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.”
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.
“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.