NextGen Carbon Reduction
Macro NextGen Carbon Reduction Study vs. Micro Local Noise Assessments
Dr. Karen Marais has published a study, entitled Environmental Benefits of Space-based ADS-B, estimates that NextGen will reduce approximately 14.3 million metric tons of carbon dioxide (CO2) that would have been released into the atmosphere between 2020 and 2030 by the flights to be flown. She translated that figure to one more readily understood by the average consumers– introduction of this satellite-based navigation system should be compared to “removing more than 300,000 cars” annually.
Here are some of Dr. Marais’ specific findings:
- Single-engine taxi procedures.
- Continuous/idle power descents.
- Optimized profile descents and approaches during which aircraft fly shorter approach patterns at lower power settings.
- Remote and oceanic airspace…air traffic control over the Atlantic Ocean and other remote regions must be performed without radar data. With NextGen’s ability to track aircraft over these radar-less areas…aircraft will be monitored and separated aircraft over oceans.
- Space-based ADS-B offers a way to use jet streams more effectively, by efficiently routing flights as close to their wind-optimal routes as possible.
- Straightening flight routes and optimizing flight cruise levels.
While it is very useful for academics, particularly from highly regarded aviation universities like Purdue to make such independent assessments, these macro conclusions really confirm what the FAA has been saying at its website–
We applaud and agree wholeheartedly with Dr. Marais and her students’ findings.
However, there is considerable local opposition to NextGen based primarily on the local, micro impacts. In fact the virulence of these objections to the noise impact of these more precise flight patterns may result in Congress’ reconsideration of the funding on this new technology’s installation.
To assure continued progress of NextGen, the FAA would be advised to address the micro impacts of noise. While the total number of people impacted is reduced, the population under the precise flight paths are experiencing extremely increased frequency of noise from aircraft. The impact of which, may not be considered significant by the FAA (1.5 Db at 65 DNL and above). It is achieving a level of annoyance that many communities are finding unacceptable. A recent study published by JDA addresses the current FAA noise management policy relative to international standards and recommends lowering the FAA threshold of significant impact.
We believe there are three factors influencing the unidentified impacts:
- The Macro study of these implementations are done above 3,000’ and by the air traffic environmental guidance. The impacts below 3’000 feet are normally evaluated by the airport environmental guidance and have not been conducted. Significant impact may be occurring below 3,000’.
- NextGen is bringing the two worlds of airport and air traffic environmental analysis together. The guidance, industry sector experience and customers (FAA vs. Airport) differ dramatically between air traffic and airport environmental analysis and therefore the assumptions that are input into the modeling of noise may differ.
- The current noise regulations date back to the mid 1980’s. It is time to update the regulations to take into account:
- The increase in traffic.
- Significance thresholds that consider both noise level impacts and frequency over narrower paths of population.
More research about these issues might provide the FAA with better means of assessing the impact of RNP procedures on communities and of designing more community-friendly routes:
- The predicted noise levels of select Environmental Assessments (perhaps Phoenix) need to be verified by actual noise measurements within the new PBN flight corridors to determine why the reaction to noise impact is so much greater than the predicted noise impact.
- If the predicted noise impact is found to be accurate through physical noise measurements, then the threshold for significant impact needs to be evaluated and adjusted to account for factors such as aircraft operation frequency and differing community tolerance for noise.
- As illustrated above the issue of frequency may not have a significant impact on the DNL value but certainly appears to be having an impact on community tolerance of noise. The current FAA threshold of significance does not account for the significant increase in frequency that occurs under the new PBN corridors.
Further study which addresses these questions and which provides better metrics should reduce the growing resistance to NextGen, which does benefit the nation’s and the globe’s environment as Dr. Marias demonstrated.