KC-10 Extender

The KC-10 Extender is an air-to-air tanker aircraft in service with the United States Air Force derived from the civilian DC-10-30 airliner. Though there are 59 Extenders currently in service, they are greatly outnumbered by the older KC-135 Stratotanker, though the KC-10 has a significantly larger fuel capacity. Conversion to the KC-10 involved only minor modifications to the DC-10, the largest of which was the addition of a boom control station in the rear of the fuselage and extra fuel tanks under the main deck.

The KC-10 is currently the world's longest-ranged production aircraft, and will continue to hold that record past the introduction of the Boeing 777-200LR, though future 777 variants may range further. The KC-10 is due to be retired when the Northrop Grumman KC-45 comes into service.

Description
Beginning with the Vietnam War doubts began to be raised about the ability of the 700+ strong KC-135 fleet to meet the needs of the United States’ global commitments. The air-refuelling fleet was deployed to South-East Asia in support of tactical aircraft and strategic bombers, while maintaining the US-based support of the nuclear bomber fleet. As a result, studies began into the feasibility of acquiring an air-to-air tanker with a greater capability than the KC-135 fleet, but did not progress well due to lack of funding.

The 1973 Yom Kippur War and the US Operation Nickel Grass demonstrated the necessity of adequate air-refuelling capabilities. Denied landing rights in Europe, USAF C-5 Galaxies were forced to carry a fraction of their maximum payload on direct flights from the continental United States to Israel. As a result C-5 Galaxy crews were soon trained in aerial-refuelling and the Department of Defense concluded that a more advanced tanker was needed.

In 1975, under the "Advance Tanker Cargo Aircraft" program, four aircraft were evaluated: the C-5 itself, the Boeing 747, the McDonnell Douglas DC-10, and the Lockheed L-1011. The U.S Air Force selected McDonnell Douglas's DC-10 over Boeing's 747 in December 1977.

The design for the KC-10 involved only modifications from the DC-10-30CF design. The major changes were the addition of a boom control station in the rear of the fuselage and extra fuel tanks below the main deck. The KC-10 has both a centerline refuelling boom and a drogue/hose system on the right side of the rear fuselage. Other changes from the DC-10-30CF include the removal of most cargo doors and windows. The KC-10 first flew on 12 July 1980. Early aircraft featured a paint scheme with light gray on the airplane's belly and white on the upper portion. A gray-green camouflage scheme was used on later tankers. Aircraft have since been switched to a medium gray color. The KC-10 boom operator is located in the rear of the airplane with wide window for monitoring refuelling. The operator controls refueling operations through a digital, fly-by wire system.

A total of 20 KC-10s were later modified to add wing-mounted pods for added refuelling locations. In addition to the USAF refuelling boom, the KC-10's hose and drogue system allows refuelling of U.S. Navy, Marine Corps, and most NATO allied aircraft. This gives the KC-10 the ability to refuel USAF, USN, USMC and other NATO aircraft, all in the same mission.