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This article appeared in the Second Quarter 2001 issue of Code One Magazine.
The X-Planes, that unique family of mostly exotic research aircraft that first came into being with the advent of Bell Aircraft Corporations X-1 of 1945, have appeared only sporadically on aircraft manufacturers design boards. Today, well over half a century since the advent of the X-1, only forty-five X-designators have been assigned. From 1944 through 1970, the military services and various government agencies funded almost thirty X-plane programs, or approximately one per year. These programs explored everything from variable-swept-wing technology to homebuilt amphibians for Southeast Asian police operations. From 1971 through 1983, the experimental aircraft programs rolled to a haltnot a single X-aircraft was built.
The forward-swept-wing-equipped Grumman X-29 ended the hiatus in 1984, though not for long. Another six years passed before the X-31 flew. In the interim, the much-anticipated X-30A hypersonic transport failed to materialize. Six more years passed before the McDonnell Douglas (now Boeing) X-36 made its first flight.
The 1990s offer a different story. At least fourteen new X-planes were designated since the first flight of the Rockwell International/MBB X-31 in 1990. Of these, virtually all were conceived and scheduled for flight test during the past six years. This unexpected resurgence in X-plane popularity comes mostly from a philosophical shift in prototype funding, or the industrys desire to spread the high cost of research across a broader base.
Lockheeds inimitable Clarence L. Kelly Johnson was the first to use the X-plane designator to facilitate government funding for what was effectively a prototype fighter. (He applied it in 1961 to the unsuccessful X-27.) The approach worked at first. Eventually, the Department of Defense found the designation to be inappropriate for prototype fighter aircraft.
Today, the gray area between research and prototyping all but disappears. Both objectives are regularly achieved with a single airframe. Thus, the competing Joint Strike Fighter demonstrators from Lockheed Martin and Boeing are identified as X-planes. With this new X-plane age comes an exciting and precedent-setting trend in aerial exploration. No longer are the quests necessarily for greater speeds and higher altitudes. They are for archetypal designs of production transatmospheric vehicles, space rescue platforms, stealthy surveillance and weapons delivery platforms, and more. With few exceptions, expanding the envelope no longer forms the raison detre of contemporary research aircraft.