Sky Posse Palo Alto

Dear Friends, 

In this update, we are pleased to share the following,

  • NEW! Aircraft Noise Study by MONA (Metroplex Overflight Noise Analysis) and Stanford
  • FAA Noise Policy Review
  • The FAA Reauthorization

Landmark Study - THANK YOU to local experts for leading on this work

We are excited to share with you the publication of the MONA study, “A large-scale validation study of aircraft noise modeling for airport arrivals,” Thomas C. Rindfleisch et al., this week in The Journal of the Acoustical Society of America. It is the first analysis with robust arrival flight noise data for areas not only in the vicinity of the airport to evaluate the FAA’s noise quantification and prediction tools AEDT-R and AEDT-AE. We encourage everyone to follow the methodology of the study. Pairing AEDT noise predictions for SFO arrival flights with ground sound level meter noise measurements, the study found that the FAA’s regulatory compliance prediction tools systematically underestimate arrival noise metric levels both near and far away from SFO depending on aircraft type.

The study analyzed a dataset of over 200,000 AEDT noise predictions and ground sound level meter SLM measurements, and focused on SFO arrivals along three high-density routes covering a year of observations from 2021 to 2022.

Per the study, it “compared AEDT's noise predictions using two different modeling approaches: 

  • AEDT-R: ANP/BADA 3, with only ground-track positions specified; no altitude or airspeed controls are provided. This is the modeling approach required by FAA for regulatory purposes.
  • AEDT-AE: BADA 4, with both altitude and airspeed controls specified for each ground-track position.”

A summary of the analysis about AEDT-R states that. “The resulting statistical data indicate that this type of modeling is overly simplistic and gives far from accurate comparison with ground SLM measurements." The study goes on to say that despite the deficiencies of AEDT-R, it is the only FAA-approved regulatory mode for the use of AEDT. Regarding AEDT-AE, the study points to “a systematic underestimation by AEDT-AE in its predictions for LAmax and SEL metrics by significant but highly varied amounts depending on aircraft type and performance model.”

Please find the study at this link:

FAA Noise Policy Review:

At the UC Davis Noise & Emissions Symposium held on March 4, we heard a deep dive into the history, evolution and legal aspects behind the FAA’s current 65 DNLnoise threshold policy. It supported our view that the threshold policy crafted for meeting airport-specific noise statutes (Part 150 and land use) is not appropriate for National Environmental Policy (NEPA) compliance. Federal agencies do have the discretion to choose how to comply with NEPA, and this could be positive in that an act of Congress is not necessary for the FAA to improve how the FAA complies with NEPA; however, we see serious conflicts if the FAA were to continue to “bootstrap” airport-specific policies for different laws or aims. Noise assessments, pursuant to airport rules and NEPA have in common that both require the calculation of cumulative exposure, but the use and purposes are different. For example, with airport statutes, AEDT is used to establish 65 DNL noise contours for voluntary insulation programs to mitigate noise near airports, and for land zoning decisions. Whereas with NEPA, AEDT is used to predict a change in impacts to evaluate airspace actions for environmental reviews and disclosures. Noise information for NEPA is meant to allow for local input, to consider local context irrespective of the distance from an airport (depending on the level of NEPA review). The 65 DNL pre-judges decisions about the level of review to carry out, effectively saying that the process to inform and engage communities will only be funded for issues at the 65 DNL and not to address citizen concerns outside that scope. The FAA faces ongoing legal NEPA challenges from communities outside the 65 DNL; instead of federal resources going to fight communities, they should be used to address these urgent concerns. We will have a further review of the FAA’s noise threshold policy in our next update as well as more on the symposium. 

The FAA Reauthorization:

The FAA’s funding, last authorized for five years in 2018, was planned to complete a five-year reauthorization in 2023. It is currently on a third short-term funding extension through May 10. Without extensions, the FAA would lose its authority to collect revenues from the Airport and Airway Trust Fund. The House passed its version of an Authorization bill last summer; the Senate Commerce Committee passed a version in December focused on Improving Safety and Advancing Technology. Lawmakers are now in the phase of negotiating a comprehensive Reauthorization. We expressed our priorities to Rep Eshoo and the eight priority issues were reported by the Airport Noise Report on February 24, 2023. We continue to emphasize their importance with Rep Eshoo’s office. The most challenging issue we see is how airports receive revenues from excise taxes on passengers, cargo and fuel to fund airport infrastructure and other aviation programs yet are prohibited from funding permanent noise monitors or other needs to support noise abatement initiatives for areas not in the vicinity of airports (historically deemed “revenue diversion”). The FAA’s policies state that managing aviation noise is a “shared responsibility;” we hope that we can see more of that ahead.


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Sky Posse Palo Alto