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42 Years Of Flight: The McDonnell Douglas KC-10 Extender’s History

42 years ago this week, the McDonnell Douglas KC-10 Extender took its first flight. The United States Air Force (USAF) operates several different types of aircraft ranging from fighter jets like the F-16 Fighting Falcon to large transport planes like the C-5 Galaxy. While each aircraft type has its own distinct role, there is one type of asset that comes in handy during all operations: the aerial refueler. The McDonnell Douglas KC-10 Extender is one such aircraft in service with the USAF for more than four decades now. Let’s take a closer look at how this aerial refueler came to be.

Early development

The KC-10 Extender is based on McDonnell Douglas’ DC-10 airliner, which first entered commercial service in 1971. It was the first widebody aircraft from McDonnell Douglas at the time and would go on to serve close to 50 airlines carrying passengers all over the globe.

After 1971, McDonnell Douglas began working on a military version of the jet for use by the USAF. The Air Force formally selected the MD-10 on December 19th, 1977 as part of its pursuit for an aircraft to supplement the KC-135 Stratotanker in aerial refueling operations. The US military felt the need for a new aerial refueling aircraft towards the end of the Vietnam W4r, as the KC-135 was falling short on some parameters.

The KC-10’s first flight was on July 12th, 1980 and the first aerial refueling sortie was performed later the same year on October 30th on a C-5 transport aircraft. Deliveries to the USAF followed quickly after with the first airframe handed over on March 17th, 1981.

Capabilities

Despite sharing around 88% components with the commercial version, the KC-10 Extender is a highly capable refueler. Major modifications to the military version include upgraded military avionics, satellite communications, an air-to-air refueling mechanism, and the addition of six extra fuel tanks. As a result, the KC-10 can carry more than 356,000 lbs. (160,200 kg) of fuel, which is nearly twice as much as the KC-135.

The KC-10 can refuel other aircraft either using a refueling boom or a hose & drogue system. It uses a fly-by-wire system for refueling operations under the command of a boom operator. During boom operations, fuel transfer rates can go up to 1,100 gallons (4,180 liters) per minute. On the other hand, fuel is transferred significantly slower in hose and drogue refueling operations at just 470 gallons (1,786 liters) each minute.

In addition to aerial refueling, the Extender can also carry passengers and cargo. Maximum passenger capacity is capped at 75 and there is enough space for 17 to 27 cargo palettes depending on the number of passengers onboard. A fully-loaded KC-10 Extender can fly for 4,400 miles without mid-air refueling.

The United States Air Force currently owns 59 units of the mighty KC-10 Extender, with 58 listed as active on ch-aviation.com at the time of writing. KC-10 deliveries to the USAF were completed by 1988 making the last delivered airframe more than three decades old. The Air Force has begun gradually retiring some of these airframes from active service to make way for the newer KC-46 Pegasus aerial refuelers.