How Ornithopters Fly

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Other flapping wing designs

In designing of ornithopter models there are mainly two major tasks, the development of the drive technology and the development of the flapping wing. In general, the wide interest lies in the drive systems and components. But the main problem of the development of such aircrafts are the flapping-wings. In this field of design desire differs very widely from reality.

Below, the attempt is being made, to give a rough overview about the physical characteristics of known flapping wings. But this collection doesn't claim to be complete.


1. The bird wing, the ideal

Naturally, the great archetype for technical flapping wings is the living bird wing. His great effectiveness due to his manifold possibilities to move purposeful and to change the shape will certainly be unobtainable in aero modelling for a long time. This is also true for his weight distribution and his sensor technology.

In this drawing by K. Herzog the anatomic subdivision of the bird's wing in arm- and hand section is pictured. It can also to be used advantageously when describing technical flapping wings. The longitudinal parts of these wing sections are rather different depending on bird species.


2. Membrane flapping wings

Application range

Membrane flapping wings especially are changing the direction of chamber in the hand wing section according to the flapping direction. This way, they can produce much thrust and achieve steep climbing flights (flying with Thrust). But up to now they are less suited for gliding flights and for flying with lift.


3. Profiled flapping wings

Range of application

Profiled flapping wings or double-sided covered wings may work with a very high efficiency. With their mostly relatively low flapping frequency and the small operating range of lift coefficient of a simple airfoil not much thrust can be produced. Not, at least, if the full lift must be generated concurrently (flying with lift). Therefore, profiled flapping wings are suited especially for a level flight, the gently inclined climbing flight and of course for changing to gliding flight.


4. Notes

In the essay Flapping Wing Designs (in German, PDF 1.8MB) can be found additional informations about these flapping wing constructions.

In conjunction with the EV-models developed flapping wings are to find on the site: Articulated flapping wings.

The wings of pterosaurs have worked differently than today's bird wings, please look at Wing-function of flying saurian.

Ideas and suggestions for a further development are enclosed in the paper Lift during wing upstroke, version 10.1, (PDF 1.0 MB).