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3. Emissions
Pages 30-38

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From page 30...
... These improvements were driven by economic requirements for longer range, higher fuel efficiency, larger capacity, and increased speed, and the net result was an air transportation system with aircraft that are more capable, yet consume less fuel and produce fewer emissions per revenue-passenger-kilometer than ever before. In the past 30 years, approximately 60 percent of the total improvement in fuel efficiency has been attributable to advances in engine technology, with the rest due to improvements in airframe design and more-fuel-efficient operations.
From page 31...
... As with any carbon-based fuel, the major combustion products of conventional jet fuel are CO2 and water vapor. Reducing the emission of CO2 and water requires either reduced fuel consumption (through the development of more efficient engines, aircraft, and operational systems and procedures, as discussed above)
From page 32...
... 1997 1998 1999 Fiscal Year NOx emissions (landing and takeoff) 2000 2001 2002 FIGURE 3-2 Allocations of NASA's emissions research funding (adjusted to constant year 2000 dollars)
From page 33...
... Burning hydrocarbon fuels to produce electricity to produce hydrogen to replace the use of hydrocarbons as a jet fuel would release more CO2 than continuing to use conventional hydrocarbon jet fuel. Given the magnitude of these challenges and the long time it would take to develop and deploy significant numbers of new commercial aircraft equipped to operate with alternative fuels, it seems highly likely that commercial aviation will be dominated by aircraft powered by conventional jet fuels for the foreseeable future.
From page 34...
... 34 g c' 0 g rO O ." Cal C ~R ~ ˘ ~ 00 =0 cot C)
From page 35...
... 35 ~ 8 y 8 ~ 8 8 2 Y 8 0 ~ R ~ a go Y ~ O a e 8 ° e 8 ~ A ~ 8 ~ ~ == Y a ~ 69 ED ~ =~ ~ ~§ ~ 733~ T ', · ~ !
From page 37...
... good fair poor poor fair very fair fair poor Relative Scientific Understanding of Effects FIGURE 3-3 Radiative forcing caused by the global Heet of commercial subsonic aircraft as of 1992. The vertical line embedded in each bar depicts a two-thirds uncertainty range, meaning that there is one chance in thee that the tme value falls outside the ranges shown.
From page 38...
... Current needs also include better understanding of the health concerns, if any, posed by aircraft emissions of hazardous air pollutants (Ozone Transport Committee, 2001 and Holzman, 1997~. Very few data exist for characterizing aircraft exhaust with regard to hazardous air pollutants, many of which are mutagenic and carcinogenic, or for comparing the possible effects of aircraft exhaust with those of other potential sources of hazardous air pollutants, such as automobiles.


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