Concorde Airport Noise
Engine noise during takeoff and landing has been a problem ever since turbojet aircraft were first introduced to the airlines. Noise suppression in jet aircraft has been a concern virtually since their inception. This is particularly true with commercial aircraft which, of necessity, must take-off, pass over, and land at or near populated areas. When new airports are built, where possible they are built away from populated areas and in a manner that the take-off and landing patterns avoid causing noise problems. In airport facilities such as San Diego, Calif. where the airport is very near the city, elaborate measures are mandated in an attempt to reduce the noise impact on the urban area. Even Los Angeles, Calif. has restrictions on aircraft performance upon take-off until the immediate urban area has been sufficiently cleared in distance and altitude. Many airports require engines to be throttled back as soon as it is safe to do so and restrict the rate of climb in the immediate vicinity of the airport.
Exhaust noise led to development of turbojet-noise suppressors and also contributed later the introduction of dual flow (turbofan) engines having reduced exhaust noise. Noise reduction efforts were then oriented towards attenuation of acoustical emission from the fan and compressor.
The situation has changed since SST studies began and exhaust noise of the required highthrust, low frontal area engines is again a major factor. Unfortunately, the presence of a noise suppressor in the exhaust produces thrust losses which, in general, become greater with increased acoustical effectiveness. The thrust loss is not great when the suppressor is designed for an engine with only a convergent primary nozzle. But in the case of an ejector or convergent-divergent nozzle, a considerable thrust loss of 10 to 15% can occur in the sub- and transonic stages of flight.
The Concorde exhaust noise suppressor makes a radial injection of mixing air in the primary jet stream using ten lobes in the form of triangular prisms hinged to the divergent section of the ejector nozzle. When suppression is no longer necessary, a feedback linkage allows the lobes to retract so as to eliminate all thrust losses in the cruise position. Model tests were used to develop detailed geometry of the design.
A noise evaluation process began formally with an advance notice of proposed rulemaking in 1970, and involved three notices of proposed rulemaking ("NPRM"), numerous public hearings, demonstration of the Concorde at Dulles and J.F.K. Airports, the preparation of two comprehensive environmental impact statements, and the consideration of over 11,300 comments from airport neighbors and other concerned citizens, airport proprietors, aircraft operators, aircraft manufacturers, and Federal, State, and local governmental agencies. These comments greatly assisted the effort to develop requirements that are balanced in their responsiveness to divergent public concerns, and are effective in terms of public relief from the noise of civil supersonic air transportation. These rule were developed over the course of 1 year in close consultation between Secretary of Transportation Brock Adams and FAA Administrator Langhorne Bond. The rules reflected the Secretary's responsibility for overall national transportation policy and his concern that these final rules properly take into account all aspects of that policy - including environmental, economic, and international aviation considerations.
On August 4, 1970, the FAA issued advance notice of proposed rulemaking No. 70-33, published in the Federal Register (35 FR 12555) on August 6, 1970. That notice initiated the public process of determining the nature and scope of the factors that must be considered in the development of noise ceilings for SST's. Notice No. 70-33 requested public comment on a number of issues and stated FAA's intent to ensure that SST's like subsonic airplanes, are subject to type certification standards that require the application of all economically reasonable noise reduction technology. Many public comments were received in response to this early invitation to public participation in the FAA's rulemaking on this matter and were considered in the adoption of these rules.
In early 1975, EPA proposed noise rules for supersonic transports (SSTs) applying FAA's standards for subsonic jets to future SSTs. On February 27, 1975, EPA transmitted FAA proposed regulations for the control and abatement of SST noise. These proposals were developed and submitted pursuant to sec. 611(c)(1) of the Federal Aviation Act of 1958, as amended. The 1975 EPA proposal would have required: (1) future design SSTs to meet noise standards applicable to new type subsonic airplanes; (2) existing types of supersonic airplanes (the Concorde and Russian TU-144) upon which "substantive productive effort" had not commenced before the date of the EPA Notice to meet the Stage 2 requirements of Part 36; and (3) SSTs already under production (at least 9, possibly 16, Concordes and an unknown number of TU-144's) to be treated separately.
The Port Authority of New York and New Jersey, the operator of JFK, banned the Concorde from landing because of its higher noise levels and low frequency vibrations. The British and French airlines subsequently filed suit to invalidate the ban. Numerous lawsuits ensued, but landings were ultimately approved.
This would have effectively banned the Anglo-French Concorde, so in January 1976, EPA reversed its stand, exempting the Concorde. President Ford responded to the controversial question of whether the Concorde should be permitted to operate in the U.S. by ordering a thorough investigation and study. The Secretary of Transportation decided to allow Concorde landings at Kennedy and Dulles Airports for a 16-month trial period.
On application of British Airways and Air France to operate the Concorde into the United States, Secretary of Transportation William T. Coleman, Jr., completed extensive hearings and authorized a 16-month trial of Concorde operations at New York and Washington, DC, Airports. On February 4, 1976, deciding an issue that had rekindled America's own SST debate, Coleman permitted, for a 16-month demonstration period, a limited number of Concorde supersonic flights between Europe and Dulles Airport. "Through these operations . . . we can get specific technical information . . . on . . . noise or any interference with the environment . . . and at the end of that 16-month trial period there will be an evaluation made by the Secretary of Transportation . . . But the only way you can find out is to actually undertake them on a limited basis for a limited period of time, and I fully support Secretary Coleman's decision" President Ford said on April 23, 1976.
On May 24, 1976, following a 3-hour 35-minute flight from London, the first Concorde supersonic commercial airliner landed at Dulles Airport. The French Concorde arrived from Paris approximately two minutes later. Although Concorde operations accounted for less than one percent of the take-offs and landings at Dulles International Airport, they resulted in 1,387 complaints or 79 percent of the total noise complaints received. The greatest percentage of Concorde complaints concerned take-off. Complaints were also made about structural vibrations. Studies of low frequency noise vibrations during the Dulles test period showed that, although the vibrations generated by the Concorde were greater than those of subsonic aircraft, they did not result in structural damage. Monitoring confirmed that, compared to the loudest jet subsonic transports, the Concorde was twice as noisy on takeoff and approximately as loud on approach. The 100 EPNdB contour from a Concorde departure may extend 20 miles or more from the start of takeoff roll. In terms of practical effects, outdoor communication at a distance of 2 feet could require shouting for those persons within the 100 EPNdB single-event contour.
On September 23, 1977, at the end of its 16-month trial at Dulles Airport, Adams proposed that the Concorde SST could land in eleven additional U.S. cities, unless banned by fair and nondiscriminatory local standards. In view of its exceptional loudness, however, he retained the ban on Concorde operations between 10:00 p.m. and 7:00 a.m., as well as the absolute prohibition on supersonic flight over land. On October 17, 1977, the U.S. Supreme Court lifted the ban by New York's JFK Airport on the Concorde SST, clearing the way for immediate trial flights. And on November 22, 1977, the first Concorde flights landed at New York City's John F. Kennedy International Airport.
Except for the 16 Concordes which were expected to have flight time before January 1, 1980, all SSTs are required by these rules to comply with the noise limits of Part 36 in effect on January 1, 1977 ("Stage 2 noise limits") in order to operate in the United States. The first 16 Concordes, which was the maximum number that the Britain and France are expected to manufacture before January 1, 1980, are expected from compliance with the Stage 2 noise limits of Part 36. There was no expiration date on this exception. However, under these rules, the excepted Concordes may not be operated on flights scheduled, or otherwise planned, for takeoff or landing at U.S. airports after 10 p.m. and before 7 a.m. local time. Moreover, these rules subject the expected Concordes that operate in the U.S. to an "acoustical change" requirement identical to that applied to U.S. type certificated subsonic airplanes that have not been shown to comply with Stage 2 noise limits. Like those subsonic airplanes (which are called "Stage 1 airplanes" in Part 36), the noncomplying Concordes may not be operated in the U.S. if their design is changed in a way that increases their noise levels.
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