Accurate measurement of the exhaust emissions of aircraft gas turbine engines presents a challenge not only because of the high velocities and temperatures of the exhaust stream, but also because of the variation of the exhaust constitutents over the relatively large-cross-section of the jet stream itself. Other factors which affect exhaust emission level include ambient temperature and humidity. This paper presents the results of independent efforts by Pratt & Whitney Aircraft to identify emission variation characteristics together with results of an exhaust emission documentation program funded by the Environmental Protection Agency. Methods and techniques employed in the above programs are also discussed. The results of these programs indicate that additional effort is required to properly evaluate and understand the emission characteristics of aircraft gas turbine engines.

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