Analyzing its aerodynamics, the engineers realized a curious aspect: modifying the position of its wiper improves its aerodynamics so much that it can save millions of dollars a year in fuel.
The U.S. Air Force Engineer Team did a computational analysis of the fluid mechanics of the KC-135 Stratotanker.
KC-135 Stratotanker is a really “old” airplane, it is a derivative of the Boeing 707 and the first models are from 1954, in fact the “newest” that the Air Force has bought it in 1965.
The technology, tools and Aerodynamic knowledge has greatly improved since then.
The results of the analysis revealed something curious, the aerodynamic efficiency of the plane improved by 0.8% if the wipers rested vertically.
To this can be added a change of the windshield for a lower profile, which improves aerodynamic efficiency by 0.2% to have a total of 1% increase.
This really is not something new, as explained in 557 Weather Wing (Department of the US Air Force), commercial aircraft such as the McDonnell Douglas MD-11 that is used as cargo have already demonstrated that this system of windscreen wipers resting vertically reduce resistance considerably.
1% doesn’t seem like much, but this is where you have to start calculating. The US Air Force currently has 396 KC-135 Stratotankers active.
According to Popular Mechanics, these aircraft consumed about 290 million gallons of fuel (more than 1,300 million liters) in the 2018-2019 period, 14% of all the fuel used by the Air Force.
If they continue to use both the 396 aircraft and until now, that change of 1% represents a fuel saving of around $7 million a year.
Will the wipers change? Hard to know, after all it’s just a computational test and a project to modify the planes themselves.
On the other hand, they comment in Popular Mechanics that the plan is to replace the KC-135 Stratotanker fleet with the KC-Z and the Boeing KC-46A Pegasus, a better aircraft that will begin to operate in 2030.
$7 million during at least 5 years are still many millions of dollars.