KC-135Rs on the ramp at Diego Garcia in 2003. With a B-52H taxiing for take-off in the background.
Because the KC-135A's original engines are of 1950s technology, they don't meet modern standards of increased fuel efficiency, reduced pollution and reduced noise levels. By installing new, CFM56 engines, performance is enhanced and fuel off-load capability is dramatically improved. In fact, the modification is so successful that two-re-engined KC-135Rs can do the work of three KC-135As. This improvement is a result of the KC-135R's lower fuel consumption and increased performance which allow the tanker to take off with more fuel and carry it farther. Since the airplane can carry more fuel and burn less of it during a mission, it's possible to transfer a much greater amount to receiver aircraft.
The KC-135R uses as much as 27 percent less fuel than the KC-135A, the USAF can expect huge fuel savings by re-engining its fleet of KC-135s - about $1.7 billion over 15 years of operation. That's enough to fill the gas tanks of some 7.7 million American cars each year for a decade and a half. Annual savings are estimated to be about 2.3 to 3.2 million barrels of fuel, about three to four percent of the USAF's annual fuel use.
Photo via Ted Morris