88

It's for wing bending relief (for cantilevered wings). As the generated lift bends the wings upward, the weight of the fuel will counter that. As the plane loses weight in-flight due to burning fuel, so does the need for wing bending relief (less weight → less lift), that's why the wing tanks are the last to be used. For context, a Boeing 777-200ER can ...


55

Fuel Quantity Unlike smaller fighter jets, you would need to offload a substantial quantity of fuel. For a B777, you're looking in the range of 60 tonnes of fuel for half a tank. The boom of a KC-135 (faster than a basket) can do around 3 tonnes a minute. The math comes to then 20 minutes of aerial refuelling. The KC-46 can do perhaps 180 tonnes, so you ...


48

Having all the payload of a plane concentrated at the fuselage creates a large bending load on the wings in order to support that weight. Storing fuel in the wings allows some of that weight to be placed at the same place where it's being supported, in the wings. Distributing the weight into the wings reduces the loads where the wings meet the fuselage.


46

Ex US Navy pilot here. I flew the S-3 Viking, which refueled via the probe/drogue method, as opposed to the USAF flying boom method. I can confirm that the receiving plane is below the wake turbulence of the tanker, maybe by 8–10 feet. Although, even if you should ride up into the wake, the sensation is perhaps not as violent as you might think....


39

Don't look at the fuel consumption of the airline flight in isolation. An airline would need to combine the fuel used by both the revenue-earning flight and the tanker, and then add the cost of operating it, too. Even if this could be shared by four or five revenue-earning flights, the total would still be worse. To find out how big the fuel saving by in-...


33

That photograph distorts the perspective. Just Google for "helicopter air-to-air refueling" and look at the image results. Many show other perspectives from which you can see that it is not possible for the blades to contact the hose or basket - the probe is longer than those on a fixed-wing craft for exactly that reason. This video shows a CH-53E Super ...


32

According to the Washington Post, Air Force One never refueled in mid-air with the president on board. If it needs to refuel, it usually does so at one of the U.S. military bases across the world. The retrofitted Boeing 747 that usually serves as the presidential jet can indeed refuel in flight — but it has never done so with the president on board, ...


30

In some contexts, the economics depends on how special the aircraft you're refueling is. Consider something like an AWACS mission. You have this very complex specialized aircraft, with a large, highly trained, crew in addition to the flight crew. If you didn't refuel that during the mission, it might need to spend a lot of its active hours being ...


28

Since the 1960's and 1970's when political hijackings were a problem, airplanes started to only carry the fuel required for the flight. This means a typical fuel load will be something on the order of: taxi fuel at the departure airport fuel to fly and land at the destination at a given altitude and forecast winds if an alternate is needed: fuel to fly to ...


26

Former B-52 crewdog here...The receiver aircraft flies below the wake turbulence of the tanker. In the case of the typical USAF method, using the boom, the receiver aircraft flies into a "contact" position and holds there. The boom operator (boomer) then "flies" to boom to the correct final position, then extends the nozzle into the refueling receptacle, ...


26

It depends on a number of factors like: the aircraft size and variant the range required the aircraft load equipment available Ground crew proficiency ...among others things. This figure from the 737 Airport Planning document gives 9 minutes for the fueling time for a Boeing 737-600: Image from B737 Airplane characteristics for Airport Planning The ...


25

First to the issue of cost-effectiveness: If fighter or strike aircraft would need to take more fuel with them, they would have to be larger and more fuel-hungry themselves. This is hard to quantify, but with air refuelling you can cap the size at a much smaller value and still be sure that all future range and endurance requirements can be met. Next, ...


23

I can't confirm whether either VC-25 has refueled in flight while acting as AF1 but the aircraft is so equipped for the job. I do know refueling on the ground depends on where the jet is and the quantity and quality of fuel available onsite. The USAF insists on using fuel that it supplies for security reasons. For operations in Western Europe the fuel is ...


22

It's not a question of saving money, or emergencies. The reason militaries use mid-air refueling is so they can reach anywhere in the world. Aircraft have a limited range, without mid-air refueling they would have to have enough fuel to get to and from their area of operations back to a base. This would limit where military aircraft (or espionage aircraft) ...


22

The flying boom method uses a rigid boom which is "flown" by an operator in coordination with the pilot in order to make a connection with a receptacle on the second aircraft. The boom is retracted when not in use. Though it can do damage if it comes in contact with an aircraft, the operator can quickly move the boom if needed. The probe and drogue method ...


19

It would chop it right off. Watch the video. It's fun. When the helicopter pitches up right after refueling, the rotor disc cannot follow the movement (its hinges allow the blades to pitch up and down, and inertia makes it change its plane of rotation only slowly). The refueling probe is cut cleanly in half. However, I would not try this on purpose. The ...


17

Large airplanes are pressure refuelled so vapor escaping through the fuel port is not an issue as it is in smaller airplanes. You are correct, however, that the fuel/air mixture existing in the tank will be displaced by the incoming fuel. The wings will have vents installed that will allow the air mixture in the tank to escape (and fuel in the case of over ...


16

Cost effective? Look up the Black Bucks raids, then work out how much that refuelling cost.... Then compare that to the cost to the UK of losing the Falklands Islands. Those raids were absolutely not possible without midair refuelling. Similarly Cold War patrols and reconnaissance missions. It's not about whether it's cost effective, it's about whether the ...


16

As I said in my comment, I don't think there's any single answer to this question because there are just too many variables and the scenario itself seems a little artificial. But, the first thing you can do is negotiate with ATC. Accept the descent instruction but request a return to FL250 as soon as possible. Offer to fly at another altitude (including ...


15

At airport with a standalone self-serve facility, it's a Self Serve Fuel(ing) Station. If it's a business selling fuel in addition to other services, that is a Fixed Base Operator, or FBO.


14

Both the KC-135 and KC-10 can burn the fuel it carries on board for refueling (the notable exception was the KC-135Q, which carried separate tanks of JP-7 for the SR-71 Blackbird). Both indeed do have significant fuselage tanks - the KC-10 is notable for being 'dual-mission' capable, meaning it can carry both fuel and cargo, and the KC-10 is also air-...


14

It depends on how many equipment are being used to refuel and how much fuel an aircraft needs. But in general there are some ratings which manufacturers issue for handling and ground time. For example, a B747-8 has (according to 747-8 Airplane Characteristics for Airport Planning): maximum usable fuel capacity of about 59,734 U.S. gallons or 226,113 liters ...


14

The boom operator (or boomer) can freely move around the aircraft. The boom operator position is usually accessible from the cargo hold and the operator can use the opening to move from his/her position. This is especially important for the KC-135 Stratotanker, which has the boom operator working in a prone position. Image from sobchak.files.wordpress.com ...


12

On the first flight of the day, after every refueling, and if you have flown through precipitation or the plane is left in the rain, you check the fuel for water and to make sure you have the right kind of fuel. Since water is heavier than fuel, if there is just a little bit of water in the fuel it could cause the engine to stop. You can’t pull over to the ...


12

On cars I think it's because static charges don't build up as much but theoretically it's still possible for a spark to occur when the nozzle touches the tank inlet and provides a ground path. On airplanes there are two issues: Static charges built up in the airframe in flight. For this it is essential to ground the aircraft before the fuel nozzle is ...


12

On a small GA airfield we just refer to them as "The pumps". As in my typical radio conversation goes like this [Airfield] [service], G-ABCD request taxi to pumps.


11

The stall speed is around 95-100 knots for the older F variant, and something like 90-95 knots for the newer J variants. A KC-130 can refuel between around 100 and 270 knots. The lower end of this is well within the maximum speed of many military helicopters, eg the Pave Hawk, Black Hawk, Chinoook or Sea Stallion. That leaves an "overlap" of around 20-40 ...


11

With a pressure fueling system, rather than fueling through holes in the tops of the wings, a fuel truck or fuel hydrant is used to push fuel into the airplane through a fitting at about 50 psi. The fuel fitting is generally in the right wing. A fueling control panel allows the fueler to fill the tanks to the amount called out by the flight plan. These ...


11

Tankering fuel means that an aircraft carries more fuel than required for the flight to the destination, because difference in fuel price at airports makes this operation less expensive than natural refueling at destination. Wikipedia: Tankering fuel When fuel prices differ between airports, it might be worth putting in more fuel where it is cheap,...


11

Refueling with passengers onboard is quite normal and is done according to the recommendations of regulatory bodies/manufacturers and operators. Refueling with some fuel types are not permitted, while others are. From Airbus Flight Operations Briefing notes: Refueling with wide cut gasoline type fuel (JET B, JP4 or equivalent) or when a ...


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