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reservations about the technical details of the FNL, the FNL formula offers a useful tool for analyzing where we stand in relation to Part 36 and where we are headed.
Figure 1 shows the actual total ATA FNL for 1972 in the takoff and approach regimes, which are all that are considered in the proposed ru'e. This is plotted against the FNL which would exist if all aircraft met FAR Part 36.
Assuming that no aircraft are modified but that all new 727, 737, DC-9 and 747 aircraft delivered after 1972 meet Part 36, Figure 2 is a plot of the ATA FNL for 1972, 1977 and 1982. This shows that while we would get "quieter" we would still exceed Part 36 noise levels in 1982. Figure 3 shows the noise gaps from Part 36 levels which would exist; note that the largest gaps are in the approach regime.
Now let us consider how the gaps might be closed. Several hardware possibilities exist-assuming that the R&D now underway on nacelle treatment and refanning verifies current engineering estimates on noise reduction to be achieved and on costs. Until this verification takes place, and until this hardware is certificated by F.A.A., no action is possible.
Suggestion 1: Assuming we replace all of the 707, 720 and DC-8 aircraft remaining in the fleet in 1977 or 1982, with new, quiet wide body jets on a 2 for 3 basis, Figure 4 shows the resulting FNLs. It also shows that, while we would achieve the Part 36 FNL in the takeoff regime, a gap would still exist in the approach regime. This would cost over $5.3 billion if accomplished by 1977, or $3.8 billion if accomplished by 1982.
Suggestion 2: It is obvious from the analysis of Suggestion 1 that the approach regime is the problem area and we will limit our subsequent analysis to that area. The FAA R&D is not as yet complete on the 707 aircraft, as flight tests do not start until April 1973. Nothing outside of commonality analysis of the potential use of the 707 modification has been done on the DC-8. Using predicted noise level reductions we find that if the FAA retrofit were installed on all JT3D powered airplanes, the gaps on approach FNL still exist as shown in Figure 5. Firm costs on these modifications are unavailable but are estimated to be about $327-467 million for the 1977 fleet, and $246-352 million for the 1982 fleet. All cost estimates are for hardware only and do not include labor, aircraft downtime, or higher operating costs, which could be substantial. Higher fuel consumption would also result from this treatment.
Suggestion 3: The NASA new front fan program offers possible significant noise reductions for the JT3D and possibly the JT8D. If we should refan the JT3D powered airplanes the new FNLs for 1977 and 1982 would be as shown on Figure 6 for the critical approach regime. It can be seen that a gap would still exist between the Part 36 FNL and the actual FNL. This modification if applied to the 1977 fleet would cost about $766-934 million. If applied to the 1982 fleet the cost would be about $580–704 million. Performance would be at least as good as at present.
Suggestion 4: It therefore becomes obvious that something must be done to the JT8D fleet to close the gap between the Part 36 FNL and actual FNL. Figure 7 shows what would occur if the JT8D fleet alone were retrofitted to meet Part 36. The cost would be about $164-196 million for the 1977 fleet or $151-179 million for the 1982 fleet. Again this is shown for the critical approach regime. The gap on approach still exists. Further analysis shows the gap would still exist if all the JT8D aircraft were modified to incorporate the new front fan at a cost of $1.699 billion if done on the 1977 fleet, or $1.681 billion for the 1982 fleet. It can thus be seen that selection of either the JT3D or JT8D feet for retrofit or refanning, or even replacement of the JT3D fleet with wide body, quiet aircraft will not bring the fleet noise level down to the Part 36 level.
However, if both the JT3D and JT8D fleets were retrofitted with acoustically treated nacelles, the actual fleet noise level would meet Part 36. As indicated in Figure 8, this would cost $491-$663 million and would involve increased operating costs, fuel increases of 100–150 million gallons per year, and increased engine emissions.
Considerable doubt has been expressed that reduction of a fleet noise level to meet Part 36 would provide meaningful relief to the public. In the absence of solid knowledge of what is meant by “meaningful relief" we have strongly recommended additional government R&D to learn more about the subjective reaction 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 proce dure 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 pro grams; 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