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How Ornithopters Fly

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Ornithoptermodel EV7

1. Ornithopter model EV7a

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1.1 Pictures of the flying EV7a

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1.2 Flight stability of ornithopters

With all EV-ornithopters the powered flights often had to be interrupted prematurely because the ornithopters lost their flight stability. Causes include the following:

  • Loss of stabilizing force due to changes in the air speed or the angle of climb.
  • Lacking practice und nervousness of the pilot.
  • Visibility problems because far distance or large turning radius.

Probably the constantly changing longitudinal dihedral by the wing pitching and twisting has a part of this. In any case, in nearly all EV ornithopter models the horizontal stabilizers were too small after a new design was built.

The unstable forces of a flapping wing by variation of the speed could also duplicated by calculation (please look at the handbook, chapter 8.6).

The stability problems are apparent from the varying presentation of the fuselage in some of the following pictures of a circle flight.

wing downstroke
wing downstroke
wing upstroke
wing upstroke
upper final wing stroke position
upper final wing stroke position
lower final wing stroke position
lower final wing stroke position
gliding flight
gliding flight
middle of wing downstroke
middle of
downstroke
in banking flight
in banking flight
unstable flapping flight
unstable
flapping flight
unstable flapping flight on downstroke
unstable flapping flight
gliding flight
gliding flight
unstable flapping flight on upstroke
unstable
flapping flight
in the middle of upstroke
middle of
upstroke
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1.3 Videos of the EV7a (1990)

Cutaway of a 8 mm film from EV7a

Scene 1:

It shows a short powered flight with a changing to gliding flight. Thereby, a rack-and-pinion drive system with an electronic switch was used.

Download

640 x 480 mp4 (0.8MB)

480 x 360 mp4 (0.5MB)

320 x 240 mp4 (0.2MB)

Scene 2:

In this powered flight the cyclical changes of the wing twisting is clearly to be seen.

Download

640 x 480 mp4 (0.5MB)

480 x 360 mp4 (0.3MB)

320 x 240 mp4 (0.1MB)

Scene 3:

With a length of about one minute it shows one of the few longer flights.
In particular one can see:

  • a high start to a height of about 10 meters,
  • a changing from gliding flight to powered flight
    with a rack and pinion drive unit,
  • the relatively slow stroke motion with a flapping
    cycle of about 1.1 s,
  • nevertheless there is only to be seen a little
    bobbing up and down of the fuselage,
  • a horizontal flight over a longer distance without
    upcurrent due to a slope or thermal and
  • the result of the breakdown of lift and thrust due
    to stalling after a short climb. For details please
    look above to the chapter Flight stability of ornithopters.
Download

640 x 480 mp4 (1.3MB)

480 x 360 mp4 (0.7MB)

320 x 240 mp4 (0.4MB)

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2. EV7b with primary feathers

Flight in dawn
The pixel-aligned adjustment of the picture series only can be made by using landmarks. Therefore the last two pictures of the flapping wing vehicle with feathers are only approximately correct.

Sequence of a flapping flight
Sequence in large size (321 KB)

Fly-by of an ornithopter
These pictures of a photo series of an ornithopter in flight are composed in an arbitrary manner.

some flight pictures of the wing-beat cycle
Sequence in large size (335 KB)
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2.1 Three meter bird on approach

- an aero modellers highlight -

Following pictures show the EV7b model (with feathers at the wing tip) during approach. With a few wing strokes it overcomes large distances (in this case nine wing beats). The different twisting of the wing during up- and downstroke can be well detected.

wing upstroke far away
wing upstroke
wing upstroke far
wing upstroke
wing downstroke in distance
wing downstroke
wing upstroke more nearly
wing upstroke
wing downstroke more near
wing downstroke
wing upstroke nearly
wing upstroke
wing upstroke nearby
wing upstroke
wing downstroke nearby
wing downstroke
wing downstroke close
wing downstroke
wing upstroke close
wing upstroke
wing downstroke from below
wing downstroke
wing upstroke frome below
wing upstroke
.
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3. Ornithopter model EV7c