Emissions tested in flight

Research team compares JP-8 and biofuel exhaust

May 14, 2014

A DLR Falcon jet and a NASA DC-8 flew formation at various altitudes to test the DC-8’s emissions while burning biofuel. NASA photo.

In simplest terms, the international research collaboration launched this month is dedicated to sniffing jet exhaust at altitude. For the pilots, it is a challenging assignment: Deliberately probing exhaust plumes, contrails, and wake vortices at altitude, trailing a NASA DC-8 at distances ranging from a little over 300 feet up to 11 nautical miles.

Wake turbulence is certainly a factor.

The airborne emissions test is being conducted under a collaboration between NASA, the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, or DLR) and the Canadian National Research Council, which operates a T-33 flown specifically to explore the DC-8’s wake turbulence dynamics, while a Falcon jet operated by DLR focuses on collecting air samples. The project will compare the emissions produced by burning standard fuels against various biofuel blends, to better understand the exact nature of biofuel emissions.

Behind the DC-8, the scientists on board the DLR Falcon measured the exhaust gas composition. NASA photo. “Our Falcon is an extraordinarily robust research aircraft and ideal for taking measurements in the exhaust plume and in condensation trails," said DLR test pilot Philipp Weber, in a news release. "Heavy structure loads that not all aircraft are designed for can occur in aircraft wake turbulence."

The subtext: Don’t try this at home.

The collaboration between NASA and DRL dates back more than 15 years, and the latest round of test flights is comparing straight JP-8 emissions to a one-to-one mixture with biofuel derived from the oil of Camelina plants, a weed also known as “false flax” that has long been cultivated for its oil. Researchers expect the blend to reduce the sulfur content of jet exhaust, reducing soot emissions that may also lead to larger ice crystals in the condensation trail.     

Jim Moore

Jim Moore | Online Associate Editor, AOPA

AOPA Online Associate Editor Jim Moore joined AOPA in 2011 and is an instrument-rated private pilot who enjoys competition aerobatics.