnished staterooms and vast salons obviously must. Futuristic as it was, Bel Geddes’ vision failed to foresee that the operational economics of airliners would not duplicate those of luxury liners. Indeed, modern air travel is, with various degrees of detail modification, more like steerage.
Today, the world’s largest real airplane is, to no one’s surprise, again Russian. It is the Antonov An-225 Mriya. I wish I could tell you that Mriya is Ukrainian for hummingbird, but it’s not. The gigantic Mriya was built to transport the Buran, a near-clone of the Space Shuttle. The Buran made a trip to Paris on the back of the 225 in 1989; but it went to space only once, the previous year, and was unmanned. It was destroyed in 2002 when its rusting hangar collapsed from sheer neglect. Consequently, only one
An-225 was built. Not a fresh design, it was made by stretching an An-124 (which was Russia’s answer to the C-5), adding a 50-foot center section with two additional engines to its wing, and redesigning the empennage with twin fins set endplate-fashion at the tips of the stabilizer in order to remove them from the wake of the Buran riding piggyback. It continues in service carrying large cargo; last year it airlifted a generator weighing 350,000 pounds from Germany to Armenia, this having been the heaviest single object ever carried in an aircraft.
Immense airplanes continue to be proposed and occasionally even built. It is difficult to select a single measure of an airplane’s size, but wingspan is a strong candidate, and by that measure we seem to be near some sort of limit. Nothing has yet come close to a 500-foot wingspan, let alone a 1,250-foot one. The sizes of airports are fundamental constraints with which even the comparatively small — 262-foot span — A380 had to struggle. The record for wingspan is still held by Howard Hughes’ sexagenarian Hercules, better known as the Spruce Goose, at 320 feet. Wingspan, however, is a poor indicator of weight for airplanes of different eras. The Spruce Goose, powered by eight Pratt & Whitney four-row, 28-cylinder radials of 3,000 hp each, had a design takeoff weight of a mere 400,000 pounds; that of a C-5 Galaxy is 840,000 pounds, a 747-8 975,000 pounds, an A380 1.2 million pounds and the An-225 1.3 million pounds.
One million pounds is the weight of a solid steel cube 12.4 feet on a side. Could the Wrights, or even Kalinin, ever have imagined supporting that on air?