The RAF tanker using cooking oil to boldly go where no other UK aircraft had gone before

ON November 16, an RAF Voyager aircraft took off from Brize Norton to undertake a 90-minute test flight over the south east of England, flown by a crew made up of personnel from the RAF, Airbus and Rolls-Royce.

Among the procedures carried out was a replication of the Voyager’s primary purposes, an air-to-air (AAR) refuelling sortie, but the crucial part of the test wasn’t how liquid is pumped into other aircraft at 30,000 feet, but the liquid that kept the A330 in the air during its hour-and-a-half test – a concoction primarily made up of used cooking oil!

It was the first time any aircraft had flown in UK airspace using 100% sustainable aviation fuel, SAF, reducing carbon emissions by up to 80 per cent when compared to the conventional kerosene-based fuel it was replacing.

While the RAF is still a very long way from seeing all its military planes powered by SAFs, the fact that one of the RAF’s biggest beasts was able to operate using a mixture composed predominantly of waste cooking oil, bodes well for an aviation future that doesn’t rely solely on fossil fuels.

(A Voyager at RAF Brize Norton on its return with troops from Afghanistan)

The Voyager itself has been part of the RAF’s fleet for more than a decade, becoming the service’s sole aerial refuelling aircraft, mainly serving the fast jets, acting as a force multiplier to extend their task endurance. The AAR support it provides also allows larger aircraft like the Atlas A400M and the Hercules to extend their range and deploy to further locations without the need to land and refuel.

The A330 MRTT is a military derivative of the Airbus A330-200 airliner, used for both transport and AAR, provided with a range of adaptations to suit whatever customer it’s supplying: in the RAF’s case the KC. Mk 2 version is equipped with two underwing pods for refuelling fast jets and the KC. Mk 3 with an additional centreline hose for use with larger aircraft.

The plane is powered by a pair of Rolls-Royce Trent turbofan engines and cruises at a speed of around 550mph, capable of maximum speed of 655mph. It has a maximum range with full fuel load of 8,000 nautical miles (9,200 miles), with the upper limit of its fuel capacity being 245,000lb, without the use of additional fuel tanks

(10 Sqn RAF Airbus Voyager leaves Akrotiri in support of Operations across the Middle East)

The first unit equipped with the Voyager was No. 10 Squadron in July 2011, followed by 101 Squadron in October 2013; an additional Voyager is operated by the No. 1312 Flight, based in the Falkland Islands (RAF Mount Pleasant). No. 10s switch came seven years after the MoD announced they had chosen the A330 MRTT variant to provide tanker service, replacing the TriStar and VC10.

The purchasing of the Voyager fleet came under a March 2008 private finance initiative, PFI, arrangement that saw the AirTanker consortium selected to provide 14 aircraft under a 27-year contract: a ‘core fleet’ or eight military and one civilian-registered aircraft, supplemented by a ‘surge fleet’ of five civilian registered aircraft that AirTanker uses in a commercial capacity to generate additional revenue when they are not needed by the RAF. The surge planes are maintained close to A330-200 airliner standard, and can be recalled for military use as and when required.

The AirTanker consortium owns, manages and maintains the aircraft, as well as providing infrastructure and training options, and by 2016 the 14 Voyagers had been delivered with the annual cost to supply 18,000 flying hours, including personnel, coming in at around £450million.

(C130J Hercules conducting low-light refuelling with a Voyager)

The home fleet of Voyagers are based at Brize Norton and are capable of probe and drogue refuelling, employing a flexible hose that trails from the tanker aircraft with the drogue (sometimes referred to as a basket) at its narrow end which approaches the aircraft needing refuelling – the pilot on the receiver aircraft guides a probe to connect with the hose.

While the probe and drogue is ideal for refuelling smaller fast jets, it has its limitations in that certain current and future aircraft – namely the Globemaster, the P-8 Poseidon and the E-7 Wedgetail – can only be refuelled using a boom, a rigid telescopic tube with movable flight control surfaces that an operator on the tanker aircraft extends and inserts in a receptacle on the receiving aircraft.

The RAF indicated in 2016 that it had investigated the possibilities of fitting booms to a certain number of the Voyagers; however, last year in an answer in the House of Commons, Defence Minister Jeremy Quin admitted there were “no current plans to fit an aerial refuelling boom system to the Voyager aircraft”.

In 2015 it was announced that one of the Voyager fleet would be refitted to carry Government ministers and members of the Royal Family on official visits, with a refit cost of £10million, but an annual saving of £775,000 compared to the use of charter flights.

(ZZ336, the Prime Minister’s Voyager at RAF Brize Norton)

Former PM David Cameron effectively christened the new aircraft, taking the plane to the 2016 Warsaw summit, before four years’ later it was again in the news with then PM Boris Johnson ordering a respray – the tail of ZZ336 painted red, white and blue and earning the nickname, Boris Force One. The Voyager ZZ336 remains stationed at Brize Norton and is available to the RAF for its prime duty of AAR when not in use by ministers or the Royal Family.

While ZZ336 may not be earmarked for SAF tests, the RAF will no doubt continue its attempts to move away from fossil fuels with SAF flying time extended, and it is hoped that the development of fuel substitutes will wean aircraft off their reliance on kerosene, and push the RAF closer to its low emissions targets. Air Chief Marshal Sir Mike Wigston described the ‘cooking oil’ flight as another “important milestone” en route to becoming the world's first net-zero air force, and reducing its reliance on global supply chains. The plans to reduce the RAF’s carbon footprint has also seen it target creating the first net-zero airbase by 2025.