How do fighter jets refuel mid-air?
RAF Voyager is a flying tanker, on a mission to keep fighter jets aloft for as long as possible
Staring out of the window of an Airbus A330 aircraft, the sight of a fighter jet flying alongside is something not many people get to see. However, for members of RAF 10 and 101 Squadrons, it’s a daily occurrence. A seemingly standard-looking airliner that’s larger than most passenger jets, the RAF Voyager has been commissioned to act as the air force’s flying ferry and fuel supply. During this year’s Joint Warrior exercise, How It Works was given the opportunity to hop aboard the valiant Voyager and see first-hand the important role this aircraft plays in keeping pilots in the sky.
More than 10,000 military personnel from the UK and NATO took part in the large-scale training exercise, which spanned land, sky and sea. During the two-week event 59 aircraft took to the skies in participation, including the RAF Voyager (A330 MRTT) to offer fighter jets air-to-air refuelling.
Heading towards the west coast of Scotland, waves of Typhoon and F-35 Lightning II jets approached either side of the Voyager before disappearing momentarily to get into position for refuelling. Making a connection to a deployed fuel hose, the overall process mimics that of a mechanical hummingbird, gently approaching the fuel basket and inserting its slender steel beak to draw its fill of jet fuel – all while travelling at 885 kilometres per hour. Refuelling takes around five minutes before the next jet is ready to get in position.
Although part of a legacy of refuelling aircraft, the Voyager is the UK’s first to sport three locations on its body where it can dispense fuel. Previously, air-to-air refuelling could only be achieved at the rear of an aircraft. However, the Voyager is equipped with additional refuelling pods on both of its wings.
This improved design is the result of some clever cut-and-paste engineering. “This aircraft was built from scratch, they used an Airbus A340 wing and bolted it to an Airbus A330”, said Martin Blythe, RAF mission systems operative. “An A340 is a four-engined airliner, but the Voyager is two-engined. Where the other engines would have been is where we have put our pods”.
These pods are where the fuel hoses and baskets are held during flight and deployed for refuelling. Air-to-air refuelling occurs at around 6,000 metres, much lower than the altitude at which a commercial flight travels. Aboard the Voyager is a single fuel tank, not only to dispense to jets in need of a top-up but also for the Voyager itself. Burning at a rate of around six tons an hour, it’s a balancing act between the amount of fuel the Voyager can supply to other aircraft and what it needs to retain for itself. However, with the ability to hold over 100 tons of fuel, this flying fuel station can stay in the sky for hours.
“This plane is a game-changer in how much fuel it can carry, Blythe says. “Legacy aircraft such as the TriStar could go equally as far, but that aircraft only had one hose and this one has three hoses, one on each wing and one on the tail, so the benefit to us is we can simultaneously refuel aircraft at the same time”.
How do fighter jets pump petrol from flying fuelling stations?
Deploying the hose
The fuel hose and basket, also known as a drogue, is released from the wing pod and can extend up to roughly 27 metres to meet the receiving fighter jet.
Having extended its fuel probe, the fighter jet gently accelerates and inserts the probe into the inflated basket to collect fuel.
Once in the correct position, the fuel valve will open and jet fuel will flow down into the hose across the coupling, and through the probe to the fighter jet’s fuel tank.
With a full tank of fuel, the fighter jet reduces its speed and pulls away from the hose, closing the fuel valve to prevent fuel leakage as it disconnects.
This article was originally published in How It Works issue 126
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