McDonnell Douglas KC-10

The McDonnell Douglas KC-10 Extender is the military version of the three-engined DC-10 airliner for the United States Air Force (USAF). The KC-10 incorporates military-specific equipment for its primary roles of transport and aerial refueling. It was developed to supplement the KC-135 Stratotanker following experiences in Southeast Asia and the Middle East. The KC-10 was the second McDonnell Douglas transport aircraft to be selected by the Air Force following the C-9. A total of 60 KC-10s were produced for the USAF. Two similar tankers were sold to the Royal Netherlands Air Force under the designation KDC-10.

The KC-10 plays a key role in the mobilization of US military assets, taking part in overseas operations far from home. These aircraft participated in the 1986 bombing of Libya and 1999 NATO bombing of Yugoslavia, and more recently, Operations Enduring Freedom, Iraqi Freedom and Noble Eagle. However, the KC-10 was most notable for its participation in the Gulf War, where it was central to the airlift and aerial refueling effort. The aircraft is expected to serve until 2043.

Requirement and design effort

The KC-10 Extender was born out of the need to augment the Air Force's large fleet of more than 700 Boeing KC-135 Stratotankers. During the Vietnam War, doubts began to be raised regarding the KC-135s' ability to meet the needs of the US' global commitments. The aerial refueling fleet was deployed to Southeast Asia to support tactical aircraft and strategic bombers, while maintaining the US-based support of the nuclear-bomber fleet. Consequently, the Air Force sought an aerial tanker with greater capabilities than the KC-135. In 1972 two DC-10s were flown in trials at Edwards Air Force Base, simulating air refuelings to check for possible wake issues. Boeing performed similar tests with a 747.

During the 1973 Yom Kippur War, the Air Force commenced Operation Nickel Grass to supply Israel with weapons and supplies. The operation demonstrated the necessity for adequate air-refueling capabilities; denied landing rights in Europe, C-5 Galaxies were forced to carry a fraction of their maximum payload on direct flights from the continental United States to Israel. To address this shortfall in mobility, in 1975, under the Advanced 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 only serious contenders were Boeing and McDonnell Douglas. On 19 December 1977, McDonnell Douglas's DC-10 was chosen. The primary reason of this choice was the KC-10's ability to operate from shorter runways. Initially, a batch of 12 aircraft was ordered, but this was later increased to 60.

The KC-10 Extender first flew on 12 July 1980, but it was not until October the same year that the first aerial refuel sortie was performed. The design for the KC-10 involved modifications from the DC-10-30CF design. Unnecessary airline features were replaced by an improved cargo-handling system and military avionics. Meanwhile, the KC-10 retains 88% commonality with its commercial counterparts, giving it greater access to the worldwide commercial support system. Other changes from the DC-10-30CF include the removal of most cargo doors and windows. Early aircraft featured a distinctive light gray, white and blue paint scheme, but a gray-green camouflage scheme was used on later tankers. The paint scheme was switched to a medium gray color by the late 1990s.

However, the major changes were the addition of the McDonnell Douglas Advanced Aerial Refueling Boom (AARB) and extra fuel tanks below the main deck. The extra tanks increase the KC-10's fuel capacity to 356,000 lb (161,478 kg), nearly doubling the KC-135's capacity. The KC-10 has both a centerline refueling boom and a drogue-and-hose system on the starboard side of the rear fuselage. The KC-10 boom operator is located in the rear of the aircraft with wide window for monitoring refueling. The operator controls refueling operations through a digital fly-by wire system. Unlike the KC-135, the KC-10's hose-and-drogue system allows refueling of Navy, Marine Corps, and most allied aircraft, all in one mission. The final twenty KC-10s produced included wing-mounted pods for added refueling locations. In addition to its tanking role, the KC-10 can carry a complement 75 personnel with 146,000 lb (66,225 kg) of cargo, or 170,000 lb (77,110 kg) in an all-cargo configuration. The KC-10 has a side cargo door for loading and unloading cargo. Handling equipment is required to raise and lower loads to the cargo opening.

Further developments

A need for new transport aircraft for the Royal Netherlands Air Force was first identified in 1984. In 1991 four categories of transport requirements were established. Category A required a large cargo aircraft with a range of at least 4500 km and the capability to refuel F-16s. In 1992, two DC-10-30CFs were acquired from Martinair in a buy/leaseback contract. When one of the bought aircraft was lost in the Martinair Flight 495 crash, a third aircraft was bought from Martinair.

The conversion was handled via the United States foreign military sales program, which in turn contracted McDonnell Douglas. Costs for the conversion were initially estimated at $89.5 million (FY 1994). The aircraft was to be equipped with both a boom and a probe and drogue system. However, because McDonnell Douglas did not have any experience with the requested Remote Aerial Refueling Operator (RARO) system, and because the third aircraft differed from the original two, the program could not be completed at budget. By omitting the probe and drogue system and a fixed partition wall between the cargo and passenger, the cost could be limited at $96 million. To make up for the cost increase McDonnell Douglas hired Dutch companies to do part of the work. The actual converting of the aircraft for instance was done by KLM. Conversion of the aircraft was done from October 1994 to September 1995 for the first aircraft and from February to December 1995 for the second. This was much longer than planned, mostly because McDonnell Douglas did not deliver the parts in time. This would have again increased the cost, but in the contract for the AH-64 Apaches which the Royal Netherlands Air Force also bought from McDonnell Douglas, the price was agreed to be kept at $96 million.

In an attempt to modernize the platform, the USAF has awarded Boeing a US$216 million contract to upgrade its fleet of 59 aircraft with new communication, navigation, surveillance and air traffic management (CNS/ATM) system. Boeing claims that this will allow the aircraft to fly in civil airspace after 2015 as new ICAO and FAA standards take effect.

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