As jumbo jets and other large modern aircraft approach an airport to land, pilots deploy flaps on the leading edges of the wings—this allows the plane to fly at much lower speeds without stalling. The discovery of such technology improving safety during take-off and landing has been a key factor in the development of modern aviation.1
Leading edge flaps were unknown on birds—until now. Oxford University researchers studying flight manoeuvres of the steppe eagle (Aquila nipalensis) now have video evidence of ‘leading edge feather deflections’ during landing sequences.2 As New Scientist put it, the film footage shows that the birds ‘deploy a wing flap on the front edge of the wing’ just as jumbo jets do.3 The leading edge wing flap is thought to act as a high-lift device, increasing the lifting force of the wing at low speeds and high angles of attack, delaying stall and affording the bird increased control during landing and other manoeuvres.4 In other words, the effect of the flap is ‘to stabilize the wing during these unsteady maneuvers’.2 And it’s not just the steppe eagle—other large birds, too, are thought to use leading edge wing flaps.
So why didn’t researchers see that birds had such ‘leading edge’ technology before? Basically because it seems the birds only deploy the flap at precisely the exact instant needed—e.g. at the critical moment when landing. So for the researchers to be able to observe it required the use of a high-speed video camera—500 frames per second in this case. The camera caught the wing-flap movement as a feathery ‘travelling wave’ that spread from the wrist of the wing to the shoulder. Previous footage using fewer frames per second had been too slow to catch this movement.
The researchers say that this finding could help the development of bird-sized surveillance aircraft known as micro air vehicles. It would not be the first time that technology has been inspired by seeing what already exists in nature. (See, e.g. Amazing Abalone Armour, Going batty over evolution, Crayfish tail inspires Mars robot design, Snail trail.)
If only aeronautics engineers had been able to discern the existence of leading edge wing flaps in nature, then aircraft may have been fitted with them sooner! Recently strong evidence has been discovered that pterosaurs, too, had a forward-moving leading edge flap on the wing.