Fifty-five years ago this week, the USAF/Boeing KC-135A Stratotanker took to the skies for the first time. The jet-powered aircraft would go on to become the most famous military tanker in the history of aviation.
The KC-135A Stratotanker was a derivative of the famous Boeing Model 367-80. The type was the only jet-powered aircraft designed specifically for the aerial refueling mission. As such, it replaced the older and slower propeller-driven KC-97 Stratotanker. For the first 15 years of its operational life, the KC-135 was the only tanker flown by the Strategic Air Comman (SAC).
The KC-135A measured 136.25 feet in length and had a wingspan of 130.8 feet. Gross take-off weight and empty weight were 297,000 lbs and 109,000 lbs, respectively. Four (4) wing pylon-mounted Pratt and Whitney J57-P-59W turbojets provided a sea level thrust of 58,000 lbs in afterburner. The aircraft was designed to have an unrefueled range of 4,000 miles, a cruise speed of 552 mph and an operational ceiling of 40,000 feet.
Jet fuel was carried internally within six (6) wing tanks and four (4) fuselage tanks. All but 1,000 gallons of this fuel could be pumped to the receiver aircraft via an extendable boom located at the rear of the tanker. The KC-135 boom operator would lie in a prone position and actually flew the boom into the receiving aircraft’s fuel receptacle.
On Friday, 31 August 1956, the first KC-135A Stratotanker production aircraft made its maiden flight from the Boeing airfield at Renton, Washington. Known as the “The City of Renton”, this aircraft was the first of 820 KC-135 aircraft that Boeing would ultimately produce. Roughly 90 percent of these production aircraft were true tankers while the remainder were employed as cargo transports and flying command posts.
The service that the KC-135 has provided to our nation’s aerial warfighters has truly been astounding. For example, during nine years of the Vietnam conflict, KC-135s made 813,000 aerial refuelings of combat aircraft. In support of the Persian Gulf conflict, KC-135 tankers made 18,700 hookups and transferred 278,000,000 lbs of fuel.
The KC-135 has evolved into numerous variants over the course of its long operational life. A variety of modifications have extended the service life of the KC-135 into its sixth decade. Key upgrades include reskinning the wings with an improved aluminum alloy and more powerful and fuel-efficient CFM-56 turbofans. Total sea level thrust is more than 90,000 lbs in afterburner.
As a tribute to this venerable aircraft, her designers and her flight crews, we note here that the KC-135 Stratotanker remains the primary USAF aerial refueling aircraft to this very day.
Having flown the KC-135A/E/Q for 22 years, I always knew what a great airplane she is. The KC-135 has become one of the best airplanes of all time. The C/KC-135 has been modified into 29 different mission versions in 32 different models, no other airplane in history has proven to be so versital.
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