Flapping NAV Performs Controlled Hovering Flight

An anonymous reader writes "AeroVironment, Inc. was awarded a Phase II contract extension in April from the Defense Advanced Research Projects Agency (DARPA) to design and build a flying prototype for the Nano Air Vehicle (NAV) program. As part of this program AV has accomplished a technical milestone never before achieved: the controlled hovering flight of an air vehicle system with two flapping wings (video) that carries its own energy source and uses only the flapping wings for propulsion and control. Two wings for propulsion and control, nothing else."

Slashdotted!!

[anonymousNR]

here's a link to another article which atleast has a computer generated image [firetrench.com]

Ornithopter

[fiannaFailMan]

Shouldn't this sort of thing be called an Ornithopter [wikipedia.org]?

Youtube

[reg106]

Here is an AeroVironment NAV video [youtube.com] on YouTube. Not sure if it's the same one, but it was uploaded today...

Re:WowWee's Bat and Dragon also hover on wings.

[bughunter]

"Almost as good?" Hardly. The WowWee toys fly with moving wings, yes, but they're more glider than ornithopter, and require a rudder. The Aerovironment NAV is a true ornithopter, the flapping movement of its wings provides all lift and thrust and 3-axis control. But because this is slashdot, you're excused for opining out of ignorance, even when it could be cured by RTFA.

Re:Ornithopter

[metaforest]

"Nope. As you can see, the wings flap horizontally, which means it is a completely different concept, from what birds do."

You obviously have never taken a really close look at a slow motion video of a hummingbird doing the stationkeeping thing.
The NAV is mimicking a simplification of the hummingbird's vertical stationkeeping fight mode.

    Head, Tail and back are in a vertical orientation, (like a person standing) wings flapping in a 'sculling' motion to direct thrust downward. The wing shape is used more like a propeller blade in this mode than a lifting wing.

If you tread water, while swimming using arm-sculling, your arms are doing a slow motion version of roughly the same motions, with corrections, and for the same reasons, to maintain balance and position. Take particular note of how the hands are used as blades and tilted to direct force down against the water.
Our arm geometry is somewhat different so we don't orient the hand portion or our 'wing' vertically, and lacking feathers we rotate the thumb down to generate lift on the return stroke, rather than up and out as the hummingbird does.

The only difference with the NAV is that it's wing geometry is not as complex as a hummingbird so the system cannot switch to the more efficient horizontal orientation for cruising flight, the mode most birds use commonly. Hummingbirds use this more typical flight mode when they are not hovering.

I have witnessed some types of sparrows kind of manage the vertical flight mode, but their body's are not balanced correctly to make it very stable IMO. Consequently, they must use a lot more energy to stabilize the maneuver. This reduces their ability to hover to a matter of ten seconds or so before fatigue sets in.

Larger birds cannot mange the vertical flight mode at all. They simply can't move their wings fast enough to generate stable raw lift when their bodies are oriented vertically. The closest they can get is a cupped wing geometry used for VTOL maneuvers, and this too uses a lot of energy and is not stable enough for hovering.

One other variation I have seen is in small hawks where they seem to induce a low-speed stall and use small wing movements at the "wrist joint" to hold position for a few moments before committing to an attack dive. This is not a stable flight mode. After a few seconds they must either resume forward motion and normal flight, to mitigate the effects of the stall, or begin their attack dive.