Exhibition Statement After the aircraft changed the world, the world changed the aircraft. Exhibition Abstract Why do airplanes look the way they do? Airplanes are built to fulfill requirements set forth by customers, both military and civilian, for the creation of working flying machines capable of fulfilling specific work requirements for speed, payload, range, altitude, and endurance. They are the logical expression of the labor of designers and engineers using the best techniques and materials available to them at the time. Invented in the United States by Wilbur and Orville Wright, the airplane changed humankind’s perception of the world, bringing to reality the age-old dream of powered flight. Initially designed simply to solve the problem of heavier-than-air powered flight, the airplane revolutionized the world, becoming one of the transformative technologies of the 20th century. Using the best materials and technologies available at the time, the classic wood and fabric biplane with externally braced biplanes wings emerged as the design configuration of choice. This form was highly successful for a time, capable of carrying decent loads reasonable distances at speeds below 150 miles per hour. The potential of the airplane was made clear during the First World War but it was far from realized. Performance reached a plateau; it would take a combination of innovations in structures, powerplants, and especially materials for the airplane to become a practical and widely accepted tool of modern society. It would now take the vastly expanding requirements of the world to change the airplane into the ubiquitous tool of modern society that it has become. The second aeronautical revolution entailed the technological innovations necessary to reinvent the airplane as a practical tool for commerce and war. This would require that these new designs become faster, larger, and more powerful. This encompassed the use of newer more predictable materials, new technologies to improve safety and performance, new powerplants and propellers, and new structures. This revolution occurred during the 1920s and 1930s and succeeded in producing the first so-called modern aircraft using methods and materials that are little changed today. The third revolution occurred immediately after the conclusion of the Second World War and involved a new propulsion technology – the jet engine. Coupled with the aerodynamic innovation of the swept wing initially developed in Germany, jet-powered aircraft dramatically increased productivity by dramatically increasing the speed, payload, and range of contemporary aircraft. That revolution was essentially over by 1960, since then aircraft development has been a constant struggle to gain incremental, evolutionary improvements. In 1960 it took six hours to fly from New York to San Francisco. Today, the flight time is the same. The exhibition will examine in detail how the airplane was developed and reinvented into the recognizable form it takes today. “Reinventing Flight” will introduce the visitor to this technology that is taken for granted but has transformed the planet in a myriad of ways, known and unknown. It is the story of the modern airplane. 3 NASM EPPIC Proposal Revised February 7, 2015 Scope, Unit Topics, and Discussion of Major Elements in Each Unit Unit 100 Introduction “The Vegetable Airplane” Almost all of the combat aircraft built during the titanic struggle of the First World War were constructed from organic fabric and wood, particularly spruce, which is well known for its excellent strength and lightness. The properties of wood were well-understood from centuries of use in countless building projects. Most aircraft designers were well versed and comfortable in its use. If wood was so widely accepted, then why was it so quickly replaced? This unit examines how the first generation of aircraft were made and why. Biplanes are light and immensely strong; with low horsepower engines the high drag of this configuration is not a factor limiting its performance. As aircraft designs evolved quickly, the limited lifespan of fabric and wood was not critical. This first generation proved that aviation had the potential to change warfare and commerce but that the airplane still needed significant improvements in order to become a practical, widely accepted tool. ARTIFACTS: Wing off a Standard J-1, Le Rhone rotary engine, newly built fabricated wing section/fuselage, World War I models Unit 200 Airframe: Structure and Materials For subsequent aircraft to become practical, they had to be bigger, stronger, but feature a lighter airframe relative to the overall weight of the aircraft. While wood was the original material of choice, it was unpredictable and vulnerable to temperature and humidity extremes. Most metal was either too soft or too heavy until the discovery of duralumin, an aluminum alloy as light as aluminum but almost as strong as steel. Duralumin was widely used on German airships before and during World War I and would have been more widely used except that it was vulnerable to rapid corrosion. It was not a suitable material until after 1927 when an anodization process together with the creation of Alclad made the aluminum alloys the material of choice for its strength and lightness. During this time lighter and stronger construction methods became accepted. Monocoque – i.e. “single shell” construction resulted in a hollow fuselage which could carry a larger load unencumbered by wires and cross bracing while the aluminum alloy sheet metal skin could now help carry the weight of the structure itself. When combined with the cantilevered wing which was internally braced also with stressed skin construction, the road was paved for sleeker, stronger and larger designs. The monocoque design itself made possible the eventual pressurization of aircraft which allowed airliners to fly into the stratosphere at much higher speeds with concurrent improved smoothness and comfort for passengers. ARTIFACTS: Boeing P-26A, Hughes 1B, North American F-86, Lockheed Vega “Winnie Mae,” monocoque aircraft cross section (may need to be fabricated) Unit 300 Aerodynamics 4 NASM EPPIC Proposal Revised February 7, 2015 For larger aircraft to fly faster and more efficiently, they required better airfoil shapes and lower drag features. In efforts to streamline aircraft designs and to reduce the drag resulting from the external wire bracing of the wings of traditional wood and fabric aircraft, the Germans, particularly Dr. Hugo Junkers, pioneered the internally supported, cantilevered monoplane. The cantilevered wing eliminated an extra wing as well as external struts and bracing wires. Retractable landing gear and enclosed cockpits smoothed the airflow around the airframe. New engine cowls streamlined the air flow around bulky radial engines reducing drag and increasing performance. Wing flaps decreased takeoff and landing runs allowing aircraft to carry greater payloads into more airfields. Research on a large scale was conducted by state-run aeronautical laboratories equipped with numerous large and small wind tunnels to test current theories. Engineers at the National Advisory Committee for Aeronautics in the U.S. were among the leaders in the 1920s and 30s publishing comprehensive tables of airfoil data and working tirelessly to develop better wings and lower drag. Other innovations, such as wing fillets reduced drag on larger aircraft of the mid-1930s. After World War II German-designed 35 degree swept wing became the model for the next generation of high-speed wing planforms for America’s leading bombers and jet airliners. Subsequent research expanded into transonic and supersonic regions that have had a lasting effect of contemporary aircraft performance. ARTIFACTS: Boeing P-26A, Hughes 1B, North American F-86, Lockheed Vega “Winnie Mae,” NACA cowling. Unit 400 Powerplants and Propulsion During the early 1920s, the only engines producing enough horsepower for huge performance aircraft were bulky, unreliable water-cooled types. The U.S. Navy was anxious to find an engine that could produce sufficient power without the weight and maintenance problems of water-cooled motors. The aluminum Lawrance J series of engines seemed ideal for the task as they had no troublesome and heavy radiator, water pumps, or vulnerable cooling lines. The Navy cajoled the Wright Aeronautical Company into purchasing Lawrance in 1923. By 1924, the Wright J-3 and J-4 air-cooled radial engines, better known as Whirlwinds, were in service. Incorporating Englishman Samuel D. Heron’s revolutionary sodium-cooled exhaust valves, which virtually eliminated the chronic problem of burned exhaust valves, the improved J-5 was the first aero engine to offer power and great dependability. This powerplant, the first truly reliable aero engine, made Charles Lindbergh’s epic non-stop solo 33 ½ hour transatlantic flight possible in 1927 with no problems. Concurrently, water-cooled engines received a new lease on life with the development of ethylene glycol as a coolant additive. Sold under the trade name “Prestone,” ethylene glycol enabled engine designers to use much smaller radiators which greatly reduced the liquid-cooled engines’ drag problem. From this point onwards advocates of both engine types were able to produce advanced designs that emphasized the best characteristics of the engine type for the aircraft’s design requirement. Neither of these engines could work efficiently however, until the development of the variable-pitch propeller. Spinning propellers