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The Need for Speed

Everything is in place for the development of a supersonic business jet-except U.S. Federal Aviation Regulations.

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In 2000, the National Research Council conducted a study to identify breakthrough technologies for overcoming key barriers to the development of a commercial supersonic aircraft that would be both environmentally acceptable and economically viable. The study,

"Commercial Supersonic Technology, The Way Ahead," concluded that none of the anticipated obstacles to commercial supersonic aircraft are insurmountable. It went on to note that while NASA should have its eye on supersonic commercial transport, research was also needed to determine the impact of sonic booms produced by smaller supersonic business jets.

The Quiet Supersonic Platform (QSP) program, sponsored by the Defense Advanced Research Projects Agency, began in 2000 and is a Congressionally mandated effort to develop technologies that could reduce the impact of a sonic boom to 0.3-pound-per-square-foot pressure propagated to the ground by the shock wave. This is significantly less than the 2.0 pounds per square foot created by the Concorde, an impact that restricted it from flying at supersonic speeds over land.

Last year, the QSP Program, in conjunction with Gulfstream Aerospace and Raytheon Aircraft Company, demonstrated that aerodynamic shaping of a modified Northrop F-5E fighter reduced the craft's sonic boom signature in flight. The modification consisted, most visibly, of an enlargement to the forward fuselage to make it more bulbous. The test also confirmed that the size of the aircraft has a direct effect on the noise heard on the ground. The QSP demonstration was a success in that it indicated that by simply altering the shape of the fuselage and other aerodynamic elements, designers can dramatically reduce the noise produced when an aircraft exceeds Mach 1.

Even without advanced shapes, the smaller the airplane, the smaller the sonic boom it will create. In fact, the overpressure produced by advanced designs may not be described accurately by the term "sonic boom." Those familiar with the QSP demonstration flights suggest that "sonic whoosh" or "sonic poof" may more accurately convey the sound.

Therefore the development of a quiet supersonic business jet is not only feasible, it is likely.

In light of this research, and because the FAA's rules had not been re-examined for more than two decades, last November the agency requested public comment on the issue and sponsored a workshop on supersonic flight. Gulfstream Aerospace, long interested in developing a supersonic business jet, submitted substantial details for what it calls a Quiet Supersonic Jet. The initial design requirements for the QSJ are presented in the sidebar (opposite).

At the FAA workshop, Gulfstream Aerospace was the most vocal company among the participants, but all manufacturers of business jets attended, along with the makers of business jet engines. The General Aviation Manufacturers Association (GAMA), which chaired the panel of airplane manufacturers, will place a high priority on getting the FAA to change the regulations that govern operation and design of this important new class of airplane.

GAMA told the FAA that it is essential to begin immediately the process of changing the regulations that prohibit supersonic flight. Since these rules were established in the 1970s, technologies have advanced significantly, and recent studies have shown that safe and environmentally acceptable designs for aircraft and engines are not only possible but likely to have sufficient market demand. The first new supersonic airplanes are likely to be advanced general aviation aircraft—business jets.

GAMA also noted that it is essential that the FAA maintain sufficient research and development activities to support this rulemaking process. And as most supersonic civil operations will involve international flight, the FAA should also begin negotiations with its counterpart agencies in other nations to revise international standards and recommended practices to allow advanced supersonic aircraft to operate internationally.

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