Secrets of falcon’s flight could help drones fly in turbulent conditions

By Stephen Beech via SWNS

Kestr els could be key to allowing aerial drones to operate in windy conditions, say scientists.

They have unlocked the secrets of the bird of prey's remarkably steady flight.

Researchers believe their findings will eventually make unmanned aerial vehicles (UAV’s) safer and more stable in turbulent conditions, or in cities where wind gusts from skyscrapers make flying more difficult.

The breakthrough would make parcel delivery, food delivery and environmental monitoring by drone more feasible.

University of Bristol scientists teamed up with colleagues at RMIT University i n Australia for the new study, published in the Journal of Experimental Biology .

The research conducted in RMIT’s Industrial Wind Tunnel facility - one of the largest of its kind in Australia - is the first to precisely measure the stability of a Nankeen Kestrel’s head during hovering flight.

The team found that the kestrel's head moves less than five millimeters (0.19 inches) while on the lookout for prey.

RMIT lead researcher Dr. Abdulghani Mohamed said: “Typically, aircraft use flap movements for stabilization to achieve stability during flight.

“Our results acquired over several years, show birds of prey rely more on changes in surface area, which is crucial as it may be a more efficient way of achieving stable flight in fixed wing aircraft too.”

Kestrels and other birds of prey are capable of keeping their heads and bodies extremely still during hunting.

Dr. Mohamed explained that the specialized form of flight - known as "wind hovering" - allows the birds to "hang" in place under the right wind conditions without flapping their wings.

He said that by making small adjustments to the shape of their wings and tail, they can achieve "incredible" steadiness.

Thanks to advancements in camera and motion capture technology, the research team was able to observe two Nankeen Kestrels at high resolution.

After being fitted with reflective markers, the birds’ precise movements and flight control techniques during non-flapping flight were tracked in detail for the first time.

Dr. Mohamed said: “Previous studies involved birds casually flying through turbulence and gusts within wind tunnels.

"In our study we tracked a unique wind hovering flight behavior whereby the birds are actively maintaining extreme steadiness, enabling us to study the pure control response without flapping.”

By mapping the movements, the research team gained insights that they say could be utilized to achieve steadier flight for fixed-wing aircraft.

Dr. Mohamed said: “The wind hovering behavior we observed in kestrels is the closest representation in the avian world to fixed-wing aircraft.

“Our findings surrounding the changes in wing surface area could be applied to the design of morphing wings in drones, enhancing their stability and making them safer in adverse weather.”

Study co-author Dr. Shane Windsor, Associate Professor of Bio-Inspired Aerodynamics at Bristol University, says the usefulness of current fixed-wing UAVs is significantly decreased by their inability to operate in gusty conditions.

He said: “UAVs are being used in the UK to deliver post to remote islands, but their operation time is limited because of regular gusty conditions.

“Current commercial fixed-wing aircraft have to be designed with one fixed geometry and optimized to operate at one flight condition.

“The advantage of morphing wings is that they could be continually optimized throughout a flight for a variety of conditions, making the aircraft much more maneuverable and efficient.”

The research team now plans to study the kestrels under gusty and turbulent conditions,.

While initially focused on smaller aerial vehicles, they hope to simplify the data collected so that it can be adapted for larger-scale aircraft.

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