KC-767 Tanker Transport Aircraft, USA

The Boeing 767 tanker transport aircraft, designated KC-767 for the US Air Force, is a high-performance version of the Boeing 767-200ER twin-aisle jetliner equipped for fully integrated tanker operations. It is fitted with either boom and receptacle refuelling, hose and drogue refuelling or both.

The commercial 767 first entered service in 1982 and more than 880 aircraft have been delivered. The cabin of the tanker can be configured for passenger transport, as a freighter, convertible (passenger or freighter) or Combi (passenger and freighter).

In the 1980s and in 1990/91 Boeing conducted studies directed towards the identification of an appropriate successor to the KC-135 Stratotanker, a derivative of the Boeing 707 jetliner. In 1991 the 707 production line was finally closed and studies confirmed that the long range twin engine 767 was a strong candidate to replace the KC-135.

In May 2003, the US Air Force announced that it would lease 100 tankers to replace the oldest of its KC-135 tankers, subject to congressional approval. The lease would be for six years, starting in 2006. An option to buy at the end of the lease was included in the deal. A Defense Science Board review of the USAF's proposed lease concluded that further studies were required before a decision could be taken. An analysis of alternatives was completed in April 2006. A revised request for proposals for the KC-X was issued in December 2006.

Boeing submitted a revised bid for the KC-X in April 2007, the KC-767AT Advanced Tanker based on a newer version 767-200LR long-range freighter aircraft (rather than the 200ER) with Pratt & Whitney PW4062 engines. The contract was awarded to the Northrop Grumman KC-30 in February 2008.

Boeing has appealed against the award and has asked the US Government Accountability Office (GAO) to review the decision in relation to the evaluation award criteria established for the competition. The GAO sustained the protest and in June 2008 recommended that the USAF reopen the bidding process. In September 2008, the US Department of Defense cancelled the competition, citing the need to defer any decision until the next presidential administration took power in January 2009.

In July 2001, the Italian Air Force ordered four 767 tanker transports in the combi variant with deliveries scheduled to begin in mid-2008. The aircraft is designated B-767 and Alenia Aeronautica is assisting in development and production. The maiden flight of the first aircraft was in May 2005.

In April 2003, the Japanese Air Self Defence Force ordered four of the convertible freighter variant. The maiden flight of the first aircraft was in December 2006. The first two aircraft were delivered in February and March 2008. The third is scheduled for delivery in 2009 and the final aircraft in 2010.

Boeing announced in May 2009 that the three KC-767J aerial refuelling tankers had achieved initial operational capability (IOC) and have been placed in an active air wing in the Japan Air Self Defence Force (JASDF). Boeing is scheduled to transfer the fourth tanker to Itochu in December for delivery to the Japanese Ministry of Defence in the first quarter of 2010.

Design

The structure incorporates new materials such as improved aluminium alloys, graphite composites and hybrid Kevlar graphite composites, which give enhanced strength, durability and longevity.

The configuration of a commercial 767 for the tanker transport role involves the installation of additional pumps and auxiliary fuel tanks together with the fuel distribution lines below the floor of the main cabin, leaving the main cabin free for cargo, passenger or both cargo and passenger transportation. The concept allows simultaneous refuelling and airlift operations or successive refuelling and airlift missions.

In the cargo configuration, the aircraft can transport 19 standard military 463-L pallets; in the passenger configuration, 200 passengers can be accommodated; and in the Combi configuration ten cargo pallets and 100 passengers can be carried.

Cockpit

The 767 Tanker Transport aircraft has an advanced two person all-digital flight deck. Smiths Aerospace supply the mission control system which interfaces with the refuelling system. The control system is a derivative of the flight management system on the commercial Boeing 737. Innovative Solutions & Support Inc. will supply the flat panel pilot's mission display (PMD) and aerial refuelling operator control display (AROCD).

Rockwell Collins will supply the communications and navigation suite. Kaiser Electro-optics (a Rockwell Collins company) will supply head-mounted display systems for the remote aerial refuelling operator.

The 767 tanker transport will be equipped with military avionics, navigation and communications and an optional defensive aids suite with radar warning receivers and electronic and opto-electronic countermeasures.

Refuelling

The 767 aircraft can be modified to accommodate refuelling wingpods and a centreline hose for probe and drogue refuelling. The 767 will accommodate any combination of these configurations. Smiths Aerospace supply the hydraulically-powered hose and drogue refuelling system. The fuselage can also be fitted with a centreline refuelling boom for boom and receptacle refuelling missions.

Boeing will produce the boom itself and Smiths the boom actuation system. BAE Systems has been selected to supply the CsLEOS real-time operating system for boom control. The boom can refuel at the rate of 600gal/min, the centreline hose at 600gal/min and the wingpods at 400gal/min.

The USAF air fuel transfer method is through the boom and receptacle air refuelling technique. The US Navy, the US Marines and Nato aircraft have traditionally used the hose and drogue air refuelling method.

Aircraft using hose and drogue refuelling include US Navy F/A-18E/F Super Hornet and USMC AV-8B Harrier Plus aircraft. Aircraft using the flying boom refuelling system include the USAF F-111, F-15, F-16, the UK Eurofighter and the French F-1 Mirage. Future aircraft such as the joint strike fighter will be developed for the optional installation of either refuelling system according to the customer country's operational requirements.

Tankers are fitted with tactical floodlights on the engine pylons, wing pods and the boom area to assist night-time refuelling operations. The drogue itself is fitted with small lights around the perimeter to help night operations.

New-generation highly ruggedised and impact resistant air-to-air refuelling drogues have been fitted with gaseous tritium lights with no wires or moving parts.

Fly-by-wire boom

In January 2007, KC-767's advanced fifth-generation fly-by-wire boom (a telescoping tube used to deliver fuel to military aircraft) made a series of 'dry contacts' with a B-52 bomber assigned to the Air Force Flight Test Center, Edwards Air Force Base, California.

Built on an aerodynamic shape, the advanced boom can transfer 900gal (3,400l) of fuel a minute. It provides for greater precision and control to the operator. The boom automatically corrects its position to reduce potential damage to the receiver aircraft. It is easier to maintain for it has 2,600 fewer parts than previous booms.

Engines

The two turbofan podded engines are mounted below the leading edges of the wings. 767 tankers for the Italian Air Force and the Japanese Air Self Defence Force will be equipped with GE Aircraft Engines CF6-80C2 engines, rated at 276kN. In March 2004, Boeing announced that the Pratt & Whitney PW4062 engine, rated at 282kN, would be the standard production engine for the USAF and future aircraft.

Boeing's KC-767 and Northrop Grumman's KC-45

Stalemate continues as the Obama administration insists on a winner-take-all strategy for the US Air Force's tanker replacement contract, while congress proposed to split the KC-X tanker purchase between the two duelling competitors - the Boeing KC-767 and the Airbus A330-based Northrop Grumman / EADS North America KC-45.

In 2008, Northrop's team won the KC-X contract, but the award was overturned by the US Government Accountability Office due to procedural breakdowns by the air force. The USAF plans to buy at least 100 KC-X tankers to replace the oldest of more than 400 Boeing KC-135s in its fleet.