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Building a Bridge...


The United States Air Force/McDonnell Douglas KC-10A advanced tanker/cargo aircraft is a version of the intercontinental-range DC-10 Series 30CF (convertible freighter), modified to provide increased mobility for U.S. forces in contingency operations by: refueling fighters and simultaneously carrying the fighters' support equipment and support personnel on overseas deployments: refueling strategic airlifters (such as the USAF C-5 and C-l4l strategic transports) during overseas deployments and resupply missions, building a bridge reaching anywhere in the world.

In most instances, the KC-10A performs these missions without dependence on overseas bases and without depleting critical fuel supplies in the theater of operations. Equipped with its own refueling receptacle, the KC-10A can support deployment of fighters, fighter support aircraft and airlifters from U.S. bases to any area in the world, with considerable savings in both cost and fuel compared to pre-KC-l0A capabilities.

The aerial refueling capability of the KC-10A nearly doubles the nonstop range of a fully-loaded C-5 Galaxy. In addition, its cargo capability enables the U.S. to deploy some fighter squadrons and their unit support people and equipment with a single airplane type, instead of requiring both tanker and cargo aircraft. When the KC-10 deploys, she is usually carrying her own maintenance and support personnel, additional flight crews, and cargo.

The Air Force is calling their advanced tanker/cargo aircraft the "Extender", because of its ability to carry out aerial refueling and cargo mission without forward basing, thus extending the mobility of U.S. forces.

The KC-10A's primary mission is aerial refueling, but it can also combine the tasks of tanker and cargo aircraft by refueling fighters while carrying the fighters' support people and equipment during overseas deployments. The KC-10A can transport up to 75 people and about 170,000 pounds (76,560 kilograms) of cargo a distance of about 4,400 miles (7,040 kilometers). Without cargo, the KC-10A's unrefueled range is more than 11,500 miles.

CHARACTERISTICS

Fuel offload vs. range comparision.The KC-10A tanker can deliver 200,000 pounds (90,719 kg) of fuel to a receiver 2200 statute miles (3539.8 km) from the home base and return, or it can carry a maximum cargo payload of 169,409 pounds (76,843 kg) a distance of 4370 statute miles (7031 km). Unrefueled ferry range of the KC-l0A is 11,500 statute miles (18,503 km).

The KC-10A is powered by three General Electric CF6-50C2 high bypass-ratio turbofan engines, each generating 52,500 pounds (23,814 kg) of takeoff thrust. Engine thrust has actually been reduced to 52,500lbs by the Air Force to reduce wear and extend engine life. Versions of the CF6 engine family are installed on most of the DC-l0s in airline service and have compiled an impressive reliability record.

Like the DC-10-30CF, the tanker/transport is 181 feet 7 inches (55.35 m) in length and has a wingspan of 165 feet 4 inches (50.42 m) and a tail height of 58 feet 1 inch (17.7 m). Gross takeoff weight of the KC-10A is 590,000 pounds (267,619 kg), up from 555,000 pounds (251,701 kg) for the standard DC-10-30CF model.

Design fuel capacity is 356,000 pounds (162,272 kg), including a maximum of 147,000 pounds (67,272,kg) in three wing tanks and a maximum of 209,000 pounds (95,000 kg) stored in three body tanks below the main deck.

The KC-10A takes full advantage of the inherent capability of the commercial DC-10, retaining some 88 percent commonality with the commercial aircraft. KC-10A modifications to the commercial DC-10-30CF include:

The KC-10A supplementary fuel tank system, selected after extensive studies, includes three tanks divided into seven unpressurized integral-body fuel cells, four aft of the wing and three forward, all located in underdeck vented cavities. A crashworthy design makes use of keel beams and strategically placed energy absorption material to protect the tanks. Under-fuselage panels permit direct access to each cell for installation, removal, system inspection and maintenance and structural inspection.

The KC-10A's boom operator controls refueling operations through a digital fly-by-wire system. Sitting in the rear of the aircraft, the operator can see the receiver aircraft through a wide sighting window. During boom refueling operations, fuel is transferred to the receiver at a maximum rate of 1,100 gallons (4,180 liters) per minute; the hose and drogue refueling maximum rate is 470 gallons (1,786 liters) per minute. The KC-10A can be air-refueled by a KC-135 or another KC-10A to increase its delivery range.

The advanced aerial refueling boom designed by McDonnell Douglas offers significant advantages in operational safety, efficiency and fuel-flow rates. It features larger disconnect and control envelopes, independent disconnect capability, an active control system with digital fly-by-wire controls, automatic load alleviation, position rate sensing to assure disconnect within control limits, precision hand controllers with low force requirements and operator-selectable disconnect limits and trim settings. An additional feature in the KC-10A refueling system is the installation of the hose and drogue and the capability to change from drogue to boom refueling and back, while in flight. (The KC-135 is incapable of this feat.)

The aerial refueling operator's station in the KC-10A, located aft of the rearward lower fuselage fuel tanks, features improvements in comfort, viewing capability and environment. Instead of assuming the prone position required in Strato Tanker, the refueling operator sits in an aft-facing crew seat. Station equipment includes handy refueling controls, a wide viewing window facing and additional periscopic viewing arrangements for traffic management. Accessible from the upper deck, the station is pressurized and has independent thermal control, a quiet environment and 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. The instructor and operator seats have interconnected controls to allow for hands on training with instructor assistance, if needed.

For its cargo-carrying assignments, the KC-10A has a total usable cargo space exceeding 12,000 cubic feet (346 cu m) in its spacious cabin. The cabin has a maximum width of almost 19 feet (5.7 m), ceiling height of 8.5 feet (2.5 m) and a floor area of 2200 square feet (304.25 sq m). In all-cargo configuration, the KC-10A acccommodates 27 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 omni pad area to permit loading and rotation 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.

Several configurations exist for personnel and crew accommodations, but most often only two are used. The 'Baker' or B config and the 'Delta' or D config. A Baker config consists of 16 seats with two, double crew bunks between the cargo net and environmental curtain. In the Delta config, the bunks, environmental curtain and cargo net can be shifted rearward, making room for 75 people, along with the necessary utility, lavatory and stowage modules, raising the personnel capacity to a total of 80 crew and support people. Although all eight of the DC-10 main deck passenger doors are installed as standard, the overwing and right aft doors are deactivated. Normal entry and exit is through the forward and mid cabin doors on each side. The aft right-hand door is available as a ground emergency exit (by rope) for people in the aerial refueling operator's station. Slide rafts are installed in the forward cabin doors. When in an extended passenger configuration, slides are installed in the mid cabin doors as well.

BACKGROUND

The Air Force announced the selection of McDonnell Douglas on December 19, 1977. The selection was based on integrated assessment of capability, price, life-cycle costs and technical features of the McDonnell Douglas DC-10. The initial contract of $28 million funded production engineering, tooling and other non-recurring activities, with quantities of aircraft to be determined by available funding in future years.

An additional logistics support sum of $429,000 was awarded to McDonnell Douglas as part of a basic contract for logistics planning in preparation for subsequent total support of the KC-l0A force, with annual options for spare parts and support equipment, intermediate and depot-level maintenance, systems management and technical support. McDonnell Douglas provides maintenance support under Federal Aviation Administration ground rules. USAF personnel are responsible for accomplishing flight line maintenance tasks, as well as maintenance management functions.

The commercial DC-10 entered airline service in 1971, the same year McDonnell Douglas began engineering work on the USAF version that led to the KC-10A contract. The commercial DC-10, chosen by 47 airlines, carries more passengers to more cities worldwide than any other wide-cabin jetliner.

With the KC-10A program, the USAF is taking advantage of the nearly $2 billion invested by McDonnell Douglas and its subcontractors in development of the DC-10 and of the huge investments by the airlines in establishing a worldwide support system, thus reducing both the acquisition and operation costs of the KC-10A as compared to an all-new military development. The U.S. Air Force and McDonnell Douglas signed contracts totaling $148 million in November 1978 for production of the first two KC-l0s, for the balance of the non-recurring engineering costs and for the initial spare parts and other support for the KC-10 program. A second contract, calling for production of four additional KC-l0s at a cost of $173 million, was signed November, 1979. At the same time, a $10.1 million logistics support contract option to provide spares and support equipment was signed.

A third contract, calling for production of six more KC-l0s at a cost of $284 million, was signed in February of 1981. A $14 million logistics support contract for those aircraft also was signed. A fourth contract, calling for production of four more KC-l0s at a cost of $196 million was signed in January, 1982, along with a $21 million contract for logistic support.

The first flight of the KC-10A took place on July 12, 1980, with the first aerial refueling occurring during testing on October 30, 1980. The receiver aircraft was a C-5 Galaxy. The KC-10 was also the first tanker to ever refuel a Boeing 747; the jumbo jet - on its maden flight - was Air Force One. The first KC-10A was delivered to the Air Force on March 17, 1981. The KC-10A force of 60 aircraft was based with the Strategic Air Command (SAC) at Barksdale AFB, La. and March AFB, CA, and with Air Combat Command (ACC) at Seymor Johnson AFB, NC, beginning in the fall of 1982. In 1994, the remaining 59 aircraft were reassigned; 27 KC-10's were assigned to Air Mobility Command (AMC) at Travis AFB, CA, and 32 were assigned with AMC at McGuire AFB, NJ.

During Operations Desert Shield and Desert Storm, the KC-10 fleet provided in-flight refueling to aircraft from all branches of the U.S. armed forces as well as those of other coalition forces. In-flight refueling extended the range and capability of all U.S. and other coalition fighter aircraft. Air operations continued without costly and time-consuming ground refueling. In-flight refueling was key to the rapid airlift of material and forces. In addition to refueling airlift aircraft, the KC-10A, along with the smaller KC-135, moved thousands of tons of cargo and thousands of troops in support of the massive Persian Gulf build-up. The KC-10A 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.

The KC-10A acquisition program was directed by the Air Force Systems Command's Aeronautical Systems Division (ASD) at Wright-Patterson Air Force Base, Ohio. Prime contractor for the design, development and production of the KC-10A is the Long Beach, California-based Douglas Aircraft Company division of McDonnell Douglas Corporation, St. Louis, Missouri.

Specifications

3-view diagram
Primary Function:Aerial refueling/transport.
Contractor:McDonnel Douglas Aircraft Co. (Now Boeing)
Power Plant:Three General Electric CF-6-50C2 High Bypass Ration Turbofans
Thrust:52,500 pounds (23,625 kilograms), each engine
Length:181 feet, 7 inches (54.4 meters)
Height:58 feet, 1 inch (17.4 meters)
Wingspan:165 feet, 4 1/2 inches (50 meters)
Speed:619 mph (Mach 0.825)
Ceiling:42,000 feet (12,727 meters)
Maximum Takeoff Weight:590,000 pounds (265,500 kilograms)
Range:4,400 miles (3,800 nautical miles) with cargo; 11,500 miles (10,000 nautical miles) without cargo
Unit Cost:$86.3 million (1992 dollars)
Crew:Four (aircraft commander, pilot, flight engineer and boom operator)
Date Deployed:March 1981
Inventory:Active force, 59; ANG, 0; Reserve, 0

Editors note: Although no aircraft are assigned to reserve components full time, they are in fact maintained and flown by reserve forces to augment, and at times, replace active duty ground and flight personnel. Many thanks goes out to our reserve brothers and sisters!


Thanks to John Pike for his research in this article.