US Air Force refuels a tanker plane backwards

US Air Force refuels a tanker plane backwards
A C-5M transport aircraft prepares to refuel a refueling tanker
A C-5M transport aircraft prepares to refuel a refueling tanker
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A C-5M transport aircraft prepares to refuel a refueling tanker
A C-5M transport aircraft prepares to refuel a refueling tanker

In a topsy-turvy bit of military aviation, the US Air Force used a C-5M Super Galaxy heavy transport to refuel a KC-10 Extender refueling tanker aircraft, pumping fuel backwards up the boom from transport to tanker instead of the other way around.

First conceived in the 1920s, inflight refueling has developed from a dangerous stunt to a vital part of the infrastructure of the major military powers. The idea is to vastly extend the range of warplanes to prevent problems often seen during the Second World War when bombers had the flight unescorted by their shorter range fighter planes, which had to turn back. It also allowed for extremely long range missions like the famous raid on Port Stanley Airport during the Falklands War in 1982, where Vulcan bombers based in England flew nonstop to the South Atlantic and back.

The process of a tanker plane using a mechanical boom to hook up to a trailing aircraft and pumping fuel into it may look the same today as in the opening credits of Dr. Strangelove, but it's undergone considerable evolution over the past six decades. Instead of relying on two attentive pilots and a highly skilled boom operator, engineers have developed increasingly autonomous systems that control both aircraft as well as the boom for increased safety and efficiency.

However, there's still the problem of how to refuel the refueler. The obvious answer is to return to base for another load or to use a second tanker to refuel the first, but both of those mean taking a tanker out of service when they could be tending to other aircraft.

To overcome this, the US Air Force's 22nd Airlift Squadron (AS) is experimenting with a new concept where, on December 12, a C-5M Super Galaxy transport in the skies over Northern California and Oregon hooked up with a KC-10 Extender. From the outside, it looked like a normal refueling maneuver, but it was actually running in reverse. Instead of the aviation fuel going into the C-5M, the C-5M was pumping the fuel into the KC-10 tanker. In this case, 23,500 lb (10,700 kg) of fuel in approximately 30 minutes.

According to the Air Force, it's still early days and the recent demonstration was intended to gather data to further refine the technique, especially since the two aircraft fly differently as their weights shift. If it succeeds, it could mean air missions can remain in the air longer with more aircraft operating at longer ranges.

"By using a C-5 as a huge floating gas station, it allows more tankers to be positioned for offloading to fighter or mobility aircraft, versus having to use one tanker to refuel another, which takes away a tanker asset from the mission," said US Air Force Major Justin Wilson, 22nd AS chief of standards and evaluations and C-5M evaluator pilot. "This allows more tanker aircraft in the theater and extends their range or orbit time."

Source: US Air Force

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Thank you, B. J. Thomas.
What a concept. The C-5 has enough cargo capacity to carry almost twelve fuel loads of this volume.
So eventually will we be limited only be the food/drink requirements of the tanker aircrews, or (with autonomy) the maintenance intervals of the engines?
CraigAllenCorson. It is not volume but weight. Most tanker planes have large spces left over because the entire plane full of fuel would weight too much to fly.
It's interesting that they "push" (pump) the fuel up to the KC-10 through the refueling boom. I would have expected the KC-10 to have a 'standard' refueling port above the cockpit like other aircraft do and they would have had a way to switch that from fueling the planes fuel reserves (for flight) and to filling the refueling tanks. That seems like a less challenging - I assume the pilots of the aircraft should have experience with refueling in that position rather than through the tail refueling boom.

Or are the systems which handle "fuel for the engines" and "fuel for refueling" tanks separate for a reason?
@Dan_Linder. They do have a normal refuelling receptacle above the cockpit but, as the article says, that would mean taking another tanker out of service. This experiment shows that they can do it another way by using the capacity of the C-5M.
Christopher Terronez
Why backward? Most likely the reason is alot of tankers are not Air Refuel Receive capable. They don't have the port needed above the cockpit. And it would cost too much money and BS to do so. So with this method it makes non ARR tankers....ARR capable.
Mark Markarian
File this under making the best of a bad or non-existent condition. I have to assume they never put inlets into takers for in-fight refueling of the tankers and because of that they've got to suck in fuel uphill rather than having it drop with gravity. David Szondy, whats the real reason?
I find this interesting. Is the capacity of the C-5 that much greater than the other tankers? How much more fuel can it carry? Of course the C-5 cannot refuel other aircraft in the normal fashion, because it doesn't have a refueling boom, but is it worth it to take a C-5 out of regular service for this? The same logic applies, unless the larger fuel capacity of the C-5 makes a difference.

And Dan Linder, I know of only one reason for the fuel systems to be separate- back when the SR-71 was flying, The JP-7 it used was incompatible for regular jets.