SONIC BOOM COMPLIANCE
The Aerion SBJ is designed to operate effectively under the existing sonic boom regulations with the potential to adapt as the regulations are changed. For flights over the United States where aircraft must stay below Mach 1.0, Aerion cruises efficiently at Mach 0.98. In other populated parts of the world the regulations require that a sonic boom does not reach the ground. There, Aerion can cruise as fast as Mach 1.1 without creating a sonic boom on the ground. Over the oceans and other uninhabited areas, Aerion can cruise at up to Mach 1.6.
The baseline Aerion aircraft has a relatively low sonic boom, with an initial overpressure of about 0.8 psf. This is less than the boom of many supersonic fighters and much less than the Concorde. Relatively minor changes to the Aerion design can reduce the overpressure to 0.5 psf. Over the next several years, regulations for low sonic boom will be developed and low-boom technology will be improved. Aerion will then develop low-boom aircraft to operate under the new regulations.
Aerion is briefing government groups on its supersonic business jet program as regulators consider how to treat a new generation of supersonic aircraft. In Europe and America, government bodies and state-funded programs are discussing environmental concerns in public forums. Aerion participates in these forums to encourage the development of new standards for supersonic aircraft. Because the outcome of these early discussions with regulators is uncertain - and any new regulations are many years away, Aerion is not seeking a rules change to introduce its supersonic aircraft. Among these forums:
FAA: The FAA's Office of Aviation Policy, Planning and Environment - the branch of the FAA focusing on new noise standards for supersonics - held its first public hearing on the subject in October 2008 in Chicago. A second meeting was held in February in Palm Springs, with a third yet to be announced. As intended, the first meeting attracted those curious about the potential for supersonic aircraft: community leaders, business jet operators, airport management, OEMs, environmental activists and members of the public at large. Richard Tracy from Aerion discussed the company's supersonic aircraft, which will meet Stage 4 noise requirements, and ICAO emissions criteria, but does not incorporate technology to suppress a sonic boom. The FAA - the only national aviataion authority that sets a speed limit of Mach 1 - is gathering information from the public and from government research groups, including NASA. The agency is responding to growing interest in supersonic aircraft among manufacturers and potential operators.
For its next open meeting, the FAA has requested that Aerion present more information on Mach Cut-Off flight, a means of cruising at low supersonic speeds without creating an audible disturbance. The agency is interested in the physics of the technology, and how onboard systems would collect atmospheric data and adjust speed allowing for cruise up to about Mach 1.2 without producing a boom on the ground. Mach Cut-Off relies on the principle that the speed of sound increases with temperature, and therefore is lower at cruise altitude than on the ground. By adjusting cruise speed based on temperature data, the sonic shock wave can be kept from htiting the ground, dissipating instead at a selected altitude, for example, 5,000 feet.
ICAO: The International Civil Aviation Organization, which sets global aviation standards, is looking at similar issues. In April 2009, Aerion's business and testing manager, Jason Mtisheck, participated in a Paris meeting of ICAO's Working Group 1, which establishes noise and noise testing critera. Working Group 1 has established a Supersonic Technical Group to look into determining criteria for supersonic aircaft. This subcommittee is examining sonic boom shaping for noise reduction, and the effects of boom pressure waves on structures such as buildings and homes.
HISAC: Aerion is also participating in HISAC, a European Commission-funded consortium led by Dassault with 37 partners from 13 countries. Aerion is not a formal partner, but has been welcomed to the group to brief it on the Aerion SSBJ. HISAC, an acronym for Environmentally Friendly High Speed Aircraft, is studying the technical requirements and feasibility of business-jet-sized supersonic aircraft with reduced sonic boom signatures, low airport nose and low emissions.
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