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SAE Aerospace Recommended Practice ARP1533 is a procedure for the analysis and evaluation of the measured composition of the exhaust gas from aircraft engines. Measurements of carbon monoxide, carbon dioxide, total hydrocarbon, and the oxides of nitrogen are used to deduce emission indices, fuel-air ratio, combustion efficiency, and exhaust gas thermodynamic properties. The emission indices (EI) are the parameters of critical interest to the engine developers and the atmospheric emissions regulatory agencies because they relate engine performance to environmental impact. While this procedure is intended to guide the analysis and evaluation of the emissions from aircraft gas turbine engines, the methodology may be applied to the analysis of the exhaust products of any hydrocarbon/air combustor.

This Aerospace Information Report (AIR) describes the use of FTIR analyzers for measurements of gaseous emissions from aircraft gas turbine engines and combustion rigs. The use of FTIR analyzers can be demonstrated as a suitable and cost-effective equivalent to NDIR and chemiluminescence analyzers as prescribed in ARP1256 for the measurement of CO, CO2, NO, and NO2, where NOx is closely approximated by the sum of NO and NO2 concentrations. FTIR analyzers may be proven suitable for equivalency of analyzers used in current emission testing. Additionally, FTIR analyzers have potential for equivalent measurements of “total” hydrocarbon (THC) as currently defined in ARP1256.

This report describes the concept and data analysis of the probe factor (pf) scheme. Conclusions are drawn and recommendations made for action to further the requirements for improved methods and procedures in emissions sampling technology.