PULSAR White Paper: Research on aircraft noise and emissions is mandatory to keep a leading and competitive EU aviation sector

Research on aircraft noise and emissions is mandatory to keep a leading and competitive EU aviation sector 

The current white paper has been prepared by the PULSAR consortium gathering European key Aviation OEMs, RTOs and Universities, with supportive inputs from coordinators of several recent relevant consortia such as Horizon 2020 / Horizon Europe projects ANIMA, ARTEM, DJINN, ENODISE or INVENTOR. It gives rationale and recommendations to keep on a significant support to aviation research on noise and emissions to allow aviation playing its role along with other modalities in an efficient and competitive transport system. 

1. Key Messages

In view of realizing the 4th revolution of aviation towards sustainability and reaching a climate-neutral growth of the aviation sector, the European Commission should further support research on aviation noise, aviation emissions and climate effects.

Why? Such a support to aviation research is mandatory:

1.1. To meet the rising social demand towards well-being and healthy living around airports, in line with the “Fly the Green Deal” and the recent “Zero Pollution Action Plan” objectives,

1.2. To develop competitive products, in terms of both noise and emissions, that would be otherwise commercially disadvantaged by drastically increasing local restrictions and fees in densely populated areas, 

1.3. To contribute to the overall effort by all sectors to minimize the impact of anthropogenic emissions on climate in line with the Fly the Green Deal objectives. 

How? For the sake of efficiency, such aviation research on noise, emissions and climate should: 

1.4. Focus on both an ambitious evolutionary path, to ensure short-term entry into service of new products, as well as revolutionary solutions ensuring longer term pathways. Both are required to sustain technological advantage in view of global competition and new market entrants, 

1.5. Increase the support to research on reduction of aviation noise at source which recently came to a critically low level. Although decarbonisation of aviation and, in general, the reduction of the climate impacts of aviation emissions, must remain a key EU priority, noise is a local issue that is severely affecting EU citizens living in the vicinity of airports, associated with increased health risks and high societal costs. With respect to this challenge, research on aviation noise is currently not sufficiently supported. 

These key messages are detailed in the following sections: 

2. Rationale and Recommendations for research on aviation noise

Aircraft noise has significantly decreased in the past twenty-five years pulled by the ICAO noise regulations known as the “balanced approach” and pushed by research achievements. This trend will last roughly up to 2035 thanks to the gap between new important noise reduction at source that have been achieved through Clean Aviation and other collaborative research projects, and foreseeable new noise regulations that are limited at this time horizon. 

However, these progresses are not sufficient because: 

• Although at present fleet replacement is compensating traffic growth, overall noise will start to increase again if no additional effort is made to further improve the noise performance of the next generation aircraft, 

• Existing improvements due to the introduction of new aircraft and the ban of older ones are not sufficient to counteract the increase of annoyance and complaints of EU citizens. Local authorities are under increasing pressure to further limit operations of air traffic far more often because of noise than because of emissions because noise is as a local issue directly perceptible and severely affecting EU citizens living in the vicinity of airports, 

• Research on noise quality, annoyance and on the various noise impact fostering interdisciplinarity between engineering sciences and Social and Human Sciences (SHS) must be renewed because previous worldwide studies gave evidence that a very significative part of annoyance and other social impact of aviation noise are not directly linked to noise intensity though correlated to noise exposure, 

• If the European aviation industry is not able to cope with the European societal demand about aviation noise, it may lose its current leadership as the air transport market – airlines and airports – and consequently the aviation industry could then shift even more than today to more economically dynamic regions with less stringent environmental rules. 

Therefore, we recommend launching a new series of ambitious technology research programmes on reducing noise at source with an appropriate balance favouring low TRL research and disruptive concepts but also considering incremental development for close-to-market applications. 

More specifically, the above requires: 

2.1. To keep on the research effort on lowering existing noise sources than have been less treated so far, such as airframe noise coming from landing gears and high lift devices, and new noise sources that could arise from disruptive aircraft architectures with a strong emphasis on installation and interaction effects, 

2.2. To renew the effort on engine sources providing that various new engines architectures designed for energy efficiency with shorter nacelles or no nacelles at all may lead to detrimental and disturbing noise patterns, 

2.3. To put a special emphasis on improved Computer Fluid Dynamics / Computer Aerodynamics (CFD/CAA) that are on the brink of a new age with new methods allowed by Artificial Intelligence (AI) and massive treatment of data, a research field in which European players could be overwhelmed by competitors, 

2.4. To give a staunch support to Research & Technology Infrastructures for applied research on aviation, such as wind tunnels, measurement and simulation capabilities that are critical for the European aviation industry and need to be upgraded to make extensive use of AI and massive data technologies, 

2.5. To keep a vivid support to research and implementation of new ATM procedures such as Noise Abatement Procedures but within reinforced dialogue and exchanges with land-use planning and Social and Human Sciences (SHS) experts. 

3. Rationale and Recommendations for research on aviation emissions and induced climate & air quality effects 

Aviation emissions affect both climate and air quality in the airport vicinity. ICAO CAEP started to work on non-CO2 emission standards in the late 70s to improve Local Air Quality (LAQ), while the first CO2 standard, aiming at reducing the contribution of aviation to global warming, was defined in 2016 and has been recently updated during the last CAEP/13 cycle (2022-2025). Emission reductions have been achieved over the past decades at engine/aircraft level thanks to fuel burn and combustor technology improvements. Besides, assessing the impact of aviation emissions on air quality/human health and climate remain challenging, in particular for non-CO2 emissions, since it involves complex engine plume chemistry and atmospheric processes which are dependent on time, location as well as atmospheric chemical background composition. This is why there are still large uncertainties on their levels of impacts. 

Therefore, continuing research on emissions/climate effects reduction is crucial because: 

• The global share of aviation emissions (e.g. 2.4% of the total anthropogenic CO2 emissions in 2018) will continue to grow further due to the expected traffic growth, while other sectors may be easier/less costly to decarbonise (aviation appears as less amenable to electrification). 

• Our understanding of the non-CO2 impacts (e.g. climate impact of contrail cirrus and of NOx emissions) needs to be improved, as well as the quantification of their impacts and of potential environmental trade-offs, as crucial aircraft design decisions to reduce environmental impacts need to be taken quite soon. 

• Operational measures such as “avoidance of warming contrails” or “climate optimized trajectories” could be deployed on the current fleet. However significant research is still required to demonstrate their operational feasibility and environmental benefits. 

• There are several fuel and technology routes for current and future aircraft but the respective prospects for environmental value of each of these routes and any trade-offs therein have not been fully explored and/or assessed up to now, hindering the ability to select a best solution. 

  
  

Therefore, we recommend deepening research through thorough assessments of prospects for emissions and impacts (climate and air quality) of all potential mid-term to long-term mitigation options in order to accelerate the path towards a more sustainable aviation. It is also important to take for these assessments a holistic view to determine any trade-offs that may hinder their implementation (e.g. trade-offs between CO2, non-CO2 and noise). 

More specifically, the above requires: 

3.1. To pursue experimental efforts to complete the characterization of direct emissions (i.e. combustion products) and indirect emissions (i.e. volatile particles, contrails’ ice crystals) and of their effects versus the main drivers: fuel composition, engine/aircraft design & architecture, combustor technology. These experiments require the development of enhanced atmospheric/emission measurement means, 

3.2. To encourage projects dedicated to multi-model assessments involving several research institutes, with climate and air quality models reflecting the most recent scientific knowledge, to compare results and help convergence on impact assessment methodologies. The development of these models, fed and validated via experimental data, should be strongly supported, 

3.3. To support specifically the research work around cloud (including contrails) modelling and aviation aerosol-cloud interactions. As of today, climate effects modelling assessments often exclude these processes, which are therefore not quantified at all, or by only few models, 

3.4. To continue the research work around operational mitigation approaches. This includes the improvement of weather forecasts (comprising humidity at flight level), climate effects estimates, the development and maturation of operational concepts, and the development of the capability to evaluate accurately enough the actual flight-by-flight climate effect, 

3.5. With regards to local air quality and health impacts, to support research on volatile particulate matter formation at ground level, on the transport of pollutants from altitude down to surface level, and on the toxicology of pollutants (from aviation and non-aviation sources). 

4. Additional Recommendations 

On top of the former recommendations, we would like to highlight two points: 

4.1. Research on noise on the one hand and on emissions on the other hand involve different expertise and communities. Therefore, it seems wise to keep two separate strands of programmes to allow for substantial progress on each of them, but also to plan every three years some common actions such as PULSAR for a tentative overall assessment of the technologies matured on each side and address any trade-off between noise and emissions, 

4.2. Recommendations previously elaborated through ANIMA to take benefit from the COVID crisis and its associated traffic downfall to implement, on a wide scale, best practices for both aviation noise mitigation and minimization of its adverse impacts have not (fully) been considered. It is therefore useful to keep on associating aviation operators to research projects as it has been done recently. 

PULSAR White Paper - May 2025.pdf

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