In-Situ Measurements of Contrail Properties Measured During the 2013-2014 ACCESS Project
To better understand these effects, the ACCESS-I project was conducted in 2013 to quantify aerosol emission indices for a number of petroleum-based and bio-based jet fuels at cruise conditions, while the 2014 ACCESS-II project focused on measuring the contrail microphysics. Three different fuel types are discussed: a low-sulfur JP-8 fuel, a 50:50 blend of JP-8 and a camelina-based HEFA fuel, and the JP-8 fuel doped with sulfur. Emissions were sampled using a large number of aerosol and gas instruments integrated on an HU-25 Falcon jet that was positioned in the DC-8 exhaust plume at approximately 50-500 m distance behind the engines. It was found that the biojet fuel blend substantially decreases the aerosol number and mass emissions indices, while the gas phase emission indices were similar across fuels. The effects of these fuel-induced changes of aerosol emissions on contrail properties will be discussed.