This Aerospace Recommended Practice (ARP) standardizes test equipment and procedures for the measurement of smoke emission from aircraft gas turbine engines. The procedures included are for determining and reporting the amount of smoke emission. Tests have indicated that the practically achievable precision of the smoke number is within ±3 when the system is properly used as outlined herein. This procedure is not intended for in-flight testing, nor does it apply to afterburning mode.
ARP1179 was originally developed in 1970 (with subsequent updates) as the measurement technique for Smoke Number (SN) that has been used as the basis of regulatory standards for ensuring that the exhaust plumes from aircraft engines are essentially non-visible. It has, and still does, serve this purpose.
More recent concerns relate to the health and climate impacts of particulate matter emitted by aircraft engines. Particle size, number and mass are all seen as relevant parameters as is the issue of “volatility”.
The SAE E-31 Committee is currently using all its resources in developing a new ARP on the mass and number measurement of non-volatile particles at the exhaust of aircraft engines.
Hence the Committee recommends keeping ARP1179 as it still serves its purpose of quantifying the visibility at the exhaust of aircraft engines; it does not recommend any revision of it.