Aviation SafetyJul 9, 3:56 PM
FAA Proposes Replacing 53-Year-Old Ban on Supersonic Flight Over U.S. Land With Noise-Based Rules
Global Aviation Round-Up from Aircraft Value Intelligence (AVN) A computer rendering of what the United Airlines supersonic aircraft will look like in the future. (Boom Supersonic) Editor's Note: To watch a video version of this article, click here . For 53 years, one federal regulation has stood between Americans and the return of supersonic air travel over the continental United States. That rule, adopted during the Nixon administration, prohibits civilian aircraft from exceeding the speed of sound over land. Now the Federal Aviation Administration (FAA) is preparing to rewrite it. On July 2, the agency published a Notice of Proposed Rulemaking in the Federal Register that would replace the existing speed-based restriction with a performance standard centered on noise. The proposal follows an announcement by the Department of Transportation on June 30 and represents the most significant shift in U.S. supersonic policy in decades. The change reflects a different way of thinking about the problem. Instead of asking whether an aircraft breaks the sound barrier, regulators are asking whether people on the ground are disturbed when it does. That distinction could reshape the future of commercial aviation. For many travelers, supersonic passenger service is synonymous with the Concorde, the sleek Anglo-French jet that cut transatlantic flight times in half. Its future unraveled after the fatal Air France crash near Paris in 2000. Although Concorde briefly returned to service, passenger demand weakened, operating costs climbed, and the aircraft was retired in 2003. Since then, commercial supersonic travel has largely disappeared. Today’s aircraft designers believe the technology has advanced enough to make another attempt. The original U.S. ban grew out of public frustration during the 1960s, when military testing produced frequent sonic booms over populated areas. Residents complained of rattling walls, cracked plaster, broken windows and sudden explosions of noise that interrupted everyday life. Thousands of complaints poured into government offices, convincing regulators that the public cost outweighed the benefit of faster travel. The FAA responded by banning routine civilian supersonic flight over land. With few exceptions, commercial aircraft have remained below Mach 1 across the continental U.S. ever since. Engineering, however, has changed dramatically over the past half-century. Instead of allowing powerful shock waves to merge into the classic sonic boom, engineers have learned how to shape an aircraft so those pressure waves remain dispersed. The resulting sound reaching the ground is significantly weaker than the ear-splitting boom associated with earlier generations of supersonic aircraft. The FAA’s proposal reflects those advances. Under the draft rule, future aircraft would have to meet a strict ground-level overpressure limit of 0.11 pounds per square foot. While the measurement is technical, the practical goal is straightforward: produce a sound that resembles a soft thump rather than the explosive crack historically associated with breaking the sound barrier. NASA’s Supersonic Experiment The proposed rule arrives as NASA continues work on one of its most ambitious experimental aircraft. The X-59 Quiet SuperSonic Technology (QueSST) demonstrator hardly resembles a conventional jet. Its unusually long, narrow nose and carefully sculpted airframe were designed with a single objective: reducing the intensity of sonic booms before they reach people on the ground. The aircraft recently completed another important step in its flight-test program, reaching Mach 1.4 at roughly 55,000 feet. Engineers view the milestone as another indication that the research program is progressing as expected. The most important testing, however, won’t focus on speed alone. NASA plans to fly the X-59 over selected U.S. communities while researchers gather feedback from residents who experience its sound signature. Beyond measuring decibel levels, scientists want to understand how people actually react. Does the sound surprise them? Is it annoying? Or is it mild enough to blend into the background of everyday life? Those public-response studies could prove pivotal. If communities consistently report that the aircraft produces little more than a brief, unobtrusive noise, regulators would have stronger evidence that quiet supersonic operations can safely coexist with populated areas. The research is expected to influence not only future FAA decisions but also international standards governing commercial supersonic aviation. The stakes extend well beyond NASA. Several aerospace manufacturers are investing heavily in next-generation supersonic airliners designed to shorten travel times between major cities. Because of the current U.S. ban, most development plans have centered on transoceanic routes where aircraft can legally accelerate beyond Mach 1. A new regulatory framework would dramatically broaden those possibilities. Flights that now consume most of a business day could eventually take only a few hours. A traveler leaving New York in the morning could conduct afternoon meetings in Los Angeles and return home that evening. Commercial service remains years away, but for the first time in decades, the regulatory landscape appears to be moving in the same direction as the technology. The proposal also provides something the aerospace industry values almost as much as technical innovation: regulatory certainty. Designing, certifying and manufacturing an entirely new generation of commercial aircraft requires billions of dollars and years of development. A clearer path through the approval process reduces investment risk, giving manufacturers and their financial backers greater confidence that quiet supersonic flight could become a viable commercial business rather than an engineering experiment. John Persinos is the editor-in-chief of Aircraft Value Intelligence .
