Is it possible to produce a quiet jet airplane? Though the ultimate answer is cloaked in ambiguity and controversy, the general impression seems to be that aircraft could be designed to generate tolerable noise levels—at a cost. The ideal would be to start from scratch and develop a form of propulsion in which design for quiet was given as much weight as design for speed, power, and operating efficiency. Some believe this could be done if we made the same financial commitment to developing quiet subsonic aircraft as we are making to develop the SST.
Not only have we failed to make such a commitment, we find every step towards quiet design impeded by dollar signs. A March 1966 report of the Office of Science and Technology concluded that "In general, it is technically possible to suppress the noise of an exhaust jet, however, it is very costly in terms of percent of aircraft gross weight and installed hardware."
The Federal government has embarked on a jet noise alleviation program involving modifications in air frame and engine design, airport planning, modified flight procedures, and public relations programs. It is not expected that the "quieter engine" will solve the noise problem without moving noise away from the people by means of air traffic procedures, and keeping people away from the noise by zoning to keep residential development at a distance where complaints will be minimal. Sometime in 1972 the FAA in cooperation with NASA hopes to have a quiet engine, some 20 Perceived Noise Decibels quieter than present jet engines. This research engine will provide 50 hours of flight testing. The program is budgeted at $50 million.
In essence, our research goal is for a jet engine quiet enough to reduce the number of vigorous complaints.
To decrease the number of people who will be exposed to jet noise, airports may employ "preferred" runways, runways pointed away from land with dense residential development. Unfortunately, however, uncertain weather conditions and airport congestion tend to interfere with the preferred runway concept. Even if fewer homes, through new airport planning, are noise-impacted, those homeowners who are affected will still suffer.
There have been suggestions for changes in procedure such as slowing planes down, increasing their glide angle, and so forth. Pilots resist these practices on the grounds that they diminish certain safety margins. Indeed, it is stated in the jet-noise report cited above that modifying approach/takeoff procedures can pose safety problems.
With proper planning, new airports and heliports would not be sited where they can destroy livability. America's planning officials have access to guidelines provided by the FAA to keep from making glaring errors in deciding how far from the airport residential construction and development ought to take place. (An impartial analysis of these guidelines is needed to make sure they provide a desirable environment, and not one acceptable in the terms of the aviation industry.)