This document discusses the flight adaptations of birds, focusing on the aerodynamics of their wings and mechanisms of lift and drag. Key concepts include angle of attack, stalling, and the types of wing structures that aid in flight. The text highlights the contrast between natural avian flight and human-engineered flying machines.

1. FLIGHT ADAPTATIONS
IN BIRDS

2. BIRD’S AERODYNAMICS

3. Air Pressure
 If equal on dorsal and ventral surfaces of wing,
then no lift if “symmetrically” streamlined wing
 Two ways to overcome this with the wings:
a) increase the attack angle
b) bend the surface
 Doing so, however, does increase drag (no totally
“free lunches here )
 A cambered airfoil (ventral surface of wing is
concave, dorsal surface is convex) results in the
air moving faster over the dorsal convex surface
relative to the ventral surface

5.  Man has always dreamed
of being able to fly.
 Our long years of
experiment and research
have resulted in machine
with advanced
technologies.
 However our techniques
are really primitive as
compared to nature’s
flying machine.
ABSTRACT

6. IMPORTANT TERMS
Essential for
understanding their flight
mechanism
 Lift
 Drag
 Angle of attack
 Stalling
 Covert eddy flaps
 Flapping
 Take off and Landing
 Camber

7. LIFT
 Due to difference in
pressures in upper and
lower surface of wing
 Upper surface of air
deflects the air
downwards
 Airflow follows the
tilted wing,sticks to
surface, called COANDA
EFFECT

8.  Difference in pressures
creates lift
 Air above the wing
moves faster ,creating
low pressure
above ,hence creating
lift
 Lift increases with
increase in angle of
attack

9. ANGLE OF ATTACK
 Angle between reference
line of lifting boy and
incoming air flow
 Also called as angle of
incidence
 Coefficient of lift
increases with increase
in angle of attack upto
critical angle of attack
 After critical angle of
attack,STALLING occurs

10. STALL
 After critical angle of
incidence is attained,flow
separates of the
wing,causing less lift.
 Stalling occurs generally
during beginning of flight
or at slow speeds
 Slower moving air may
not move smoothly over
the wing
 Airflow above the wing
becomes turbulent

11. ALULA
 Thumb shaped,also
called as ‘COVERTS’.
 Eddy developed starts
from trailing edge to
leading edge
 ‘COVERT EDDY FLAPS’
prevent eddy to reach to
leading edge
 Help maintain lift at low
speeds,prevent STALL.

12. FLAPPING
 Flapping in such a way
so as to create both
THRUST and LIFT.
 THRUST counteracts
DRAG, LIFT counteracts
WEIGHT.
 Flapping involves two
stages: downstroke and
upstroke
 Downstroke causes
majority of lift and thrust

13.  Upstroke also causes
some lift, depending
upon shape of wing
 During upstroke wing is
folded slightly inwards
to reduce friction
 Angle of attack
increases during
downstroke,while
decreases during
upstroke

14. DRAG
Three major drag forces
 Frictional
drag(caused by
friction of air and
body surfaces).
 Form drag
 Lift -induced drag

15. FORM DRAG
 Arises because of form of
object.
 Larger apparent cross-
section area will have
larger drag than thinner
bodies.
 Sleek design or design
that are streamlined are
critical for achieving
minimum drag.
 Form drag increases with
increase in air speed.

16. LIFT INDUCED DRAG
 Occurs whenever a
moving object
redirects the airflow
coming at it.
 Induced drag
increases with
increase in angle of
attack.
 Induced drag
decreases with
increase in air speed.

17. TAKE-OFF
 Most energetically
demanding aspects of
flight.
 Large birds like
albatrosses need to run up
in order to generate
airflow to take off
 Small birds can do so by
taking a jump
 PECTORA muscle provides
about 95% of strength
required for flight.

18. LANDING
 Problem for large birds
with high wing loadings
 Landing on water is
simpler,using their feet as
skids
 Certain birds aim at
intended landing area and
pull up before hand
 Large birds like geese
involve in rapid alternating
series of sideslips called
WHIFFLING

19. CAMBER
 Symmetry between top
and bottom curves of an
airfoil
 Symmetric airfoils( with
zero camber) generate no
lift at zero angle of attack.
 Generally upper camber
of an airfoil is greater
than lower camber.
 Supersonic flights use
supercritical airfoil;one
with negative camber

20.  When camber is
increased beyond a
limit,STALLING occurs
 Even if angle of attack
is zero,airflow above
the upper surface can
be separated due to
excessive cambering
 Idea of cambering
helps designing
aircraft wings

21. TYPES OF WINGS
 ELLIPTICAL WINGS-
(short,rounded,for rapid
take-offs)
 HIGH ASPECT RATIO
WINGS-(far longer than
they are wide,for gliding
)

22.  HIGH SPEED WINGS-
(short,pointed,for
high speeds)
 SOARING WINGS
WITH DEEP SLOTS-
(shorter size of wings
helps in take-off,slots
at tips of wings
prevent induced drag)

23. HOVERING
 Done by birds with
high aspect ratio
wings
 Humming birds are
exception as they
create lift in both
upstroke and
downstroke
 Generally small birds
hover, but some larger
birds do so by flying in
headwind