TINKER HISTORY: Boeing KC-135 Stratotanker

KC-135s line the Bldg. 3001 shop floor in the 1960s. (Photo courtesy of the Tinker History Office)

KC-135s line the Bldg. 3001 shop floor in the 1960s. (Photo courtesy of the Tinker History Office)

TINKER AIR FORCE BASE, Okla. --

The Boeing C-135 aircraft is a derivative of the popular Boeing 707 airframe modified from commercial airliner use to military missions with the largest produced model being the KC-135 “Stratotanker” purposely designed for air-refueling. The C-135 family has a large fuselage with traditional tail configuration, low-wing with two underslung engines on each side and sits on tricycle style landing gear. KC-135 refueling aircraft sport a high-speed flying boom controlled by a boom operator who lays in a bulbous refueling pod.

Tinker’s Oklahoma City Air Logistics Complex is responsible for conducting all levels of maintenance of the C/KC-135 airframes. Because the aircraft have been heavily used for many years the aircraft require extensive maintenance. Depot level maintenance typically includes the overhaul of engines, avionics, fuel systems and refurbishment of the high-speed refueling boom. The professionals at Tinker routinely perform maintenance never anticipated for the aircraft such as replacing major components of the wing structure, replacing the entire lower, forward fuselage skin.

The C-135/KC-135 aircraft was first produced in 1955 and has served in every major conflict and many other missions around the world for the U.S. Air Force. During the Cold War, it was operated on training and alert duties to refuel Strategic Air Command bombers and Tactical Air Command fighters. SAC missions required many early KC-135s be operated extensively in the low-level environment which severely stressed the aircrafts’ wings and led to their early retirement.

The KC-135 variant refuels aircraft using the high-speed refueling boom along which is configured for refueling aircraft with a refueling receptacle. A large drogue can be fitted to the end of the boom to allow aircraft with refueling probes to refuel. In this configuration the boom can only refuel aircraft for the type it is set up, which limits the flexibility of the aircraft. To overcome this problem, refueling pods have been attached near each wingtip on some aircraft for multi-mission capability.

During its program life the C/KC-135 has been modified or configured for many types of missions from VIP transport (VC-135), airborne command post (EC-135), transport (C-135), reconnaissance (RC-135S/U/V) and weather reconnaissance (WC-135). Other specialized versions include the Speckled-Trout, KC-135Q modified for refueling SR-71 Blackbirds and even a national level asset aircraft capable of releasing water from a modified boom to conduct icing tests of aircraft.

Over the years there have been many upgrade and modification programs conducted on the C-135 airframe which include the installation of GPS equipment which eliminated the necessity for a navigator on the crew, upgrade of the cockpit and fuel management system in the PACER-CRAG, replacement of the original engines to high-bypass General Electric F108 engines. These aircraft received the KC-135R designation. The latest and on-going modification is “Block 45” and will extend the aircrafts’ operational life for many years.

The KC-135 remains one of the longest serving aircraft in the Air Force inventory fulfilling the air mobility, air-refueling and special purpose mission roles. It is operated on active duty under Air Mobility Command and with the Air National Guard and Air Force Reserve. KC-135 aircraft also operate with NATO and allied nations to include France, Turkey, Chile and Singapore.

Manufacturer: Boeing

Aircraft type: KC-135

Nickname: Stratotanker

Crew: 4+

Power plant: Four Pratt & Whitney J57 turbojet engines (KC-135A), four P & W TF33 turbofan engines (KC-135E) and four General Electric F108 high-bypass turbofan engines (KC-135R)

In-service dates: 1956-present

Number produced: 808

Tinker connection: Program management, maintenance, repair and overhaul