Aviation Ancestry - July 2012
Above the Weather – The Lockheed Constellation
By Scott Schwartz
A Lockheed C-69 Constellation in flight; the C-69 was the initial military version of the Constellation.With the end of World War Two, the Lockheed Company already had an advanced airliner in production in the form of a military variant, which was used by the Army Air Corps under the designation C-69. Most readers will know this aircraft as the Constellation.
The Lockheed Constellation, however, was not designed as a military airplane, and in truth, relatively few C-69s were produced for the Army. The aircraft was intended from the outset to be an airliner, and its origins lay in design studies that were begun in 1938. At the time, the twin-engine Douglas DC-3 reigned supreme in the airline market, which left competing Lockheed aircraft in the shadows. What’s more, Douglas was about to unveil its DC-4 (which was eventually referred to as the DC-4E – “E” for “Experimental”), which was a four-engine aircraft that could carry 42 passengers. The DC-4E also featured three short vertical stabilizers that enabled the aircraft to fit into most airline maintenance hangars of the time. Those who are familiar with the DC-4 may be scratching their heads, at this point. Three vertical stabilizers? Well, the DC-4E was not a resounding success, so it was not put into production (the single-fin derivative was). In fact, the Japanese bought the DC-4E (the Pearl Harbor attack was still a few years in the future) and, with a little reverse engineering, converted the design into the Nakajima G5N Shinzan bomber. The G5N wasn’t a resounding success, either.
Nevertheless, four-engine airliners were on the horizon, and Lockheed didn’t want to be left behind. The company began with the design of aircraft known as the Model 44 Excalibur. The Excalibur was supposed to be able to carry 21 passengers and hit a top speed of 262 mph. Since this was hardly an improvement over the DC-3, the airlines weren’t interested. Lockheed engineers went back to the drawing boards and came up with an improved Model 44 that could carry 40 passengers at 300 mph. Further, its pressurization system allowed it to cruise at 15,000 feet. Pan American Airways (“Pan Am”) was sufficiently interested in this incarnation of the Model 44 that it actually entered into contract negotiations with Lockheed. The negotiations were under way, when one of the annoying characteristics of the free market system – competition – slowed things down. Boeing unveiled its Model 307 Stratoliner – which was essentially a B-17C with a large, circular, pressurized fuselage. The Stratoliner’s pressurization system enabled it to cruise at 18,000 feet, albeit at a slower speed than that of the Model 44.
While all of this was going on, the airline TWA’s long-standing interest in high-altitude, “above-the-weather” passenger transportation had coalesced into a set of requirements, which it presented to Lockheed in the summer of 1939. One of the “presenters” was a major TWA stockholder by the name of Howard Hughes. Hughes and TWA wanted Lockheed to come up with an aircraft that exceeded the Excalibur’s design parameters. Specifically, the new aircraft had to be able to fly non-stop from coast to coast, fly at 250 mph, and to be able to carry 6,000 pounds of cargo. And, of course, the cabin had to be pressurized. By this time, models of the Excalibur were being tested in wind tunnels, but Lockheed suspended development of this aircraft. Now, the name Excalibur was used to identify the aircraft being designed to TWA’s specifications. This new design was called the Model 49 Excalibur A, with Kelly Johnson and Hall Hibbard as the chief engineers on the project.
Like the DC-4E, the Model 49 was to be built with three short vertical stabilizers. Further, the Model 49 would have hydraulically boosted control services, a wing that was essentially a scaled-up version of the P-38’s wing, and tricycle landing gear.
What set the Model 49 (later to be known as the Constellation) apart from other airliners (even modern ones) was the “flattened-S” shape of the fuselage. This was the result of engineer Ward Beman’s desire to have the air flow along the fuselage in such as way that it did not interfere with the lift being generated by the wing. His original design would have required a really long nose wheel strut, so his final design has the nose of the aircraft tapering downward.
The design process progressed steadily, although slowly. By late 1939, Lockheed was marketing the design to the airlines (having received permission to sell the aircraft to other airlines from TWA). As a result, TWA and Pan Am bought 40 Constellations each.
With a top speed of 360 mph and the ability to cruise at 20,000 feet, the Constellation was on the cutting edge of airliner development. As mentioned previously, the design process was a slow one, and war was looming on the horizon.
TO BE CONTINUED…
Please check out the author’s blog at www.elpasomountains.blogspot.com
