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Development of the modern air refueling aircraft

  • Published
  • By Ellery D. Wallwork
  • Headquarters AMC History Office
SCOTT AIR FORCE BASE, Ill. --  Editor's note: This is the sixth article in a series of articles highlighting the history of aerial refueling and the important role aerial refueling has played in American military history.

By the early 1950s, Air Force air refueling tankers consisted of converted bombers and cargo aircraft. The introduction of the eight-engined B-52 Stratofortress in 1952, however, made these existing tankers highly ineffective.

A KC-97 Stratofreighter with an offload capacity of 53,000 pounds of fuel could effectively refuel two B-47 Stratojets. The larger fuel tanks (243,000 pounds worth) and the higher fuel consumption rate of the B-52 meant more KC-97s would be required to support the fleet. Additionally, mission planners had to take into consideration the differences in technology between the piston-engined KC-97 and the turbojet B-52.

Because of the speed differential, the KC-97 tanker had to be based approximately 1,000 miles ahead of the B-52 before a rendezvous could take place. Additionally, the B-52 had to descend to the KC-97's operating altitude and then burn extra fuel to return to its cruising altitude.

As an example, Strategic Air Command conducted Operation Power Flite in 1957. Designed to test and display the intercontinental capability of the B-52, the mission consisted of three B-52Bs from Castle Air Force Base, Calif. These three aircraft led by the Lucky Lady III, piloted by the commander of Fifteenth Air Force, Maj. Gen. Archie J. Old Jr., flew around the world, a distance of 21,135 nautical miles, and successfully completed the route in 45 hours and 19 minutes, less than half the time taken by the Lucky Lady II, a B-50A, in 1949.

Despite Gen. Curtis E. LeMay, SAC Commander in Chief, calling Operation Power Flite a "demonstration of SAC's capabilities to strike any target on the face of the earth," SAC planners also took note of the most challenging aspect of the mission: air refueling. The three B-52s of Operation Power Flite required the support of 78 KC-97s, plus several more standing alert at bases along the route in case of adverse winds. The operation showed it took two KC-97s to provide 26 percent of one B-52B's refueling requirements.

The operation left little doubt that SAC needed a new tanker capable of enhancing the intercontinental mission.

By this point, though, the Boeing Corporation had already initiated developing, with its own funds, a new turbojet aircraft. Boeing officials invested in such an aircraft because it would be able to serve as a base-model for a tanker, a military cargo aircraft, and even a commercial airliner. The corporation began construction of the prototype Model 367-80 (informally known as the Dash 80) in October 1952. In July 1954, the Dash 80 flew for the first time, with further testing and development following rapidly.

In November 1953, SAC issued its requirement for 200 jet tankers. The Air Force received three proposals in response -- paper-only designs from the Douglas and Lockheed Corporations. While the other companies talked about possible designs, only Boeing had an operating model. Because of the urgency of SAC's need, the Air Force procured 29 KC-135 Stratotankers as an interim measure in 1957. The number of interim tankers increased to 88, then to 118, and then 157. The Air Force ended up procuring 830 KC-135s; of which, 732 were initially identified as interim tankers.

For the next 20 years, SAC maintained nearly a one-to-one ratio of KC-135s to B-52s. Often, they set on alert status together, with the tanker providing fuel in a "buddy" fashion. On the other hand, forward basing the tankers to rendezvous with the bombers offered a significant advantage: forward-based tankers had more fuel to give the bombers since they did not have to travel such a great distance. With this in mind, SAC based KC-135s at places like Westover AFB, Mass., and Dow AFB, Maine. Secret agreements with Canada also allowed SAC to base KC-97s at Cold Lake and Namao in Alberta.

Through the years, the Air Force modified the KC-135s. The first modifications began in July 1962 when SAC developed the Q-model. A total of 56 KC-135As received fuel tanks to hold special fuel for the SR-71 and additional communication equipment used during fuel transfer operations.

In later years, when the KC-135Qs were refitted with CFM-56 engines, the aircraft were re-designated as KC-135Ts. Another model (-B) began in July 1964 as Boeing added specialized communications equipment and an air refueling receptacle in 17 KC-135As. Essentially an airborne command post, the KC-135B was re-designated the EC-135C on Jan. 1, 1965.

The two major KC-135 modernization programs began in the 1980s. The KC-135E was refitted with JT-3d engines. By the end of the program, 157 Air Force Reserve and Air National Guard KC-135s were updated.

In July 1984, SAC formally accepted the first KC-135R, equipped with new fuel-efficient CFM-56 engines and more than 25 other updates, such as generators and main landing gear. The KC-135R had 1.5 times the fuel offload capacity of the KC-135A. More than 410 KC-135s were re-engined by June 9, 2005.

Additionally, in June 1967, SAC published a requirement for an advanced capability tanker to supplement the KC-135 force. While ideal for supporting the bomber mission, planners judged the KC-135 force as inadequate to support a general force deployment of attack, rescue, air defense, and airlift aircraft.

Although Headquarters Air Force endorsed the concept, little was done while the Vietnam War continued.

A tanker support study in 1970 called for adapting a current wide-body transport aircraft as the most cost-effective solution. A limited number of feasibility tests followed in 1971 and 1972. United States material support during the October 1973 Yom Kippur War (a coalition of Arab states against Israel) highlighted the need for air refueling of airlift forces.

In December 1973, SAC reissued its tanker requirement, now entitled the Advanced Tanker Cargo Aircraft. Both Military Airlift Command and Tactical Air Command agreed that the new aircraft should be primarily a tanker with an airlift augmentation capability. As such, they agreed SAC should be the single manager for planned new tanker/cargo aircraft.

Two companies responded to the ATCA program. Boeing based its proposal on its 747, while McDonnell Douglas based its proposal on the KC-10. On Dec. 19, 1977, the Air Force selected the KC-10A as the more advantageous aircraft. While the 747 version offered a larger capacity, the KC-10 was cheaper and offered the ability to take off with a maximum load from a shorter runway. From 1981 to 1990, the Air Force received 60 KC-10s.

SAC originally assigned the 60 KC-10 aircraft to three bases: Barksdale AFB, La.; March AFB, Calif.; and Seymour Johnson AFB, N.C. Following the Air Force's reorganization and the creation of Air Mobility Command in 1992, leaders consolidated the KC-10s at McGuire AFB, N.J. (now called Joint Base McGuire-Dix-Lakehurst), and Travis Air Force Base, Calif.

Both the KC-10 and KC-135, despite their age and heavy use, continue to ensure AMC accomplishes its rapid global mobility mission, as well as sustaining America's deployed forces.