October 2003 | Volume 54, Issue 5
Overrated It is one of the most famous aircraft of the century. The Spirit of St. Louis , a small single-engine silver monoplane, carried the most famous aviator of the century on the first solo flight from New York to Paris on May 20-21, 1927. Following a hero’s welcome on two continents, Charles A. Lindbergh piloted the Spirit on a tour of the nation, stopping at least once in every state to promote air-mindedness and encourage local airport construction.
The Spirit of St. Louis did everything that was asked of it, and more. But if Lindbergh generated an unprecedented wave of enthusiasm for aviation and pointed the way to the future, his airplane was rooted in the past. With its welded-steel-tube fuselage and wooden wing covered with doped fabric, the Spirit of St. Louis represented a structural form that had come of age during World War I.
Lindbergh credited some of his success to the touchy handling qualities of the airplane. They had helped keep him awake and alert. Other pilots were less enthusiastic. “I found . . . that it takes Charles Atlas-like strength to handle the ailerons,” Frank Tallman, who flew a replica of the airplane, explained. “Rudder and elevator are adequate but must be used constantly. . . .”
Don’t get me wrong. The Spirit of St. Louis earned its fame. Still, it was a highly specialized machine, a flying gas tank designed to do just one thing: carry its own weight, and that of its 170-pound pilot, over distances of up to 4,000 miles. In order to achieve that, Lindbergh and Donald Hall, chief designer for the Ryan Company, which had built the craft, relied on tried-and-true technology and steered clear of chancy innovation. As a result, other aircraft of the period, like the Lockheed Vega, also introduced in 1927, were far better airplanes than the Spirit of St. Louis .
Underrated If the Spirit of St. Louis has gone down as one of the most famous aircraft in history, you will have to look long and hard for anyone who has even heard of the Hall XFH-1. Designed in 1928 as a carrier-based fighter for the U.S. Navy, the open-cockpit biplane was the work of Charles Ward Hall, a Cornell graduate who had cut his engineering teeth designing tall buildings and who established the Hall Aluminum Aircraft Company in Buffalo in 1927.
The advantages of tough, light-weight aluminum alloys in aircraft structures had long been apparent. But there were problems. Aluminum, with its low melting point, was difficult and expensive to weld. As a result, aircraft manufacturers that pioneered the use of the metal had resorted to bolting their structures together, a labor-intensive and time-consuming process.
Then there was corrosion. Exposure to air, especially salt air, would slowly transform aluminum alloy into a white powder. In 1927 researchers at Alcoa, the National Advisory Committee for Aeronautics (NACA), and the U.S. Bureau of Standards announced a new product, Alclad, in which a very thin layer of soft but corrosion-resistant pure aluminum was bonded to each side of a sheet of aluminum alloy.
It remained for Charles Hall to pioneer manufacturing procedures that made use of the new material, including the production of riveted Alclad structures. In riveting, a series of holes are driven through the two pieces of aluminum to be fastened. Each hole is then permanently filled with a metal pin that is flattened on the underside with a special tool. Driven while hot and allowed to cool in place, the rivet hardens over three or four days.
Quickly recognized as the most cost-efficient means of producing a sound aluminum aircraft structure, riveting changed everything. Tooling evolved over a decade. Hall acquired or developed the presses and machine tools that transformed sheet aluminum into tubes, flanges, angles, and other pieces that made up the airframe. His first “semi-portable” rivet gun weighed 136 pounds!
Hall took the next step as well. A 1933 report from the NACA Langley Laboratory focused on the importance of drag reduction. The presence of exposed rivet heads on the wings and fuselage would significantly reduce the speed of an otherwise smooth and streamlined aircraft. Hall took the lead in developing a flush riveted structure; the Hall PH-I flying boat may have been the first whose rivet heads did not protrude. By the time of his death in a 1936 aircraft accident, Hall had helped lay the foundation for a revolutionary change in aircraft design and construction.