07-07-20: In April, the FAA issued a Notice of proposed rulemaking (NPRM) to add new supersonic airplanes to the applicability of noise certification regulations, and proposes landing and takeoff noise standards for a certain class of new supersonic airplanes. For ease, I have included the executive summary of the NPRM below:
“Current noise certification regulations do not include standards for supersonic airplanes other than the Concorde. In its 2018 reauthorization, the FAA was directed to exercise leadership in the creation of Federal and international policies, regulations, and standards relating to the certification and the safe and efficient operation of civil supersonic aircraft. This rulemaking is a step in that process. The agency is proposing to amend the noise certification regulations in Title 14, Code of Federal Regulations (14 CFR) parts 21 and 36 to provide for new supersonic airplanes, and to add subsonic landing and takeoff (LTO) cycle standards for supersonic airplanes that have a maximum takeoff weight no greater than 150,000 pounds and a maximum operating cruise speed up to Mach 1.8. This proposal is based in part on the Supersonic Transport Concept Airplane (STCA) studies performed by the National Aeronautics and Space Administration (NASA), information provided to the FAA by U.S. industry, and the continuing work of the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP). These proposed certification standards would provide a means to certificate these airplanes for noise for subsonic operation domestically, but would not affect the prohibition in 14 CFR 91.817 on the creation of sonic booms (i.e., supersonic operations over land in the United States would remain prohibited).
This proposed rule would (1) amend the applicability of part 36 to include new supersonic airplanes for which type certification is requested after a final rule takes effect, (2) revise the definition of supersonic airplane to include newly certificated airplanes but exclude the Concorde, (3) provide noise certification reference procedures to be used for all supersonic airplanes, and (4) establish noise limits for takeoff and landing that would apply to Supersonic Level 1 (SSL1) airplanes, as defined in the proposed regulation. The proposed standards include noise limits that are quieter than the Stage 4 limits at which most of the current subsonic jet fleet operates, though louder than the current certification level of Stage 5 for the same aircraft weights. The proposed standards would allow Variable Noise Reduction Systems (VNRS) to be used for noise certification testing, and if used for certification, would require the system to be activated during normal operations.”
There are a few summary takeaway items to note from the full NPRM:
- These certifications only consider the landing and takeoff (LTO) cycle, not the sonic boom noise. The overland sonic boom restriction is not proposed to be lifted through this NPRM
- This NPRM only applies to aircraft less than 150,000 pounds and less than Mach 1.8 cruise speed
- These certifications are being considered due to FAA Reauthorization 2018 language
- The certifications as proposed would be allow aircraft to be louder than current subsonic Stage 5 limitations
Because the domestic over land supersonic restriction is not proposed to be lifted through this process, it is expected that when this class of aircraft is introduced into the fleet, it will operate near the coasts. Despite this expectation, I have been participating on an airport industry panel that discussed how Airports Council International – North America (ACI-NA) would comment on the NPRM. It is also expected that the production and operation of this aircraft category will benefit some airports that do not have noise concerns, thus ACI-NA will be commenting in a manner that balances the benefits against potential noise impacts. As ACI-NA will comment with a more subtle tone, the MAC submitted a comment letter that expressly objects to the proposed noise standards being less stringent than subsonic aircraft types. That comment letter is attached.
The full NPRM and current listing of comments received can be found here: https://www.regulations.gov/document?D=FAA-2020-0316-0001