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action of people to noise, and how much reduction will achieve truly meaningful relief. We suspect it is something on the order of 10-15 EPNdB or more. However a recent Swedish study on takeoff noise published in 1972 indicates that in areas expose to a high number of takeoffs (63 or more per 24 hours) noise will remain a significant problem as long as the noise levels from single takeoff overflights exceeds 73 dB(A) (approximately 86 EPNdB). Boeing studies on aerodynamic noise in the approach configuration show that this approximates 93-95 EPNdB on the 727 and 98-102 EPNdB on the 747.
None of the suggestions offered herein will provide the relief we believe may be necessary. It should be noted that, as we add more and more so-called “quiet” wide body jets the FNL allowed by Part 36 rises, as was indicated in Figure 2. The reason for this is that since Part 36 allowables are based on gross weight the larger airplanes are permitted to be noiser than the airplanes they replace.
On the other hand the FNL rule does not take into account the benefit of noise reduction through the use of operational procedures. Our main purpose, and that of the government, should be to reduce the noise for the greatest number of people. Meeting Part 36 noise levels at the specified measuring points does not necessarily accomplish this. At the same time, as depicted in Figure 9, a Boeing 727–200 aircraft executing a two-segment approach procedure can reduce the 90 EPNdB impacted area from 5.5 to 1.8 square miles—a 67% reduction. The same procedure will also reduce the 95 EPNdB impacted area from 2.1 to 1.0 square miles-a 48% reduction. This is depicted in Figure 10.
Now it seems to me that the facts are trying to tell us something. Achievement of Part 36 FNL's will provide little discernible noise relief to the public. Because of the expense of modifying existing aircraft, there must be some question as to the cost/effectiveness of this approach, regardless of who pays the bill. If the achievement of the Part 36 FNL does not give the public meaningful relief the result will be a loss of credibility by both industry and government.
Improved operational procedures offer the greatest relief to the most people in the shortest time span. Our long term efforts should concentrate on significant noise reductions on newly type certificated aircraft. The manufacturers, in response to an FAA request, have indicated a reduction of 10 EPNdB below Part 36 noise standards constitutes a "desirable goal". We think a better "target” would be 15 EPNdB. To reach this goal, however, improvements in basic aircraft design must be considered because we would now be approaching that level of noise which current aircraft would make in a power off glide-in other words, aerodynamic noise.
This brings us back to the subject of research and development which we have emphasized over the years as the surest path to meaningful noise reduction. At the present time the government is spending approximately $50 to $60 million on noise R&D. Although it is difficult to determine how much money is spent by the aerospace industry itself, the total for both government and industry is probably below $100 million a year. Presumably this total will decrease when work is finished on the acoustical nacelle research, the front fan research, and the quiet engine program. At that time the Country will lack a well rounded R&D program which assures the public that the next generation of aircraft will not produce unacceptable environmental intrusions.
Doesn't it seem imprudent to make expenditures ranging from $500 million into the billions of dollars in order to produce a few decibels of noise reduction, which may or may not be perceptible, when at the same time there is no program for insuring that future aircraft will operate at acceptable noise levels.
To put this another way, billions could be spent on retrofit or refanning programs; yet by 1980 the public could be just as unhappy with us and with the government as it is today. On the other hand, a well rounded R&D program would probably not require more than $200 million to $300 million. From this we could be assured that future aircraft would be the good neighbors that we talk about so frequently.
It is not my purpose to try to persuade the Committee what the answers to these questions should be; however, they deserve careful examination as vital issues of public policy.
NORMAL ATTRITION – ALL 727, 737, DC-9 AND 747 AIRCRAFT