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###### Department of Transportation

###### Federal Aviation Administration

          - 14 CFR Part 36

# AGENCY:

Federal Aviation Administration (FAA), DOT.

# ACTION:

Statement of policy.

# SUMMARY:

This action clarifies the Federal Aviation Administration's (FAA) policy on the calculation of derived noise levels submitted for publication in Advisory Circular (AC) 36-3, Estimated Airplane Noise Levels in A-Weighted Decibels. This action is intended to provide guidance on calculating the derived levels used in that publication.

# FOR FURTHER INFORMATION CONTACT:

                        Mr. James Skalecky, Office of Environment and Energy (AEE-100), Federal Aviation Administration, 800 Independence Avenue, SW., Washington, DC 20591; telephone (202) 267-3699; facsimile (202) 267-5594; e-mail                         *James.Skalecky@faa.gov.*

## Background

Paragraph 3 of AC 36-3 states that “14 CFR part 36 requires the reporting of turbojet and large transport category aircraft certificated noise levels in units of Effective Perceived Noise Level in decibels (EPNdB). Many airport and other community noise analyses utilize a noise rating scale that is based upon A-weighted decibels. For this reason, A-weighted noise levels for aircraft under 14 CFR part 36 conditions have been estimated to provide a reference source for aircraft noise levels that is consistent with the many noise rating scales having A-weighted noise level as the basic measure.” The noise levels published in AC 36-3 for turbojet and large transport category airplanes are usually submitted to the FAA by the airplane type certificate (or supplemental type certificate) holder. The entity submitting the noise levels for publication is responsible for deriving the A-weighted level from the EPNdB levels submitted for certification.

Recently, we received an inquiry requesting a clarification of those reference procedures, data analysis procedures, and data corrections that are to be used in deriving A-weighted noise levels for publication in AC 36-3. The question and our policy stated in this document apply only to noise levels for turbojet and large transport category airplanes.

## Policy Statement

In order to ensure that all airplane noise levels submitted for publication in AC 36-3 are derived in a consistent manner, it is the FAA's policy that the noise levels be derived using the same reference procedures, data analysis procedures, and data corrections/adjustments that were used in deriving the 14 CFR part 36 certificated noise levels. The only exceptions are for deviations necessitated by (1) differences between the effective perceived noise level and A-weighted sound level metrics, or (2) inclusion of approach noise levels corresponding to use of less than the maximum flap setting, as permitted under AC 36-3, paragraph 4.a. In the case of number 2, the deviation is limited to the use of an approach configuration other than the noise-critical configuration that is required for the noise certification approach reference procedure by part 36, Appendix B, paragraph B36.7(c)(5). Such deviations must be identified to the FAA when the data are submitted for inclusion in the AC. No other deviations will be accepted.

When an airplane model that is already listed in AC 36-3 is recertificated from 14 CFR part 36 Stage 3 to Stage 4, the noise levels corresponding to the Stage 3 configuration are not automatically replaced. The Stage 3 noise levels will remain in AC 36-3, unless noise levels corresponding to the Stage 4 configuration are submitted for publication. If Stage 4 noise levels are submitted, the FAA will remove the Stage 3 noise levels from AC 36-3 for that model and replace them with the Stage 4 noise levels when the AC is updated.

Noise levels submitted for Stage 4 configurations must conform to this policy for deriving noise levels submitted for publication in AC 36-3.

Issued in Washington, DC, on June 2, 2009.

Lourdes Q. Maurice,

Acting Director of Environment and Energy.

[FR Doc. E9-13333 Filed 6-5-09; 8:45 am]

BILLING CODE 4910-13-P