Aviation and the Global Atmosphere

Aviation and the Global Atmosphere
Aviation and the Global Atmosphere
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EXECUTIVE SUMMARY
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In a report addressing the effects of aviation on the global atmosphere, the link between emissions and the technological status of aircraft now and in the future is
clearly a central issue. The subject is complex. Our approach here, therefore, has been to identify a number of key questions, the answers to which provide an
assessment of technical issues, problems, and the prospects of solving them.
The questions and their corresponding answers are as follows:
● Question-What are the principal technological factors that determine the nature and scale of emissions from aircraft at altitude?
Answer-The overriding technological consideration in the design of aircraft today is safety. Given that prerequisite, aircraft are designed to provide an
efficient and environmentally acceptable system of transport from ground level to the demanding conditions associated with high-speed flight at high
altitudes. To achieve high efficiency, fuel consumption must be minimized by reducing the weight and drag of the aircraft. This requirement also ensures
that there is a constant drive toward the highest levels of energy conversion efficiency from the engine. Together, these factors ensure that carbon
dioxide CO 2 ) and water outputs are minimized.
The most fuel-efficient engines for today's aircraft are high bypass, high pressure ratio gas turbine engines. No known alternatives are in sight. These
engines have high combustion pressures and temperatures; although these features are consistent with fuel efficiency, they increase NO x formation
rates-especially at high power take-off and at altitude cruise conditions.
Current low-sulfur fuels minimize SOxO emissions. Small amounts of fuel-bound sulfur (400-600 ppm) and associated organic acids provide important
lubricity properties for critical fuel system components. Processing to remove all traces of sulfur would remove important organic acids, so sulfur-free
fuels are unlikely to be adopted in the short term. Sulfur removal would also result in a small net rise in CO2 .
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