Climate-friendly aviation milestone: turboprop emissions tested using 100 percent synthetic fuel

Climate-friendly aviation milestone: turboprop emissions tested using 100 percent synthetic fuel
by Robert Schreiber
Berlin, Germany (SPX) Oct 17, 2024

In a world-first, the German Aerospace Center (DLR) and Deutsche Aircraft are conducting emissions measurement flights using 100 percent synthetic, aromatics-free fuel in a turboprop aircraft. This research aims to explore the climate benefits of synthetic fuels by studying emissions at distances ranging from 50 to 500 meters from the D328 UpLift aircraft. Conducted with DLR's Falcon aircraft as a flying laboratory, the project seeks to reduce aviation's carbon footprint, particulate emissions, and the climate impact of condensation trails known as contrails. Initial tests, including ground-based assessments and four research flights, were carried out at Oberpfaffenhofen Airport, with six additional flights planned through October 2024.

"Sustainable fuels will play an important role in climate-compatible aviation in the future, and in particular electricity-based fuels suitable for large-scale production," said Markus Fischer, DLR Divisional Board Member for Aeronautics. "That is why I'm particularly pleased that our new D328 UpLift research aircraft is the first in the world to fly with such a synthetic, aromatics-free fuel in its turboprop engines for its research campaign debut. With our Falcon 20E 'flying laboratory,' we are contributing DLR's outstanding expertise to the direct measurement of emissions and their resulting contrails directly in flight."

The CLIM0ART project (Climate Impact-driven Emission and Contrail Measurements of 0 Aromatic fuels in Regional Turboprop Aircraft) is assessing whether synthetic aromatics-free fuels can achieve similar climate benefits as biofuels, which have been shown to reduce soot, ice particles, and contrail-induced warming. This initiative marks the first time emissions from a turboprop aircraft have been measured in flight, providing essential data for modeling the environmental impact of current and future regional aircraft.

Nico Neumann, Chief Operations Officer at Deutsche Aircraft, noted, "The CLIM0ART project is another piece in the puzzle of our holistic approach to optimize the environmental impact of our aircraft, with the aim of implementing the latest scientific findings for the climate as quickly as possible in our D328eco aircraft, which is currently under development. This achievement not only highlights the potential of synthetic fuels but also the importance of collaboration between industry and research institutions."

Before its research role, the D328 UpLift was modified to operate on aromatics-free fuel, which involved replacing seals and adapting the fuel system and engines. These flights are being conducted as test flights since 100 percent synthetic aromatics-free fuels are not yet fully certified for general use.

During the emissions measurements, the DLR Falcon 20E follows the exhaust stream of the D328 UpLift aircraft at a distance of about 50 meters, sampling emissions or maneuvering to measure particle concentrations in the contrails. "The close pursuit is particularly challenging for the test pilots and requires the utmost concentration," said Ingmar Mayerbuch, head of DLR Flight Operations.

Aromatics-free fuels help reduce soot particle emissions and ice crystal formation in contrails, mitigating their warming effect. According to Christiane Voigt, director of the project at the DLR Institute of Atmospheric Physics, "We are now investigating whether similar results can be achieved with synthetic fuels. We are also interested in the emissions from turboprop aircraft in the regional fleet, which we can use as a reference for future innovative propulsion technologies, for example using hydrogen."

Contrails, formed from aircraft engine soot emissions, consist of ice crystals that can persist and influence the Earth's thermal radiation balance, contributing to warming. Studies indicate that the non-CO2 effects of aviation may have an equal climate impact as the CO2 emissions generated since aviation began.

The synthetic fuel used in the project is a Fischer-Tropsch synthetic paraffinic kerosene (FT-SPK), chemically equivalent to future Power-to-Liquid (PtL) fuels, which will be produced from renewable energy sources. The fuel is provided by Sasol, and DLR is advancing efforts to test industrial production of PtL fuels, with a new facility in Leuna underway as of early October 2024.