Build Me a Plane
December 1945 Flying Age including Flying Aces

December 1945 Flying Age Table of Contents These pages from vintage modeling magazines like Flying Aces, Air Trails, American Modeler, American Aircraft Modeler, Young Men, Flying Models, Model Airplane News, R/C Modeler, captured the era. All copyrights acknowledged.

The Douglas DC−3 (C−47 was the military version designation) has always been my favorite twin engined commercial airplane. Its nickname of "Gooney Bird" amongst troops is undeserved IMHO. The DC−3 is credited with launching the commercial airline industry, and its C−47 version was listed by Dwight D. Eisenhower as being on the most important tools for winning World War II. Edward F. Burton, Chief Engineer at Douglas Aircraft Company, runs through the evolution of the DC−3 and it predecessors and descendants in this December 1945 issue of Flying Age magazine. December of 1935 marked the maiden flight of the DC−2, was was a direct follow-on the the DC−2. A single DC−4 (4 engines) was built and delivered to Japan. Then a DC−5 was built (high-wing version of the DC−3) but never went into production. The 4-engine DC−6 entered commercial service in 1946, followed by the very popular DC−7. A coaxial, counter-rotating pusher prop model DC−8 (not to be confused with the 4-engine commercial DC−8 jet) never made it off the drawing board. The next iteration was the C−54, which was a huge success with four engines and tricycle landing gear. It became the first dedicated presidential aircraft (aka Air Force One). Finally (at the time of this "Build Me a Plane" article), the C−74 Globemaster made its debut in September of 1945, right after World War II ended. 

Build Me a Plane

It takes years of patient, skilled, heart-breaking man-hours to evolve a plane that will do its job.

By Edward F. Burton

Chief Eng., Douglas Aircraft Co.

No airplane is ready-to-wear. They're all custom-made to some pretty exacting requirements.

When you buy your ticket, walk up the gangway and say "hello" to the hostess, you take your airplane for granted. It will fly to the precise destination you want on a schedule neatly predicted. There will be a seat that can he inclined at a proper napping angle. There will be ventilators that you will manipulate without a second glance. There will be ash trays at your hand.

But most thoroughly taken for granted of all the airplane's many qualities is that it will fly. And what is more important it will have the flying characteristics most needed on the particular route you must take. In short, it fits precisely.

And the story behind that perfect fit is one of meticulous planning, of countless highly skilled man-hours, of tests, failures and a success that is cumulative, growing out of all the previous successes and failures in the business.

The airlines know, or think they know, exactly what the passenger and the cargo shipper want on any particular hop. And they come to the aircraft companies with a list of requirements. We must have so much room for cargo, they say. We must have so many passengers, and this percentage of them must have berths. We must be able to feed them. The crew must have quarters. Then, it will have to go at this speed, have that cruising range, be able to fly in weather like this or that. There's what we want; they conclude, go build us a plane to do the job cut out for it.

And the aircraft companies examine the list of requirements, go over all the blueprints of previous planes, acknowledging this factor and deciding to reject that one.

A case in point is the DC-8, Douglas' latest model which with its dual props in tandem right behind the tail, promises to create a stir in engineering circles and in air passenger circles. But it is really a product of all that went before it. It is the final phase in a development that began with the DC-1 back in 1933.

The DC-1, which cruised on its two Wrights at 170 miles an hour, was the first twin-engine airplane capable. of flying and climbing with a full load on only one engine. This airplane also had retractable landing gear, but it was not entirely enclosed, It was this ship that the late Eddie Allen, during a test flight prior to its public appearance landed with the gear retracted. Eddie's only comment on debarking was, "Oh, for pity's sake!"

Before the DC-1 flew, however, much of the basic research from which all our transports have developed, was completed. Aerodynamic calculations were particularly concerned with performance and control at all attitudes of flight, both in normal and single-engine operating conditions. Special designs of the controls, wing, and fairing made possible continued, single-engine operation at high altitudes with sufficient controllability to insure safety in meeting emergencies. Performance studies to obtain the desired velocity, range and climb led to the choice of the bi-motor type with controllable pitch propellers and high-lift wing flaps. The flaps gave a gain in lift of thirty-five percent, and a drag increase of 300 percent. Three complete wings were tested with various modifications of fuselage fillets, tail surfaces, landing gears and tail wheels. Several sets of ailerons of normal and special types, six arrangements of high-lift flap devices were among other special arrangements tried.

Some of the early models tested in the wind tunnel showed instability and tests revealed that it was necessary for satisfactory stability to have a hitherto untried arrangement of center of gravity, wing sweepback and general configuration. The actual airplane was built in accordance with this new plan and its stability in flight proved to be exactly as predicted. Had not the wind tunnel tests been made, it is possible the DC-1 would have proved unstable, since ordinary investigation had indicated the original arrangement would be satisfactory.

As one result of these tests and changes, the total resistance of the complete airplane was less than twice the resistance of the wing alone!

Wind tunnel tests indicated the best aerodynamic arrangement, but did not determine the location and proportion of all structural details. To work it all out, we constructed a mockup with wooden frames, covered with heavy paper to stimulate the metal sheet covering. All frames were made in the exact sizes and locations of those in the actual airplane. A complete floor was installed and various seating arrangements tried to obtain maximum roominess and comfort. Final arrangement placed each passenger chair opposite a window, gave' ample leg room, wide and unobstructed aisles, and allowed a passenger over six feet tall to walk erect in the cabin. Many designs of passenger chairs were tried before we finally chose an aluminum alloy structure, so designed that the angle of inclination of the entire seat could be changed and the back adjusted for sleeping. The seat was also reversible, permitting passengers to face either forward or to the rear. This was the beginning of passenger comfort in the air.

As for structural development, the studies of aerodynamics and general arrangement showed the desirability of having the engine nacelles well ahead of the wing's leading edge, a practice later found even more necessary on larger aircraft. It was also found desirable to house the retractable landing gear within the nacelles. With these points in mind, it was then necessary to develop maximum strength and rigidity with minimum weight. Therefore, we designed a wing with the material so distributed that there was little variation in the stresses of the various parts. At the same time, the wing proved to have little or no torsional deflection, a minimum of vertical deflection, and no excessively large unsupported flat metal surfaces.

In a metal wing, having a thin skin rigidly attached to a heavy spar, sudden changes in cross section are apt to cause objectionable stress concentrations. Other dangers exist as well. In seeking the answer to this problem we considered single, two, three and multi-spar designs, as well as shell type and multi-cellular designs. We finally decided upon the Northrop multi-cellular wing, a type we have employed throughout all Douglas transports. This type of structure consists of a flat skin reinforced by numerous longitudinals and ribs. Because the major loads are carried in the outer surface of the wing as well as in the internal structure, inspection of the exterior gives a ready indication of the structural condition.

In the fuselage, the structural problem was basically the same. This construction consists of a smooth, stressed skin in contact with closely spaced over-strength bulkheads and numerous longitudinal stringers. All parts are securely attached together, and the skin has very small unsupported areas.

Twelve passengers flew in the DC-1, and fourteen flew in the DC-2, which appeared in 1934. The DC-2 was little more than a slight re-design of the DC-1. It really was the production version of the experimental DC-1. The DC-2's fuselage was forty inches longer to increase passenger capacity and assist in balance control.

Two years later the DC-3 appeared. This airplane, a real contribution to low-cost travel, accommodated twenty-one persons in seven rows of seats, three passengers abreast. As in the former models, wings were of full cantilever, multi-cellular construction, as were the tail surfaces, but those were of aluminum alloy, except for the fabric covering of elevator and rudder. It was in this model that the automatic pilot appeared; and here, too, wing flaps of the split-trailing-edge type extending from aileron to aileron came into service. Except for these changes of size and construction, the DC-3 follows along the lines of its family. But the DC-3 paid off much better, for, at 25,200 pounds this ship carried one and a half times as much as the 18,560-pound DC-2. Wing loading had climbed, too, from twenty pounds per square foot in the DC-2, to twenty-five pounds in the DC-3.

Next to come was the DC-4, more properly the DC-4E. We built only one of this model in 1939 and it was subsequently sold to Japan. It was Douglas' first four-engine plane, and had a gross weight of 65,000 pounds. It was designed for a pressure cabin. The airlines thought this airplane, although it was ten percent faster than the DC-3, was too large for their use. From this airplane, however, came the world famous transport, the Army's C-54.

The new C-54, whose wing span of 117 feet, six inches, is only two-thirds that of the DC-4E, was designed with the assistance of interested airline personnel and finally approved by them. But the war came, and the Army took over its production. The C-54 has tricycle landing gear, and is about two and one-half times the maximum weight of the DC-3. The commercial version will give one-stop transcontinental service. To date, some 1,000 of this type have been built, all going to the Army as C-54s. It was one of these airplanes that was produced for President Roosevelt, and became the "flying White House."

Passenger requirements and cargo requirements are somewhat different when an airplane joins the Army. Special fuel tanks may be required for longer flights. Some C-54s carried litters others accommodated forty-four passengers, yet others flew more than twelve tons of freight.

In 1940 came yet another change and the DC-5 was born. This was a high wing, twin-engine transport, of which only fifteen were built. All were sold to the Navy and to the Dutch. It was a high-wing DC-3, and to that similarity the airlines objected. At the same time, it presented differences which would have complicated their servicing problems.

Not numerically but chronologically, next is the DC-7 Globemaster, or as it is known by its first user, the Army, the C-74. The DC-7 illustrates how we must sometimes design for two services simultaneously. As a military version, the C-74 carries all cargo, no passengers. In designing and building the Globemaster, which was first flown on September fifth of this year, we found the answers to a triple-headed question: how much can we carry how far and how fast? Answers: thirty tons up to 850 miles, 7,500 miles with lighter payload, over 275 m.p.h. cruising (maximum).

The Globemaster is a big brother to the C-54 Skymaster, and is the first trans-ocean airplane capable of flying non-stop from the United States to almost any point in the world. As a military carrier, it can haul huge cargoes of jeeps, guns, fighter airplanes, small tanks and trucks. On short notice, it can be converted into a troop transport with a capacity of 125 fully equipped troops or a hospital ship with 115 litters. As the DC-7, it will carry a thirteen-man crew and 108 passengers.

Now, bearing in mind that the Globemaster's wings span thirty-two feet more than those of the Super-fortress and that her fuselage is twenty-five feet, one and one-half inches longer, how did we solve the problem of cargo carrying? First, we knew we could devote the entire main cabin to this purpose. Next, we knew we must provide proper cargo hoisting facilities. To meet these requirements, we designed a fuselage which is circular in section, with a maximum outside diameter of thirteen feet, two inches. The structure is of semi-monocoque construction, utilizing hat-section stringers with zee and channel section transverse frames. Flush rivets are used on all outside surfaces.

The floor of the main cabin contains approximately 875 square feet. The cabin is seventy-five feet long and 11.7 feet wide, with maximum usable height of eight and a half feet. Cargo may be loaded through a side loading door in the forward area and through a bottom well immediately aft of the wing.

The Globemaster is the first airplane to carry its own cranes, hoists and cargo elevator. Loading equipment consists of two traveling cranes, supported on overhead rails in the fuselage roof, and a stationary hoist forward of the cargo loading door on the left side of the cargo cabin. An elevator, supported at the corners by cables, lifts cargo into the cabin rapidly. When not in use, the elevator is secured in place by a releasable latch mechanism and becomes part of the cargo cabin floor. The slide door hoist can lift 4,500 pounds, the cranes a total of 16,000 pounds when used together.

Remember, this is a cargo version. As such, it is important to handle cargo fast, and in quantity. The Globemaster, therefore, with its self-loading equipment can load, stow and haul ten R-3350 engines and cradles, or two T-9E1 tanks, two quarter-ton trucks and two crew-and-ammunition carriers. It can carry other combinations as well.

But let's look at the commercial version briefly. How do we plan to make this airplane more comfortable for passengers? First, it should be remembered that larger and later airplanes create more trouble from the noise standpoint. Power increases faster than the art of soundproofing advances. The greatest problem is to keep the noise down to that experienced in the DC-3. Cutting propeller tip noise by keeping tip speeds well below the velocity of sound is one answer. Placing propellers sufficiently far ahead of the passenger cabin so that wash-rooms or partitions will be between props and passengers is another. Creation of "floating cabins" by separating walls and bulkheads from main walls with rubber extrusions is yet another. Pressurizing the cabin cuts the noise by about seven decibels.

The DC-6, which was delayed by war production and will not be flown until sometime in 1946, is very like the DC-4. Innovations include an extra eighty inches in the fuselage, R-2,800 Pratt and Whitneys instead of the R-2000s in the C-54 and also a cruising speed of 300 miles an hour against 240. It will be completely pressurized, with a cabin that can be either heated or cooled to an even temperature of seventy degrees F. There is no change in wing span over the C-54, but a higher lift flap will be employed. Three models will appear: the seventy-passenger day plane, the fifty-two-passenger day plane and the twenty-six-passenger sleeper.

Passengers generally consider the DC-3 to be a comfortable airplane in which to fly. But the successful airline operator knows he must compete with both air and ground facilities to provide even greater comfort in order to hold and increase his business. In the DC-6 all-sleeper deluxe, therefore, passengers will enjoy more reliable heating and ventilation, better lighting, up-to-the-minute food service. Due to its higher wing loading, 32.2 pounds, the DC-6 will ride more easily since it will be less responsive to gusts.

These are generalities. They had to be worked out in minute details. E. Hamilton Wright, chief of interior design for the company, sketched a dozen cabin interiors. He built miniature cabins with miniature furniture. He painted them in various pleasing combinations. As a result, should you ever fly in this airplane, you will enter a door conveniently set just aft of the wing. From the foyer you may turn into either the forward or aft cabin.

Once all passengers are aboard and the door is closed, the stewardess will commence preparation of your next meal, working from two buffets, one on each side of the door. From the rear buffet, she will take trays pre-loaded with fruits and load them at the forward buffet with hot foods and liquids kept warm in thermos units.

You will relax in soft, luxurious cushion-rubber chairs. Later you may stroll forward (if a gentleman) or rear (if a lady) to either lounge. In each will be found a score of built-in accessories, as ash trays and electric connections in the men's lounge. There will be a large sofa in the ladies' lounge. Indirect lighting will illuminate each, while a lens shaving light will be provided for the necessary male routine.

Long arm-rests, adjustable backs, removable and adjustable head- and foot-rests, with full clearance for legs and luggage, characterize the seats. After darkness falls, the stewardess will pull a few levers, and the seats will become berths. Nor need you dawdle in the aisle aimlessly, for lowers will be made in thirty seconds, uppers in ten!

The DC-6 and DC-7 serve the needs of long-range operations. The airlines have other needs and to fit them we shall have the DC-8. This will be a low-wing, twin-engine airplane which may well constitute as great an advance over the DC-3 as the Ford tri-motor was over the Wright brothers' original biplane. The Sky bus will cruise at 270 m.p.h. at 10,000 feet. It will perform beautifully on a single engine at more than 12,000 feet and at the same time its landing speed is extremely low. Another interesting innovation from an operations standpoint is that both take-off and landing weights are the same, a gross of 39,500 pounds.

We built for comfort in other airplanes, but in this one we tried to attain considerably greater speed than we had in the DC-3. In fact, the DC-8, which will have motor less wings and be driven by twin counter-rotating propellers, astern of the fuselage, will be fifty percent faster than the DC-3, carry twice the number of passengers and reduce direct costs per passenger-mile to half that of the plane which for twelve years has been standard equipment on ninety-five per cent of the world's airlines and supplied most of the Army's transport.

The DC-8, which will not appear for some months yet, represents a radical departure from tradition. It will be driven exactly as an ocean liner is driven. It is in the application to aircraft of this basically new principle of "center-line thrust" that we believe the DC-8 represents outstanding improvements over conventional types in speed, safety, climb and efficiency.

But it does not omit passenger comforts. A cabin innovation of great significance is a movable partition that converts the plane at short notice from a combination cargo-passenger to an all-passenger plane. By this means, the operator can be assured of a 100 percent load on all flights where passengers and/or cargo are available. The two engines, located in the fuselage below the forward compartment floor, are connected with the propellers by drive shafts and a gear box similar to those of an automobile. Allison engines were chosen because they were installed in military experimental prototypes which have been test-flying for more than a year. This power-propeller installation means a further reduction of noise within the cabin. Improved safety is derived, too, since there is no offset thrust in case of engine failure, there is an overall drag coefficient twenty percent less than in equivalent conventional planes and better lift distribution resulting from the higher effective wing span. Other details cannot be revealed to the public at this time.

There are some significant trends to be traced in the history of the DC family. High strength materials have made an average of a fourth to a third increase in strength. Later models use the new 75S aluminum alloy in all basic structures. All models up to theDC-7 have three-spar wings. However, the DC-7 incorprates two-spar wings, a change which increased fuel capacity by fifty percent, and thus increased the range by the same proportion. All models through the DC-3 used brazier head rivet construction. The DC-4, 6 and 7 have flush rivet construction, effecting lower drag. Other improvements in later models result in lower drag and better cooling in the nacelles. One of the biggest improvements is the complete sealing off of the engine from the rest of the airplane structure, a change first appearing on the original DC-4, The Skymaster.

It's a long road -fro m the DC-1 of twelve years ago to the Globemaster and the Skybus, but it is one road. We have really been writing variations on a theme. For though the granddaddy of them all weighed in at only 17,500 pounds (gross weight) and the mightiest of her progeny, the Globemaster, weighs 155,000 pounds; though the wing-load has increased three-and-a-half times, the first of the line was so well engineered that very few fundamental changes had to be made. Each late model grew out of the one that preceded it.

An airplane isn't really built; it is a process of evolution.

Posted July 16, 2022