A Utah Air National Guard KC-135R Stratotanker casts its reflection on a watered-down flight line at the Roland R. Wright Air National Guard Base, UT. USANG photo by TSgt Amber Monio
A B-52 Stratofortress prepares to receive fuel from a KC-135 Stratotanker during a flight in support of Operation Inherent Resolve, July 27, 2017. USAF photo by SSgt Michael Battles
Two U.S. Air Force B-52H Stratofortress aircraft assigned to the 96th Bomb Squadron, Barksdale AFB, LA, fly in formation during Bomber Task Force Europe 20-1, Oct. 23, 2019, over the Baltic Sea. USAF photo by A1C Duncan C. Bevan
A KC-97G 53-3816 in flight. 98th Air Refueling Squadron, Lincoln AFB, NE. AMC History Office photo

AMC Heritage: 60 Years of Service and Going Strong!

By Ms. Jeanie Hood, HQ AMC Flight Safety

Ask any fighter pilot how they feel about the KC-135 when they are halfway across the Atlantic Ocean (the pond) and running low on fuel. I have flown dozens of missions across the pond with fighters in loose trail formation and always knew when they were running low on fuel. Very slowly, they would tighten up their formation with the tanker and position themselves off the left wingtip. Once they had the tanker pilot’s attention, they would put their thumb up to their mask and tilt their head back, indicating they were thirsty. I usually acknowledged by lifting my cup of coffee as if saluting. Into the slot they would go, and the magnificent boom operator took over.

One of the earliest air refuelings occurred in the 1920s between two slow-moving biplanes. The lead pilot, using a handheld gas tank and hose, lowered the hose to the receiving pilot, who then placed the hose directly into his aircraft’s gas tank. During the years that followed, many attempts were made to make air refueling a more efficient and safe process. Fast forward to the 1950s. After years of research and development, which proved that aerial refueling was essential to airpower, the KC-97 tanker was created.

The KC-97 proved to be a valuable asset until the introduction of the B-52 Stratofortress in 1955. The bomber, powered by eight jet engines, was significantly faster than the KC-97 and also required special jet fuel. The KC-97, being piston-powered, used standard aviation gasoline and required an additional reservoir of fuel for the B-52. In order for the heavy gross weight bomber to refuel, it had to reduce its speed to near stall speed by lowering the flaps and the rear landing gear. While this approach was a feasible option, it was less than ideal. It was apparent that a tanker needed to be developed that had performance capabilities and speeds comparable to the B-52.

The KC-135 Stratotanker is a unique asset that provides the core aerial refueling capability for the Air Force, enhancing the primary mission of global reach.

Enter the KC-135, a Boeing aircraft designed specifically for aerial refueling with double the fuel capacity of the KC-97 and enough speed to keep up with the bombers. Initially, there were no buyers for the prototype, so Boeing paid for it with their own money and gave the KC-135 the initial designation Model 717. Luckily, the new design was well-received by both the military and commercial enterprises.

The KC-135 Stratotanker is a unique asset that provides the core aerial refueling capability for the Air Force, enhancing the primary mission of global reach. The KC-135 delivers fuel to Air Force assets, as well as to the Navy, Marines, and other allied nation aircraft during training, combat, and humanitarian efforts.

The first KC-135 rolled out of the Boeing plant on July 18, 1956, and flew for the first time on August 31, 1956. The first tankers were delivered to Castle Air Force Base (AFB), CA, in June of 1957 during President Eisenhower’s second term in office. The Cold War was getting warmer with alert bombers ready to strike Russia at a moment’s notice. Unfortunately, the bomber was not capable of carrying enough fuel for a round-trip mission. The bomber had to make multiple stops for fuel on its way to the target and then repeat the process to return to the home station. The Stratotanker was initially purchased to support Strategic Air Command (SAC) bombers, giving them virtually unlimited range and endurance. This procedure allowed all targets to now be within reach without needing to land and refuel several times before reaching their destination. Eventually, more than 800 tankers would be purchased by the Air Force, with the last one delivered in 1965.

The KC-135 proved to be a game-changer during the Vietnam War. The fighters were limited to minutes on the front lines because they did not have the capacity to carry large amounts of fuel, and their fuel consumption was high. Having the tanker refuel them frequently allowed them to stay on the front lines for hours rather than minutes. A total of 813,000 aerial refuelings of combat aircraft were made during the Vietnam War. Since then, the tanker has been the backbone of various conflicts, including Operations Desert Shield and Desert Storm, the Persian Gulf War, Northern and Southern Watch, Iraqi Freedom and Enduring Freedom, and other missions supporting contingencies all over the world. This tanker has refueled just about every aircraft the U.S military has flown. Even NASA, the National Aeronautics and Space Administration, has used the KC-135 in the past for zero-gravity training, with the longest-serving aircraft (1973­1995) named Weightless Wonder IV.

There have been many variants of the C-135, including the Rivet Joint and the EC-135 Looking Glass. Initially, the KC-135A model was equipped with Pratt and Whitney J57-P-59W turbojet engines, which produced approximately 10,000 lbf of thrust dry and 13,000 lbf of thrust wet. Eventually, most of the KC-135A fleet received the upgraded CFM 56 high-bypass turbofan engine, which produced 22,500 lbf of thrust. The modified tanker was designated the KC-135R Model and could offload more fuel, was more fuel-efficient, had an increased operational range, and cost less to operate than the previous engines. The R model has a takeoff weight of 322,500 pounds, and depending on the fuel storage configuration, could carry up to 83,000 pounds of cargo.

During the KC-135’s lifetime, it has transferred more than nine billion pounds of fuel into more than 600,000 aircraft, and it has remained mission-capable due to the dedicated work of incredible maintenance and support teams. Eventually, a portion of the KC-135 fleet will be replaced by the KC-46A Pegasus, the first of which was delivered in January 2019.

Oftentimes, it is the bombers and fighters that get all the glory, but let us not forget it is the tanker flying in the shadows that allows those aircraft to deliver their payloads on target and on time. This airborne gas station has been in service for more than 60 years and lingers in the skies 24 hours a day, seven days a week, waiting to refuel the next thirsty aircraft at destinations all over the world. Its service has been invaluable in sustaining Air Force capabilities.