Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
● Question-What performance might we expect from new aircraft entering the fleets in 2015 and 2050 (the dates of the scenarios discussed in Chapter 9)?
Answer-The emerging effects of research and technology programs on airframes and engines will influence future fleets of subsonic aircraft. A group of
aerospace industry experts has developed some technology projections relating to fuel efficiency and NO x emissions of aircraft by the years 2015 and 2050.
According to these scenarios, average fuel efficiency of new production aircraft in the scheduled commercial fleet may improve by 20% between 1997 and
2015. The corresponding scenarios for improvement between 1997 and 2050 involved two different technology scenarios to take account of tradeoffs between
fuel efficiency and low NO x in aircraft designs. In the first case, with fuel efficiency taking priority, a 40-50% improvement in the fuel efficiency of new production
aircraft was projected. In the second case, where NO x reductions took priority, a 30-40% improvement in fuel efficiency was envisaged.
New commercial supersonic transport aircraft, operating at speeds of Mach 2 to 2.4, have been proposed for introduction into service, though not before 2015.
It now seems unlikely that any commercial supersonic transports will exceed flight speeds of Mach 2.5 within the next 50 years as a result of engineering
problems, materials limits, fuel efficiency, and other economic considerations. Supersonic aircraft are intrinsically less fuel efficient than subsonic aircraft. They
consume about twice as much fuel, on a passenger-kilometer basis, as subsonic aircraft of the same size and range. To minimize stratospheric ozone
depletion, the major design criteria for supersonic aircraft focus on flight altitude and low NO x output. Water vapor emissions may become more important than
NO x emissions. If so, control of H 2 O emissions will depend solely on the achievement of greater fuel efficiency. Sulfur aerosols originating in the fuel are an
emerging concern in the altitude bands used by supersonic aircraft. As in the subsonic aircraft case, more data are needed to determine their true impact.
● Question-What are the likely effects of small aircraft and military aircraft on the environment?
Answer-Small aircraft, including commuter aircraft and general aviation, pose little environmental threat because they consume a very small fraction of the total
of aviation fuel. Similarly, military aircraft, which consume less than 20% of the total aviation fuel supply today and, as civil aviation grows, perhaps less than
5% in the next 50 years, are seen as having potentially small environmental impacts.
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