Aircraft Report: KC-10A Extender

On July 12, 1980, the McDonnell Douglas KC-10A Extender – a militarised and extensively-modified variant of the trijet DC-10 commercial airliner family – took to the skies for the first time.  

Configured as a tanker/transport aircraft, the KC-10A was sought to supplement the US Air Force’s Boeing KC-135 Stratotanker fleet and designed to provide an increased global mobility capability for the US military. Although it is primarily a tanker aircraft, the Extender can combine its air-to-air refuelling tasks with a cargo transportation mission. For instance, when supporting the overseas deployment of a fighter unit, the KC-10A can simultaneously provide in-flight refuelling for the combat aircraft and carry the deployment’s support personnel and associated equipment in its interior.  

The platform can also be configured to perform litter transportation and aeromedical evacuation missions, using patient support pallets to execute the latter. The USAF states that the KC-10A can carry a maximum of 75 people or can be configured to transport nearly 170,000lb (77,111kg) of cargo to ranges of up to 4,400 miles (7,081km) unrefuelled – which is almost the distance from Washington DC in the US to Rome, Italy. 

Although it was extensively modified, the KC-10A has retained 88% of its systems commonality with the DC-10. The most notable addition to the platform is its Advanced Aerial Refueling Boom (AARB) and its hose and drogue system, which were essential for it fulfilling its tanker role. It also features military avionics, a seated aerial refuelling operator station, satellite communications (SATCOM) and an aerial refuelling receptacle so that the aircraft itself can be refuelled in flight. 

As with the DC-10, the KC-10A has three main fuel tanks in its wings. However, in addition to this, it has another three large fuel tanks under the floor of its cargo compartment. According to the USAF, the combined total of fuel that can be carried by the Extender is more than 356,000lb (161,479kg), which is almost twice the capacity as its in-service counterpart, the KC-135. 

Fuel can be transferred to the receiving aircraft at a maximum rate of 1,100 gal (4,542 lit) per minute during boom refuelling operations. When using the hose and drogue system, the KC-10As maximum refuelling rate is 470 gal (1,779 lit) per minute.   

The KC-10A requires a crew of four to operate: a pilot, co-pilot, flight engineer and boom operator. However, certain missions require additional personnel. When configured in an aeromedical role, the aircraft accommodates five more crew members: two flight nurses and three medical technicians. 

Its trijet configuration is rather unique for a tanker aircraft. Three GE Aviation F103 (CF6-50C2) turbofan engines are used to power the KC-10A, with each providing 52,000lbf (231 kN) worth of thrust. According to the USAF, the platform boasts a maximum speed of 619mph (996km/h), a service ceiling of 42,000ft (12,802m) and a ferry range of 11,500 miles (18,507km). 

In 2010, Boeing was awarded a contract to modernise the USAF’s KC-10A fleet. This process provided new communication, navigation and surveillance and air traffic management (CNS/ATM) systems. These upgrades were needed to meet new international standards set by the Federal Aviation Administration (FAA) and International Civil Aviation Organization (ICAO). In 2011, Rockwell Collins was awarded a US$160m contract to provide new systems and avionics for the KC-10A’s cockpit. 

The first KC-10A was handed over to the USAF at Barksdale Air Force Base (AFB) in March 1981. The type provided tanker support during Operation El Dorado Canyon in 1986. This mission saw USAF and US Navy combat aircraft conduct airstrikes against Libya. Due to basing and overflight refusals by European nations, the US had to utilise tanker support – provided by KC-10As and KC-135s – to conduct the operation. 

The Extender, along with its KC-135 counterpart, played a key role in the build up to Operation Desert Shield and Operation Desert Storm in 1991. The aircraft was vital in the rapid airlift of troops, equipment and aircraft to the Persian Gulf. In total, KC-10As and KC-135s conducted approximately 51,700 separate refuelling operations in support of these operations. 

In May 1999, a number of KC-10As deployed to Europe to support NATO’s air campaign during Operation Allied Force. According to the USAF, the platform flew 409 missions in support of the campaign. Since the terror attacks on September 11, 2001, USAF KC-10As have been extensively used in safeguarding US airspace, flying more than 350 sorties in support of Operation Noble Eagle. The type has also flown over 1,390 missions in support of Operations Enduring Freedom and Iraqi Freedom in the Middle East since 2001. 

In total, 60 aircraft were delivered to the air arm. AirForces Intelligence data states that, as of August 12, 2020, there were 58 examples in operational service. However, the sun is setting on the KC-10As operational life, as the USAF seeks to retire the type and replace it with Boeing’s KC-46A Pegasus. 

Due to the Pegasus’ plagued development and delays, the Fiscal Year 2021 (FY2021) National Defense Authorization Act (NDAA) has limited the air force’s ability to retire the KC-10A in bulk. The act requires the USAF to have 50 operational KC-10s in FY2021, 38 in FY2022 and 26 in FY2023. It also prohibits the service from retiring any KC-135s until 2023. In July 2020, the first KC-10A – serial 86-0036 (c/n 48249, line number 424) was placed into storage with the 309th Aerospace Maintenance and Regeneration Group (AMARG) at Davis-Monthan AFB famous ‘Boneyard’ in Tucson, Arizona. 

The Royal Netherlands Air Force (RNLAF) has operated two KDC-10 tanker/transports since 1995. A third DC-10-based tanker – a DC-10-30CF – entered service in January 2012 but was scrapped due to budget constraints. The Dutch variants will soon be replaced by the Airbus A330 Multi-Role Tanker/Transport (MRTT), as the nation has joined NATO’s Multinational MRTT Fleet (MFF) with a number of other European-based NATO member states. The first KDC-10 – serial T-264 (c/n 46985) – was withdrawn from service in November 2019 and the second – serial T-265 (c/n 46956) ‘Jan Scheffer’ – is scheduled to leave service in 2021. Both aircraft will see further use as tanker aircraft, as Omega Aerial Refueling Services has acquired both examples for use in supporting military air arms. The civil contractor already operates DC-10-40s, which have been configured for tanker operations.