DLR/NASA research flights over northern Germany

One key question for the research flights, which will continue until early February, is whether it can be shown that the lower soot emissions produced by the use of alternative aircraft fuels has an impact on the ice particles in contrails, thus resulting in a lower warming effect on the climate due to long-lasting contrails. “We are also interested in finding out whether, with a targeted fuel design, a markedly more economical addition of 30 per cent biofuel will generate a similarly low level of soot emissions as a 50 per cent mixture with conventional Jet A-1 kerosene," explains Patrick Le Clercq of the DLR Institute of Combustion Technology. "We are building on the results of the ECLIF I campaign, in which two DLR aircraft, the A320 ATRA and the Falcon, were deployed in 2015 and also assisted NASA with the ground measurements."

For the ND-MAX / ECLIF 2 (NASA / DLR-Multidisciplinary Airborne eXperiments / Emission and CLimate Impact of Alternative Fuel) measurement flights, DLR’s A320 ATRA and NASA's 'flying laboratory' take off with a total of 14 measuring instruments on board, of which around half have been provided by DLR. DLR’s A320 flies in front, using an alternative fuel, while the NASA DC-8 flies a few kilometres behind and 'sniffs' the exhaust. The emissions generated by two mixtures of alternative fuels are measured at different altitudes and flight speeds, along with the resulting contrails and contrail cirrus clouds.

Flight test sequence

Each joint research flight takes off in the morning from Ramstein Air Base. "The NASA DC-8 and DLR Airbus fly some distance into an airspace reserved for flight tests," explains DLR test pilot Stefan Seydel. "So far, this has been an airspace over Mecklenburg-Vorpommern." Once there, the two aircraft fly up to 15 circuits per flight, following one another. "After a straight flight path, where we fly in the contrails of the A320, we perform a 180-degree turn, then we dive with the DC-8 onto another straight path, flying in the exhaust streams and contrails, before the next 180-degree turn," says NASA test pilot Wayne Ringelberg, describing the exercise. "We generally fly these measurement circuits for four to five hours before embarking on the return flight to Ramstein."

The NASA DC-8 lands in Ramstein shortly after the DLR A320. Final exhaust gas measurements are taken on the taxiway, before the aircraft taxi to the hangar. In addition, the researchers carry out separate static tests in which the exhaust gases of the DLR A320 ATRA are studied using ground-based measuring instruments. The researchers expect to have the results of the studies in the next few months.

Strong partnership