Birds Have Curved Trailing Edges, Why not planes?

[Kenny Sharp]

I've noticed that birds never fly "hands off". They are constantly changing the position and shape of their wings during flight.
Also, their wings change shape in a curved and compound fashion.

Has anyone attempted this with ailerons/flaps? That is, have a trailing edge that curves and has no gaps?

I'm not sure about the engineering that goes into such a setup, but if it's possible, would it work better than current aileron/flap setups?

[Sparky Paul]

NASA has an F-111 modified with a "Mission Adaptive Wing", which morphs inflight to whatever camber is needed.
Birds have better wetware than anyone has software, for the same thing.
http://www.dfrc.nasa.gov/Gallery/Graphics/F-111AFTI-MAW/index.html

[vintage1]

I've noticed that birds never fly "hands off". They are constantly changing the position and shape of their wings during flight.
Also, their wings change shape in a curved and compound fashion.

Has anyone attempted this with ailerons/flaps? That is, have a trailing edge that curves and has no gaps?

I'm not sure about the engineering that goes into such a setup, but if it's possible, would it work better than current aileron/flap setups?

soaring birds don't move their wings much at all. They have a bit of wing warp for ailerons, but thats it.

Any lack of straightness in the wing is more to do with the necessity of folding them, than aerodynamics, one suspects.

All birds are not equal either - each has evolved the flight for a particular purpose..for e.g. a pheasant, it is really only a last ditch escape mechanism. They prefer to stay on the ground. Chickens don't even get OFF the ground by and large. Penguins swim, and ostriches run.

Woodland bids compromise wing span in order to fly in crowded places..humming birds compromise duration for vertical performance..and so on.

Do not take birds as the best model for what you are trying to achieve, unless it e.g. is to be able to slop soar waves and then become a temporary submarine.

[HELModels]

I've noticed that birds never fly "hands off". They are constantly changing the position and shape of their wings during flight.
Also, their wings change shape in a curved and compound fashion.

Has anyone attempted this with ailerons/flaps? That is, have a trailing edge that curves and has no gaps?

I'm not sure about the engineering that goes into such a setup, but if it's possible, would it work better than current aileron/flap setups?

Besides liking the mobility diapers provide, NASA does like the way Eagles fly. I dont have the link, but a search on Animal Planet for "Tilly" the Golden Eagle has lots of video of how eagles manipulate wing and tail. They researched it with a 2.4GHz camera for NASA, who I suspect is interested in using Electroactive Polymers(EAP) to twist and bend wings.

[Ollie]

Here in FL, the black vultures fly all year around. Even they fly with molt season. Some of the vultures loose feathers from wings and you can see gaps in wing outline trailing edge.

Soaring birds have wing tip feathers twist to open gaps at slow airspeed and close the gaps with flying at higher speeds. The wing tip feathers control roll response much like ailerons.
See:
Turkey Vulture model plan
http://www.rcstore.com/rs/general/listproducts5.asp?catid=32&catego=PL
RAVEN II and 1160A RAVEN 11 plans by Robert G. Hoey.
http://www.rcmmagazine.com/store/store-plans-catalog-tem.html?item=plans:pl-1160&sid=0001rEoIErMQS5kgss9e4Q6
http://www.rcmmagazine.com/store/store-plans-catalog-tem.html?item=plans:pl-1160a&sid=0001rEoIErMQS5kgss5h4J4

[Majortomski]

The first airplane used wing warping, solid (well, flexible) trailing edges distorted to control roll.

[BMatthews]

Wing warping.... The ones I can remember off the top of my head.

Wright flyer, Burgess-Dunne flying bi-wing, Fokker Eindecker, Morane-Sualnier parasol and mid wing monoplanes, many of the various Taube's built by german companies, REX Gordon Bennet racer. I'm sure there were a lot more.

What you're asking is far more comprehensive than just wing warping though. The closest we have is on modern jet fighters where the LEslats, rear wing surfaces and other surfaces are all moving to adapt the wing and other surfaces to achieve the requested change in lift. For example the F18 during a simple pulling back on the stick droops the LE nose, droops both flaps and ailerons, deflects the elevators (well DUH!) and even cants the rudders inward slightly to reduce the drag of the angled vertical surfaces.

I guess that the big question is how much would the drag be reduced, if any, by moving to a flexible camber change as opposed to a camber change at a hard hinge line.

[vintage1]

I guess that the big question is how much would the drag be reduced, if any, by moving to a flexible camber change as opposed to a camber change at a hard hinge line.

Hard hinge line? have you SEEN a big jumbo land..huge sections of wing move outwards and downwards..its not one hard hinge line, its about three..the wing area increases, and the root camber is massively changed.

However the point is not efficiency - its to get the landing speed to something sane, and to slow the plane, Extra drag is a definite plus.

[yoyoML]

Besides liking the mobility diapers provide, NASA does like the way Eagles fly. I dont have the link, but a search on Animal Planet for "Tilly" the Golden Eagle has lots of video of how eagles manipulate wing and tail. They researched it with a 2.4GHz camera for NASA, who I suspect is interested in using Electroactive Polymers(EAP) to twist and bend wings.

I remember very clearly seeing a film (IMAX :D ) of a flying eagle. It tilted the tail feathers to one side (so they're not horizontal) when turning. With wings that both soar and dive at high speed, these are awesome animals.

So why don't birds need vertical stabs? Do they control yaw by differential drag?

[BMatthews]

Vintage, I've often enjoyed sitting at the wing trailing edge when flying so I can watch that show. On some planes the wing seems to open up to an alarming degree. If I didn't know what was going on I'd be screaming for a parachute and running for the exit... :D

[HELModels]

I remember very clearly seeing a film (IMAX :D ) of a flying eagle. It tilted the tail feathers to one side (so they're not horizontal) when turning. With wings that both soar and dive at high speed, these are awesome animals.

So why don't birds need vertical stabs? Do they control yaw by differential drag?

I think they use whatever their brains say will work in that situation. They can twist their tails to look almost vertical with some bias toward the useful direction. They can pull in one wing to reduce lift on that side. They can flex their wingtips to provide just a little tweak as needed. They are aeroelastic. This is where they have an advantage over most human designed stuff, they are flexible and have direct feedback which they understand intuitively. They can adapt to the chaos of their surroundings, the air. They dont need to break things down into equations, that is for certain types of humans. They are like an athlete, who can adjust a swing or footwork in infinite ways to accomplish a task according to constantly changing circumstances. The athlete doesnt consider the equation, only the movement. In the case of soaring birds, they learn to adjust to the airflow around them so as to maximize efficiency of flight, depending on the task. Do they want speed or duration or maneuverability. Whatever it is they can twitch a muscle and get it done because they have built the neural interconnections necessary, using their sensory inputs. From fledgling booted from the nest, they are rewiring the neural connections, constantly learning how to maximize the flight task at hand.

I would bet that the neural pathways of a young soaring bird are not as dense and complex as a mature bird, just like humans.

[Ollie]

"Do they control yaw by differential drag?"

The eagle's tail twists along the direction of flight. So the tail's lift vector has an horizontal component. The eagle uses its tail lift more than drag to control both yaw and pitch, in my opinion.

[Brandano]

The main issue in adopting an idea rather than another is if it's worth it or not. Also, i have never seen a bird break the sound barrier or fly in the stratosphere.

[Sparky Paul]

The main issue in adopting an idea rather than another is if it's worth it or not. Also, i have never seen a bird break the sound barrier or fly in the stratosphere.
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But neither do our models. Our models fly in the same environment the birds do.

[Kenny Sharp]

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But neither do our models. Our models fly in the same environment the birds do.
I was thinking the same thing.

Thanks for all the input on this subject.
I was thinking about it the other day, and decided it was worth a check here.

It also seems to me, to be a lot more difficult to achieve, than it is to imagine.
Perhaps the answer is a combination of software and engineering, that is simply too much for a small model. It's as if the only solution is to imput a control movement, and allow the software to determine the proper reaction from the surfaces.

After a moment of thought, this sounds exactly like the method that birds use. The difference being the software, as opposed to the neural network.

[vintage1]

.
But neither do our models. Our models fly in the same environment the birds do.

I agree I could so with something that would enable my model to perch on a branch, and then launch itself out gain.

And I guess the ability to do a 30 second flight from one tree to the next might be useful too.

But I don't fancy hunting voles at dusk with an RC plane, or sipping nectar out of tropical flowers..or even picking worms out of trees and grass..

You miss the point. Most birds don't really FLY. They merely use the air as a means to get from one bit of ground to another, or one branch to another.

The ones that DO really FLY look very similar to planes..seagulls, eagles and the like.

[Kenny Sharp]

I agree I could so with something that would enable my model to perch on a branch, and then launch itself out gain.

And I guess the ability to do a 30 second flight from one tree to the next might be useful too.

But I don't fancy hunting voles at dusk with an RC plane, or sipping nectar out of tropical flowers..or even picking worms out of trees and grass..

You miss the point. Most birds don't really FLY. They merely use the air as a means to get from one bit of ground to another, or one branch to another.

The ones that DO really FLY look very similar to planes..seagulls, eagles and the like.

Interesting and acurate take on things I would say.

[vintage1]

I did an evening class in ornithology once. Birds spend their lives doing one of three things.

Having eggs
Eating
Running away from big things with teeth.

Flight is just a way of doing all that a bit more successfully.

[HELModels]

For long distance soarers, the ability to fly efficiently is a survival skill. There is some kind of phaeton or frigate bird which will fly for a thousand miles for 1 specialized meal and then fly back to feed the young. That requires more than just an instinct to fly. A bird like that needs to read air and conserve energy.

[Ollie]

See:
http://www.wfu.edu/biology/albatross/atwork/dynamic_soaring.htm

[Kenny Sharp]

Nice link Ollie.

[HELModels]

I confused frigates with albatrosses, which belong to different orders but have a similar lifestyle. Using satellite tracking, researchers verify my comment of 1,000 mile + foraging trips. Here is a link:

http://www.naturalhistorymag.com/1004/1004_feature.html

[Ralph Walton]

Some good info on bird flight

http://animal.discovery.com/convergence/spyonthewild/birdtech/birdtech.html

[nmasters]

See:

http://forums.hattiesburg.craigslist.org/?act=Q&ID=54073194

And:

http://www.birdforum.net/printthread.php?t=10539

[Brandano]

This also could be "slightly" related: http://members.tripod.com/~diomedes/exulans/

[natoquick]

Back to the original question, the upcoming Boeing 787 has variable camber trailing edge flaps, where they can go both down (like normal) and UP (only up to about 1.5 degrees), plus the spoilers can "droop" if the TE flaps are deployed down slightly. All of these tricks are to improve cruise efficiency. I'm not terribly clear on the "how" and "why" (I'm in propulsion, not aerodynamics), but it's pretty neat how some small changes in the wing affect performance.

Not quite like what a bird does, but all the changes are done without any input from the pilots.

[rebell]

Flight is just a way of doing all that a bit more successfully.

That is true for most humans using planes for transport as well. And true for maybe the most birds.

But, I saw a lot of birds that fly because they really enjoy it, doing aerobatics, just flying around without purpose etc. Crows is doing aerobatics, sometimes alone, sometimes with others. Pigeons is flying in circles for exercise or whatever reason they have, doves just flying around to come and sit on the same spot again, etc. In Africa there is a lot of other birds that I believe love to fly and don’t only fly because they need to.

[MCarlton]

But, I saw a lot of birds that fly because they really enjoy it, doing aerobatics, just flying around without purpose etc.

Thats true enough, but, as v1 said, birds took to the air as an evolutionary adaptation to exploit ecological niches (such as airbourne prey), to escape land based predators, to exploit altitude as a display platform for attracting mates and defending territory etc etc. Yes, there seem to be birds who actively enjoy flying, but that isn't the reason for their flight capability, those skills employed in "play" are tested all the time, for example, landing in high winds, evading predation etc. Crows and Seagulls, which seem to enjoy aerobatics, need those skills in order to evade others of their own or other species which engage in aerial piracy to "mug" the bird of its food or nesting materials, pigeons etc, which seem to fly in a circle for no reason then return, are engaging in searching for food and also, the natural instinct to escape predation, which, in many cases, involves not sitting in the same place for too long!

The efficiency of bird wings is not as high as people think, if, pardon my brutality, you took a stuffed seagull and equipped it with rc gear driving normal control surfaces, you would have a pretty poor model. The efficiency comes from the fact that a bird has a very fast computer, a built in 3D propulsion system and a set of sensory equipment to detect air currents, thermals and turbulence that we cannot easily replicate.

Adaptive and flexible wing structures are not really an efficiency driven device, it is simply a means of reducing weight and fragility. Were birds to employ "hinged" surfaces, then their wings would become impossible to fold, impossible to flap etc. Remember that feathers are scales evolutionary adapted for purpose.

Birds do what they do as well as they need to.