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Regulators Eye Possible Standards for Supersonic Flight

 - June 19, 2019, 2:27 AM
Aerion’s AS2 supersonic business jet is slated to carry 12 passengers at Mach 1.6 with a minimum projected range of 4,750 nm (8,800 km).

A little more than 15 years after the Concorde took its final flight, the industry is beginning to see progress both within the U.S. FAA and the broader international spectrum on efforts to pave the way for the return of supersonic flight. But it may be at least a half-dozen years before any significant regulatory changes are in place.

“We’ve come a long way,” said E. Tazewell Ellett, senior counsel for Hogan Lovells US, which has represented supersonic business jet developer Aerion on regulatory and legislative issues. “A lot has happened. But there is a lot more that needs to happen.”

Currently, noise standards effectively prohibit civil flight at speeds greater than Mach 1 over land in most parts of the world. But at the direction of the U.S. Congress, the FAA is exploring regulatory possibilities that would make supersonic aircraft and operations feasible. In fact, it has released its first proposal in that effort, paving the way for special flight authorizations. In tandem, the International Civil Aviation Organization (ICAO) is beginning a similar exploratory exercise through its Committee of Aviation Environmental Protection (CAEP).

“Companies in the U.S. and abroad are now taking a new look at supersonic air travel,” the FAA said. “Lighter and more efficient composite materials, combined with new engine and airframe designs, may offer the potential for introduction of a viable SST.” Stressing it wants to keep pace with the latest technological innovations, the agency said it is working with the U.S. Department of Transportation to advance these technologies.

U.S. Assesses Noise Standards

In addition, the U.S. Congress has expressed an interest in seeing supersonic technologies advance. The legislative body included several directives to the FAA on supersonics in the comprehensive FAA reauthorization bill that passed last year. Those measures included a call for the agency to take a leadership role in the creation of regulations, standards, and policies surrounding supersonic aircraft. 

Under the directives, rulemaking is to address a key stumbling block to supersonic aircraft: landing and takeoff noise standards. In the U.S., Part 36 of the Federal Aviation Regulations covers noise regulations for subsonic aircraft, including standards for landing and takeoff. But except for a carve-out that applied specifically to the Concorde, Part 36 does not address landing and takeoff of supersonic aircraft.

In the past, regulators had largely taken an approach that they would address supersonic aircraft noise standards when a market necessitated it. But about five years ago, stakeholders began meeting with regulators to discuss the need for takeoff and landing standards that were appropriate to and reflected the inherent differences in the physics of supersonic aircraft, Ellett said. Appropriate regulations are important, he added, because the physics of supersonic flight are very different from those of subsonic flight, and supersonic aircraft have very different takeoff and landing profiles. Current regulations do not reflect those differences and would be unworkable for supersonic aircraft.

Those initial requests for standards that also reflect supersonic aircraft initially were met with seemingly tepid interest from government officials. Regulators remained concerned about the possible perception that new standards might constitute a weakening of environmental regulations.

That approach in recent years has begun to change for a number of reasons. More players have expressed interest in entering the supersonic market, underscoring the potential for such a market. Congress has expressed its interest in the development of a supersonic market and mandated activities to that effect. And, research activity underway within both industry and the government has begun to develop a base of data that could be used to develop regulations addressing appropriate takeoff and landing standards. This data further could be used to potentially assure regulators, and the communities at large, that supersonic flight can be conducted far more quietly than it had been in the past.

Recreating the acoustic profile of the Concorde is a non-starter, Ellett said. And, he added, industry leaders believe that the “sonic boom”—which has long been a focus of much of the opposition to supersonic flight—can be largely resolved through research conducted in areas such as shaped booms or Mach cutoff. “Nobody is proposing to create a sonic boom that will sound like the Concorde,” he said.

The Aerospace Industries Association’s (AIA) Supersonic Working Group—which has been working with both regulators and lawmakers on the issue—is encouraging regulators to develop data-driven standards that focus on the characteristics of flight rather than speed itself. At the same time, AIA also wants to ensure appropriate environmental safeguards are built into any new standards.

“AIA believes it is important that decisions including revisiting the over-land ban on supersonic flight over the U.S. are based on robust data and realistic assumptions about how these aircraft will operate and what their impact will be,” the association said, calling the congressional measure a good first step.

The FAA has initiated two rulemaking activities: the first involving the noise certification of supersonic (including landing and takeoff standards) and the second to provide for special flight authorization for conducting supersonic flight-testing in the U.S. The second effort is designed to enable certification testing. The special flight authorization proposal was released this past summer and comments closed in late August.

But while the congressional directives called for the proposals, lawmakers didn’t include a deadline for completion of the rulemakings. The FAA may wait until ICAO develops its own standards before releasing a final rule, and ICAO is only in the early stages of such an effort.

The industry is hoping that CAEP working groups—one on noise and another on emissions—would be ready to vote on a standard by 2023 with full ICAO adoption by 2025. “We won’t have an international standard until then, and we may not even have a final FAA regulatory standard until then, because the FAA often waits for ICAO,” Ellett said.

OEMs Progress, Share Data

Meanwhile, companies such as Aerion, Boom, and Spike continue to progress on their supersonic projects. Aerion anticipates that it will apply for a type certificate as soon as this year. Once an application is filed in the U.S., the FAA consults with the applicant on the certification basis, including noise standards that the aircraft must meet as it goes through the certification review process. “Until you have a certification basis, you can’t lock in a certification design,” Ellett said.

This, however, will come before changes are made to Part 36 to reflect supersonic aircraft. To account for a lack of rules governing supersonic aircraft, the FAA will have to go through a special rulemaking process: proposing for public comment and adopting a “rule of particular applicability” that applies only to the specific aircraft undergoing type certification. “Otherwise you’d hold up these aircraft type certification projects for many years,” he said.

But in doing so, the FAA must continue to work with international regulators to ensure everyone is on the same page as far as the direction of future standards. If the special rule for Aerion were to be completely out of line with the international standard, Ellett said, “It would be a huge problem.”

The FAA, however, has been talking with the foreign countries involved in the ICAO working groups to come to an agreement on initial standards. Importantly, Ellett said, there appears to be a general agreement that the standards must be based on data.

AIA added that several of its members have been working with ICAO to furnish data results from their research.

“With all of the information and data from these certification projects, everyone will continue to talk. Hopefully, as we move out on this, we’ll gradually move toward a strong consensus on what the appropriate standard should be,” Ellett said. “I can’t say that we have the consensus now, but since everyone agrees there needs to be data generated by type-certificate applicants that support the standard…by all rights there should be consensus on what is ultimately developed.”

He cautioned a number of steps still remain before regulations are ultimately in place and “things can always creep in to delay the process.” But, Ellett added, “We are moving steadily and strongly in the direction of civil supersonic aircraft flight, and we have an industry very interested in this.”