At the U.S. Air Force Academy in Colorado Springs, cadets are working on a new wing design for the KC-135 Stratotanker that could significantly increase fuel efficiency for the venerable aircraft. Illustrating how small changes can make a big difference, the secret is in subtle, almost invisible adjustments to the wingtips, using wing designs from other aircraft as a template. As for concentrating on the rather unglamorous Stratotanker, it makes perfect sense to put some extra energy into designing an aerial refueler that delivers more fuel and consumes less, especially with the development of new sustainable energy sources in view.
The KC-135 Stratotanker
The KC-135 is a true workhorse. It was first put into flight in 1957 as a refueling craft. Since then, it’s been modified a number of times to function as a mobile command post. The aircraft is also used for reconnaissance, photo mapping, and simple transportation. Along the way Boeing, the manufacturer, has made a number of significant fuel efficiency improvements including an engine replacement that achieved a 27% reduction in fuel use, estimated to save up to 3.2 million barrels of fuel annually. The aircraft with modifications is called the KC-135R.
The Air Force Academy Cadets
Research into alternative energy and fuel conservation has been a hallmark of the Air Force Academy’s mission ever since its first in-house laboratory was established in 1962. The new wing design is co-funded by the Air Mobility Command and the Air Force Research Laboratory. The cadets have been analyzing the winglet (a short extension at the tip of the wing) from another aircraft to explore how its application to the KC-135R could save fuel. They are also testing the potential fuel savings of another type of wing design used in other aircraft, called a raked wingtip.
Improved KC-135R Wing Design Saves up to 8%
According to the Air Force Academy, the research team started by “dusting off” old wing modification investigations by NASA and Boeing from decades ago. The design improvements would have achieved a 7% reduction in drag, but were shelved after the 1980’s. The aforementioned engine replacement took priority in the budget, and a drop in fuel prices made the wing redesign less cost-effective. With prices spiking and peak oil right around the corner, stretching fuel efficiency is once again a top priority. After a solid year of research and number crunching, the cadet team predicts a savings of up to 8% for its new wing design. The next step is a cost analysis to determine the impact on the budget if the design is implemented.
Sustainable Energy in the Air
The KC-135R has already been enlisted in the U.S. military’s shift away from conventional petroleum fuels. In a test run last fall, a KC-135 successfully refueled an F-22 with a 50-50 synthetic fuel blend. Aside from helping to reduce the military’s reliance on petroleum products, the Air Force Academy’s focus on redesign may point to more cost-effective ways of enhancing the viability of alternative energy sources for all aircraft, including algae biofuel, fuel cells, and electricity. Though exciting new technologies dominate the spotlight, the cadets are showing that it is still worthwhile to examine the old and familiar for new opportunities to stretch the limits of fuel.
Image: Retromodern on flickr.com.
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