The concept of flapping flight will eventually succeed!

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jedi

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Probably the most successful ornithotper I've heard of is Adalbert Schmid's, which used fixed wings for lift and a small pair of flapping wings for thrust. That is analogous to using legs to propel a wheeled car like Fred Flintstone :) It works, but you gain no functional advantage over any other kind of thruster.
I agree that the auxiliary wings for thrust is less than deal for an ornthopter but that is just what the propeller is except that it rotates rather than oscillates.

This concept of auxiliary flapping wings would be an improvement for most any motorglider. It eliminates the need to stow and unstow the propeller or the need to feather the prop for gliding. Best of all it is ready to immediately add energy with two or three quick flaps and quickly return to the gliding mode.
 

BBerson

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I think the problem of flapping is thrust (and lift) is less than half the cycle. A prop is 100% thrust with no cycle. Even a fish gets thrust on both strokes of the tail.
From wiki: “A team of engineers and researchers called "Fullwing" has created an ornithopter that has an average lift of over 8 pounds, an average thrust of 0.88 pounds, and a propulsive efficiency of 54%.[41] The wings were tested in a low-speed wind tunnel measuring the aerodynamic performance, showing that the higher the frequency of the wing beat, the higher the average thrust of the ornithopter.”

 

Dan Thomas

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Glad you ask.

This is just one reference. There are many good aero design books. Study stability and control. I hope this helps. Happy to explain further if you would like to talk. Otherwise this is too much back and forth typing for me so if you want print check the internet or a book. Diagrams work best. Easy to understand once you get the overall picture.

A quick google search gave the following.

Lift
Depending on the aircraft design and flight regime, its tailplane may create positive lift or negative lift (downforce). It is sometimes assumed that on a stable aircraft this will always be a net down force, but this is untrue.[2]

2. Burns, BRA (23 February 1985), "Canards: Design with Care", Flight International, pp. 19–21, It is a misconception that tailed aeroplanes always carry tailplane downloads. They usually do, with flaps down and at forward c.g. positions, but with flaps up at the c.g. aft, tail loads at high lift are frequently positive (up), although the tail's maximum lifting capability is rarely approached..p.19p.20p.21
That same article says this:

On some pioneer designs, such as the Bleriot XI, the centre of gravity was between the neutral point and the tailplane, which also provided positive lift. However this arrangement can be unstable and these designs often had severe handling issues. The requirements for stability were not understood until shortly before World War I - the era within which the British Bristol Scout light biplane was designed for civilian use, with an airfoiled lifting tail throughout its production run into the early World War I years and British military service from 1914-1916 — when it was realised that moving the centre of gravity further forwards allowed the use of a non-lifting tailplane in which the lift is nominally neither positive nor negative but zero, which leads to more stable behaviour.[3] Later examples of aircraft from World War I and onwards into the interwar years that had positive lift tailplanes include, chronologically, the Sopwith Camel, Charles Lindbergh's Spirit of St. Louis, the Gee Bee Model R Racer - all aircraft with a reputation for being difficult to fly, and the easier-to-fly Fleet Finch two-seat Canadian trainer biplane, itself possessing a flat-bottom airfoiled tailplane unit not unlike the earlier Bristol Scout. But with care a lifting tailplane can be made stable. An example is provided by the Bachem Ba 349 Natter VTOL rocket-powered interceptor, which had a lifting tail and was both stable and controllable in flight.[4]

It also goes on to mention lifting tails in some fighters, but those airplanes are flown by computers, with instructions from the pilot. No light airplane is legally designed that way, and the W&B information in the POH/AFM confirms that. There have been too many fresh commercial pilots who get their first job flying a Cessna 206, and the old guys tell them they can load it until the tail will barely come back up when they push it down to the ground. That gets to be a habit, and soon enough they add a bit more stuff because the boss says it has to go, and they get it off the ground and it is a constant fight to keep it from stalling. Let the nose up a bit and the CP movement accelerates it, so you have to push it down, and the CP movement tends to aggravate that, too.

I flew the prototype of a new bushplane design for a few minutes. Popular airplane, now. It came out tail-heavy due to the FAR 23 changes midway through the development process that demanded much stronger occupant seats, meaning much heavier seats, and with the seats all full it would not trim out nicely. It was hunting all the time. The CG was barely within limits, and it was no fun.

Ducks can do a lot of things that were are never likely to duplicate. They can get off the water short because of the vertical lift component at low speeds. They can fly a huge speed range, all because every feather has a muscle controlling it, never mind all the other musculature, meaning that the computing power of that bird's brain is awesome.

We talk about artificial intelligence. But a human brain, small as it is, can do so much more than any computer. Memory alone is enormous. I can see and hear things from when I was a child. AI will have a really hard time duplicating that.

The operation of an animal's cell is unknown to most people. It's not all that clear to the microbiologists. It's a tiny factory, taking orders from elsewhere in the body and selecting the assembly instructions from the DNA, making a string of RNA, and using that to form various proteins and hormones and all sorts of stuff including new cells. Inside that thing are molecular machines that move stuff around, and nobody seems to know how those tiny machines work. They have to have a propulsion system, a navigation system, an information processing system, and so on. The further they look into this thing the more complex it gets. Can we duplicate that? Not in my lifetime and probably never.

Watch this. Anyone who has designed complex machinery can only watch in wonder:


Realize, too, that your body has around 38 trillion of these factories in it. Almost all of them have that strand of DNA that would be about six feet long if uncoiled and stretched out, and if they were all laid end-to-end the string would reach to the sun and back more than 400 times. From one human body.

The fellow at the end of the clip is the guy that first wrote the book on DNA.
 

Dan Thomas

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I think Dan may have missed the point above from Jedi about the ”complete aircraft”. The tail area cancels the nose pitching moment of the wing. The tail can be lifting if it is large enough, such as a tandem wing configuration. For speed stability, the tail or rear wing needs to be large enough to operate at a lower angle of attack than the front surface (lower lift per square foot).
OK. Got that. Flying Flea stuff? Those airplanes had a terrible reputation years ago. In a dive the speed would increase and it would tumble head-over heels out of control. They must have figured it out. I would just have built a normal airplane and be done with it.
 

tspear

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@jedi

Curious; outside of a canard or tandem aircraft. Can you point to a plane which is considered stable and handles well by normal pilots in which the tail feathers have positive lift?
(I know of one for sure and suspect a second one, but wondering if anyone else does).

Tim
 

jedi

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@jedi

Curious; outside of a canard or tandem aircraft. Can you point to a plane which is considered stable and handles well by normal pilots in which the tail feathers have positive lift?
(I know of one for sure and suspect a second one, but wondering if anyone else does).

Tim
I can not verify it but I suspect most airliners have a lifting horizontal stabilizer when flown at cruise speed with the CG at the aft limit.
 

Dan Thomas

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I can not verify it but I suspect most airliners have a lifting horizontal stabilizer when flown at cruise speed with the CG at the aft limit.
I have heard that some might under rare conditions, but one must remember that they have a "coffin corner" where the max cruise speed (near Mach 1) puts the CP very far aft and tends to pitch the nose down (Mach tuck), a dangerous situation. A lifting tail would be totally unwelcome there. It would not be a normal way of flight.
 

Erik Snyman

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Dear Friends
A passenger-carrying flapping wing aircraft was already in existence in WW2.
It's name is Dakota DC3....😁😁 (fly in one and look out the window if you don't believe me)
Erik in Oz.
 

poormansairforce

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Dear Friends
A passenger-carrying flapping wing aircraft was already in existence in WW2.
It's name is Dakota DC3....😁😁 (fly in one and look out the window if you don't believe me)
Erik in Oz.
That reminds me of a joke I made several years ago about a "green" airliner that's powered by having the passengers jump up and down in unison...:pilot:
 

Woodenwings

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I missed the initial thread that talks about some of this. Sorry.

I was trying to make the statement above with links.

I have spent time with the people above. Their achievements were a real sacrafice and testament to perserverance and inginuity.

It is proven now. But it could be more practical. How is the question. What scinario would warrant the technology?

For most of us an airscrew is adequate...we are only screwing around afterall. No real mission to speak of apart from entertainment....i speak for myself.

Festo in Germany also make some very interesting ornithopters and other things. Birds. Butterflies. Dragon flies. Manta rays and jellyfish. Worth a look if you havent googled it!
 

Victor Bravo

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One of my gliders incorporated a very flexible wing which "flapped" (bent upwards and downwards like a spring) to take advantage of air gust energy. Not flapping flight specifically, but used the flapping style of movement to create thrust (reduced drag).

You can look up technical soaring papers on "the Katzmayr Effect" IIRC which is what Dr. Waibel was pursuing when he designed the layup schedule for the wings.
 

jedi

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It is proven now. But it could be more practical. How is the question. What scinario would warrant the technology?
This concept of auxiliary flapping wings would be an improvement for most any motorglider. It eliminates the need to stow and unstow the propeller or the need to feather the prop for gliding. Best of all it is ready to immediately add energy with two or three quick flaps and quickly return to the gliding mode.
I suspect motorgliders will be the first practical application of Oscillatory Propulsion Technology (OPT).

Hasn’t flapping flight already succeeded? Both mechanically powered and human powered IIRC.
Yes, but there is much development work needed to improve efficiency and create cost and performance competitive systems.
 
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