Why don't aircraft use multiple sets of wings like dragonflies?

[kurious]

Dragonflies can create 20 times the lift/weight ratio of an aircraft by using turbulent air which passes from one set of wings to another.Why don't we give airplanes a second set of wings to do the same?

 

[enigma]

Because dragonfly wings flap.

Research into ornithopters is currently going on. I'm not sure if they are sophisticated enough yet to have a control system to take advantage of two sets of wings.

 

[faust9]

Because dragonflies utilize the movement of the wings to generate vortices that travel down the LE of their wings. Its more than just the turbulent flow passing from one wing to the next.

watch the gif at the top of this site:
http://www.news.cornell.edu/releases/March00/APS_Wang.hrs.html

And read this:
http://www.physicstoday.com/pt/vol-53/iss-12/p22.html

Would you fly in an airplane with wings that moved like that?

BiPlanes are an old concept but they have a limiting flaw--drag. Without the figure 8 motion to produce and utilize the turbulent air the second set of wings would add a substantial amount of drag.

P.S. I'm not an aeronautical engineer or physicist so take the above with a grain of salt.

 

[Robert Korobelnik]

R/C Mechanical flying Dragonfly

R/C Mechanical flying Dragonfly

Video, photos
http://ovirc.free.fr/ornithopteres_ovirk.php
Regards
Robert Korobelnik
http://ovirc.free.fr

 

[RAD4921]

Biplanes

Planes with two wings were developed in the early part of last century, though the wings themselves didn't flap like an insect.
Some early experimenters with flight tried the flapping method for flight to no avail. Using flapping wings to try and create lift is very inefficient method for heavy objects such as airplanes. I don't know where you got these ratios but
a dragonfly is much much lighter than a human.

 

[Robert Korobelnik]

Flapping Wings

Objective is to prove by a model that flight with flapping wings is practicable.
Leonardo da Vinci had no current materials composits (Carbon, fiberglass etc.)
The already model shows that it is possible .The necessary power is lower than that of a classic plane of the same weight by disregarding the Cx.
For the human transport it is still UTOPIA.
Robert Korobelnik
http://ovirc.free.fr

 

[salamander]

Can they hover? Can they be made fast? Cab they be made big?

 

[Robert Korobelnik]

Can they hover? yes
Can they be made fast? Yes and so bought ready to fly
Cab they be made big? Certainly in a few years

 

[russ_watters]

Aerodynamics for small airfoils is different than for large ones. Structural loadings scale as well. Because of these two issues, flapping wings will not scale to human-sized craft.