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."
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:drafting... (Score:5, Informative)
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:Who's up first? (Score:2, Informative)
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:drafting... (Score:2, Informative)
Re:Commercial Aircraft Possibilities? (Score:4, Informative)
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.
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.
Re:Big, clumsy, fast and close (Score:2, Informative)
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 separation times in those situations, e.g., small plane landing after a large one.
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.
What's taking them so long? (Score:4, Informative)
They've been talking about doing this for years [economist.com].
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.