The Air Force recently proved through a series of tests that its KC-135 Stratotanker aircraft can fly more efficiently just by mounting the cockpit window’s wiper blades vertically instead of horizontally. The potential fuel cost savings: about $7 million per year.
Researchers with the Advanced Power and Technology Office, part of the Air Force Research Laboratory, and the Southwest Research Institute, assessed the KC-135 after similar tests were conducted on a commercial McDonnell Douglas MD-11 cargo airliner. The commercial tests showed the new blade direction reduced its flight drag by 1.2%.
“Across the KC-135 fleet, blades are positioned horizontally on the windshield as part of the aircraft’s original 1950s design,” officials said in a news release. “However, as the understanding of aviation aerodynamics advanced, research indicated placing the wipers vertically when not in use could improve aerodynamic efficiency and optimize fuel use.”
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The data collected revealed drag was reduced 0.8% just by moving the blade vertically, and 0.2% for a slimmer wiper design on the cockpit’s window.
Computational fluid dynamics analysis, conducted by Air Force Research Laboratory and Southwest Research Institute, shows the nose of a KC-135 Stratotanker, as the wiper blades are positioned horizontally, left, and vertically, right. The red indicates an area of high aerodynamic drag. (U.S. Air Force courtesy photo)
“While 1% efficiency may not seem like a lot, it equates to millions of dollars in fuel savings each year, which can then be re-invested into other programs,” Daniel Pike, acquisition manager and chief of future operations for Air Force Operational Energy, said in a statement.
For example, the KC-135 fleet used more than 260 million gallons in fiscal 2019, the service said, citing the Air Force Total Ownership Cost database. That accounts for roughly 14% of the Air Force’s total fuel use across its aircraft fleets.
