Boeing KC-135

The first attempts to refuel in the air from one plane to another took place in the 20s of the 20th century. They were quite successful, but at that time the idea did not receive significant support among military leaders. The situation changed radically after the Second World War, in the early 1950s, simultaneously with the beginning of the era of jet aviation. Jet engines required a fairly high amount of fuel, and the appearance of strategic jet bombers again raised the question of creating a special refueling aircraft. One of the most successful in this class of winged machines was the Boeing KC-135, the first flight of which took place back in 1956. The Boeing company created an extremely successful concept Boeing -367-80, which will soon become an icon of aviation under the name Boeing -707. The military version of the Dash-80, which was the closest to the initial concept, was initially considered as a transport, but at the request of the military, which urgently needed a replacement for the already outdated KS-97, the company very quickly converted the aircraft into a modification of the fuel tank. In the same year, a preliminary order was issued for a series of 29 KS-135A aircraft, which were transferred to the Air Force in the following 1957.
Soon the orders were significantly increased and in total more than 600 KS-135 aircraft were built. The first modifications were equipped with Pratt & Whitney J57-P-59W engines with a thrust of 44 kN each. In the early 1980s, the aircraft was modernized, the latest avionics and other Pratt & Whitney TF33-PW-102 engines were installed on it, which were mainly taken from decommissioned civilian Boeing -707s. This made it possible to reduce own fuel costs and take 20 percent more fuel for refueling other aircraft. The next modernization of these aircraft took place already in the 1990s, by this time their operation had been going on for almost 40 years. General Electric CFM56 (F108) engines were installed on them. The power of this engine was 100 kN, which was more than twice the power of the first power plant of the aircraft. Even compared to the TF33 engine, the capabilities of this modification have increased by 60 percent in terms of key indicators.
From the very beginning, the KS-135 was tasked with being a fuel donor in the air for strategic bombers, but for more than 60 years it had to «cooperate» in the air side by side with almost all the main types of aircraft of the US Air Force, including the unsurpassed SR -71 Blackbird, for refueling with special fuel, a separate KS-135Q modification was created. They took an active part in all known conflicts, starting with the war in Vietnam and ending with the second war in Iraq in 2003. Only in 2010, 53 years after the adoption of the KS-135, the question of their replacement by a more modern type, the KS-46, created on the basis of the Boeing-767, was raised. The first KS-46 were handed over to the Air Force in 2019, by this time the KS-135 had been in service for over 60 years, making it one of the longest-serving types in the history of aviation. In addition to the US Air Force, the KS-135 was operated by the French Air Force and the Singapore Air Force. Currently, many aircraft of this type occupy places of honor in the most famous aviation museums of the United States of America.