2. Aircraft Operating Procedures
Operational procedures for the control of aircraft departures and arrivals at airports can effectively complement the reduction of aircraft source noise emissions. For example, operational controls that apply reduced thrust settings near the ground augment the noise reduction achieved through retrofitting because with the sound absorbing material or "quiet nacelle" modification of the JT3D and JT8D aircraft the noise reduction achieved becomes more effective at lower thrust levels. It must be clearly understood that, although much can be gained by operational procedures, they are not alternatives to reducing noise at the source by replacing or retrofitting the noisier airplanes.
Many air traffic and airspace management operational procedures are now used at particular airports to meet their particular needs. For some airports, normal approach paths cover substantial residential populations (Los Angeles); others are particularly sensitive to takeoffs (Miami). Where possible, approach paths are designed to avoid residential neighborhoods. At some airports, steep climbs are used on takeoff over water areas so that aircraft will be higher than they would be otherwise when they reach inhabited areas. Where aircraft must climb over residential areas, they often do so with reduced power in order to minimize excessive noise from greater engine thrust.
In addition to these measures, which are used at many airports, two standardized operational procedures have been under consideration by the FAA. One EPA approach proposal involved the development and implementation of the use of a two-segment landing approach path for aircraft. Briefly, that procedure entails the use of a steeper glide slope (e.g., 5 to 60) during the early stages of approach, followed by stabilization of the aircraft on the normal 3° glide slope for final approach and touchdown. During the steeper portion of the approach, the aircraft is higher from the ground and requires less engine power, thus achieving noise reductions at more distance points from the airport on the approach pattern. However, this would not provide significant noise relief to persons living close to an airport and could exacerbate their problem since there would probably be an increase in power required as the aircraft changes configuration from the steeper glide slope to the reduced glide slope. Additionally, this procedure has an inherent safety problem related to the impact of aircraft wake vortices on aircraft flying a standard 30 approach behind an aircraft utilizing a two-segment approach. Finally, this two-segment approach procedure could be applied at a limited number of airports because of limited equipment availability.
The second standardized approach procedure involves the use of minimum certificated flaps. This procedure was developed by FAA to abate airplane noise and then proposed by EPA as a regulatory action. Through the use of minimum certificated flaps during approach, aerodynamic drag is reduced, whereby less engine thrust is required. This has multiple advantages because reduced thrust results not only in a fuel saving but also a reduction in the source noise of the airplane over the entire approach phase, there by providing a noise reduction along the entire approach path. Moreover, it is a procedure which can provide noise benefits at all rather than a limited number of airports. Because it is a stabilized approach procedure, it reduces cockpit workload in that no transition is required from a 6° to a 3° glide slope and the inherent potential wake vortex problem a serious safety problem for following aircraft of is eliminated. Final regulations and procedures on a noise abatement approach procedure will be issued by FAA by January 1, 1977.
Several opinions exist regarding the best noise abatement departure procedure following takeoff. The FAA requires that turbine-powered and large aircraft climb as rapidly as possible to 1500 feet above the ground. This procedure provides some noise relief by getting the noise source -- the airplane - away from populated areas as rapidly as possible. FAA is in the process of evaluating different departure procedures which could be implemented after the 1500 foot altitude is reached. The issue is complicated by the fact that airports are unique in terms of their surrounding geography and adjacent land use. This means that there may be no single optimum noise abatement departure procedure.
The FAA currently recommends, in Advisory Circular 91-39, (January 18, 1974) a procedure that incorporates a reduction in engine power from takeoff thrust to normal climb power at an altitude of 1500 feet above ground level after takeoff with subsequent acceleration and climb after passing through 3000 feet by changing the deck angle and retracting the flaps. This procedure is generally used by scheduled air carriers. Northwest Airlines regularly uses a somewhat different departure procedure, in which the airplane is accelerated at takeoff power with an accompanying reduction in the deck angle and flap retraction followed by a larger power reduction than with the Advisory Circular procedure. Both procedures have merit in that both provide noise relief by reducing source noise through a reduction in engine power. The degree of perceived noise, however, depends or the location of noise sensitive areas beneath the departure path and the altitude and engine power of the airplane over those areas. The FAA expects to complete regulatory action on this subject by January 1, 1978.
Another operational rule under consideration involves possible restrictions on minimum altitudes in terminal areas by keeping airplanes high. Such restrictions would reduce the noise impact on the ground by maximizing the distance between the airplane and persons on the ground. This has been the FAA "Keep 'Em High" Program. A proposal on this subject to convert it from an air traffic management program to a regulatory requirement was submitted to the FAA by the EPA and was published in the Federal Register on January 6, 1975, as NPRM 75-40.
The design of each terminal area air traffic pattern is carefully constructed to meet the particular characteristics of the airport or airports encompassed within that terminal area. The runway configuration of the airport, character of the surrounding terrain, proximity of other airports, the requirements to avoid when possible low altitude flight over communities when arriving or departing the airport, are among the many considerations that must be made in designing terminal area procedures. It is not feasible to develop a single rule that would be applicable to all terminal areas for all airports. Regulations, which are relatively difficult to change, could have a severe and far-reaching impact on the air traffic system in the flexibility required to adjust air traffic procedures to compensate for weather changes, traffic congestion and safety considerations. Regulatory action in this area would be unduly restrictive without achieving significant improvements in aircraft noise abatement since the proposed rules were not significantly different from the existing air traffic management program and would have adverse energy and economic impacts through increased flight time and increased fuel consumption.
The FAA concurs with the objective of the EPA proposed regulations, specifically to reduce the noise exposure on the ground. Through recent FAA studies of ways to improve the efficiency of the air traffic control system to conserve fuel, a new procedure has been developed which improves safety through reduced low altitude flying time, standardizes high performance aircraft arrival procedures, equalizes the arrival delays through regulating the traffic flow, and provides for departures to climb to cruise altitude unrestricted. These new procedures will soon be made final in an FAA Order on Local-Flow Traffic Management. The Order will apply to all airports where high performance aircraft operate. The existing "Keep-'Em-High" Order will be phased out as the provisions of the new Order are implemented. A substantial noise benefit can be realized through the implementation of the Local-Flow Traffic Management Order over those benefits achievable under the FAA "Keep-'Em-High" program or the EPA proposed minimum altitude regulatory proposal.
All of these operational procedures designed to provide noise relief have been the subject of a number of discussions with the EPA and have been the subject of formal consultation between the FAA, the EPA and the Secretary of Transportation. That consultation process has been completed and the FAA has taken final action to implement these operational procedures.
3. Federal Research and Development Technology
As is the case with most fields of technology, continuing research and development on aircraft noise is necessary to insure that advances in the state-of-the-art are available for each successive generation of aircraft. Historically, there has been a ten year lag in the aircraft industry between demonstration of new technology in the laboratory and the appearance of that technology in commercial airplanes. For example, the present generation of quieter wide-body airplanes, such as the 747, DC-10 and L-1011, which began to enter commercial service in 1970, applied quieter technology of the high-bypass ratio engine developed about 1960. Similarly, more advanced engine quieting technology, which is being developed today, cannot realistically be expected to enter commercial service for at least five to six years.
Aircraft noise is generated primarily by two major sources in the engines: the external turbulent jet exhaust and the internal compressors and combustion process. High-bypass ratio engines, such as the Pratt and Whitney JT9D, the General Electric CF-6 and the Rolls Royce RB-211 now used on the 747, L-1011 and DC-10 aircraft, reduce the primary jet exhaust velocity and thus reduce its noise At the same time, improved sound absorbing materials in the nacelle surrounding the engine absorb much of the internal noise produced by the compressors and the combustion process. Current technology in new engines, such as the Pratt and Whitney JTIOD, and the General Electric CFM56, show potential for further reductions in engine noise levels through improved designs of the internal compressors which, if combined with more efficient wing design, and more effective control surfaces (flaps, spoilers, etc.) will require less engine thrust for safe flight, thereby providing further noise reductions.
It is expected that the technology for use in the next generation of commercial airplanes should provide further significant reductions below current noise standards. These will be evaluated carefully in considering both the applicability and scheduling of lower level requirements, such as proposed in NPRM 76-22.
A recent NASA analysis* has shown quite clearly that substantial long-term (through the year 2000) reductions in noise, fuel consumption, and aircraft emissions are achievable through the development and introduction of more advanced technology than that currently available. Realization of potential advantages through the extensive use of composite materials to reduce airframe weight, stability augmentation to reduce drag, and improved performance of advanced-technology engines such as the prop-fan will depend on the research and development necessary to demonstrate these factors. Such features can become available for service in the late 1980s, assuring continuing progress in aircraft quieting along with fuel economy, cleaner operation, and greater productivity.
* "Cost/Benefit Tradeoffs for Reducing the Energy Consumption of Commercial Air Transportation," NASA CR-137877, June 1976.
The federal government will continue to sponsor and support aviation research and development, in cooperation with the aviation industry. As engine noise levels are reduced, the aerodynamic noise from airflow over and around the airframe itself and its necessary appendages, especially at low altitudes, when flaps and landing gear are extended, may become the major approach noise source. Research on this noise source to determine how it may best be reduced is now underway and will continue.
D. Protecting the Airport Environment
There are over 13,000 public airports operated in the United States today and they vary considerably in size, proximity to populated areas and function as well as in the type and volume of operations. For example, only about 500 airports are fully certificated* by the FAA, while another 500 have limited certificates. Only 437 airports have an FAA air traffic control tower. American airports are also the busiest in the world; 84 airports have a total of over 200,000 annual operations,** while 160 airports have 150,000 or more annual operations. Busy airports are not only found in the larger metropolitan areas; while 244 airports have 100,000 or more annual operations, of these only 151 are located in large or medium hubs.*** Most of these operations are general aviation; only the top ranked 24 airports each have 100,000 or more annual air carrier operations.
* Under section 612 of the Federal Aviation Act, 49 U.S.C. 1432, the FAA issues operating certificates to airports served by Civil Aeronautics Board certificated air carriers that the FAA finds "properly and adequately equipped and able to conduct a safe operation."
** An operation is a takeoff or a landing; a flight thus consists of two operations, one takeoff and one landing.
*** A "hub" is defined by the FAA as a city in a standard metropolitan statistical area, as defined by the Bureau of the Census, requiring air service.
The variety of airports in the United States demonstrates that an airport noise reduction strategy cannot be completely generalized. The problem must be approached on an airport-by-airport basis, and all levels of government and the private sector should act with the recognition that solutions to the noise problem must be designed to meet the needs of a particular airport environment.
1. The Airport Proprietor's Responsibility
Substantial benefits will be achieved through federal actions to abate source noise and control operational flight procedure and airspace, but much of the noise problem is airport-specific and must be addressed by individual proprietors. Noise impact at any airport is in part due to local decisions on airport location, continuation of airport operations on a particular site, the layout and size of and airport and the purchase of buffer areas for noise abatement purposes. It is local decision-making that permits residential development near an airport. For these reasons, the Supreme Court concluded that proprietors are liable for aircraft noise damages. In addition, airport proprietors, particularly those that are public agencies, Generally encourage more service to their airports in Civil Aeronautics Board route proceedings.
The need for local action is apparent. Without effective land use planning, the implementation of land use plans and zoning, the benefits achievable from federal source noise reduction requirements could be greatly reduced. Where land use controls have not been imposed, the need for substantial airport land acquisition has increased, and as aircraft operations increase, the need for land acquisition as well as its cost will rise unless source noise levels are reduced.
The airport proprietor is closest to the noise problem, with the best understanding of both local conditions, needs and desires, and the requirements of the air carriers and others that use his airport. The proprietor must weigh the costs the airport and the community must pay for failure to act, and consider those costs against any economic penalties that may result from a decision to limit the use of the airport through curfews or other restrictions for noise abatement purposes.
FAA officials have and will continue to work with and assist airport operators and representatives of communities affected by airport noise to encourage the development of compatible land use controls. What constitutes appropriate land use control action depends on the proprietor's jurisdiction to control or influence land use. This, of course, varies with airport location. Almost all airport proprietors, however, are public-agencies with a voice in the affairs and decisions of their respective communities.. In some instances they have land use control jurisdiction and are required to document how they will exercise it before receiving federal airport development funds. In other instances, where they lack such direct control, before receiving federal airport development funds they are required to demonstrate that they have used their best efforts to assure proper zoning or the implementation of other appropriate land use controls near the airport and will continue to do so. Although the airport proprietor may not have zoning authority, he is often the local party in the best position to assess the need for it and to press the responsible officials into action.
2. State and Local Government Responsibility
State and local governments are directly and uniquely responsible for ensuring that land use planning, zoning, and land development activities in areas surrounding airports is compatible with present and projected aircraft noise exposure in the area. They should work closely with airport proprietors in planning actions to be taken in confining serious aircraft noise exposure to within the airport boundary and reducing the number of people seriously affected by airport noise.
State and local governments should support airport land use acquisition programs developed by airport proprietors. As federal noise source regulations shrink the contours of cumulative noise exposure, local governments concurrently should develop complementary land use plans preventing residential development and other incompatible land use in areas adjacent to the airport. Now that the federal government has defined a program extending the application of Part 36 standards, the local authorities will be able to plan effectively on the basis of a reasonable set of assumptions about the shrinkage in noise contours that will occur as a result of the federal action,
State and local governmental agencies can improve the insulation of housing, schools, community facilities, institutions providing health services and public buildings in areas exposed to serious airport noise. To date, such action would have been prohibitively costly. To achieve a 3 to 7 dBA reduction in the level of noise heard inside buildings by insulation would currently cost $1.9 billion nationwide, while a reduction of 8 to 12 dBA would cost $3.8 billion, and a reduction of 13 to 16 dBA would cost $7.2 billion. Given a federal program to require compliance with Part 36, a housing insulation program becomes more manageable and far less expensive. State and local governments should therefore develop appropriate programs to insulate public buildings and to finance insulation by private residents. In this regard, the Department is under a mandate in the Airport and Airway Development Act of 1976 to study the feasibility, practicality, and cost of insulating schools, hospitals, and public health facilities near airports and report legislative recommendations by July 1977. Local regulations should require proper insulation in the construction of new buildings and insulation of public and residential buildings. State and local governments should help finance the sound insulation of schools, hospitals, libraries, and other noise-sensitive public buildings.
Where appropriate, state and local governments should consider the development of new airport sites so that dense population areas will not be exposed to excessive noise and develop the necessary ground transportation to make them accessible. They should also require that notice of airport noise exposure be given to the purchasers of real estate and to prospective residents in areas near airports so that they will be aware of the problem. Finally, they should support improvements at existing airports which would help reduce the noise impact on surrounding communities.