Air-to-air refuelling
The Ministry of Defence is currently negotiating a delayed contract to replace the current fleet of RAF air-to-air refuelling tankers. The shape and form of the contract and its timing are matters of concern. Although low profile and unglamorous, having a modern and flexible tanker fleet is key to successful British air operations. It matters what is decided and when.
What is air-to-air refuelling?
The ability to refuel military aircraft in the air is a vital factor in augmenting the often limited range of combat aircraft and significantly enhance the tactical flexibility of deploying such aircraft.
The techniques for refuelling aircraft in the air without the need to return and land at an airbase were pioneered in the UK before the Second World War. They were perfected after the war, in part to extend the range of tactical airpower in a potentially messy closing stage of the island hopping War in the Pacific, but essentially to meet the needs of the new generations of jet powered aircraft. Jets have a heavier consumption of fuel compared with the old piston-engined designs, and early jets carried limited supplies of fuel on board, leaving them with a reduced radius of action.
The availability of a tanker aircraft to provide short-range fighters or tactical strike aircraft with fuel became a key aspect of RAF and USAF operations post war. Indeed, UK air defence throughout the 60s and 70s was heavily reliant on the availability of tankers to keep the interceptor fleet in the air over the Northern approaches.
Although the fuel capacity and power of the jet engines has been significantly enhanced since the war, fuel consumption rates have increased and the use of afterburners for rapid acceleration further increases the rate of fuel burn. Moreover, reliance on external fuel tanks on combat aircraft is inefficient from many perspectives.
Tanking has also been increasingly used also to extend the ranges of larger transport, surveillance (AWACS) and patrol aircraft.
Refuelling tanker aircraft are essentially converted or adapted passenger jets, although the RAF used part of its old bomber fleet in the past.
The Low Profile, High Impact Service
Refuelling hit the headlines during the Falklands war when UK bombers were able to drop bombs on the Port Stanley airfield, missions that involved multiple refuelling encounters.
In more recent times the RAF made a major contribution to the US air offensive over Afghanistan, earning praise from the US Navy and Marine crews who found their operational flexibility and availability hugely professional, and generally more helpful than the US’ own tankers.
Tanker aircraft support the RAF’s overseas deployments on exercises or potentially any conflict in Iraq. The availability of a quality fleet of serviceable tankers is key to the RAF’s preparations and planning.
How Does It Work?
Technically air-to-air refuelling is surprisingly simple. There are two systems now in use- the ‘hose and drogue’ system and the ‘flying boom’ method. The former is used by the RAF and US Navy/Marines. The latter employed by the US Air Force.
‘Hose and drogue’ involves a tanker aircraft unfurling a long hose with a ‘basket’ at the end containing a high-pressure coupling. The receiving aircraft plugs a probe into the coupling to tank up, requiring some precise flying skills on the part of the pilot to manoeuvre his aircraft to make the connection and maintain formation until the fuel is transferred. Up to three aircraft can be refuelled from a single tanker (more usually two) at a time as the tankers have in some cases three hoses.
The ‘flying boom’ is literally a long pole that is deployed from the rear of the tanker and steered by the tanker crew to dock with a special port on the recipient aircraft. Only one refuelling can take place from a tanker at a time. The boom can be adapted to take a hose and drogue attachment. Many USAF aircraft cannot use the hose system as they are not equipped with probes. The US Navy and Marines adopted the hose method as this is more flexible and hose units can be attached to carrier launched strike aircraft to serve as tankers if necessary.
What is Wrong With The Existing Tankers?
Due to the current increasingly international and long- distance role of the RAF significant pressure is being put on the RAF’s small and ageing fleet of tankers. They soon will not be able to cope.
The existing fleet of aircraft is made up of a motley collection of three different modified versions of the old VC10 passenger jet (19 aircraft) that has been out of airline service for many years. There is also a small number of adapted ex BA Lockheed Tristars.
There are serviceability issues with these old aircraft. They have not been in production for many years and spares for the VC10 is an issue. One version of the VC10 (the Mk 2s) has been scrapped already as they were suffering fatigue and spares depletion.
It is a priority for the RAF to obtain a modern, standardised aircraft type to increase reliability and fulfil the expanding roles demanded by the government.
What are the Americans Doing?
The USAF operates a fleet of some 550 tankers. The type they use, the KC135 is an adapted Boeing 707 airliner. The US Defence Department has just taken the decision to order modified Boeing 767 aircraft.
The 767is one of the options being considered by the MoD.
What is the Delay About?
Signing of a contract to replace the RAF fleet of tankers has been delayed by a year. The reasons given are vague but probably centre on the fact that the government is trying to tie the contract up as a PFI. This raises considerable questions about how to draft a contract for the provision of front line (or nearly front line if not actually combat) aircraft of which a huge degree of flexibility will be required. The contract would be not only to supply the aircraft and maintain them, but potentially to operate them.
There are many issues that arise concerning the use of non-military crews, the availability of aircraft that might be used for other Civilian purposes when not on military business, maintenance, military modifications and upgrades and so on. With the small number of tankers envisaged relative to the task, trying to write a contract that covers all the possible – and by their nature unpredictable- requirements of key military assets is likely to be difficult. Financially, it could prove costly if operational requirements subsequently demand a change in the nature of the aircraft use, rate of deployment or technical modifications.
In the meantime the forces are obliged to make do with the existing fleet and live with the uncertainty of what arrangements will be imposed when decisions are made.
The Two Competing Consortia
There are two groups competing for the contract. Inevitably there is a European option and a US package, centred on the Airbus A330-200 and Boeing 767-300 respectively. In each case the hose and drogue system would be fitted to the 20-25 aircraft sought and the aircraft would be able to be configured into cargo and passenger configurations. From a technical perspective, it probably doesn’t matter which airframe is selected. The choice will, no doubt, come down to economics, contractual detail and a decent dose of politics.
The consortia are: Air Tanker Ltd- Airbus
Tanker and Transport Service Company- Boeing
The contract value has been reported as being in the area of £13-14bn.
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