More than a dozen instruments mounted on the Falcon jet will characterize the soot and gases streaming from the DC-8, monitor the way exhaust plumes change in composition as they mix with air, and investigate the role emissions play in contrail formation. Specific measurements will include aerosol number, size, composition, and volatility; cloud particle size, number, images, and water content; CO₂; CO; NO_x; O₃; and water vapor.

Also, if weather conditions permit, the Falcon jet will trail commercial aircraft flying in the Southern California region, in coordination with air traffic controllers, to survey the exhaust emissions from a safe distance of 10 miles.

Objectives of the ACCESS program, as outlined by Dan Bulzan, NASA Technical Lead - Clean Energy and Emissions (CEE) Subsonic Fixed Wing Project, at the January AIAA Aerospace Sciences Meeting, include:

1. Characterize fuel effects on aircraft particle and gas phase emissions at cruise altitudes.

2. Examine the evolution (growth, changes in composition/ microphysical properties) of exhaust and contrail particles as plumes age and become mixed with background air.

3. Investigate the role of black carbon concentrations and properties and fuel sulfur in regulating contrail formation and the microphysical properties of the ice particles.

4. Survey black carbon and gas-phase emissions and contrail properties from commercial aircraft at cruise in air-traffic corridors.

We believe this study will improve understanding of contrails formation and quantify potential benefits of renewable alternate fuels in terms of aviation’s impact on the environment.

—Ruben Del Rosario, manager of NASA’s Fixed Wing Project

ACCESS flight operations are being staged from NASA’s Dryden Aircraft Operations Facility in Palmdale, Calif., and will take place mostly within restricted airspace over Edwards Air Force Base, Calif.

The flight campaign began 28 Feb. and is expected to take as long as three weeks to complete.

ACCESS follows a pair of Alternative Aviation Fuel Experiment (AAFEX) studies conducted in 2009 and 2011 in which ground-based instruments measured the DC-8’s exhaust emissions as the aircraft burned alternative fuels while parked on the ramp at the Palmdale facility. (Earlier post.)

A second phase of ACCESS flights is planned for 2014. It will capitalize on lessons learned from the 2013 flights and include a more extensive set of measurements.

The ACCESS study is a joint project involving researchers at Dryden, NASA’s Glenn Research Center in Cleveland and NASA’s Langley Research Center in Hampton, Va. The Fixed Wing Project within the Fundamental Aeronautics Program of NASA’s Aeronautics Research Mission Directorate manages ACCESS.