In operation since 1957, the KC-135 Stratotanker is used primarily to re-fuel aircraft during flight. Modified KC-135s, however, serve as flying command posts, pure transport, electronic reconnaissance, and photo mapping craft.
Tanker Characteristics
The KC-135 possesses the following characteristics:
- Flying boom to provide fuel transfer
- Drogue to re-fuel probe-equipped aircraft (attached to the boom)
- Passenger and cargo deck located above the fuselage-mounted tanks
KC-135 Skin-Replacement
During a 13-year period ending in 1988, Boeing replaced the lower wing surfaces with an improved aluminum-alloy skin. The program included the following tasks:
- Skin replacement on 746 aircraft (1500 square feet per aircraft)
- Replacement of the engine strut fittings
- Installation of 564 parts, 32,200 steel fasteners, and 19,500 aluminum rivets
CFM Engine-Replacement
To increase takeoff and carrying capacity, improve fuel efficiency, and reduce engine noise and pollution levels, Boeing replaced the original KC-135A engines with CFM56 engines for the U.S. Air Force. The serviced aircraft were re-designated as KC-135Rs, and the engine-replacement program achieved the following results:
- Reduced fuel consumption 27%, saving 2.3 to 3.2 million barrels of fuel annually
- Reduced decibel levels from 126 to 99 decibels (98%) while reducing the noise-impact area near airports from 240 to 3 square miles
JT3D Engine-Replacement
The Air Force Reserve and Air National Guard retained Boeing to replace KC-135-A engines with refurbished JT3D engines taken from used commercial 707 airliners. The aircraft designation changed to KC-135E, and the program achieved the following results:
- Increased engine power 30%
- Reduced noise levels 85%
- Replaced/refurbished struts and cowling, brakes, cockpit controls, and instruments
Continuing Improvements
The U.S. Air Force retained Boeing to provide the following improvements: add wingtip, hose, and drogue refueling pods; modernize the cockpit; provide new compasses and radar systems; and install a global positioning system (GPS).