Drag Reduction Initial Conditions on Various Legacy Fleet Aircraft: Surface Roughness Measurements
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© 2017 by Alexander Moyes, Heather Kostak, Colin Cox, Travis Kocian, William Saric, Helen Reed, Juan Rivera, Gary Dale. The viscous portion of drag on transport aircraft is significant, contributing over half of the total drag at cruise conditions. Lowering the viscous drag can impact aircraft per- formance significantly by reducing fuel burn and thus increasing range. Because transport aircraft are the largest users of fuel in the United States military and aviation fuel accounts for 85 percent of the total Air Force energy costs, the Air Force has initiated the Engineered Surface, Materials, and Coatings for Aircraft Drag Reduction Program, which seeks novel approaches for reducing viscous drag. As a first step, the Air Force Research Lab has paired up with Texas A&M University to establish baseline roughness distributions for legacy eet aircraft. Four different in-service and three different newly painted airframes were accurately measured using a precise laser profilometer near the leading edge of each wing; the measurements were then translated from the measured root mean square roughness value to an equivalent Coated Abrasive Manufacturers Institute sandpaper grade. The grades of the qualitative study for in-service aircraft were ~600 for the C-5 and greater than 1500 for the C-17, C-130, and KC-135. The grades of the qualitative study for newly painted aircraft were between 1350-1500 for the C-17, C-130, and KC-135. Measurements were also made for two pre-fabricated plates with 3M riblets and the results closely resembled the specifications provided on the data sheets.
author list (cited authors)
Moyes, A., Kostak, H., Cox, C., Kocian, T. S., Saric, W. S., Reed, H. L., Rivera, J. A., & Dale, G. A.