The KC-10 Extender tanker aircraft

During the late 1960s and early 1970s it became clear to the United States Air Force that it's current fleet of KC-135 tankers was insufficient. The KC-135, although a capable aircraft was of an earlier generation. The first KC-135 was produced in 1957, and the final KC-135 was rolled out in December of 1964. The Vietnam war placed considerable demands upon the USAF's fleet of KC-135 tankers, and consideration was given to the acquisition of an air-to-air tanker of greater capacity. At this stage however plans were not advanced due to lack of funding.

The advent of the Yom Kippur War in 1973 again exposed the US Air Forces lack of adequate air-refueling capacity. The USAF was denied landing rights in Europe, and as a result the USAF Lockheed C-5 Galaxy transport aircraft were forced fly direct from the United States to Israel, carrying only a fraction of their maximum payload. The US Department of Defense quickly concluded that a more advanced Tanker aircraft was required.

The Advanced Tanker Cargo Aircraft

Consideration of an Advanced Tanker Cargo Aircraft (ATCA) was started in 1967, although many years would pass before an aircraft was selected and contracts issued. In the event, the contract for two prototype aircraft would not be issued until 1976.

In 1968 the Strategic Air Command had produced a requirement for for a more advanced tanker aircraft, but continuing uncertainty about the number of aircraft that were needed were part of the ongoing delays to the project. From an initial Air Force requirement for 100 aircraft, the numbers were whittled down over the intervening years until in 1976 the Air Force planned to buy just 41 advanced tankers, and on this basis a contract for two prototype aircraft was issued.

Despite this, the decision on the number of aircraft to be procured was not finished yet! At the end of 1976 in the last days of the Ford administration, the Office of the Secretary of Defense issued a Program Budget Decision requiring 91 advanced tanker aircraft. After President Carter took office in January 1977, the decision was delayed to allow the new administration to consider the requirement, and eventually the number went back to just 41.

The ATCA competition

Four aircraft were considered for the ATCA program. The evaluation considered many factors, including initial costs and operating costs, performance, capacity and risk factors. The four aircraft considered were:

The Lockheed L-1011 Tristar.

The Lockheed L-1011 was rejected as there was no existing freight version of the aircraft. It is ironic therefore that after the Falklands War in 1982, the RAF purchased nine Lockheed L-1011-500 Tristars to bolster the long range transport and tanker roles!

The Lockheed C-5A Galaxy.

The other Lockheed offering, the C-5 Galaxy was rejected as no C-5s were flying at that time. Aircraft procurement over the years has been littered with projects that failed to meet cost performance or timescale targets and the unproven C-5A, even though based upon the successful C-141 Starlifter , was felt to be potentially risky.

The Boeing 747.

The Boeing 747 was felt to be a good offering. It was already in Airline service, having entered service on 22 January 1970, on Pan Am’s New York–London route. A freight version was already available, and could offer a high capacity for fuel and freight.

The McDonnell-Douglas DC-10.

Like the Boeing, The McDonnell Douglas DC-10 was already in Airline service, having been introduced in 1968 and developed in several versions. The capacity would good, but would not be as great as the 747. However, this was offset by a lower unit cost and lower running costs.

Eventually, on the 19th December 1977, it was announced that McDonnell Douglas had won the contract to develop what would become the KC-10 extender.

KC-10 Extender development

The KC-10 development program was a fairly straightforward project, as it was quite closely based upon the DC-10-30F freighter design. The main changes made were:

• Removal of most Cargo doors and windows.
• Extra fuel tanks below the main deck.
• Addition of both a centerline refueling boom, and a drogue/hose system on the right side of the rear fuselage.
• Addition of a Air Refueling Officer (ARO) station at the rear of the aircraft.
• Flexible accommodation for additional support crew.
• Addition of in-flight refueling capability for the KC-10 itself.
• Addition of military avionics.
• An improved cargo handling system.

The supplementary fuel tankage system for the KC-10 was selected after extensive studies. In addition to the three main DC-10 wing fuel tanks, the KC-10 has three large fuel tanks under the cargo floor, one under the forward lower cargo compartment, one in the center wing area and one under the rear compartment. Combined, the capacity of the six tanks carry more than 356,000 pounds (160,200 kilograms) of fuel - almost twice as much as the KC-135 Stratotanker. The additional tanks are located in under deck vented cavities. Panels are provided to permit direct access to each cell for installation, removal, and system inspection.

Advanced Aerial Refueling Boom

Even before the contract for the KC-10 had been won, McDonnell Douglas had been developing the "Advanced Aerial Refueling Boom", for the Advanced Tanker/Cargo Aircraft System Program Office (ATCA SPO).

The purpose of the AARB development program was to demonstrate that an advanced technology boom system could eliminate some of the limitations of the existing KC-135 boom. By late 1976, development of the AARB had been mainly oriented toward achieving the design requirements. Now the ATCA SPO wanted to examine the costs of supporting the proposed design if it was produced, and in particular to compare performance and costs with the existing KC-135 boom.

Joint development and initial operational test and evaluation was completed in April 1978. During 184 hours of flight testing the new boom made 1,398 couplings with a range of aircraft; the C-5A Galaxy, the F-4 Phantom, the NKC-135 (a modified experimental KC-135), the TF-15 (early F-15), and the A-10 Thunderbolt II. The AFTEC test report, dated June 1978, indicated that the new boom demonstrated an enhanced aerial refueling capability and was substantially easier to maintain than the KC-135 boom.

The Air Refueling Officer station is located at the rear of the aircraft, and is provided with a large rear facing window, through which the refueling aircraft can be observed. Located aft of the rearward lower fuselage fuel tanks, the Air refueling operator sits in an aft-facing crew seat. An additional periscope viewing capability allows for traffic management. Accessible from the upper deck, the station is pressurized and has 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.

Cargo and pasenger accomodation

Cargo carrying capability while closely based upon the freighter version of the DC-10 has been updated and improved, with the addition of powered rollers and a powered winch system, to facilitate the loading of cargo. The large 102 by 140 inch (2.59m x 3.55m) cargo door swings upward on the left side of the forward fuselage for loading and unloading.

The cargo area of the KC-10 exceeds 12,000 cubic feet (346 cubic meters), with a ceiling height of 8.5 feet (2.5m) and a maximum width of 5.7m (18ft 8inches). Up to 27 standard 88 x 108-inch (2.23 x 2.74 m) cargo pallets with a single aisle. or 25 pallets with aisles on both sides.

Part or all of the cargo area can be flexibly utilised for passenger/additional crew accomodation. Maximum crew and passenger/additional crew accomodation is 80 people. An alternative arrangement allows for a crew of five, plus six seats for additional crew and four bunks for crew rest with an environmental curtain between bunks and the cargo net. Other arrangements are possible, to match the mission requirements.

Although the eight doors of the DC-10 upper deck are installed, 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.

KC-10 Extender Rollout

In November 1978, McDonnell Douglas and the USAF signed a contract for the first two KC-10 Extenders, along with support and the balance of the non-recurring engineering costs. In November 1979 a further contract was agreed for the production of a further four aircraft.

Further contracts were agreed - for six more aircraft in Febuary 1981, and four more in January 1982. Eventually, 60 KC-10 Extenders would be supplied to the USAF, of which 59 remain in service. One was lost in a fire on the ground in 1987. The eventual unit cost per plane would be $88.4 million (fiscal 1998 constant dollars).

The official rollout ceromony took place at the McDonnell Douglas plant Long Beach on the 16th April 1980. The Air Force Reserve Band pipers played, and speeches were made by dignatories including Secretary of Air Force Dr. Hans Mark. The KC-10 Extender first took to the air on July 12, 1980 and after further testing, the first re-fueling flight of the KC-10 took place on October 30th 1980, when a C-5 Galaxy was sucessfully re-fueled.

Early aircraft were painted light gray on the aircrafts underside and wings, and white on the upper fuselage, except for the area around the cockpit, which was blue. (See rollout image above).

For a short time a blue painted lower fuselage with a white painted upper fuselage was used for a short time, before going to a gray on green paint scheme. At the time of writing, aircraft are painted a medium gray color. (see right above)

The KC-10 in USAF service

The first KC-10 Extender aircraft was delivered to the USAF in March 1981 and KC-10s were based with the Air Combat Command at Barksdale AFB, La., and at March AFB, CA. Barksdale's 32nd Air Refueling Squadron received the first operational KC-10A Extender aerial tanker in November of 1981. The squadron deployed aircrews and tankers to various locations for air refueling support in Southwest Asia, from August 1990-April 1991. It was redesignated as the 32nd Air Refueling Squadron on 1 September 1991, when it was reassigned to the 2nd Operations Group, and relocated to McGuire AFB, NJ.

The 32nd ARS with its KC-10 Extenders refueled the F-111s that took part in the bombing of Libya and flew KC-10s in Operations Just Cause, Desert Shield/Storm and Southern Watch.In October 1994 the last KC-10 departed for McGuire AFB.

Twenty KC-10s have been modified, adding wing-mounted pods to further enhance refueling capabilities. Ongoing modifications include the addition of communications, navigation and surveillance equipment to meet future civil air traffic control needs, and the incorporation of service bulletins to maintain Federal Aviation Administration certification.

During operations Desert Shield and Desert Storm in 1991, the KC-10 fleet provided in-flight refueling to aircraft from the U.S. armed forces as well as those of other coalition forces. In the early stages of Operation Desert Shield, in-flight 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 buildup. The KC-10 and the KC-135 conducted about 51,700 separate refueling operations and delivered 125 million gallons (475 million liters) of fuel without missing a single scheduled rendezvous.

In March 1999, a NATO air campaign, dubbed Operation Allied Force, was launched against the government of Yugoslavia. The mobility portion of the operation began in February and was heavily tanker dependent. By early May 1999, some 150 KC-10s and KC-135s deployed to Europe where they refueled bombers, fighters and support aircraft engaged in the conflict. The KC-10 flew 409 missions throughout the entire Allied Force campaign and continued support operations in Kosovo.

Since Sept. 11, 2001, KC-10s have played a prominent role in the on-going Global War on Terrorism. The KC-10 has flown more than 350 missions guarding U.S. skies as a part of Operation Noble Eagle. During operations Enduring Freedom and Iraqi Freedom, KC-10s have flown more than 1,390 missions delivering critical air refueling support to numerous joint and coalition receiver aircraft.

Last KC-10 Extender delivery

The final KC-10 Extender was handed over to the USAF on April 4th 1990. The ceromony at the Douglas Aircraft Co. plant at Long Beach was attended by the Commander in chief, Strategic Air Command GEN John T. Chain Jr.

This final KC-10 aircraft, known as "The Spirit of Kitty Hawk," was assigned to the 68th Aerial Refueling Wing at Seymour Johnson Air Force Base, North Carolina. It recieved special artwork on the nose of the aircraft (see picture above).

Robert Kent