SAE ARP1256E

This SAE Aerospace Recommended Practice (ARP) describes the continuous sampling and analysis of gaseous emissions from aircraft gas turbine engines. The measured gas species include carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), nitrogen dioxide (NO2), hydrocarbons (HC), and water vapor (H2O). This ARP excludes engine operating procedures and test modes, and is not intended for in-flight testing, nor does it apply to engines operating in the afterburning mode. It is recognized that there will probably be major advances in the gas analysis measurement technology. It is not the intent of this ARP to exclude other analysis techniques, but to form the basis of the minimum amount of conventional instruments (those in common industry usage over the last fifteen years) required for the analysis of aircraft engine exhaust. It is the responsibility of the analyst to demonstrate the alternative measurement technology has comparable (or better) performance than the techniques described in this ARP. The measurement of other exhaust gas species is beyond the scope of this ARP. It should be noted the measurement of oxygen (O2) is generally accepted as essential for assessing data quality, but is not covered by this ARP. Sulfur dioxide (SO2) is normally not measured using conventional systems but is calculated from fuel sulfur content. Again this is not covered by this ARP. This SAE Aerospace Recommended Practice (ARP) provides a limited scope update regarding sampling probe information and the previous requirement that at least 80% of the total probe pressure drop be taken across orifices at the probe tips for multi-tip sampling probes where the samples are ganged together before measurement. Now that the same probes used for gas may also be used for nvPM measurements (ARP6320), sample inlet requirements for the nvPM system can make this 80% pressure drop requirement challenging in some situations. Both analytical and test data have shown that the 80% pressure drop is not necessary to achieve the goal of approximately equal flow through all sample ports, at the same probe inlet conditions thus achieving representative sampling. Other equally viable approaches, together with the carbon balance check, are recommended to achieve this goal. The sampling probe section has also been updated to improve clarity and include examples. Document formatting and editorial updates have been implemented to reflect current SAE standards for ARPs.