Air Force Lab Test Out "Aircraft Surfing" Technique To Save Fuel 205
coondoggie writes "It's not a totally new concept, but the Air Force is testing the idea of flying gas-guzzling cargo aircraft inline allowing the trailing aircraft to utilize the cyclonic energy coming off the lead plane — a concept known as vortex surfing — over long distances to save large amounts of fuel. According to an Air force release, a series of recent test flights involving two aircraft at a time, let the trailing aircraft surf the vortex of the lead aircraft, positioning itself in the updraft to get additional lift without burning extra fuel."
Who's up first? (Score:2)
What about the lead aircraft? Does he run out of gas first and crash and burn, leaving a new lead to continue the cycle?
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Just because the lead craft doesn't get to save gas, doesn't mean there is not a net gas savings for the entire system.
Re:Who's up first? (Score:4, Funny)
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Birds in formation do that periodically.
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You can switch lead on-the-fly.
Re:Who's up first? (Score:4, Interesting)
Actually, in most examples of drafting, the benefit extends to the leader as well, reducing the tail drag associated with a solo player. As I recall, the benefit generally increases as you add cars to the train as the lead drag and tail drag are spread over more units.
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Given the distance involved (200 feet or so) I doubt that effect will be present in aircraft "vortex surfing". I think the physics involved are quite a bit different from drafting in a car, but that is really just a guess.
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Re:Who's up first? (Score:5, Insightful)
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Of course it is drafting. It relies on mitigating the detrimental vortex effects associated with moving object terminations in a fluid environment by spreading the wasted energy over a longer object. Same as the efficiencies of longer boats in water, and longer props, whether on planes or windmills. No different in concept.
Re:Who's up first? (Score:5, Informative)
If you feel it is drafting, please state the definition of drafting you are using, as I've not seen a definition of drafting that would include this.
It does not depend on mitigating detrimental vorticies. NASCAR drafting does, and the lead car gets the benefit from the reduced drag. This does not benefit the vehicle in the front and is the following car using a predicted vortex to its advantage, while traveling through otherwise undisturbed air. Thus "drafting" where the folower uses the lead car to "break the air" is not happening.
Rather than having to define "drafting" to a bunch of morons who are too stupid/lazzy to google, I'd rather discuss the efffect of this on commercial aircraft for the rest of us, flight lanes with airplane flocks saving fuel. Or discussions on how much the winglets affect this effect. But no, it's all a discussion of the definition of "drafting" with a bunch of google-illiterite people.
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The definition does not include acts outside the slipstream. But then they do include acts outside the slipstream later, as you note. The definition in Wikipedia agrees with me that you are wrong, but the examples of that definition do not agree with
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Secondly, the lead would likely swap periodically, as birds have done for thousands of years.
But isn't that because birds get tired? Planes don't get tired - the lead plane will just burn more fuel than the rest, but as long as it's got enough for the trip, why does it need to swap out?
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But isn't that because birds get tired? Planes don't get tired - the lead plane will just burn more fuel than the rest, but as long as it's got enough for the trip, why does it need to swap out?
Migratory birds like geese have insane flight muscles, composed almost entirely of red muscle, and they are not really susceptible to muscle fatigue. The main limitation for them is fuel.
So the reason planes would want to swap leaders is more or less the same reasons as the birds do: To increase the range of all members of the formation.
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combat formation flying during WWII was about far more than making impressive shadows to scare the enemy. Bomber crews learned fairly quickly that wingtip drafting extended the range of every bomber in the squadron - albeit only by about 1-2%, but this was enough to afford the pilots some wriggle room during cannon fights. The lead was by relay: the lead bomber would peel up about 100 feet and throttle back to the rear, the new lead taking the next thirty or forty miles.
source: a distant relative was a wais
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as long as it's got enough for the trip, why does it need to swap out?
To share. You should always be fuel limited (even if that includes a buffer/reserve). So if you have a fixed maximum, then using less increases range. So you extend the range of two airplanes if they swap out. If they don't swap, then the range is limited to the range of the one with the lowest range (the front one). Like birds, swapping with planes extends the range of the flock.
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Bah, slip of the mouse and modded this redundant... Bye bye, wasted mod points, you had such a short and not so fruitful life...
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You could have them change off every so often, so none are in the lead for the full time. But that's really only if you're doing this to extend your range. If your concern is mainly decreasing costs, you would just fly them like this, but within the range of a solo aircraft. You would probably even fuel up each craft with enough fuel to handle it solo, just in case something happens.
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Put more fuel or less cargo in the lead aircraft.
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True, but say the maximum capacity for the plane is 5. You can now fly for 6 units worth of distance with only 5 units of capacity. And, 10 is still better than 12.
If you can't figure out how to make 11 the best, you haven't worked hard enough.
Commercial Aircraft Possibilities? (Score:2)
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Companies operating commercial aircraft have different regulations about how they fly vs the military.
If this were ever used commercially, I don't think it would be allowed with passenger aircraft, just cargo. The risk is just too damn high for so little reward.
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The risk is just too damn high for so little reward
That depends on the cost of fuel vs lawsuit
Re:Commercial Aircraft Possibilities? (Score:4, Informative)
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That was made so independent planes don't crash in to each other. In theory planes flying in this formation will be working in concert and may have computer/radar control over each other. It's likely a whole new set of rules would need to be drafted for this kind of operation. Honestly it makes the most sense for cargo planes flying over the open ocean to use a system like this. They stand to get the biggest gains, and present the least amount of danger to others that way.
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Big, clumsy, fast and close (Score:4, Interesting)
Re:Big, clumsy, fast and close (Score:5, Funny)
I think you are attending the wrong dance clubs ...
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Very close formation flying has been standard training and practice since aerial refuelling was adopted.
Maintain your altitude and distance or you force disconnect, or even get a boom through your canopy and die.
http://en.wikipedia.org/wiki/Aerial_refueling [wikipedia.org]
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When I read about the F/A-18 probing the airspace behind a DC-8 I thought the F/A-18 pilot had to have big brass ones.
Back in the 70's there was a story in the San Diego Union about a private airplane that got flipped on its back as it was approaching Lindbergh Field in San Diego. The flip happened too close to the ground and the occupants were killed. The flight controllers had allowed the private plane to come in too soon after a large commercial jet had landed. The accident led to a doubling of separat
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Happened again in 1993 in Orange County; a private jet for In-N-Out burgers crashed on approach to John Wayne, killing their top 2 executives, a consultant, and both pilots. A 757 was ahead of them.
https://www.google.com/search?q=in-n-out+plane+crash+john+wayne [google.com]
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Apparently 757's are known to create severe turbulence, but they In-N-Out pilots were not told the plane ahead of them was a 757.
http://articles.latimes.com/1994-01-22/news/mn-14297_1_wake-turbulence-warnings [latimes.com]
Now Hiring: Cyclists (Score:2)
In order to expand our pool of aeronautic expertise, the USAF is offering research positions to those with experience at bicycling long distances. ...Or something like that.
Mythbusters (Score:5, Interesting)
I'm in I'll engage! (Score:5, Funny)
The Airlines should take notice. (Score:4, Interesting)
The Airlines should take notice.
Judging by the formations of geese and pelicans I've watched flying by in large groups, I have to assume this effect can be carried from one flyer to the next in a chain and isn't confined to just two flyers. The next question would be "Do all trailing flyers receive this 10% fuel savings, or is there some sort of diminishing return at play?"
If all of the flyers receive the savings, then the airlines might find that sending a small squadron of aircraft, say five DC-10 sized aircraft in formation as opposed to one large "super-liner", is economically beneficial both in terms of lower costs AND lower CO2 emissions. It would also relieve a common problem with current flight scheduling--empty seats. If the "flight" (I'm referring to the squadron idea) did not sell all the seats, they could simply send one less plane--it allows for options in balancing demand vs resource allocation, which would, I assume, allow the airlines to lower costs across the board including ticket prices. It would also allow the airlines to scale specific routes based on demand more accurately--if there is a sudden surge in demand on specific route, they simply increase the squadron size as required.
There is the added benefit of "diluting" the severity in repercussions as a result of mechanical failures/human error--when a super-liner suffers catastrophic failure, everyone dies. In a squadron of planes, a failure on one craft wouldn't mean the death of everyone. Not putting one's eggs in one basket has it's benefits.
Wait a Minute (Score:4, Interesting)
What's taking them so long? (Score:4, Informative)
They've been talking about doing this for years [economist.com].
Risk? (Score:3)
I remember an airplane crash near Pittsburgh in the early 1990s, when a plane got too close to another plane and got caught in the wake, causing the plane to plunge.
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Flight 427 was actually the result of a faulty rudder ending up locked in an extreme position. The plane toppled over and plunged straight into the ground. Initial speculation was the wake of another pane as they had not discovered the rudder defect yet.
Mythbusters Did It! (Score:2)
Re:prior art (Score:5, Funny)
(They were actually sparrow scratches, but never mind that.)
Re:prior art (Score:5, Funny)
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Clearly, you have an eagle eye, to have spotted that.
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These jokes are real turkeys
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Depends on how the first to file/first to invent law gets interpreted once it goes into effect. Birds never filed AFAIK. (They found it "obvious.")
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Sorry, I was just making a joke. Didn't mean to step in your pet shit pile.
Apparently different than drafting... (Score:5, Informative)
Apparently things are a bit more complicated in the air...
Drafting helps by reducing air resistance (drag) and requires you to be really close, this technique is a bit more subtle in that it involves using trailing air vortices to get free "lift". The article had a handy link to explain this... http://www.av8n.com/fly/vortex.htm [av8n.com]
Of course I'm sure that someone will draw such an analogy in a pop-science article...
Re:Apparently different than drafting... (Score:5, Insightful)
OTOH, nature already provides a perfect example: Geese have been doing it for literal ages [wikipedia.org] and likely for the same reason (though instead of burning excess liquid fuel, it keeps them from being tired).
Re:Apparently different than drafting... (Score:4, Funny)
The Waterfowl Association will file suit for Patent violation and Trade Secret violations.
Re:Apparently different than drafting... (Score:5, Funny)
Re:Apparently different than drafting... (Score:5, Funny)
It will be tied into the aircrafts autopilot system, thus being done "with a computer" thus invalidating any prior art and qualifying for patent protection for that reason as well.
It'll be okay as long as the planes don't have rounded edges thus inciting apple's rage... oh wait... nevermind.
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Works for cars, bikes, motorcycles, swimmers, why not planes?
Turbulence due to the plane and it's engines. At least that is what I would assume to be a problem with drafting in the air.
It's not like this works for boats.
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It does work for boats. You can surf the stern wake.
But you need to get fairly close, and control your speed carefully. Not worth the effort.
Swimming (Score:2, Funny)
It also works for swimming. Swimmers do it, dolphins do it...even educated, bees, oh never mind.
Re:drafting... (Score:4, Interesting)
Not really true - I do it occasionally in my 19" skiff in heavy water - I'll tail a bigger fishing boat like a 60 -70' seiner. He's bouncing around at 10 - 15 knots and not having a care in the world. In such seas, I would be limited to 7-8 knots and the boat (and my back) would be getting clobbered. I sit about 100 feet back in the wake and as long as the wind isn't blowing so that I have inhale his diesels, it saves fuel, my back and gives me a speed boost.
The nice thing about water is you can see the wake 'vortex', no additional software required.
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Works for cars, bikes, motorcycles, swimmers, why not planes?
Turbulence due to the plane and it's engines. At least that is what I would assume to be a problem with drafting in the air.
I've talked to some pilots and they call it jet wash. The larger the plane the more severe it is. When I fly I occasionally listen to the air traffic control chatter. Larger planes like 747, 757, 767, 777, etc are always referred to as "heavy" after their call sign. It's to help ATC remember to keep the spacing a little further behind these planes due to more jet wash. At least that's what I've been told. I assume it's true as it makes sense.
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This is correct. Jet wash is basically the vortex effect in the air after the plane passes that is caused by drag. It causes extreme turbulence and is dangerous enough for large aircraft to have mandated spacing on take off or land from the same runway. For example, one of the issues with A380 has been that it's so big, that they had to increase the biggest "slot" allocated for take off and landing due to jet wash caused by it.
Actually it's called "wake turbulence"... (Score:5, Interesting)
...not jetwash. Jetwash is the turbulent stream of air behind a jet coming from out of the back of the engines. That is mostly dangerous while on the ground, when there is a small, light aircraft sitting behind the jet.
Wake Turbulence comes off the wingtips of *all* airplanes in flight, while the wing is generating lift. It's like horizontal tornadoes spinning off the wingtips. It can flip another airplane upside down Lots of pictures of what it looks like here [google.com].
I almost got rolled 90 degrees on short final while landing at EAA Airventure in Oshkosh, WI a few years ago landing behind a P-51 Mustang. I was in a Van's RV-8, which fortunately is very aerobatic and has a quick roll rate. It took full right stick to get the aircraft rightside up again and the whole event was over in a split second, and I landed normally. but with quite the adrenalin dump flowing in my bloodstream, and almost experienced a brown smelly dump flowing in my pants! As soon as I touched down, the tower controller said, "Nice job RV.... Uh, sorry bout that..... (sheepishly) Uh, caution wake turbulence?"
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. Lots of pictures of what it looks like here [google.com].
Nevermind.
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A friend of mine (now sadly deceased - in a recent plane crash unfortunately) was working as an air taxi operator in the 1960s. IIRC he was ferrying airline pilots in an Aztec - and in these days wake turbulence was not well understood. On final approach the wake of an airliner rolled him inverted, he had no option but to continue the roll because to reverse direction would have taken too long - fortunately he had aerobatic experience. He landed shortly afterwards with three very ashen airline pilots.
Aircra
Re:drafting... (Score:5, Informative)
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Re:drafting... (Score:4, Informative)
This is "drafting" like a skateboarder holding on to the back of a bus in city traffic is "drafting." There is a benefit, but it is not from reducing air resistance.
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yep, they have to stay within the vortex cone. There's a dead zone right through the middle of this, and if they can keep their nose in it (like literally follow right behind the wingtip) then they'll benefit on both wings. Too far left or right and they'll roll, too low they'll get downdrafted, too high and they'll skip and possibly stall. Two smaller aircraft could follow one larger one, one in each vortex, or one larger aircraft could pick either vortex (or even both if it's big enough). Oh, and as autop
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It always blows my mind seeing geese flying in such perfect V formations as they migrate in the spring and fall. I can't help but wonder if this is some sort of instinct that is pre-programmed into their brains, or if they can actually feel the difference and thus simply do whatever is easiest, or if there is some other aspect (maybe visual or even social?) that prompts the behavior and it just so happens that it is also more efficient.
Re:drafting... (Score:5, Funny)
I think it is learned behaviour of not flying in the poop-stream of the bird directly in front of you.
Re:drafting... (Score:4, Interesting)
But there are other kinds of flocking behavior: think of starlings, who make those big, pulsating clouds that are so mezmerizing to watch. I don't know if those are for feeding or protection or what, but they're certainly not optimized for distance as geese are. Maybe those are the descendants of the birds that couldn't stick to the formation and stopped their migrations in different places, met like-minded fowl and created their own flocking legacy.
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Re:drafting... (Score:5, Informative)
But I'm surprised someone didn't patent it and charge the military for doing it.
The innovation isn't in the concept of "drafting" another plane. The innovation is in the autopilot system that does it safely and automatically. As shown on Mythbusters the concept is viable, but a human is not capable of keeping the plane in the "sweet spot" safely for an extended period of time.
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mid air refuelling.
That is all.
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I believe the federal government exempts itself from patent law anyway.
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I believe the federal government exempts itself from patent law anyway.
Nope.
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If an aircraft were drafting, they would been to spend more fuel because the lower pressure provides less lift. Since they can't counter than by going faster (smashing in to the plane they are following) they would need to increase their own lift, which produces more drag.
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I have done this many times in sailplanes. You have two positions: high and low tow. Both are outside the wake of the tug. This waveriding trick must be inside the wake so I reckon it would be a bumpy ride.
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Next on FOX:
"Perpetual Motion Machines... IN THE AIR!!!11"
Re:NASCAR (Score:5, Informative)
Drafting is also used in racing leagues that turn right and have drivers and fans educated enough to read.
Re:NASCAR (Score:5, Funny)
racing leagues that turn right and have drivers and fans educated enough to read.
Q) What has two hundred legs and twelve teeth?
A) The front row at a Willie Nelson concert.
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oyfg, to have mod points!
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A. Anyone else would have called it a teethbrush
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Well yeah, and it's been known for a long time they do this to save energy for those behind the leader, and that they trade off leaders from time to time.
Sometimes it takes a while for something in one discipline to reach another (I'm guessing ornithologists and military aerospace engineers probably don't rub elbows too often, but what do I know), and it's not always obvious that an idea in one area would apply to another (geese and airplanes are in fact different).
Still, I can't help but scratch my head th
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If you recall the movie Top Gun from 20+ years ago, getting caught in the jet wash of another plane was something that happened twice at pivota
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Because it costs a shit-ton of energy to get up to that high altitude. Much more than just going directly from point A to point B.
Re:Fuel Saving (Score:4, Informative)
Half right. It does take a lot of energy to climb, but you regain most of that on descent making it approx 0 net change. However, flying at high altitude reduces air density, and therefore, drag, resulting in a net fuel savings.
It's a bit more complicated still, propeller driven planes may lose some propeller efficiency in the thinner air. For any given plane, there is a limit on how high it can fly, and trade-offs in drag vs propulsion efficiency, lift vs weight, as well as design (pressure and operational temperature) limits. However, as a rule, the higher you can fly the plane (within it's design limits), the more fuel efficient the trip will be. Short flights may be constrained a bit because the optimal climb rate and optimal descent rates might limit the max height to less than what the optimal height the plane is capable of.
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Interesting, I didn't realize that the reduction in air density at height greatly offsets the cost to get there. I assumed it would be similar to how gunning it to 130 MPH in a car and then costing down to 55 will kill your fuel economy.
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Automation. Drafting isn't safe if you depend on your own reaction times and vigilance. But with automation, it should be safe for both cars and airplanes.
Besides, airplanes tend not to slam on their brakes like cars and trucks do.
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>
Besides, airplanes tend not to slam on their brakes like cars and trucks do.
No, but the sky is capable of doing scary shit...
http://en.wikipedia.org/wiki/Vertical_draft [wikipedia.org]
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The important things to remember, are
1) No matter how big your plane is, it's tiny in comparison to the air;
2) There is a mind-blowingly huge amount of energy in the atmosphere, especially around thunderstorms and changes in the land. It can be beneficial (see gliders and updrafts) or detrimental (low level wind shear & downdrafts), and you must pay constant attention to it.