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New Generation Tankers – True Multi-Role Aircraft

By Rob Russell


Airbus A330MRTT vs Boeing KC46 Pegasus


Air-to-air fuelling has been around, in some form now for over a hundred years. Some of the earliest experiments in aerial refuelling took place in the 1920s; two slow-flying aircraft flew in formation, with a hose run down from a hand-held fuel tank on one aircraft and placed into the usual fuel filler of the other.



As the 1920s progressed, greater numbers of aviation enthusiasts vied to set new aerial long-distance records, using in-flight air refuelling. One such enthusiast, who would revolutionize aerial refuelling was Sir Alan Cobham, member of the Royal Flying Corps in World War I, and a pioneer of long-distance aviation. Sir Alan Cobham's grappled-line looped-hose air-to-air refuelling system borrowed from techniques patented by David Nicolson and John Lord, and was publicly demonstrated for the first time in 1935. In the system, the receiver aircraft, at one time an Airspeed Courier, trailed a steel cable which was then grappled by a line shot from the tanker, a Handley Page Type W10. The line was then drawn back into the tanker where the receiver's cable was connected to the refuelling hose. The receiver could then haul back in its cable bringing the hose to it. Once the hose was connected, the tanker climbed sufficiently above the receiver aircraft to allow the fuel to flow under gravity.



Whilst not much in-flight refuelling was done during World War 2, much research and development was going on. Whilst not used in the Cold War era, air-to-air refuelling came into its own in the Korean and Vietnam wars. The main tanker used was the Boeing KC135, and to a lesser degree, some C130s were also used. The Americans would not have been able to survive the Vietnam War, were it not for the in-flight refuelling support provided by the KC135.



During the Falklands War, both sides made extensive use of tankers, to enable bombers and fighters to complete their missions. The British made use of their base at Ascension Island The most famous refuelling missions were the 8,000 nmi "Operation Black Buck" sorties which used 14 Victor tankers to allow an Avro Vulcan bomber (with a flying reserve bomber) to attack the Argentine-captured airfield at Port Stanley on the Falkland Islands. With the aircraft flying from Ascension, the tankers themselves, needed in-flight refuelling.



The raids were the longest-range bombing raids in history until surpassed by the Boeing B-52s flying from the States to bomb Iraq in the 1991 Gulf War.


An extremely useful tanker in Desert Storm was the USAF's KC-10A Extender. Besides being larger than the other tankers deployed, the KC-10A is equipped with the USAF "boom" refueling and also the "hose-and-drogue" system, enabling it to refuel not only USAF aircraft, but also USMC and US Navy jets that use the "probe-and-drogue" system, and also allied aircraft, such as those from the UK and Saudi Arabia. Likewise, the KC-130 also proved a vital aid in the various wars.



With a full jet fuel load, the KC-10A is capable of flying from a base on the American East Coast, flying nonstop to Europe, transferring a considerable amount of fuel to other aircraft, and returning to its home base without landing anywhere else. With the help of these tankers, B52s and later, B2s were able to operate from their home bases, in the USA and deliver their bombs in the Middle East, before returning to their bases in the USA.. To this day, both the KC135 and KC10s are extensively used in the Middle East, in support of various operations that are being conducted there.


But, as with all aircraft, many of the first-generation tankers, namely the KC135 and KC10, are coming to the end of their useful operational lies. They started flying in the early 1960s and with many upgrades have managed to keep in the air and provide the vital service they do. But they have many limitations and they are being replaced by modern generation jets, developed from civil airliners.


The two most successful of these are the Airbus A330 MRTT and the Boeing KC46 – developed from the Boeing 767.



Of course, with just two modern jets being available, the inevitable comparisons are being made and which one is the most suitable? Depending on which side of the Atlantic you are, you will get a very different opinion and answer!


The Airbus A330 MRTT


The Airbus A330 Multi Role Tanker Transport (MRTT) is a European aerial refuelling and military transport aircraft based on the civilian Airbus A330. It is designed as a dual-role air-to-air refuelling and transport aircraft. The A330 MRTT has a maximum fuel capacity of 245,000 lb without the use of additional fuel tanks, leaving space for 99,000 lb of additional cargo. The A330 MRTT's wing has a common structure with the four-engine A340-200/-300 with reinforced mounting locations and provision for fuel piping for the drogue refuelling points.



Standard commercial A330-200s are delivered from Airbus's Final Assembly Line in Toulouse, France to the Airbus Military Conversion Centre in Getafe, Spain for fitting of refuelling systems and military avionics. The facility is also able to convert used A330-200s as well.



Whilst predominantly delivered with the hose and drogue system, for fuel delivery, which is what most European Air Forces and Nato use, there are other options available: There is an option for a centre drogue and hose as well. There is also an option to have a boom system fitted as well. Some Air Forces have opted to take delivery of their aircraft, equipped with both systems fitted, ie the centre boom and drogues on the wing points



The A330 MRTT cabin can be modified to carry up to 300 passengers in a single-class configuration, allowing a complete range of configurations from maximised troop transport to complex customisation suitable for VIP and guest missions. The A330 MRTT can also be configured to perform Medical Evacuation (Medevac) missions; up to 130 standard stretchers can be carried. The main deck cargo configuration allows the carriage of standard commercial containers and pallets, military, ISO and NATO pallets (including seats) and containers, and military equipment and other large items which are loaded through a cargo door. Like the A330-200, the A330 MRTT includes two lower deck cargo compartments (forward and aft) and a bulk area capability. The cargo hold has been modified to be able to transport up to eight military pallets in addition to civilian unit load devices (ULDs).



An optional crew rest compartment (CRC) can be installed in the forward cabin, accommodating a spare crew to increase the time available for a mission. The passenger cabin of the A330 MRTT can be provided with a set of removable airstairs to enable embarkation and disembarkation when jet bridges or ground support equipment are not available.


The tanker was certified by Spanish authorities in October 2010. The first delivered aircraft (the third to be converted) arrived in Australia on 30 May 2011 and was formally handed over to the Royal Australian Air Force.


Operators


As of 30 November 2023, a total of 78 A330 MRTT had been ordered from Airbus Military. 59 have been delivered, including seven of the ten ordered by NATO's Multinational Multi-Role Tanker Transport Fleet (MMF).


Australia 7

Brazil 2

Canada 9 – 8 MRTT and 1 VIP configuration

France 15

Netherlands by

NATO crews 10, 7 of these will be supplied to, crewed and flown

Saudi Arabia 6

Singapore 6

South Korea 4

Spain 3

UAE 3 with 2 more on order

UK 14 – these are owned and managed by Air Tanker services, of which 9 are available to the RAF. Air Tanker Services wet leases the balance of the fleet, with the understanding the RAF will have priority on them in urgent situations. RAF training is provided by Air Tanker Services as well. Air Tanker Services pilots are also RAF Reserve pilots and can fly for both services. Air Tanker Services is Headquartered at Brize Norton, which is also the main base of the RAF Mobility Command


Boeing KC46 Pegasus


The Boeing KC-46 Pegasus is an American military aerial refuelling and strategic military transport aircraft developed by Boeing from its 767 jet airliner. In 2001, the US Air Force began a procurement program to replace around 100 of its oldest KC-135E Stratotankers, and In February 2011, the tanker was eventually selected by the United States Air Force (USAF) as the “winner” in the KC-X tanker competition. The Airbus A330MRTT was originally chosen by the USAAF, but political pressure caused the USAF to cancel that choice and re-open the programme and Boeing was then the politically desired eventual winner.



In December 2013, Boeing joined the wings and fuselage for the first 767-2C to be adapted into a KC-46A. The first of four 767-2C provision freighters were to complete assembly by the end of January 2014, and after an extensive test flight programme, during which many problems were identified and needed correcting, the first deliveries were due to take place in January 2015. However, ongoing production problems pushed the delivery date back further



The KC-46 will fly faster and farther and be more fuel-efficient than the KC-135 it replaces. It also will have greater air refuelling capability for a variety of military aircraft including those operated by NATO members because it comes equipped with a traditional tail-mounted refuelling boom and a hose-and-drogue system. But the programme has not been without many problems, many of which delayed delivery of the aircraft and many problems were often only discovered during flight testing and required considerable corrections and modifications to the aircraft and its equipment.


It was in March 2015, a refuelling test with a C-17 transport was stopped because of a higher-than-expected boom axial load while delivering fuel. The problem was caused by the turbulent "bow wave effect" generated by two large aircraft flying in line. In May 2016, a further delay of at least six months due to technical and supply chain issues was reported, potentially requiring program re-structuring and cuts. At the time, only 20% of the flight tests were completed. Slow progress was made with the flight test programme and eventually, it was announced the first deliveries would be in early 2019.



In April 2019, it was confirmed that the USAAF halted all deliveries until further notification, as loose material and debris were found in planes already delivered. Deliveries were to eventually continue in August 2019. Further problems were discovered and in September 2019, the USAAF restricted the KC-46 from carrying cargo and passengers due to an issue with the floor cargo locks unlocking mid-flight. A fix was approved by the USAAF in November 2019 and was retrofitted upon delivery of the aircraft. By 20 December 2019, four KC-46As had received new cargo locks and the USAF had closed the Category 1 deficiency and cleared retrofitted aircraft for cargo and passenger operations.



In early 2021, the USAF cleared the KC-46 for limited operational use. The type can conduct U.S.-based refuelling only, requiring other tankers for deployments to combat areas. At the time, the KC-46 could refuel the B-52, F-15, F-16, and F/A-18, but it was not approved to service the A-10, F-22, F-35, B-1, or B-2. It was expected to be fully combat-ready by the end of 2023



The flight deck has room for a crew of four with a forward crew compartment with seats for 15 crew members and in the rear fuselage either palletized passenger seating for 58, or 18 pallets in cargo configuration. The rear compartment can also be used in an aero-medical configuration for 54 patients (24 on litters). Quick crew access from the ground is available via a ladder that can be pulled down near the front landing gear. The KC-46A can carry 212,299 lb of fuel, 10 per cent more than the KC-135, and 65,000 lb of cargo. Survivability is improved with infrared countermeasures and the aircraft has limited electronic warfare capabilities. It uses manual flight controls, allowing unrestricted manoeuvrability to avoid threats anywhere in the flight envelope.


Operators


Israel 8 of which 4 have been delivered

Japan 4

USAF 77 delivered with an eventual order of 179


Airbus A330 MRTT - General characteristics


Crew: 3: 2 pilots, 1 AAR operator

Capacity: Various passenger configurations are available including 291 passengers (United Kingdom) and 8 military pallets + 1LD6 container + 1 LD3 container (lower deck cargo compartments)

Payload: 99,000 lb non-fuel payload

Length: 58.80 m (193 ft)

Wingspan: 60.3 m (198 ft)

Height: 17.4 m (57 ft)

Wing area: 362 m² (3,900 ft²)

Empty weight: 125,000 kg (275,600 lb)

Max takeoff weight: 233,000 kg (514,000 lb)

Powerplant: 2× Rolls-Royce Trent 772B, General Electric CF6-80E1A4, or Pratt & Whitney PW 4170; turbofans, 320 kN (72,000 lbf) 320 kN each

Fuel capacity: 111,000 kg (245,000 lb) max, 65,000 kg (143,000 lb) at 1,000 nmi (1852 km) with 2 hours on station


Performance

Maximum speed: 880 km/h (475 knots, 547 mph)

Cruise speed: 860 km/h (464 knots, 534 mph)

Combat radius: 1,800 km (972 nmi) with 50 tonnes of fuel for 4 hours

Ferry range: 14,800 km (8,000 nmi) maximum

Service ceiling: 13,000 m (42,700 ft)



Boeing KC46 - General characteristics


Crew: 3 (2 pilots, 1 boom operator) basic crew; 15 permanent seats for additional/optional aircrew members, including aeromedical evacuation crew members

Capacity: seating for up to 114 people, 18 463L pallets, or 58 patients (24 litters, 34 ambulatory) and 65,000 lb (29,500 kg) payload

Length: 50.5 m

Wingspan: 48.1 m

Height: 15.9 m

Empty weight: 181,610 lb (82,377 kg)

Max take-off weight: 415,000 lb (188,240 kg)

Fuel Capacity: 212,299 lb (96,297 kg)Fuel Capacity (vol): 31,220 US gal (118,200 L)Maximum Transfer Fuel Load: 207,672 lb (94,198 kg)

Powerplant: 2 × Pratt & Whitney PW4062 turbofan, 62,000 lbf (280 kN) thrust each


Performance

Maximum speed: 500kn

Cruise speed: 460kn

Range:6,385 nmi global with in-flight refuelling

Service ceiling: 40,100 ft

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