The Aviation Safety and Noise Abatement Act of 1979 required the Department of Transportation -- after consultation with the Environmental Protection Agency -- to establish, by regulation, a single system for measuring noise from airports and surrounding areas. The act also required the Secretary to establish a single method for measuring the exposure of individuals to noise resulting from airport operations; that method had to consider noise intensity, duration, frequency, and the time of occurrence. According to a Senate committee report, the act was intended to establish a uniform approach for measuring airport-related noise in order to facilitate the administration of a federal noise abatement program that could, in turn, lead to a uniform approach for dealing with noise problems in general. Pursuant to that directive, in 1981, FAA selected the A-weighted decibel and the Day-Night Sound Level method for measuring airport-related noise. [FN 16]
[FN 18] Federal Interagency Review of Selected Airport Noise Analysis Issues (Federal Interagency Committee on Noise; Aug. 1992).
To address this concern, the 1992 interagency committee report noted that supplemental information -- particularly information on noise generated by individual takeoffs and landings -- has been, and could continue to be, useful, especially in characterizing specific events and in conveying a clearer understanding of the potential effects of noise on people living and working in the area. The interagency committee recommended that federal agencies continue to be allowed to use supplemental information at their discretion when dealing with environmental impact analyses and requirements. An official of the interagency committee noted, however, that while single event information is useful as a supplement, there is no methodology for aggregating the effects of a single event into cumulative impact analysis, as is the case with the Day-Night Sound Level method.
Because the interagency committee reiterated the usefulness of the Day-Night Sound Level method, all federal agencies have adopted it for analyzing airport-related noise in their environmental assessments and impact statements. Some agencies, however, such as the Department of Defense, use supplemental noise information, such as single event noise measures, to provide a fuller picture of noise conditions and their potential effects. A proposed revision to FAA’s requirements for environmental analyses states that FAA will also use supplemental information where warranted. [FN 19] The revision adds new guidance on the kinds of supplemental information available and their use.
FAA establishes the standards limiting the noise that civil subsonic turbojet aircraft are permitted to generate. [FN 1] Those standards are generally based on an aircraft’s weight and the number of engines and generally allow heavier aircraft to generate more noise than lighter aircraft. The statutory deadline of December 31,1999, for compliance with "stage 3" standards did not apply to aircraft weighing 75,000 pounds or less that were already in operation. As of October 1, 1999, more than 2,750 aircraft were not subject to the stage 3 compliance deadline.
Noise Standards Generally Permit Heavier Aircraft
to Generate More Noise Than Lighter Aircraft
FAA regulations establish the maximum noise levels that civil subsonic turbojet aircraft are allowed to generate for takeoff, landing, and "sideline" measurements. The standards for each of these kinds of measurements are different, but, in general, these standards vary with the weight of the aircraft. The standards allow heavier aircraft to be noisier than lighter aircraft because, according to FAA, the noise generated by an aircraft is generally determined by the thrust powering the aircraft; the amount of thrust an aircraft needs is proportional to the weight of the plane -- that is, the heavier the aircraft, the more thrust it needs. [FN 2] According to an aircraft noise expert, lower noise standards for lighter aircraft is one of the reasons that a stage 2 aircraft weighing 75,000 pounds or less may make less noise than a heavier aircraft that meets the more stringent stage 3 standards. For takeoff, stage 3 noise standards also vary on the basis of the number of engines; generally, the more engines an aircraft design has, the higher the permitted takeoff noise levels. Stage 3 standards for takeoff, sideline, and approach are shown in appendix VII.
Existing Aircraft Weighing 75,000 Pounds or Less
Have Been Exempt from Operating Restrictions
Both stage 1 and stage 2 aircraft that did not meet more stringent noise standards by specified dates have been prohibited from operating after those deadlines, but that prohibition does not apply to aircraft in service that weigh 75,000 pounds or less. FAA did not require the retirement of the lighter stage 1 aircraft that did not meet stage 2 standards because FAA concluded it was not technologically practicable or economically reasonable to modify these aircraft. The statute prohibiting the operation of stage 2 aircraft that did not meet stage 3 standards by a certain date does not apply to aircraft weighing 75,000 pounds or less.
Exemption From the Stage 1 Operating Deadline Was for Technological and Economic Reasons
When FAA amends regulations controlling aircraft noise, it must consider several factors, including whether the proposed regulations are technologically practicable, economically reasonable, and appropriate for the types of aircraft, aircraft engines, or aircraft certifications that the regulations apply to. [FN 5] FAA must also consider the extent to which any proposed amendments protect the public health and welfare.
FAA chose not to apply the operating deadline for stage 1 aircraft to aircraft weighing 75,000 pounds or less. FAA concluded that it could not impose operating noise limits on the lighter aircraft at that time in a manner that was fully consistent with its obligations under the law for two reasons. First, FAA determined that the cost-effectiveness of implementing the kinds of modifications needed to retrofit an existing aircraft was questionable and, therefore, not technologically practicable. It concluded that noise reduction modifications to the lighter aircraft could be applied during the original design and manufacture of an aircraft, but such modifications involved substantial redesign efforts that, while reasonable when spread over the production process, were of doubtful cost-effectiveness if accomplished by retrofitting. FAA considered only retrofitting options -- engine modification or replacement -- as acceptable for meeting noise standards; flight operation noise abatement procedures were not an acceptable means for complying with the noise standards. [FN 6]
In December 1997, however, the National Business Aviation Association, a membership organization of companies that operate aircraft, passed a resolution calling for the group’s 5,200 members to refrain from adding new stage 1 aircraft to their fleets beginning in January 2000 and to end the operation of stage 1 aircraft by 2005.
Statutory Deadline for Stage 2 Retirement Did Not Apply to the Lighter Aircraft
The Airport Noise and Capacity Act of 1990 established December 31, 1999, as the deadline for phasing out stage 2 aircraft that were not modified to meet stage 3 noise standards. The statute, however, specifically applied the phaseout only to aircraft weighing more than 75,000 pounds. The legislative history of the act provides no discussion on why the statutory phaseout was not applied to the lighter aircraft. [FN 7] As of October 1, 1999, just over 9,000 civil subsonic turbojet aircraft that weighed 75,000 pounds or less were certified by FAA as airworthy. [FN 8] About 31 percent of those, or just over 2,770, are stage 1 or stage 2 aircraft that may still operate at U.S. airports after December 31, 1999.
[FN 8] As of Oct. 1, 1999, FAA had certified nearly 300,000 fixed-wing aircraft as airworthy. About 5.3 percent, or just over 15,500, of those were civil subsonic turbojet aircraft.
[FN 10] The statute requires analyses of such things as the costs and benefits of the proposed restriction and a description of alternatives. The airport operator also must describe alternative measures considered that do not involve aircraft restrictions and a comparison of the costs and benefits of these measures with those that do involve aircraft restrictions. (49 U.S.C. 47524).