In-flight emission measurements with an autonomous payload behind a turboprop aircraft

Abstract

This paper reports on the successful first deployment of a new, autonomously operating measurement sys�tem on a Grob G 520 Egrett aircraft, which was used as a chase aircraft to perform in-flight aerosol and trace gas measurements of engine exhaust from other aircraft. A suite of custom-built and commercially available instruments was selected, modified, and adapted to operate in the unpressurized compartment of the Egrett over a wide range of ambient temperatures and pressures. We performed these first inflight emission measurements at cruise altitudes between 7.6 and 10.4 km (FL250 and FL340) behind a Piper Cheyenne, a twin-turboprop aircraft powered by Garrett/Honeywell TPE 331-14 engines over Texas in April 2022. The instrumentation and inlets on the Egrett were designed to measure non-volatile particulate matter (nvPMDp>10), total articulate matter (tPMDp>10), nitrogen oxides (NO and NO2), water vapor (H2O), carbon dioxide (CO2), and contrail ice particles. All nstruments were operated in relevant plume conditions at cruise altitudes and distances ranging from 100 to 1200 m between the two aircraft. The instruments proved to have high reliability, a large dynamic range, and sufficient accuracy for measuring the emissions of the turboprop engine.