With an estimated cost of $35 billion, according to figures from the United States Department of Defence, the United States Air Force (USAF) KC-X contract will replace scores of Boeing KC-135R tankers with 179 Boeing KC-46A Pegasus refueling aircraft. It is the world’s largest tanker programme.

Adapting a jet commercial aircraft as a tanker – in the case of the KC-76A the baseline aircraft is a Boeing 767-2C airliner – dates back to the iconic Boeing 707, although when Boeing signed up its first customer for the type in March 1955, it was the USAF that ordered an initial fleet of 29 KC-135A Stratotanker aircraft. A total of 732 were built, the last leaving the Renton, Seattle production line in 1966. Since then the type has been subject to numerous upgrades, including new more powerful and fuel-efficient engines in the form of the General Electric/SNECMA F108-CF-100 powerplant. Another military derivative of a commercial aircraft, the three-engine civilian McDonnell Douglas/Boeing DC-10-30CF, known as the KC-10A Extender, first entered USAF service in March 1981. While its primary mission was aerial refuelling, incorporating an in-flight refuelling boom with hose and drogue coupling, the KC-10A combined the tasks of tanker and cargo aircraft by refuelling fighters while carrying the fighters’ support personnel and equipment during overseas deployments. The aircraft is capable of transporting up to 75 people and some 170000 pounds (76560 kilograms) of cargo a distance of 3825 nautical miles (7040 kilometres). In its four wing tanks and two underfloor fuselage tanks, the KC-10A carries almost twice as much fuel as the KC-135 Stratotanker which has a maximum transfer fuel load of 200000 lbs (37,648 kgs).

The United Kingdom also resorted to modifying commercial aircraft into military tankers for the Royal Air Force (RAF) but they were ex-airline airframes rather than new-build aircraft. The first was the last all-British long-range commercial airliner, the British Aircraft Corporation/Vickers VC-10. A total of 14 C.Mk.1 passenger variants entered RAF service in 1966, 13 of which were converted to a dual role as transports and tankers in 1992. These aircraft joined a growing fleet of 23 ex-civil VC-10 and Super VC-10 aircraft that were converted to their tanker role between 1981 and 1995, although only four of the latter had the dual tanker-transport capability designated K.Mk.4 in RAF service. The RAF VC10 fleet served with distinction until its withdrawal from service in September 2013.
Following the Falkland Islands campaign in 1982, the RAF decided to augment its tanker-transport fleet, selecting another long-range passenger aircraft for the role, namely the three-engine Lockheed Martin L1011-500 TriStar. The initial purchase of six ex-British Airways aircraft was followed by three ex-Pan American Airlines aircraft in 1984. Converted by Marshall Aerospace in Cambridge, eastern England, the two-point tanker-transport K.1 variant had 100000lb (45350kg) of transferable fuel available plus seating for up to 100 passengers. The L1011-500 together with the KC-10A Extender tanker-transports became the role models for the current crop of long-range Multi-Role Tanker-Transport (MRTT) aircraft.

KC-X
In 2001 the USAF began its long and convoluted KC-X programme to replace some 400 KC-135R Stratotankers and 58 KC-10A Extenders. The first proposal was to lease 100 tanker derivatives of the Boeing 767-200ER (ER – Extended Range) airliners for ten years with an option to eventually purchase these planes. This project was abandoned in 2004 following US Congressional Budget Office criticism of the programme as being fiscally irresponsible, and a plan to procure 179 new aircraft was launched with a draft Request For Proposals (RFP) released by the USAF on 25 September 2006. Boeing offered the KC-767 while EADS (now Airbus Group) teamed with Northrop Grumman and proposed a tanker variant of a hybrid version of the Airbus A-330 airliner equipped with the same wings as the A340-200/300 jet, with the latter bid being selected as the winner on 29 February 2008. Almost immediately, Boeing submitted a formal protest alleging flaws in the acquisition process and six months later the US Department of Defence (DoD) cancelled the competition.
A new revised KC-X competition was launched a year later with the same two bidders for the 179 aircraft contract, although Northrop Grumman had withdrawn from the contest, leaving EADS to contest it unilaterally. After submission deadlines were extended by nearly a year, the DoD announced that Boeing’s contender had been selected as the winner of the $34 billion KC-X contract, with the aircraft now designated as the KC-46A.
The KC-46A is a wide body aircraft with a digital flight deck featuring cockpit electronic displays that are also used on the Boeing 787 Dreamliner airliner. It will accommodate a crew of three, two pilots and a boom operator, along with up to 114 passengers, 18 cargo pallets, or 24 stretchers.
New defensive systems and cockpit armour protection to enhance crew survivability include a Northrop Grumman Large Aircraft Infrared Countermeasures (LAIRCM) system, a Raytheon AN/ALR-69 digital radar warning receiver and digital anti-jam Global Positioning System. The KC-46A will be capable of refuelling all fixed-wing receiver aircraft including simultaneous multi-point refuelling, with an advanced design fly-by-wire boom based on the proven Cobham KC-10A boom, plus centreline and wing-mounted hose and drogue systems. The KC-46A will have a total of 207672lb (94200kg) of transferable fuel available.
The programme’s Critical Design Review (CDR) milestone took place in September 2013, which determined that the design of the KC-46A was mature and ready to proceed to the manufacturing phase. Although the USAF programme office claimed in April 2014 that development of the KC-46A was more than fifty percent complete, the production schedule is tight with flight of the first prototype, which will be the 1065th 767 airframe produced, planned before the end of 2014. Delivery of the first aircraft to the USAF will take place in 2016, with 18 combat-ready tankers delivered by 2017 and the last of the 179 airframes on order by 2027.
Already the programme has encountered problems, chiefly with its electrical wiring systems and delays in production of the refuelling boom due to design changes and subsequent late parts deliveries, according to a report in the Air Force Times official publication of the USAF. There is also a risk that software-related issues may have an impact on the programme and that the dual Federal Aviation Administration (the US body tasked with certifying commercial aircraft) certification process, which is intended to yield an amended type certification for the 767-2C to cover the KC-46A, and a supplemental type certification for the militarized tanker configuration, may take longer than anticipated according to unconfirmed reports. In March 2014, USAF estimated that the cost of development would rise to $1 billion over budget, but any additional cost over the capped $4.4 billion Engineering and Manufacturing Development (EMD) programme must be covered by Boeing.
The basic KC-767A is already in service with the Italian and Japanese air forces, each of which operates four tanker-transport aircraft, although their introduction into service was delayed by a number of development issues including buffet problems with the wing pods of the Italian KC-767A. Israel Aerospace Industries (IAI) converted a commercial Boeing 767 into an MRTT for the Fuerza Aérea Colombiana (Columbian Air Force) and is converting two B767-300ER aircraft for the Força Aérea Brasileira (Brazilian Air Force) under its KC-X2 programme to replace four Boeing KC-137 Stratotankers.

Airbus
The Boeing KC-767 was offered for the UK’s Future Strategic Tanker Aircraft (FSTA) requirement to replace the RAF VC-10 and L-1011 fleets but the Airbus A330 Multi-Role Tanker-Transport (MRTT) aircraft was instead selected in January 2004.
Through a Private Finance Initiative (PFI) contract worth some $20 billion, the AirTanker consortium comprising EADS, Rolls-Royce, Thales and Babcock, is providing a comprehensive service for the RAF with a total of 14 A330-MRTT aircraft, powered by two Rolls-Royce Trent 772B engines to ensure the full operational availability of the fleet over a 27-year period.
AirTanker is providing the K.2 Voyager (as the aircraft will be known in RAF service) variant of the A330-200 airliner, which are two-point tankers equipped with Flight Refuelling Limited Mk. 32B-900E pods, plus the three-point K.3 tankers fitted with an upgraded Fuselage Refuelling Unit (FRU). Under the PFI contract, AirTanker is to deliver to the RAF a core fleet of four K.2 aircraft and five K.3 aircraft, with the remaining aircraft accessible on request and available for lease to other military users or commercial operators. Very few internal changes were required to the A330-200 to modify it for the Air-to-Air Refuelling (AAR) role. No additional fuel tanks are required, and as K.2/3 shares the same wing as Airbus’s four-engined A340, there is a pre-strengthened location available for mounting the Mk. 32B-900E underwing pods where two of the aircraft’s engines would have been if the wing had been fitted to an A340 airliner. The AAR systems are controlled from a Fuel Operator Console positioned in the cockpit which can display refuelling on a two-dimensional and three-dimensional screen to perform day and night refuelling. Its defensive aids sub-system includes the Northrop Grumman LAIRCM which also adorns the KC-46A (see above).
The full passenger and cargo capability can be used while K.2/3 is configured for AAR operations. On a typical RAF deployment across the Atlantic, a single aircraft would be able to refuel Panavia Tornado GR4/A and Eurofighter Typhoon F.GR4 Multi-Role Combat Aircraft (MRCA) and still carry up to 291 passengers plus eight NATO-standard freight pallets. The A330-MRTT design can also be used on towline mission, whereby it can be on station for five hours at about 500nm (930km) from its base, with the capability to provide 132000-lb (60000kg) of transferable fuel for receivers.
Built by Airbus in Toulouse, southwest France, the AirTanker A330s were converted to their MRTT configuration at Airbus Military’s facility at Getafe outside the Spanish capital Madrid, before being equipped for the tanker role by Cobham Aviation Services in the UK.
Since entering service in April 2012, four K.2 and five K.3 Voyagers have been delivered to the AirTanker Hub at RAF Brize Norton airbase in southern England, flown by crews of 10 and 101 Squadrons, each of which has a complement of 15 crews which are supplemented by seven RAF Reservist crews. The Voyager has taken over the operational role of support of the air bridge between the UK and Afghanistan and is now supporting RAF Typhoon F.GR4 MRCAs on Quick Reaction Alert (QRA) cover for the UK and the Falkland Islands.
As the A330 MRTT has both civil supplemental type certification from the European Aviation Safety Agency (EASA), which acted as the certification authority for the aircraft, and military certification by the Spanish Instituto Nacional de Tecnologia Aerospacial (INTA/National Institute for Aerospace Technology), one aspect of AirTanker’s contract is the facility to lease the aircraft for civil operations or to other military operators when not immediately required for RAF use and with UK Ministry of Defence authorisation. The first commercial customer for the AirTanker consortium is reported to be the travel company Thomas Cook which plans to operate the A330-MRTTs on UK routes from Glasgow, Manchester and London to the United States and Mexico.
The second military A330-MRTT customer was Australia which selected the aircraft for its AIR 5402 requirement in December 2004. Five General Electric CF6-80E1A3-powered aircraft were purchased for the Royal Australian Air Force (RAAF). They were converted to the tanker role by Qantas Defence in partnership with Australian Aerospace, ADI and GKN Aerospace but the first aircraft was not delivered to the RAAF until June 2011 after delays in the development of the fly-by-wire boom.
Equipped with the Airbus Aerial Refueling Boom System (ARBS), Cobham 905E underwing pods, FRU, and the Universal Aerial Refueling Receptacle System Installation (UARRSI) for self in-flight refuelling, the RAAF aircraft, designated as the KC-30A in RAAF service, has a similar specification to the AirTanker A330-MRTT but is equipped with the Northrop Grumman ALN/AAQ-24 DIRCM [(Directional Infrared Counter-Measure) system instead of the LAIRCM (Large Aircraft Infrared Counter-Measure) system. They can carry up to 380 passengers in a single class configuration and also easily be converted to accommodate up to 130 stretchers for Medical Evacuation (MEDEVAC) missions. The KC-30As are operated by 33 Squadron based at RAAF Amberley airbase southwest of Brisbane and were released for service in February 2013.
Six A330-MRTTs have been sold to Saudi Arabia and three to the United Arab Emirates. Earlier this year the Royal Saudi Air Force (RSAF) deployment of eight McDonnell Douglas/Boeing F-15S Strike Eagle MRCA to Nellis Air Force Base (AFB) in the United States for the Red Flag 2014 exercise were supported by two of its A330-MRTTs by the RSAF’s first combat-ready tranche of ARBS-qualified crews who successfully offloaded around a million pounds (188,240 kgs) of fuel through the fly-by-wire boom during the mission.
This year Singapore ordered six for the Republic of Singapore Air Force (RSAF) with Qatar ordering two for the Qatar Emiri Air Force to bring the total sold to 34, while India is in the final stages of contractual negotiations for six aircraft and France has a declared requirement for twelve A330 MRTTs

Other Players
Israeli Aerospace Industries revealed in August 2014 that it had completed successful test-flights of a Boeing 767-300ER aircraft equipped with a fly-by-wire boom refueling system. The firm says that this boom can outfit a number of aircraft types including Boeing 707 series transports, and Lockheed Martin C-130 series and Ilyushin Il-78 turboprop and turbofan medium and strategic freighters. The company’s Bedek division specialises in converting airliners into MRTT platforms and has twelve customers for its aircraft to this end, including the Israeli Air Force.
Although selling in small numbers, strategic tanker-transport aircraft are a niche market but with a five-year lead over Boeing’s rival KC-46A, Airbus is confident that there will be several new customers for its A330 MRTT, particularly in the Asia-Pacific region, as well as Europe. Both the North Atlantic Treaty Organisation (NATO) and the European Defence Agency (EDA), which overseas aspects of defence procurement in the European Union, have recognised that recent operations demonstrated a significant European AAR shortfall and are considering buying or leasing a multinational MRTT capability by 2020. However, AirTanker’s projected over capacity may provide a solution to the NATO/EDA problem while the defence community, as well as the US DoD, waits to see if the KC-46A Pegasus, named after the mythical ‘Winged Stallion’, can keep to its tight schedule and capped costs to become a viable competitor in the international MRTT market.
http://www.asianmilitaryreview.com/fueling-fires/