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Old Dec 06, 2013, 08:35 AM
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aha ....

I finally figured out why the tips [and length] of Kiki's long tail feathers describe ovals when he is flying FAST and doing abrupt flight corrections:

since he steers by pushing harder with one wing -- and since like ALL birds his wing motion is this "aerowing" -- the long tail feathers are forced to oscillate in sympathy with
the harder-"rowing" wing!

I assume both aerodynamic [vortex] and mechanical induction for this phenominon. Further, as I have noticed this in videos of other birds with long tail-feathers, I might guess that this is also a kind of visual warning, etc., of such abrupt flight-direction change.

Or it could have no meaning, just what happens ....


Lee
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Old Dec 16, 2013, 06:27 AM
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The comments about Kiki interesting to me, having seen a budgie flying in company with a group of Swifts flying around houses at very high speed, and screaming with delight at the same time, actually looked to be faster than the swifts at some times; and they are QUICK! I suppose it had escaped from somewhere, wonder how it got on when Winter came.
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Old Dec 18, 2013, 07:11 AM
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Quote:
Originally Posted by macboffin View Post
The comments about Kiki interesting to me, having seen a budgie flying in company with a group of Swifts flying around houses at very high speed, and screaming with delight at the same time, actually looked to be faster than the swifts at some times; and they are QUICK! I suppose it had escaped from somewhere, wonder how it got on when Winter came.
There was, maybe still is, a large park outside Köln/D, I think, where "escaped" Budgies are brought. There were/are many Budgies and similar birds living wildly there. The environment in the Australian Outback, to which these birds are adapted, is extremely harsh: I was told if these former "house-birds" survive the first Gerrman winter outdoors, they can have a long life ....

Lee



P.S. Kiki has had many chances to "escape", and he likes adventure and flying, but he knows me like I was his flock, and thus important for his survival. And we ARE very good friends.
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Old Dec 22, 2013, 07:45 AM
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up in the air, Junior Birdman ...

.... up in the air, upside down



Kiki did an incomplete loop when we were videoing him piloting* his Flying Carpet [freeflight landings and longer tethered flights]. He did one complete circle inverted, re-balancing and re-stabilizing it to everyone's amazement, then recovered by half-looping upright again.

In the next days we found that he can easily keep it inverted and even do horizontal eights! But several times he has partially lost his grip and had to "flap" to get back in position. For his whole life he has been able to "flap" around a perching stick to make a 360° flip around the stick. But in the Flying Carpet case he was unusually redirecting his lift/thrust vector --- on ONE wing only, the "outside" one, to counter the centripetal force -- in a very not-normal but obviously functionally correct way.


So I must conclude that my [fullsize] helicopter rotor-blade analogy,. re: Aerowing [or whatever one wishes to call what birds actually do] is even more pertinent as I might have supposed.

And the birds figured out these complex movements quite a few years before Mr. Sikorsky.**


leaky
[Lee + Kiki]




*it is unstable and requires skills he'saquired with 2yrs. of hanggliding experience

**http://en.wikipedia.org/wiki/Igor_Sikorsky
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Old Dec 22, 2013, 07:48 AM
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and this cool video shows how much fwd & back movement is involved in "Aerowing" >

seagull round up Ornithopter style (4 min 37 sec)
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Old Dec 27, 2013, 04:52 AM
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kingly aerowing

Pied Kingfisher catching fish in split second - BBC wildlife (2 min 47 sec)
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Old Aug 22, 2014, 09:49 AM
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This is true. As an aside, birds and pterosaurs do power their upstroke (so do bats).
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Last edited by JimC3; Aug 22, 2014 at 10:49 AM.
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Old Aug 26, 2014, 02:59 AM
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yes, but .... ;-)

Quote:
Originally Posted by JimC3 View Post
This is true. As an aside, birds and pterosaurs do power their upstroke (so do bats).
Based on my albeit crude experiments and observations [incl. the observation that the rearward velocity of the wingtip on the up+backstroke approaches the fwd airspeed of gulls when I've carefully watched them "aerowing", an effect which is the same as when another type of reaction engine, rocket/jet, has maximum efficiency when the exhaust velocity is exactly equal to the fwd speed] .... while I can accept that birds don't ALWAYS let the relative airflow pull their wings up and back, and given that some muscle-power must be used to get the wing in the right position and attitude to be pulled up & back, I am pretty sure there is a significant amount of bird muscle-power not used to pull the wing up and back when and insofar as it wouldn't be necessary.

OK, my bird-friend Kiki is smart, but he is perhaps therefore lazy .... and I have never seen him consciously waste effort doing something [like all of us, he can make mistakes and have "missed approaches", etc.].

Lee
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Old Aug 26, 2014, 05:41 AM
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Birds and pterosaurs power their upstrokes quite differently, but in both cases, the upstroke muscle mass and alignments mean that less power is available for the upstroke even though they maximize the specific power available from the upstroke muscles by increasing the upstroke contraction rate (they do the upstroke in slightly less time than the downstroke). Typically, about 54% of the wing beat duration will be spent in the downstroke and 46% in the upstroke. Ratio is quite variable though.

Birds roll and turn by increasing the stroke amplitude on the outboard side of the turn. Typically they do not do so by differential pitch of the wings. I speculate that pterosaurs did the same.

I've seen a crow in cruise flight develop a cramp in his right wrist. He quit flapping on that side and shook it out just like a human would. Kept flapping on the left side. Did about a 3/4 roll and then reversed it back to level flight. A beautiful thing to watch.
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Old Aug 26, 2014, 07:36 AM
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Cool! I was delighted to watch Kiki regain his grip when flying his Flying Carpet inverted as I would occasionally "push the envelope" : he can use the outboard wing either rigidly or flapping to produce negative + centripetal lift/force [positive w.r.t. the Earth]. Crows don't like him: they can sense his intelligence and take that as a threat [most animals can "read" each other telepathically -- Boeing has been working on this for decades for thought pilot-control of aircraft; NOT pretty! -- and the only animal most birds can't read are cats, who attack movement, without give-away thought].

L
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Old Aug 26, 2014, 08:22 AM
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Wingtip locus with speed variation.
Pigeons and magpies
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Old Aug 26, 2014, 08:55 AM
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Nice. Fig 3, lower left, 12m/s looks kind of like what I see the local gulls here do. It may not be a perfect ellipse, but connecting dots is not perfect either ....

Anyway, we are all sort of on the same page, and it is important to try to observe and learn from nature and millions of years of trial, error and success.

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Old Aug 26, 2014, 09:34 AM
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There are often significant departures from ellipticity, and as you move inboard the pattern changes entirely. It is interesting to plot the locus of each joint in the wing so you can see how they vary.
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