Aircraft Environmental Impacts and Certification Criteria
Although the effect of aircraft pollution on the environment has been widely addressed by engine manufacturers achieving reductions in noise and emission levels, the current certification does not give a sufficient basis for assessing impacts on the environment, in particular on airport surroundings.
The study's main aim is to identify gaps or issues to be revised in existing certification procedures related to aircraft emissions. All known, foreseen or possible impacts of aircraft emissions will be outlined in order to specify data requirements for environmental assessment. The evaluation of existing certification procedures against common flight operations and the identification of feasible, effective and economically viable modifications are among the key objectives.
The secondary objective relates to the impact of operational and maintenance procedures to aircraft performance, especially for noise and emissions, with particular focus on the negative effects of engine deterioration during the maintenance cycle. Recommendations will be given on how to keep operational procedures close to defined certification levels.
The project will involve:
- a description of certification procedures and summaries of available data from certification processes;
- survey of typical aircraft/engine configurations with reference to their type certification levels;
- documentation of current flight profiles, including airport ground operations for the above mentioned configurations at representative European airports;
- a literature survey on specific environmental impacts and related parameters that are necessary to calculate descriptor values;
- an assessment of the effects from operational procedures that deviate from given certification standards on noise and engine gas emissions;
- an assessment of the degradation of engine emissions during its service life.
- Assessed noise impacts based on certification data relies upon a few basic methods, with a large numbers of derivative methods, and found that significant improvements regarding accuracy of impact assessment are possible if additional noise data could be obtained;
- Found – through the investigation of flight profiles – a large variation in thrust settings at take-off, especially for large twin engined aircraft that offer many opportunities for using flexed thrust in take-off, intersection take-offs and earlier turns;
- Not identified the need to recommend changes to noise certification procedures, but proposed to secure certification noise map data that can be used for noise assessment purposes;
- Identified possibilities for better impact assessment, regarding emissions at and around airports, by having information available on more aircraft and engine types, and obtaining certification data for additional thrust levels used in actual operations, because the current Landing and Take-off (LTO) cycle is regarded as a worst case situation for aircraft emissions at airports though it's still viable for certification purposes;
- Found that inevitable in-service deterioration of components does not significantly alter an engine's noise performance;
- Found that deterioration of noise protection liners in aircraft engines negatively influences fuel consumption and NOx emissions.
The major observations and results of the AEROCERT project – based on a wealth of flight data – are considered a sound basis for future research on tools, models and data required for improved impact assessment and certification. A number of particular findings have already been identified as relevant to ongoing analysis within the noise work programme of ICAO. Especially comparisons between certificated and actual noise performance are of interest to the JET-10 working group, which is looking at noise certification requirements. In summary, there remains a strong need for gathering more basic flight data on various combinations of current aircraft and jet engines.
- Defence Evaluation and Research Agency, DERA (UK)
- Deutsches Zentrum für Luft- und Raumfahrt e.V., DLR (D)
- The Aeronautical Research Institute of Sweden, FFA (S)
- Loughborough University of Technology (UK)