Code of Massachusetts Regulations
740 CMR - MASSACHUSETTS PORT AUTHORITY
Title 740 CMR 24.00 - Logan Airport Noise Abatement
Appendix B - Methodology to Establish Tier I and Tier II
Criterion Values
The following pages describe the methodology for establishing for years subsequent to 1986 both the stage 3 percentage level (hereinafter referred to generally as "Tier I") and the NPSI level (hereinafter referred to as "Tier II) required of certain air carriers in order to comply with 740 CMR 24.03(1)(a) or (b).
I DATA SOURCES
These calculations will be based on data routinely supplied by each carrier in compliance with the reporting procedures specified in 740 CMR 24.00. This data will include the following:
A Aircraft Type Characteristics
Each aircraft type in a respective carrier's fleet that operates at Logan Airport will be defined in terms of the following characteristics.
- model series
- engine type
- maximum certificated landing weight
- maximum certificated takeoff weight
- Part 36 certificated approach and takeoff noise level in EPNdB
- Part 36 stage certification (i.e.,1, 2, or 3)
B. Operations by Aircraft Type
The number of operations to be conducted by aircraft type as defined in step IA will be reported by the respective carriers. Reported operations will be uniformly changed based on projected growth for the upcoming year.
II CALCULATE ANNUAL AIRPORT CUMULATIVE NOISE
Based on the operations data by and aircraft type characteristics supplied above and projected growth calculate annual cumulative noise at Logan Airport for the upcoming year per the following steps:
A. For each carrier and aircraft type determine the proportion of scheduled daytime and nighttime takeoffs and landings conducted during the reporting period. The proportions will be computed using the OAG database. Daytime is defined as 7:00 AM to 10:00 PM and nighttime from 10:00 PM to 7:00 AM. Based on the proportions above, sub-divide the number of operations reported for each aircraft type into daytime departures, nighttime departures, daytime landings, and nighttime landings. Compute the total noise energy generated by the operations conducted in individual aircraft types as follows:
1. Take the antilogarithm to the base 10 of the TAKEOFF EPNdB noise level defined in IA and multiply it by the number of daytime departures.
(TAKEOFF EPNdB/10)
10 X Total daytime departures
2. For nighttime departures, take the antilogarithm to the base 10 of the same takeoff EPNdB noise level and add 10 to account for the 10dB weighting for each operation conducted at night. Multiply this value by the number of nighttime departures.
((TAKEOFF EPNdB+10)/10)
10 X Total daytime arrivals
3. Take the antilogarithm to the base 10 of the Approach EPNdB noise level and multiply it by the number of daytime arrivals.
(APPROACH EPNdB 10)
10 X Total daytime arrivals
4. As in step 2 above, add the 10 dB nighttime penalty to the antilogarithm to the base 10 of the approach EPNdB level and multiply it by the number of nighttime arrivals.
((APPROACH EPNdB+10)/10)
10 X Total nighttime arrivals
5. Add the values derived in steps 1 through 4 above to yield the total noise energy generated by the operations conducted by each aircraft type.
B. Add the total noise energy value computed for each aircraft type to yield total noise energy for all airport operations.
C. Take the logarithm to the base ten of the total airport noise energy value obtained in step IIC and multiply by ten. The result of this calculation is the cumulative EPNdB noise level for all airport operations.
III ANNUAL GOAL ASSESSMENT
Compare the cumulative annual EPNdB level computed in step II to the 1984 base case level. of 156.34dB. If the computed level falls within the range of 0.1 to 0.3dB below the 1984 base level then no adjustment in the stage 3% share for the Tier I criterion or the NPSI for Tier II is necessary.
If the computed annual noise level is not at a minimum of 0.1 dB below the 1984 base level then Tier I and Tier II criterion will require adjustment to produce greater cumulative noise reduction. If, on the other hand, the computed noise level proves to be greater than 0.3 dB below the 1984 base level, then the Tier I and Tier II criteria will be adjusted to bring the cumulative noise reduction back within the range of the projected goal of the regulations.
The methodology for calculating the adjustment to the Tier I stage 3 % criteria and the Tier II NPSI are described in the following.
IV TIER I AND TIER II ADJUSTMENT METHODOLOGY
A Adjustment where cumulative noise not reduced in compliance with goals.
In this case the Tier I stage 3% and the Tier 2 NPSI criteria have to be constrained further to produce at a minimum a reduction in cumulative airport noise of 0.1 dB. The method to compute the required adjustments follows:
The methodology is based on the use of the database developed in section II to derive the cumulative airport noise level.
1. Determine the increase in the stage 3 share necessary to achieve the minimum 0.1 dB noise reduction as follows. First, compute the stage 3 share of the existing fleet. Next, holding seats and day/night proportions constant substitute stage 3 for stage 2 operations and then recalculate the cumulative noise level. Repeat this calculation in an iterative manner until the 0.1 dB minimum reduction in cumulative noise is accomplished. Recalculate the stage 3 share for the adjusted fleet that meets the goal. Then compute the net difference between the stage 3 share for the existing fleet that did not satisfy the goal and share for the adjusted fleet that met the goal. Add the net difference in the stage 3 share to the Tier I % criteria scheduled to be used during the upcoming evaluation period.
2. Determine the reduction in the NPSI criteria for Tier II th at is necessary to achieve the minimum cumulative noise goal. First compute the NPSI value for the existing fleet per the methodology described in attachment Appendix A Next, compute the NPSI for the fleet defined in step IV AI that satisfied the noise goal. Compute the net difference between the NPSI for the adjusted fleet that meets the goal and the existing fleet that did not meet the goal. Subtract the computed difference from the NPSI value scheduled to be used for the upcoming evaluation period, which effectively reduces the NPSI value scheduled to be used for the upcoming evaluation period, which effectively reduces the NPSI in order to achieve a greater reduction in cumulative noise.
B. Adjustment Where Cumulative Noise Reduction in Excess of Goal
In this case, Tier I stage 3 share and the Tier II NPSI criteria can be relaxed to produce a maximum reduction in cumulative noise of 0.3dB. The method to compute the required adjustment follows. In each case, the methodology essentially reverses the procedures described in section IV A
1. Again, using the fleet database developed in section II, determine the decrease in the stage 3 share that would produce a maximum noise reduction of 0.3 dB. First, compute the stage 3 share of the existing fleet. Next, holding total seats and day/night proportions constant sub stitute stage 2 for stage 3 operation iteratively until cumulative noise reduction is cut back to 0.3 dB. Then recalculate the stage 3 share for the adjusted fleet mix that produces noise reduction within the goal range. Next, compute the net difference between the stage 3 share for the existing fleet that produced excessive noise reduction and for the projected fleet that produces the maximum reduction goal. Finally, subtract the computed net difference in stage 3 share from the Tier I share scheduled to be used for the upcoming evaluation period.
2. Determine the increment to be added to the NPSI value for Tier II th at is consistent with a maximum cumulative noise reduction of 0.3 dB. First, compute the NPSI for the existing fleet that produced the excessive noise reduction (per the methodology in Appendix A). Next, compute the NPSI value for the projected fleet that produced the preferred maximum noise reduction in step B1. Then compute the net difference between the NPSI for the existing fleet that produced excessive noise reduction and the adjusted fleet mix that meets the maximum goal. Then add the computed difference to the NPSI value scheduled to be used during the upcoming evaluation period which effectively relaxes the constraint on cumulative noise reduction
