KC-135 Stratotanker

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Product Type:

Military Airlift/Aerial Refueling Aircraft (KC-135)
Military Special Mission Aircraft (RC-135/WC-135/OC-135)

Using Service (US):

Air Force (USAF)

Program Status:

No more new aircraft will be procured.
Focus is on upgrades and sustainment.

Prime Contractor:

The Boeing Company

The KC-135 Stratotanker

About the KC-135:

The Boeing KC-135 is a long range cargo, passenger airlift, and aerial refueling aircraft (+military special missions (RC-135)). In its latest configuration, the aircraft is powered by four CFM International CFM56-2B1 (F108) high-bypass turbofan engines, each providing 21,634 pounds of thrust. The Boeing model 367-80 jet transport and tanker prototype was the basic design for the commercial 707 passenger plane as well as the KC-135A Stratotanker. Built in Renton, WA, out of a total of 820 C-135s built, 732 were KC-135As, 17 were KC-135Bs, 45 aircraft were built as C-135A or C-135B "Stratolifter" transport aircraft without onboard tanker equipment (no longer in service), and another 14 aircraft were built and configured for military special missions (some of these are still in service - more info later in this article). The remaining 12 aircraft were C-135F Stratotankers built for the French Air Force. The KC-135 was purchased to replace U.S. Air Force KB-29, KB-50 and KC-97 four-engine, propeller-driven aircraft.

The KC-135 Stratotanker variant provides aerial refueling. Nearly all internal fuel can be pumped through the flying boom, which is the KC-135's primary fuel transfer method. A special drogue attached to and trailing behind the flying boom, may be used to refuel aircraft fitted with probes. Some KC-135s have been configured with the Multipoint Refueling System or MPRS. MPRS configured aircraft are capable of refueling two receiver aircraft simultaneously from special pods mounted on the wingtips.

On the KC-135, a cargo deck above the refueling system can hold a mixed load of passengers and cargo. Depending on fuel storage configuration, the KC-135 can carry up to 83,000 pounds (37,650 kg) of cargo or six standard 463L pallets or 37 passengers. The KC-135 is also capable of transporting litter and ambulatory patients using patient support pallets during aeromedical evacuations. In 1954, the U.S. Air Force purchased the first 29 of its future fleet of 749 KC-135A/B aircraft. The first aircraft flew on August 31, 1956 and the initial production Stratotanker was delivered to Castle Air Force Base in California in June 1957. The last KC-135 was delivered to the Air Force in January 1966. The KC-135 fleet will be replaced by the Boeing KC-46 Pegasus (KC-X New Tanker). Deliveries will start in 2017 and KC-135 Stratotankers will gradually be retired as KC-46 aircraft arrive.

Of the original KC-135As (powered by Pratt & Whitney J57 turbojets), more than 415 were upgraded with new CFM56 engines from CFM-International. The re-engined tanker, designated KC-135R or KC-135T, can offload 50% more fuel, is 25% more fuel efficient, costs 25% less to operate and is 96% quieter than the KC-135A. Under another re-engining program, tankers with Pratt & Whitney TF33-PW-102 engines were designated the KC-135E. In 2009, the last KC-135E was retired.

The KC-135R/T aircraft continue to undergo life-cycle upgrades to expand their capabilities and improve reliability. Among these are improved communications, navigation, auto-pilot and surveillance equipment to meet future civil air traffic control requirements. As of April 2014, there are 396 KC-135s in the Air Force inventory with an average age of 52 years with 26 years of service life remaining (projected service life of 2040). On February 21, 2013, after more than 50 years of service (delivered in 1962) and 22,500 flying hours, the first operational KC-135R Stratotanker was retired from service.

FY 2020 & FY 2021 - KC-135 DoD Program:

This data is available in Forecast International's U.S. Defense Budget Forecast, a comprehensive analytical database containing historical and forecast budget figures, year-to-year funding comparisons, congressional budget markups, program justification documents, and much more.

Source: U.S. Department of Defense (DoD) and The Boeing Company.

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