Introduction

If I were to truthfully and thoughtfully choose which of the two great passions of my life was the most important, I believe that I would choose aviation above astronomy or telescope building. Of the two airplanes I have owned and flown, one was an old World War II primary training airplane, and represented "old" aviation technology (technology extant in 1941). This beautiful old airplane flew very well, and was exciting to fly with its sliding canopy, which I left open most of the time. My scalp always tingled for thirty minutes or so after each flight.

The four engine airliners (airplanes) which briefly plied the Atlantic ocean just before World War II were radically different from the four engine airliners that would routinely cross the Atlantic after World War II. With this article, I would like to tell you how and why, and as is usual for me, lament the passing of the earlier technology, because the airplanes it spawned were very beautiful and elegant. What I want to show you is what was wrong with the pre-war airliners, and why their design philosophy proved a dead end, and the type they represented passed quickly into history after their very brief use on a very small scale before the second World War.

"Wing Loading"

Wings hold an aircraft up while passing through the air by displacing a volume of it constantly downwards; you have all seen and had explained to you the "Bournelli Principle" of how wings make lift; forget it- it is a myth. A wing does not have to be curved on top and flat on the bottom to make lift; should you not believe me, next time you are at an airshow and can find an aerobatic airplane whose design is dedicated to flight at all attitudes, including extended flight upside down ("inverted") study the shape of its wing carefully: it is curved by equal amounts on top and underneath. This type of wing is known as a "symmetrical" wing, as its top and bottom surfaces have identical curves. You may test the assertion I have made about how wings generate lift yourself: take a small piece of something that is flat, thin, and relatively rigid, and hold it outside of a car window as you are moving: hold it edgewise to the oncoming air as it passes through it while the car is moving, and then briefly tilt it up into the oncoming air: I assure you that it will quickly lift your arm up.

Thus, the wings of an aircraft provide upward lift through the famous elementary law of action and reaction: a wing accomplishes the action of displacing air downwards as it passes through it, while the reaction against this downwards displaced air is in the opposite direction on the wing: upwards.

Wing loading is simply a measure of how much weight each square foot of the wing carries; one merely divides the gross weight of the aircraft by the total square feet of the wing area of the aircraft to arrive at the figure for each square foot's part of the load. As a rule, aeronautical engineers do not talk about an airplane's "wings"; they talk about the wing in the singular; the fact that there is usually a fuselage in the middle of the wing is not relevant to the discussion of the wing; since the wings are not "tacked on", but rather the main spar continues uninterrupted through the fuselage, engineers talk about an airplane's "wings" as the airplane's "wing"; we will adopt that convention here, also.

Before the nineteen thirties, aeronautical engineers believed that there was probably an upper limit for how many pounds a square foot of wing area would carry; however, there wasn't any consensus as to what this figure might be, and it hadn't really occurred to aeronautical engineers or aerodynamicists that there was any pressing reason to test for what the upper limit might be; but World War II urgently "pressed" the aeronautical engineers to find out.

Flying Boats

At first, air travel across the Atlantic belonged solely to LZ-127 "Graf Zeppelin" and LZ-129 "Hindenburg"; these aircraft were not airplanes. They were giant "rigid" airships; they were unlike modern airships, whose shape is maintained by having the pressure of the lifting gas (helium) at a slightly higher pressure than the ambient pressure of the air outside. These giant rigid airships had full superstructures to maintain the shape of their hulls, contain the multiple gas lifting cells, and act as secure anchoring for the cabins, engines, and fuel and ballast tanks. They made crossing the Atlantic seem easy; they had enormous range, and despite the fact that they used dangerous hydrogen as lifting gas, they were otherwise very safe. Their "Achilles Heel" was of course the fact that they used the highly volatile hydrogen gas as the medium for their "static" lift. Helium was available, but not used, because America would not export it to Germany for use in her airships; at that time, only America (the United States) could produce helium.

But even at that time, there were engineers who believed that the future of trans-Atlantic flight would belong to heavier than air flying machines: large airplanes. And so the early development of trans-Antlantic four engine airliners (airplanes) began just before the mid-nineteen thirties. Before the end of the mid-thirties, the first of these four engine airliners had been thoroughly developed, tested, and entered service. Their careers would be brief, and not extensive.

These early, first four engine aircraft that had trans-Atlantic range were "flying boats". The newly emerging airline corporations that wanted to launch intercontinental airliner operations with airplanes had, as their first priority, safety. Although even by the nineteen thirties the engines used for large airplanes were relatively dependable, the executive offices of the new airline services were very cautious, and therefore elected for flying boats to be the first new airliners for their intercontinental services.

Flying boats, in an emergency, could "land" on the water! Landing on the water is, relatively speaking, a contradiction in terms, but one understands what is meant by it. These large flying boats could even very safely land on the water with all four engines inoperative. Therefore, their operators believed them to be very safe. If a flying boat became disabled and becalmed on the water, all she had to do was wait for a tow by a ship. For this contingency, their operators kept them well stocked with food and water, in order to endure a short stay on the ocean.

Flying boats were always marginal in terms of their profitability. To begin with, the idea of high density seating was neither contemplated nor was it practical for these aircraft; they were so slow that for passengers to be confined for the entire duration of the flight to only a seat would have made the trip uncomfortable for them. And so, they did not really carry enough fare paying passengers to be profitable.

However, they had an even more serious drawback: they were desperately short of range, compared to the eight hundred and four feet long luxury airship Hindenburg. These "Clipper Ships", as they were somewhat romantically called, were always almost out of fuel when they docked at their destination terminal. Why?

Wing Loading

In the nineteen thirties, aeronautical engineers were not interested in pursuing the "experiment" of less wing area for aircraft: less wing area meant higher stalling speeds, and therefore, higher landing speeds. And the concept of very high wing loading was simply not even entertained as a viable possibility (it wasn't, then, because the kind of engines required to drive a very highly loaded wing did not exist; this development had to await the development of the gas turbine engine, either driving propellers through a gear box, or used as turbojets).

So the flying boats had a wing, each one of them, with a large "wetted area"- a term used by aeronautical engineers to describe area in contact with the swiftly moving "boundary layer" of air passing over the surfaces of the aircraft; particularly, the wings represented a large wetted area. Wetted area meant: drag. Drag meant: low airspeeds. Low airspeeds meant a longer duration flight, and therefore: high fuel consumption. High fuel consumption meant: reduced range.

Nevertheless, this is what aeronautical engineers wanted to do in the mid-thirties: build big, slow, marginally profitable flying boats, and the airlines were convinced that this was the best technology that could be evolved for their intercontinental airliners. If the Hindenburg had been supplied with helium, and if World War II had not intervened, the future of intercontinental air travel very likely would have been the prize of the airship builders and operators; their use might have perhaps lasted a decade, or maybe longer.

The China Clipper

On the east coast, out of New York harbor, the Boeing 314 "Silver Clipper" operated to England; from England, the Short Brothers' "Sunderland" flying boat operated to New York; both were pretty much out of gas when they got to port, each way, and didn't deliver a very large crowd of passengers, either. They were very safe, though: big, powered gliders that could land on the water at a safe, low speed, on their boat shaped, stepped hulls.

On the Golden west coast, Martin's very beautiful four engine "China Clipper" was ready to begin her service for Jaun Trippe, president of Pan American Airlines. Jaun Trippe and Roosevelt were going to build a Pacific Empire (one wonders if the Japanese were watching) and Pan American was building hotels and facilities in the Pacific for the new fleets of Sikorsky, Boeing, and Martin "Clipper Ships". Alas, it was not to be.

World War II obsoleted all of the Clipper ships immediately. However, it is interesting to relate the anecdote of Captain Edwin Musick's maiden flight to Hawaii in the China Clipper. Hawaii is a pretty good stone's throw from the mainland, and there were few airplanes (other than a couple of military types) that could carry any payload from San Francisco to Hawaii. The beautiful Martin Clipper ship could. Captain Musick took the China Clipper to Hawaii; the city wanted to see their beautiful Martin Clipper ship overhead when it returned (Martin Aircraft had truly designed and constructed a very beautiful flying boat) and the good captain was not going to disappoint them, even after looking at his fuel guages as he approached the Golden bay, and noticed that they were virtually on empty!

He told interviewers later that when he flew over the city, he was virtually "flying on fumes"; he made it seem like it had been a risky thing; however, any good pilot knows that Captain Musick knew he could have glided back to the bay for a perfect and safe landing, even if all four windmills became quiet and stiff in the slipstream over the middle of the city, or he would not have risked it. After all, the China Clipper was mostly wing- it would have glided very well.

Bristol's Folly

The first "long range" four engine bombers of World War II had low to moderate wing loading; they could easily reach their targets in Europe from England with a payload and return. Longer trips were pretty much out of the question, but not really an issue because of the availability of the English air bases.

However, a look into the crystal ball of the future of the war was suggesting the necessity of airplanes capable of carrying larger payloads and/or capabilities for longer stage lengths for missions. Before the war was over, America would launch the "Peacemaker" design and development project, for a giant bomber capable of bombing Germany from the American east coast, and returning with its crew again. This resulted, after the war, in the giant Convair B-36 "Peacemaker". England, early in the war, was also thinking about a giant bomber; mostly they were interested in greater payload; however, greater payload in peacetime could be translated into greater range (heavier fuel load for longer endurance).

Bristol aircraft proposed a giant bomber in response to invitations from the Air Ministry and Ministry of Defense, and though they did not receive any contracts for this large bomber (no one else did either; the British just kept frantically building Lancasters, Sterlings, and Halifaxes- mostly Lancasters) they resurrected their proposal after the war, as modified for an airliner, in response to Lord Brabazon's committee to recommend what kind of civil airliners might be needed if and when Britain and her allies won the war. One of the types this committe turned their gaze on was a transmogrified version of Bristol's giant, neglected bomber design.

The Bristol "Brabazon" (named after Lord Brabazon) was a truly monstrous airplane -- it was actually larger than the giant B-36 "Peacemaker" (larger, but not heavier). Bristol built a truly elegant, rather beautiful large airplane, with eight colossal radial engines "buried", English fashion, inside the very thick wing (crew members could reach the engines in flight). The engines were paired, two to a nacelle, driving the Brabazon's six bladed contra-rotating propellors through a very complex and nightmarish transmission. Here is a picture of the giant Brabazon on one of her early test flights:

What is the matter with this picture?

In case you haven't guessed, it's just this: the colossal, unnecessary wing area. What could Bristol's, the Air Ministry, and BOAC possibly have had in mind when they opted for an airliner with such a colossally large wing, for such generously low wing loading? The answer is obvious enough to suggest itself: they wanted an airliner that could land very slowly, so that it could land anywhere.

What no one seems to have thought about were the penalties that this design dedication would have: low cruising speed due to the enormous parasitic drag from all the air rubbing against the huge surface area of that wing, resulting in unnecessarily higher fuel consumption because the stage lengths for trips would be long, time wise. In fact, this was the reason that the Brabazon had to be so large: she had to be large enough to carry the huge amount of fuel to make her long distance stage lengths possible.

Even so, she still had to be built with an unnaturally light superstructure; the British would later reap disaster and tragedy when they tried to do this again with another airliner: the DeHaviland Comet, the world's first turbojet propelled airliner.

Ugly cracks began appearing in the giant Brabazon's stuctural components after only a few hundred hours' flight testing. "Metal fatigue" was a newly discovered phenomenon then, and underappreciated: this was especially obvious after the investigations into the two Comet jet airliner disasters (these two disasters ruined the Comet's reputation, even though the defect was remedied; in any case, the new Boeings could carry far more passengers than the lightly built Comets with their ineffecient radial flow engines).

The British lacked the foresight that the Americans had; the Americans rightly assumed that the rest of the world's capitols, if they wanted American trade in and out of their cities, would dutifully extend their runways to the required lengths for the American Lockheed, Douglas, and Boeing airliners, with their much higher wing loading and their much higher landing speeds.

It was Boeing engineers who recognized the requirements for very high wing loading in order to get their "Superfortress" bombers with useful payloads over stage lengths exceeding two thousand five hundred miles; the nearest base they could secure to attack Japan from was Tinian Island in the Pacific, a long ways from Japan. And so Boeing went through the very considerable agony of bringing the concept of the large multi-engine aircraft with very high wing loading to fruition; after the war, the Superfortress bomber was developed into their first intercontinental airliner, the model 377 Strato Cruiser, with its elegant upper deck connected to the lower deck with a spiral stair case. The Douglas airliners quickly followed into service upon the heels of the Boeing transport, and then the beautiful Lockheed Constellation became popular. The "Super Constellation", with its compound engines (part reciprocating, and part gas turbine) could fly, with the throttles all the way to the wall, at nearly 375 miles per hour!

The poor Brabazon never had a chance. At full chat, the eight coupled-in-pairs radial engines could push the big airplane at only 250 miles per hour. And then, in less than a decade and a half, the reciprocating engine airliners themselves passed into history, as the gas turbine engine made its appearance, changing intercontinental aviation forever. The new turboprop airliners had even higher wing loading, and could fly even faster than the Super Constellation. Almost simultaneously the turbojet driven airliner appeared on the world history stage of aviation, and wing loading went up to "impossible" amounts: airliners were built and entered service that had well over one hundred pounds of wing loading per square foot.

Older aeronautical engineers, designing in the nineteen thirties, would have said it was impossible. But today's dreams have a way of becoming tomorrow's realities.

One kind of airliner, confidently predicted to come into existence, never did: the ballistic airliner. When I was a little boy, I was excited by pictures, paintings by Chesley Bonestell and others, in popular books for young people about the coming age of the flowering of aerospace technology, including space travel, of rocket propelled swept wing airliners climbing into space, propelled by the thrust of their large, single liquid propellant rocket engine, for their long, elliptical ballistic coast to Europe or the Orient, to re-enter the atmosphere and glide to a landing as an airplane, delivering their passengers literally breathless after a very quick trip a third of the way around the globe. The ballistic airliner never happened.