The McDonnell Douglas KC-10A Extender is an advanced aerial tanker and cargo aircraft designed to
provide increased global mobility for U.S. armed forces. Although the KC-l0's primary mission is aerial
refueling, it can combine the tasks of a tanker and transport aircraft by refueling fighters and
simultaneously carrying the fighter support personnel and equipment on overseas deployments.
Based on the McDonnell Douglas DC-10 Series 30CF Convertible Freighter, the KC-10A
Extender emerged victorious in a contest with Boeing's Model 747
aerial tanker variant to satisfy the U.S. Air Force's Advanced Tanker Cargo Aircraft requirement. In
December 1977, it was selected by the USAF based on integrated assessment of capability, price,
life-cycle costs and technical features of the DC-10.
The KC-10's maiden flight took place on 12 July 1980. The first aerial refueling
occurred during testing on 30 October 1980, with the receiver aircraft a
C-5 Galaxy. The first KC-10
was delivered to the USAF on 17 March 1981. The 60th and last was formally handed over on 29
In the mid-1990s, the major USAF reorganization that witnessed the elimination of
the Strategic Air Command (SAC) resulted in the KC-10 Extender fleet being reassigned among units of
the Air Mobility Command (AMC) and Air Combat Command (ACC), before all being controlled by AMC. All
KC-10's, apart from a single aircraft that was destroyed in a fire on the ground in September 1987,
are still in service.
The KC-10 is powered by three General Electric CF6-50C2 high bypass-ratio turbofan
engines, each generating 52,500 pounds of thrust. Versions of the CF6 engine family are
installed on most of the DC-10s in commercial airline service and have compiled an impressive
reliability record. One of the engines is mounted at the base of the tail above the aft fuselage,
and the other two are installed on pylons beneath the wings, one on each side of the fuselage.
Although the KC-10 retains 88 percent of systems commonality with the DC-10-30, it
has additional systems and equipment necessary for its Air Force mission. Additions include military
avionics, director lights for receiver aircraft, an aerial refueling boom, an aerial refueling
hose and drogue system, a 3-seat aerial refueling operator station (ARO) and an aerial refueling
receptacle. Several aircraft in the KC-10 fleet have been modified with wing-mounted pods to further
enhance aerial refueling capabilities. The hose and drogue WARP (Wing Air Refueling Pod) modification
allows for the aerial refueling of two aircraft simultaneously. This is extremely helpful when
refueling naval fighter groups - a fighter group can be refueled two at a time, reducing the waiting
period of the other aircraft and allowing each aircraft to "save" fuel.
In addition to the DC-10's standard wing and auxiliary tanks, the KC-10 has a bladder-type
supplementary fuel tankage system which includes seven unpressurized integral-body fuel cells, four
aft of the wing and three forward, all located in under-deck vented cavities. A crashworthy design makes
use of keel beams and strategically placed energy absorption material to protect the tanks.
Under-fuselage panels permit direct access to each cell for installation, removal, and system,
maintenance and structural inspection. Combined, the tanks carry more than 356,000 pounds
(160,200kg) of fuel - almost twice as much as the KC-135 Stratotanker.
During boom refueling operations, fuel is transferred to the receiver aircraft at a
maximum rate of 1,100 gallons (4,180 liters) per minute; the hose and drogue refueling maximum rate is
470 gallons (1,786 liters) per minute. The KC-10 can be air-refueled by a KC-135 or another KC-10 to
increase its delivery range.
The aerial refueling operator's station in the KC-10, located aft of the rearward
lower fuselage fuel tanks, features improvements in comfort, viewing capability, and environment.
Instead of assuming the prone position required by the KC-135, the refueling operator sits in an
aft-facing crew seat. Station equipment includes handy refueling controls, a wide viewing window facing
aft and additional periscope-type viewing arrangements for traffic management. Accessible from the upper
deck, the ARO station is pressurized and has independent thermal control, a quiet environment and an
arrangement suited for both training and operational missions. While refueling requires only one
operator, two additional seats are provided to accommodate an instructor and an observer.
For cargo-handling, the KC-10 is equipped with a large, upward-hinging cargo door,
located on the left side of the forward fuselage, which provides the capability to transport a significant portion
of the tactical support equipment of fighter squadrons. The cargo loading system, adapted in part from
the commercial DC-10 freighter, has been enhanced with the addition of powered rollers, powered winch
provisions for assistance in fore and aft movement of cargo, and an extended ball mat area to permit
loading of larger items. The cargo compartment can accommodate loads ranging from 27 pallets to a mix of
17 pallets and 75 passengers. In an all-cargo configuration, the KC-10 accommodates 25 standard 88 x
108-inch 463L cargo pallets in the cabin with aisles down both sides, or 27 pallets with a single aisle.
Other modifications to the aircraft include elimination of most upper deck windows
and lower deck cargo doors, and provisions for additional crew. Several configurations exist for
personnel and crew accommodations. One arrangement is for a crew of five, plus six seats for additional
crew and four bunks. The same area also has space for the installation of 14 more seats for support
personnel. In another arrangement, the bunks can be shifted rearward, making room for 55 more support
personnel, along with the necessary utility, lavatory and stowage modules, raising the capacity to a
total of 80 crew and support personnel. Although all eight of the DC-10 upper deck passenger doors are
installed as standard, three are deactivated. Normal entry and exit are through the two forward passenger
doors on each side, and the aft right-hand door is available as a ground emergency exit for people in
the aerial refueling operator's station.
During Operations Desert Shield and Desert Storm (1990-91), the KC-10 fleet provided
inflight refueling to aircraft from all branches of the U.S. armed forces as well as those of
coalition forces. This allowed for continued air operations without costly and time-consuming ground
refueling. Aerial refueling was key to the rapid airlift of materiel and forces. In addition to
refueling airlift aircraft, the KC-10, along with the smaller KC-135, moved thousands of tons of cargo
and thousands of troops in support of the massive Persian Gulf build-up. The KC-10 and the KC-135
conducted about 51,700 separate aerial refueling operations and delivered over 125 million gallons
(475 million liters) of fuel without missing a single scheduled rendezvous.
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