AIR TRAVEL GREENER BY DESIGN—R&T RECOMMENDATIONS

  1.  The Air Travel Greener by Design Technology Sub-Group see the next decade as a period over which research, technology demonstration and design study will be crucially important to achieving the objectives of the Greener by Design Associated Foresight programme. The following, not in any particular order, are considered priority areas:

  2.  Atmospheric Effects of Aircraft Emissions. There are important programmes in Europe, the USA and Japan but there is much more that needs to be done. CAEP has defined five-year goals in a number of specific research fields but continued research beyond then is likely to be needed. Quantitative understanding in this field, particularly of the significance of NOx and contrails and their dependence on flight altitude, latitude, climate and season, is the key to framing aircraft design concepts and requirements to minimise impact on climate change.

  3.  Aero Engine Combustion. Research is needed both to develop engine combustion systems with reduced Nox emissions and to improve understanding of the fundamental processes of Nox generation at high temperatures and pressures. Advanced combustor development is a particularly high priority, given the number of conventional turbofan engines that are in service, or will enter service in the coming decades. Nevertheless, the investigation of the ICR engine cycle should also be taken to the point where its practicability can be assessed and its potential to reduce Nox emission evaluated. For both conventional and ICR systems, research which holds out real promise needs to be followed by appropriate demonstration.

  4.  Natural and Hybrid Laminar Flow Control. For short and medium range aircraft, up to 150-200 seats, the potential of natural laminar flow design merits further study, despite the disappointing conclusions of (26). Hybrid laminar flow control has far wider ranging potential, however, and merits further study both to develop and validate aerodynamic design principles and to develop and demonstrate the necessary manufacturing and systems technology. The goal should be to bring this technology to the state where it can be incorporated into chosen production aircraft in order to obtain an adequate base of experience of operation and maintenance of the system in airline service. Wind tunnel testing of hybrid laminar flow designs will present novel technical problems relating to aerodynamic scaling which should also be addressed.

  5.  Blended Wing-Body. The current studies of the blended wing-body configuration should be carried forward to the point where all key issues have been addressed on paper or by experiment and the more critical issues earmarked for further investigation. These are likely to include stability and control, aerodynamic and structural optimisation, powerplant integration and acceptability to passengers. Ride quality control may be a key issue. In the longer term, the studies should be extended to cover the aerodynamic and engineering aspects of applying hybrid laminar flow control to the outboard wing and other appropriate surfaces and to the re-optimisation of the configuration with HLFC.

  6.  Laminar Flying Wing. A new aerodynamic and engineering study of the all laminar flying wing should be undertaken in order to re-assess its potential in the light of technical advances since the concept was first proposed.

  7.  Alternative Fuels. Current research into the hydrogen fuelled aircraft concept should be carried forward to provide a basis for assessing the practicalities of converting to hydrogen fuel for civil aircraft in the event of the fuel becoming generally available at an environmentally acceptable cost. Research into the feasibility of carbon-neutral fuels derived from biomass should also be pursued.

  8.  Multi-Sector Long Distance Travel. A total system study should be made of the concept of undertaking long distance travel in sectors not exceeding some defined maximum (in Appendix A4 a provisional figure of 7,500 km is suggested). The study should cover engineering, operational, infrastructure, safety, market, economic and overall environmental issues.

  9.  Design for Minimum Impact on Climate Change. A study should be made of aircraft and engine design concepts aimed specifically at minimising impact on climate change rather than fuel burn. Possibilities might include aircraft optimised to cruise at lower altitudes, with less efficient engines having higher exhaust temperatures and lower Nox emissions. Further progress in the atmospheric sciences is needed before such a study can reach definitive conclusions, but it is not too soon to begin to formulate the key questions and build a framework for weighing the balance between commercial and environmental goals, the latter including noise and local air quality as well as impact on climate change. Such a study is likely to help shape future research priorities. For example, any conclusion that it would be beneficial to design for lower cruise altitude, which implies higher wing loading, would highlight the need for research to develop more capable and lighter high lift systems, possibly using some of the novel flow control technology which is now emerging.

  10.  Associated Research. In parallel with the above, environmentally related research areas, mainstream research in aircraft and engine aerodynamics, structures, materials, systems and noise must continue. All are capable of contributing to future reductions in the effect of air travel on climate change and to improvements in the airport environment.