KC-135 Stratotanker

As part of its Center for Aircraft Structural Life Extension contract with the USAF, Sabreliner performed a structural teardown to determine current status and long-term structural viability of the aircraft


It was the ‘50s. The days of Elvis and James Dean, where Saturday night meant drive-ins and roller rinks. From the fins on a pink Plymouth convertible to the leather jacket that fit just right, aviation-inspired style had arrived and it was everywhere. From small town USA to the big city lights, this was the jet aviation era — a time of iconic style, innovation, and quality built to last.

It was the ‘50s. In Perryville, a small town nestled in the farmlands of southeast Missouri, fledgling aviation company Sabreliner Corporation was creating the first twin-engine business jet, its namesake Sabreliner. At the same time the Sabreliner 40 Model was coming to life, another unique aircraft was being born out on the West Coast, the KC-135 Stratotanker. This aircraft and aircraft expert Sabreliner Corporation would continue to share a path leading to the present day.

The KC-135 Stratotanker

The Boeing Company’s 367-80 platform evolved into the 707 passenger plane as well as the KC-135 Stratotanker next generation aerial refueling platform. In August 1956, the Stratotanker completed its first flight and it began its military service life a year later. Since then, it has provided the core aerial refueling capability for the U.S. Air Force, while offering support to the Navy, Marine Corps, and allied nation aircraft for more than 50 years. This aircraft enhances the military’s capability to accomplish its primary mission of global reach. While it’s primarily known for its refueling capabilities, the KC-135 also has been used for transporting cargo, as well as ambulatory patients using patient support pallets during aeromedical evacuations.

According to the aircraft’s Air Force spec sheet, four turbofans, mounted under 35-degree swept wings, power the KC-135 to takeoffs at gross weights of up to 322,500 pounds. Depending on fuel/storage configuration, the KC-135 can carry up to 83,000 pounds of cargo.

Nearly all internal fuel can be pumped through the flying boom, the KC-135’s primary fuel transfer method. A boom operator is stationed in the rear of the plane and controls the boom during in-flight air refueling. Some aircraft have been configured with the multipoint refueling system, which consists of special pods mounted on the wingtips. These KC-135s are capable of refueling two receiver aircraft at the same time.

In 1954, the Air Force purchased the first 29 of what would become a fleet of more than 700 aircraft. The last KC-135 was delivered in 1965 and more than 400 of the aircraft are still in service today.

The KC-135 was expected to retire years ago based on a predicted number of flight hours accrued on the airframe. As with many other military aircraft, the KC-135 is now flying well beyond its original design service goal in terms of flight hours. Mission changes and structural modifications including upgrades and repairs have changed the life expectancy of the KC-135 in ways not envisioned by the original designers.

An aging aircraft meets an aging aircraft expert

In 2010, Sabreliner was awarded a U.S. Air Force (USAF) contract with the Center for Aircraft Structural Life Extension (CAStLE). The research and engineering activities performed by CAStLE, a USAF Center, located at the Air Force Academy in Colorado Springs, CO, cover a variety of tasks that follow aircraft and other structures through their life cycle from cradle to grave.

CAStLE provides aircraft structural integrity technology to the Air Force and private sector organizations. Its experts research ways to keep the Air Force’s aging aircraft fleet in operation by ensuring the existence of extended life cycles, lower maintenance costs, and improved pilot safety.

So, why keep these aircraft in service?

“Simply put, continuing to keep older aircraft flying may sometimes be more cost effective than procuring new ones. Economical sustainment requires moving away from a ‘find and fix’ mentality to one of ‘anticipate and manage,’” says Mike Fallert, director of Sabreliner Corporation’s Ste. Genevieve, MO, operations where the KC-135 work is performed.

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