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US Air Force Begins Retirement Of KC-10 Extender Tanker

The July 13th 2020 farewell event hosted at New Jersey-based McGuire-Dix-Lakehurst Joint base saw a single KC-10 Extender attached to the the 305th Air Mobility Wing based there receive full water cannons honors before departing for the 309th Aerospace Maintenance and Regeneration Group at Davis-Monthan Air Force Base in Arizona also referred to as the Boneyard.

The particular aircraft retired that day is ending a thirty-year career and will be gradually followed by 58 other KC-10s. A June’s decision by the Senate Armed Forces Committee had put a cap on the number of highly valuable aircraft that may be allowed to leave the service to six aircraft in 2021, twelve in 2022 and thirteen in 2023. This interim measure will allow the force to maintains capabilities while the new KC-46 Pegasus fleet delivery schedule builds-up. However for the KC-10 Extender fleet and the community that has been involved in its operation since first delivery to the Air Force on March 17th, 1981, an extraordinary era is ending. In a airforcetimes.com article, Stuart Lockhart, historian for the 305th, referring to the particular aircraft leaving that day indicates that:

« This plane flew more than 33,000 flight hours, supporting missions across six continents and refueling more than 125,000 aircraft from 25 different countries, … Nearly 11,000 aircrew members have flown it, and another 12,000 took care of it. »

A Commercial Aircraft Background

The KC-10A Extender aircraft was proposed as a supplement to the Boeing 707-derived KC-135 which the US Air Force has adopted in very large numbers from the early 1960s (more than 400 aircraft still flying today). A brief competition with the Boeing 747 saw the modified DC-10-30CF Freighter variant selected in December of 1977 as it could operate from shorter runways than the 747. The order for 60 aircraft provided the force with a tanker that would relies on the underbelly cargo hold to carry additional fuel, while the aircraft main deck remained available to load freight. The dual mission concept added significant global logistics value on top of strategic refueling capability. The aircraft was later to prove most effective at conducting “dual-role missions”.

With its distinctive gray paint scheme, a handful of windows visible on the fuselage, and no underbelly cargo door, the aircraft still retained its DC-10-30CF (Convertible Freighter) appearance (the three main landing gear set instead of two on the DC-10-10) but with a very convincing “mission aircraft” stance. It had a special Mc Donnell Douglas-designed refueling boom sticking slightly below the tail cone and was fitted with two refueling drogues and hoses for NATO, US Navy and Marines aircraft refueling compatibility.

Below the main deck, where commercial DC-10s would normally house luggages, the KC-10 had installed seven fuel cells able to store a maximum of 117,500 pounds (53,297 kg). This added to a maximum of 238,565 pounds (108,211 kg) in the standad wing tankage allowing the aircraft to remains within its designed fuel capacity of 356,065 pounds (161,508 kg), almost doubling that of the USAF Boeing KC-135 Stratotanker.

Other than that, the KC-10 Extender had almost everything else in common with its DC-10 commercial variant. Namely the 181 feet 7 inches (55.35 m) in fuselage length and 165 feet 4 inches (50.42 m) of wingspan along with the 58 feet 1 inch (17.7 m) tail height. Powered by three high bypass General Electric GE CF6-50C2 turbofan, generating 52,500 pounds (23,814 kg) of takeoff thrust each, one of whom mounted atop the fuselage at the base of the vertical tail, the aircraft developped a 590,000 pounds (267,619 kg) gross weight, up from the 555,000 pounds (251,701 kg) observed on the standard intercontinental commercial model. Yet the design was able to retain a 88% commonality with its commercial variant. Its performance included a 4,400 mi (7,100 km, 3,800 nmi) range with a maximum passenger capacity and 3,800 nmi (7,038 km; 4,373 mi) with maximum cargo capacity.

This also translated into 170,000 lb (77,110 kg) of freight in a pure cargo mission. In dual role mission, the aircraft could accommodate 75 personnel together with 146,000 lb (66,225 kg) of cargo. Its forward large cargo door allowed on board loaders to efficiently operate a self contained loading platform.

As the USAF Airhead logistics study explains, just relying on its main deck space the KC-10A Extender was an extremely potent cargo by design:

In all-cargo configuration, the KC-10A acccommodates 25 standard 88 x 108-inch (223.5 by 274.3 cm) cargo pallets.

To facilitate the handling of cargo, the KC-10A is equipped with a versatile system to accommodate a broad spectrum of loads. The system, adapted in part from the commercial DC-10, has been enhanced with the addition of powered rollers, powered winch provisions for assistance in fore and aft movement of cargo, an extended ball mat area to permit loading of larger items, and cargo pallet couplers that allow palletizing of cargo items too large for a single pallet. The features, plus the large 102 by 140-inch (259 by 355 cm) cargo door that swings upward on the left side of the forward fuselage for loading and unloading, give the KC-10A the capability to transport a significant portion of the tactical support equipment of fighter squadrons.

By the year 2011, the USAF bent on allowing its 1980s era aircraft to operate safely in an incresingly modernized airspace contracted Rockwell Collins with integrating new Communication (includes HF, VHF, mode-S TCAS, and TACAN/DME/ADF), Navigation, Surveillance/Air Traffic Management (CNS/ATM), flight management system and data link aboard the aircraft while installing a modern multi function “glass” display cockpit (integrating weather radar and a digital moving map with a multifunction display) built on the proven Flight2 integrated avionics system. The upgrades of the entire KC-10 fleet completed in 2017.

With such robust capabilities, the aircraft achieved stellar performance during the 1991/1992 Desrt Shield and Desert Storm operations. According to the USAF-produced Gulf War Air Power Survey, referring to Desert Shield’:

KC-10s flying dual-role missions moved more than 4,800 tons of cargo and 14,200 passengers while providing air refueling support for deploying Air Force and Marine Corps fighter units.

The parts commonality with a highly popular commercial aircraft model also proved a logistics and support advantage:

« when the KC-10 was procured, SAC chose not to establish a KC-10 intermediate level maintenance capability because of the aircraft’s high reliability and the ready availability of Douglas Aircraft commercial support. So it should come at no surprise that KC-10 support was unproblematic.

As in the end tha aircraft proved:

very useful at moving fighter en route and maintenance, Oklahoma City Air Logistics Center dispatched a Douglas logistics survey team to Europe to establish contingency distribution centers to expedite movement of spare parts. The fifty-seven KC-10 aircraft deployed were for all intent and purposes problem-free during Desert Shield and Desert Storm.

In all, the aircraft operational record in that conflict testifies on the overall very high readiness, reliability and endurance of the aircraft with 57 aircraft mobilized and 46 aircraft actually operated out of a fleet of 59 aircraft translating into 81% of the type committed.

 

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