birds of prey: dynamics of flight

Birds of Prey:Dynamics of Flight

Birds of Prey:Dynamics of Flight

Michael P. Jones, DVM, Dipl. ABVP (Avian)

Tennessee STEM Leadership Academy

Oak Ridge Associated Universities

June 27, 2012

Michael P. Jones, DVM, Dipl. ABVP (Avian)

Tennessee STEM Leadership Academy

Oak Ridge Associated Universities

June 27, 2012

[email protected] or [email protected]

The History of Aviation and Aerodynamics

The History of Aviation and Aerodynamics

• Man’s desire to fly and study of flight

– Religion

– Mythology

– Art and History

• Leonardo da Vinci

– Codex on the Flight of Birds (1505)

– Armed Forces (F22 Falcon)

– My own experiences:

• Flight

• Falconry

• Man’s desire to fly and study of flight

– Religion

– Mythology

– Art and History

• Leonardo da Vinci

– Codex on the Flight of Birds (1505)

– Armed Forces (F22 Falcon)

– My own experiences:

• Flight

• Falconry

http://en.wikipedia.org/wiki/File:Lockheed_Martin_F-22A_Raptor_JSOH.jpg

Aerodynamics of Flight Aerodynamics of Flight

• Objectives:

– Facilitate the understanding of principles of aerodynamics as they relate to flight in bird

– Facilitate an appreciation of birds of prey

• Objectives:

– Facilitate the understanding of principles of aerodynamics as they relate to flight in bird

– Facilitate an appreciation of birds of prey

Aerodynamics of Flight Aerodynamics of Flight

• Major forces acting on a flying raptor:

– Lift

– Drag

– Gravity

• Major forces acting on a flying raptor:

– Lift

– Drag

– Gravity Lift

Weight (Gravity)

DragDirection of flow

Aerodynamic Forces and Flight


• Any “fluid” passing over an object exerts a force

– Lift—component of force that is perpendicular to the direction of air flow

• Upward or downward (downforce)

• Newton’s Laws of force

• Bernoulli principle and pressure

– Pressure above (decreased) and below the wing (increased)

– Lift Coefficient (CL): capacity of airfoil to generate lift

• Any “fluid” passing over an object exerts a force

– Lift—component of force that is perpendicular to the direction of air flow

• Upward or downward (downforce)

• Newton’s Laws of force

• Bernoulli principle and pressure

– Pressure above (decreased) and below the wing (increased)

– Lift Coefficient (CL): capacity of airfoil to generate lift



• Lift

– Airflow around the wing

• Lift

– Airflow around the wing

Any obstruction to airflow around (especially above)the wing would interfere with lift.

Birds flying in formation take Advantage of vortices produced by the wings



• Lift

– Boundary layer—airflow close to the wing’s surface (can be laminar or turbulent)

• Air viscosity affects flight

• If airflow velocity is not strong enough to overcome viscosity then airflow “detaches” from the wing and becomes turbulent

– Stalling

• Lift

– Boundary layer—airflow close to the wing’s surface (can be laminar or turbulent)

• Air viscosity affects flight

• If airflow velocity is not strong enough to overcome viscosity then airflow “detaches” from the wing and becomes turbulent

– Stalling



• Lift and Stalling

– Stalling

• Enhanced by:

– Defects in the wing—increase drag and decrease lift

• Prevented by:

– Alula

– Feathers that create an “eddy flap” on the dorsal aspect of the wing

– Active and passive modification of the wing shape and airfoil

• Lift and Stalling

– Stalling

• Enhanced by:

– Defects in the wing—increase drag and decrease lift

• Prevented by:

– Alula

– Feathers that create an “eddy flap” on the dorsal aspect of the wing

– Active and passive modification of the wing shape and airfoil

Birdsasart.com



• Drag—component of force parallel to air flow

– When a bird flies through the air it is affected by

• Obstacle force (bird is an obstacle to airflow)

• Friction between air and wing surface


– When a bird flies through the air it is affected by

• Obstacle force (bird is an obstacle to airflow)

• Friction between air and wing surface




– Drag—Air or fluid resistance (3 components)

• Profile drag—generated by friction

• Induced drag—loss of kinetic energy

• Parasite drag—of the body

– Drag Coefficient—quantifies ability of an airfoil to generate drag

• Form drag

• Friction


– Drag—Air or fluid resistance (3 components)

• Profile drag—generated by friction

• Induced drag—loss of kinetic energy

• Parasite drag—of the body

– Drag Coefficient—quantifies ability of an airfoil to generate drag

• Form drag

• Friction

The Dynamics of FlightThe Dynamics of Flight

• The Anatomy of Flight (Form and Function)

– Avian flight is an extremely complex and energy demanding form of locomotion

– Musculoskeletal System

• Pectoral muscles, others

• Humerus, radius and ulna

– Integumentary System

• Feathers and receptors

– Nervous System

– Special Senses—Eyes


– Avian flight is an extremely complex and energy demanding form of locomotion

– Musculoskeletal System

• Pectoral muscles, others

• Humerus, radius and ulna

– Integumentary System

• Feathers and receptors

– Nervous System

– Special Senses—Eyes



– The Airfoil


– The Airfoil

Lift Coefficient (CL): capacity of airfoil to generate lift


Beaufrère 2009


• Types of Flight

• Raptors (birds) move forward under the influence of gravity, slowing sinking

• Lift from airfoil of the wing

• Climb rate vs. Sinking rate

– Gliding and Soaring

– Powered Flight

– Hovering Flight

• Types of Flight

• Raptors (birds) move forward under the influence of gravity, slowing sinking

• Lift from airfoil of the wing

• Climb rate vs. Sinking rate

– Gliding and Soaring

– Powered Flight

– Hovering Flight


• Types of Flight

– Gliding flight—”Traveling flight”

• Continuously sinking in the air

• Trading height for distance

– Glide angle (ratio of height to distance traveled)

– Weight—alters speed but not glide angle

• Types of Flight


• Continuously sinking in the air

• Trading height for distance

– Glide angle (ratio of height to distance traveled)

– Weight—alters speed but not glide angle


• Types of Flight


• Lift-to-drag ratio

– Optimal ratio depends on bird’s hunting strategy/biology

»Wing span, wing tip slots, and wing loading

• Aspect Ratio = Span2/wing area

– Trade speed for maneuverability (falcons)

• Wing Loading = body weight/wing area

– Higher speed with increased wing loading

• Types of Flight



– Optimal ratio depends on bird’s hunting strategy/biology

»Wing span, wing tip slots, and wing loading

• Aspect Ratio = Span2/wing area

– Trade speed for maneuverability (falcons)

• Wing Loading = body weight/wing area

– Higher speed with increased wing loading


• Types of Flight

– Gliding flight


– Hunting strategy

• Aspect Ratio

– Span2/wing area

• Wing Loadiing

– body weight/wing area

• Types of Flight

– Gliding flight


– Hunting strategy

• Aspect Ratio

– Span2/wing area

• Wing Loadiing

– body weight/wing area


• Types of Flight

– Soaring (a form of gliding)

• Purpose(s): cooling, searching for prey, display

• Surrounding air (thermals) rising faster than the birds is sinking

• Air speed is sacrificed

• Affected by wing loading, drag, and lift

• Primary feather structure and slotting affects air turbulence

• Types of Flight

– Soaring (a form of gliding)

• Purpose(s): cooling, searching for prey, display

• Surrounding air (thermals) rising faster than the birds is sinking

• Air speed is sacrificed

• Affected by wing loading, drag, and lift

• Primary feather structure and slotting affects air turbulence


• Types of Flight

– Powered Flight (Flapping Flight)

• Aerodynamics of flapping flight is unsteady

• Lift and Thrust generated by movement of the wing

• Wing beat is a very complex elliptical movement

– Downstroke—pronation, abduction and extension

– Upstroke—flexion, supination and adduction

• Types of Flight

– Powered Flight (Flapping Flight)

• Aerodynamics of flapping flight is unsteady

• Lift and Thrust generated by movement of the wing

• Wing beat is a very complex elliptical movement

– Downstroke—pronation, abduction and extension

– Upstroke—flexion, supination and adduction


• Types of Flight

– Powered Flight

• Various speeds/gaits

– Slow speeds—upstroke is passive, there is no lift and no continuous vortex created

»Creates a circular vortex with no lift

»Energy /power consuming

»All raptors; especially hawks and eagles

• Types of Flight

– Powered Flight


– Slow speeds—upstroke is passive, there is no lift and no continuous vortex created

»Creates a circular vortex with no lift

»Energy /power consuming

»All raptors; especially hawks and eagles

Fox 1995

• Types of Flight

– Powered Flight


– High speeds—upstroke is active, airspeed raises the wingtips and generates trailing vortices

»Economical

»Decreased wing-beat amplitude, wing-beat frequency, duration and angle of attack

»Falcons and Accipiters

• Types of Flight

– Powered Flight


– High speeds—upstroke is active, airspeed raises the wingtips and generates trailing vortices

»Economical

»Decreased wing-beat amplitude, wing-beat frequency, duration and angle of attack

»Falcons and Accipiters


Fox 1995

The Dynamics of Flight and Vision


• Types of Flight

– Powered Flight

• Propulsion (Thrust)

– Most birds generate propulsion on the downs stroke of the wing

– Elliptical motion of wings when flapping

– Accipiters (“sprinters”) produce propulsion on downstroke and upstroke

• Types of Flight

– Powered Flight

• Propulsion (Thrust)

– Most birds generate propulsion on the downs stroke of the wing

– Elliptical motion of wings when flapping

– Accipiters (“sprinters”) produce propulsion on downstroke and upstroke

Flickr.com Flickr.com



• Types of Flight

– Powered Flight and Speeds

• Golden eagle—29-32+ mph

• Red-tailed hawk—20-40 mph

• Merlin—30-45

• Gyrfalcon > 45 mph in level flight

• Peregrine falcon—28-32 mph level flight

– 175-250+ mph diving

– Change body shape increase speed

• Types of Flight

– Powered Flight and Speeds

• Golden eagle—29-32+ mph

• Red-tailed hawk—20-40 mph

• Merlin—30-45

• Gyrfalcon > 45 mph in level flight

• Peregrine falcon—28-32 mph level flight

– 175-250+ mph diving

– Change body shape increase speed



• Types of Flight

– Powered Flight

• Maneuverability

– Symmetry in forces between both wings through rolling motion of the body

– Modification of wing shape

»To produce more drag in one wing

– Position of the legs and feet

• Types of Flight

– Powered Flight

• Maneuverability

– Symmetry in forces between both wings through rolling motion of the body

– Modification of wing shape

»To produce more drag in one wing

– Position of the legs and feet


• Aerodynamics of the tail

– Functions:

• Flight (lift, roll and stability)

– Prevents upward pitch as wings flap downward and change center of pressure

– Aerodynamic flap-redirect airflow from wings

– Maneuvering

• Display

• Aerodynamics of the tail

– Functions:

• Flight (lift, roll and stability)

– Prevents upward pitch as wings flap downward and change center of pressure

– Aerodynamic flap-redirect airflow from wings

– Maneuvering

• Display



• Avian Vision

– Birds rely on their eyesight more than any other vertebrate

• Exceptional visual acuity allows them to find and capture prey, navigate surroundings, identify conspecifics/mates, escape predation

• Avian Vision

– Birds rely on their eyesight more than any other vertebrate

• Exceptional visual acuity allows them to find and capture prey, navigate surroundings, identify conspecifics/mates, escape predation



• Avian Vision

– Variable size and shape

• Projects large image onto the retina

• Little movement within the orbit

– 12o in American kestrels (Falco sparverius)

• Nictitating membrane

• Cornea and sclera (ossicles)

• Lens and accommodation

• Avian Vision

– Variable size and shape

• Projects large image onto the retina

• Little movement within the orbit

– 12o in American kestrels (Falco sparverius)

• Nictitating membrane

• Cornea and sclera (ossicles)

• Lens and accommodation



• Avian Vision

– Retina—contains rods, cones and oil droplets

• Color vision—birds are trichromatic to tetrachromatic

– Also see in ultraviolet/near ultraviolet spectrum

– Oil droplets act as filters for different wavelengths of light

• Avian Vision

– Retina—contains rods, cones and oil droplets

• Color vision—birds are trichromatic to tetrachromatic

– Also see in ultraviolet/near ultraviolet spectrum

– Oil droplets act as filters for different wavelengths of light



• Avian Vision

– Retina

• Fovea—specialized regions in retina that allow greater visual acuity than surrounding retina

• Humans (primates) only mammals with fovea

• Birds—Bifoveate (central and temporal)

• Avian Vision

– Retina

• Fovea—specialized regions in retina that allow greater visual acuity than surrounding retina

• Humans (primates) only mammals with fovea

• Birds—Bifoveate (central and temporal)



• Avian Vision

– Retina

• Fovea

– Central fovea (deep)

» Line of Sight (LOS) ~45o

» Highest visual acuity

– Raptors tend to look at distant objects/prey with central fovea

– Near objects viewed with temporal fovea

• Avian Vision

– Retina

• Fovea

– Central fovea (deep)

» Line of Sight (LOS) ~45o

» Highest visual acuity

– Raptors tend to look at distant objects/prey with central fovea

– Near objects viewed with temporal fovea



• Avian Vision

– Retina

• Fovea

• Avian Vision

– Retina

• Fovea

45o

Tucker et al, 2000


• Avian Vision

– “Conflict” between aerodynamics and vision

• Need to keep heads and bodies aligned to minimize drag and reach maximum speed

• Turn head towards LOS with one eye for maximum visual acuity

• Avian Vision

– “Conflict” between aerodynamics and vision

• Need to keep heads and bodies aligned to minimize drag and reach maximum speed

• Turn head towards LOS with one eye for maximum visual acuity

©2008 Richard Ettlinger


• Avian Vision

– Curved flight path

• Approach prey more quickly along curved flight path

• Hunting from the sun

• Misleading prey

• G-Forces!!

• Avian Vision

– Curved flight path

• Approach prey more quickly along curved flight path

• Hunting from the sun

• Misleading prey

• G-Forces!!


• Conclusion:

– Avian flight is a complex, biomechanical process that we don’t fully understand

– Birds of prey are “cool”

• Conclusion:

– Avian flight is a complex, biomechanical process that we don’t fully understand

– Birds of prey are “cool”

birds of prey: dynamics of flight

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