Birds have long been our inspiration for flight, and researchers at Princeton University have found a new trick in their arsenal: covert feathers. These small feathers on top of birds’ wings lay flat during normal flight but flare up in turbulence during landing. By attaching flexible plastic strips – “covert flaps” – to the top of a wing, the team has demonstrated impressive gains in aircraft performance at low speeds.
Wind tunnel tests and RC aircraft trials revealed a fascinating two-part mechanism. The front flaps interact with the turbulent shear layer, keeping it close to the wing surface, while the rear flap create a “pressure dam” that prevents high-pressure air from moving forward. The result? Up to 15% increase in lift and 13% reduction in drag at low speeds. Unfortunately the main body of the paper is behind a paywall, but video and abstract is still fascinating.
This innovation could be particularly valuable during takeoff and landing – phases where even a brief stall could spell disaster. The concept shares similarities with leading-edge slats found on STOL aircraft and fighter jets, which help maintain control at high angles of attack. Imitating feathers on aircraft wings can have some interesting applications, like improving control redundancy and efficiency.
Maintenance will love it.
Engineering will fix it.
I have been on the receiving end of many engineering “fixes”. I have doubts.
Was the engineers with sense of humor like “pilot report: left engine is missing” followed by “After careful examination, left engine found attached to left wing”
Or was it the engineer who used duct tape to fix up nasty looking crack like that famous Aloha Airline?
Management will ignore both.
I was under impression you cannot increase lift while decreasing drag. Regular flaps for landing etc on aircraft both increase lift and increase drag. Maybe these things are operating differently though.
It does kind of look like they are increasing the wing thickness, which would increase lift. In other words fatter wings make more lift. And more drag.
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Cool that it draws from nature and is passively self-regulating.
Like you said, this essentially increases wing thickness (and camber). Many airfoils are optimized more for cruise performance than low-speed. You can decrease drag and increase lift if you give yourself an airfoils better suited to the flight regime that the original airfoil wasn’t optimized for.
Of course, there is no free lunch, and any aero surface will introduce transitions (more drag, tripping airflow into turbulent flow), weight, and failure points.
As I understand it, stall appears when the pressure on top of the wing is so low that the air has not enough momentum to return into the “normal” pressure air stream behind the wing and thus reverses direction. These flaps then come up and stop the backflow, securing the low pressure on the front part of the wing. It is better visible on the birds in the video, where single feathers go up and back down during stall-prone maneuvers.
These would be excellent on bush planes (which specialize in low-speed flying with short takeoffs and landings).
Or larger planes where airstrips are surrounded by mountains?
What “new” feture will take from the birds? Aerian sacks? Hollow bones? Lateral eyes? Getting new airplanes out of eggs?
I’ll have a beer and popcorn watching DaVinci showing to the modern engineers what we had in front of our eyes and missed big time.
What in the hell kind of bird would would lay an A380 egg!?
A bird shaped as a plane factory I guess.
What if you’ll have a butterfly exiting the cocoon way for the planes (coming out of an giant egg): pump hydraulic oil in the wings to extend them, then let them dry and remove the oil. You’ll have nice and shinny and sturdy wings, weighting nothing. And the same for the body, chairs and other big main components. Except the engines, the engines will look like an egg. And use magnetoaerodynamic propulsion. Or ion propulsion.
the engines will be yellow with black letters, partly covered wit an also yellow triangle on the bottom
Turbulent shear layer? Never heard of that. Boundary layer, yup.
First: wings work because the higher pressure on the bottom PUSHES upwards. Decreasing the low pressure on top by defination must increase the differential and increase the high pressure on the bottom.
Second: birds don’t have flat bottom or semi symmetrical wings, they are pretty much thin Gottengen highly undercambered variable geometry. Cant say I have seen a full on bird stall not in a landing configuration.
Does this work? Probably somewhat
I cannot claim to see a full stall or spin from a bird, but have seen them be just barely flying when circling and thermaling. Like they become almost motionless and make a correction but it sure looks stall-like.
Turbulent shear layer? Never heard of that. Boundary layer, yup.
First: wings work because the higher pressure on the bottom PUSHES upwards. Decreasing the low pressure on top by defination must increase the differential and increase the high pressure on the bottom.
Second: birds don’t have flat bottom or semi symmetrical wings, they are pretty much thin Gottengen highly undercambered variable geometry. Cant say I have seen a full on bird stall not in a landing configuration.
Does this work? Probably somewhat
One must ask, how do the results compare to vortex generators, and can they both be use at once?