Following the retirement of Concorde in 2003, several manufacturers have been looking into developing supersonic aircraft, with some currently looking at an entry into service date of around 2030. Key environmental challenges to address include the use of significantly more fuel on a per passenger kilometre basis compared to subsonic commercial aircraft
, and noise, specifically the impact of the sonic boom generated when flying at supersonic speed.
The existing Landing and Take-Off (LTO) noise certification standard for supersonic transport (SST) aircraft was adopted by ICAO in 1976. As part of the ongoing discussions in CAEP, it is anticipated that any future SST aircraft would have to comply with the same noise limits that are currently applicable to subsonic aircraft (ICAO Annex 16 Volume I, Chapter 14) in order to avoid undermining the benefits from reductions in aircraft noise over the last few decades. Updates to engine emissions standards for SST aircraft are also being assessed within CAEP, with an attachment to ICAO Annex 16 Volume II having been developed documenting the status of discussions on provisional requirements and potential regulatory levels of CO, HC and nvPM emissions, as a basis for on-going future work.
Building on initial concepts developed by EASA
, a recommendation on a new SST LTO noise standard is due to be agreed at the CAEP/13 meeting in February 2025, alongside ‘green pages’ on SST engine emissions requirements.In order to meet the Chapter 14 noise limits, manufacturers are looking to incorporate Variable Noise Reduction Systems (VNRS) into the design of SST aircraft. VNRS systems operate fully automatically without pilot interaction and can include various aspects including reductions in thrust, changes in the setting of the high-lift devices (e.g. flaps, slats) and changes in engine inlet or outlet diameter.
Flight test campaigns with the NASA X-59 aircraft are planned in the USA to investigate community responses to the sonic boom and support discussions on a noise standard for the cruise condition and potentially other flight phases
. The practical demonstration of publicly acceptable noise levels from “low boom” design SST aircraft is crucial for any consideration to allow flights at supersonic speed over land.In Europe, various EU-funded research projects have provided support as part of these on-going discussions on appropriate environmental standards for the next generation of SST aircraft. These include RUMBLE, SENECA and MORE AND LESS
.
