“In January 2018, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, DLR) and the US National Aeronautics and Space Administration (NASA) are set to conduct joint research flights in Germany for the first time. The focus will be on alternative fuel emissions and the characterisation of ice crystals in condensation trails (contrails), using biofuel as an example. The first joint DLR/NASA flights, which were conducted from Palmdale, California in 2014, showed that adding 50 percent alternative fuel for cruising flight reduces the soot particle emissions of an aircraft engine by 50 to 70 percent, compared to the combustion of pure kerosene. The planned research flights are intended to determine particle emissions and how they affect cloud formation through contrails, thus investigating their impact on the climate. From 14 January 2018, NASA's DC-8 research aircraft will visit Germany for three weeks and fly together with the DLR A320 Advanced Technology Research Aircraft (ATRA). "We are delighted that NASA has chosen us as their partner for such an extensive joint mission in Germany," says Rolf Henke, DLR Executive Board member responsible for aeronautics research. The research flights will start from Ramstein Air Base.” 
NASA’s ongoing research into what happens with engine performance, emissions and contrail formation when you use different types of fuels in jet engines is headed for the skies over Germany this month.
The international collaboration will see the German Aerospace Center (DLR)’s Advanced Technology Research Aircraft (ATRA) A320 aircraft burning alternative biofuels, while NASA’s fully instrumented DC-8 “Flying Laboratory” trails a safe distance behind, sampling and analyzing gases and particles within the ATRA’s wake.
“NASA couldn’t do it alone. We’re bringing the two agencies together to combine resources and facilities in a way we’ve never been able to do before,” said Bruce Anderson, NASA’s principal investigator for this latest phase of airborne research.
The main goals of the joint research campaign are to assess the effects of alternate fuels on aircraft engine performance and emissions, with a special focus on discovering how soot from those emissions can affect the size, concentration and lifetime of contrail ice particles.
This current effort is the latest in a series of research campaigns during the past few years, some in the United States and some in Germany, that used different aircraft, conditions and sampling techniques to build a knowledge base about alternative fuels.
Previous research flight programs were led by NASA over California during 2013 and 2014 and called ACCESS I and II – short for Alternative Fuel Effects on Contrails and Cruise Emissions. During these campaigns NASA’s DC-8 burned the alternate fuels, while smaller business-class jets, such as the NASA Falcon HU-25 and DLR Falcon 20, flew behind to gather data.
Results of those flights showed that using a 50-50 blend of biofuel and regular fuel to power jet engines reduced soot emissions by as much as 50 to 70 percent.
“That’s good news for Earth’s environment, but it would be even better if the fewer soot particles lead to a reduction in contrail ice particles,” Anderson said. 
If any of the links above do not work, copy the URL and paste it into the form below to check the Wayback Machine for an archived version of that webpage.