Unit I TYPES OF DRAGS

EFFECTS OF VARIOUS DRAGS ON THE AIRCRAFTS

1. TypesofDrag Types
of

Drag
UNIT-I

2. Whti D ? Wh
a
t
i
s
D
rag
?
Dragisdefinedastheforcethatopposes forward
motion
through
the
atmosphere
forward
motion
through
the
atmosphere
and is parallel to the direction of the free
-
stream
velocity
of
the
airflow
Drag
free
-
stream
velocity
of
the
airflow
.
Drag
mustbeovercomebythrustinorderto achieve
forward
motion
achieve
forward
motion
.

3. •Drag is generated by every part of the airplane 

4. Theequationusedtocalculatedrag The
equation
used

to

calculate
drag

5. FactorsAffectingDrag Factors
 Affecting
 Drag
¾Thesurface
¾Thesha
p
eofthe
b
od
y
p
y
¾Frontalareaofthebodyexposed ¾
Square
of
the
velocity
of
the
airflow
¾
Square
of
the
velocity
of
the
airflow
¾Thedensityoftheair ¾Theaccelerationdueto
g
ravit
y

6. Th
h
f
th
bd
•
Th
es
h
apeo
f
th
e
b
o
dy
Theshapeoftheaircraftismadeinsucha
h
ii
i
f
h
bd
i
wa
y
t
h
at m
i
n
i
mum
p
ort
i
on o
f
t
h
e
b
o
dy
i
s
exposedtotheairflow.Ithelpsinreducingthe
drag drag
.
Th
Sf
•
Th
e
S
ur
f
ace
The less is the surface exposed to the
ifl
th
l
ill
b
th
d
a
i
r
fl
ow,
th
e
l
essw
ill
b
e
th
e
d
ra
g
.

7. •
Frontal
area
of
the
body
exposed
•
Frontal
area
of
the
body
exposed
The frontal area of the body is made in
such
a
way
that
it
is
a
streamlined
one
which
such
a
way
that
it
is
a
streamlined
one
which
willreducethedrag.
•Velocityofairflow
Th
f
d
d
i
di l
Th
e
f
orce
d
ue to
d
ra
g
i
s
di
rect
ly
proportionaltothesquareofthevelocityofthe airflow
In
order
to
minimize
the
drag
the
airflow
.
In
order
to
minimize
the
drag
,
the
aircraft is flown when the velocity of the airflow
is
less
airflow
is
less
.

8. •Densit
y
o
f
Ai
r
y
Theaircraftismadetoflyintheair,when
itsdensit
y
isrelativel
y
lowduetothechan
g
in
g
y
y
gg
weatherconditioninordertoreducethedrag.
•AccelerationduetoGravity
When
the
aircraft
is
made
to
fly
in
a
less
When
the
aircraft
is
made
to
fly
in
a
less
height that is under the influence of
acceleration due to
g
ravit
y
, then the dra
g
is
gy
g
minimum.

9. There are several t
yp
es of dra
g
yp g
¾
Formdragorboundarylayerpressuredrag
¾
Form
drag
or
boundary
layer

pressure

drag
¾Pressure drag ¾Skin friction dra
g
or surface -friction dra
g
¾Parasite drag ¾Induced drag or Vortex drag ¾
Wavedrag
¾
Wave

drag
.

10. FormDrag Form
Drag
Form
drag
profile
drag
or
pressure
drag
Form
drag
,
profile
drag
,
or
pressure
drag
,
arisesbecauseoftheshapeoftheobject.
The
general
size
and
shape
of
the
body
is
the
The
general
size
and
shape
of
the
body
is
the
mostimportantfactorinformdrag Bdi
ih
l
i
B
o
di
es w
i
t
h
a
l
ar
g
er apparent cross-sect
i
on
willhaveahigherdragthanthinnerbodies.

11. •Formor
p
ressuredra
g
iscause
d
by
theairthat
isflowingovertheaircraftorairfoil.
•The separation of air creates turbulence and
results inlowandhighpressurethatleavea
wakebehindtheairplaneorairfoil
•Thiso
pp
osesforwar
d
motionofaircraft
pp
•Sincethisdragisduetotheshape,orformof
the
aircraft
it
is
called
form
drag
the
aircraft
,
it
is
called
form
drag
.

12. PROFILE DRAG PROFILE DRAG
•Increases slightly with 
airspeed.
POWER REQUIRED
DRAG/ 
POWER
PROFILE
VELOCITY/AIRSPEED

13. Skinfrictiondrag Skin
friction
drag
•Skinfrictiondragiscausedbytheactualcontact
of
the
air
particles
against
the
surface
of
the
of
the
air
particles
against
the
surface
of
the
aircraft.
•Skin friction dra
g
is an interaction
b
etween the
g
airplanesurfaceandtheair.
•The magnitude of skin friction drag depends on
the properties of
b
oth the surface of soli
d
b
ody
andtheair.
h
il
ki
fi i
d
b
dd
•Fort
h
ea
i
rp
l
ane,s
ki
n
fi
ct
i
on
d
ragcan
b
ere
d
uce
d
,
and airspeed can be increased somewhat, by
keeping
an
aircraft
's
surface
highly
polished
and
keeping
an
aircrafts
surface
highly
polished
and
clean.

14. Induced drag or Vortex drag
•Induceddragisthedragduetolift. •The high pressure under the wing causes the
airflow at the tips of the wings to curl around
from
bottom
to
top
in
a
circular
motion
This
from
bottom
to
top
in
a
circular
motion
.
This
resultsinatrailingvortex.
•Induce
d
dra
g
increases in direct
p
ro
p
ortion to
g
pp
increasesintheangleofattack
.
•Thegreatertheangleofattack(uptothecritical
angle
of
attack
)
the
greater
the
amount
of
lift
angle
of
attack
)
the
greater
the
amount
of
lift
developedandthegreatertheinduceddrag.
•It
V
ariesinversel
y
withtheairs
p
ee
d
.
V
y
p

15. Induced drag is a byproduct of lift.

17. INDUCED DRAG INDUCED DRAG
•Results from the 
diflif
POWERREQUIRED
pro
d
uct
ion o
f
 lif
t.
•Parallel to and in the 
di tith
POWER
 REQUIRED
same 
di
rec
ti
on as 
th
e 
relative wind.
•
Increaseswith
DRAG/P
•
Increases
 with
 
increased angles of 
attack.
DRAG/P OWER
attack.
•Decreases with 
increased airs
p
eed.
VELOCITY/AIRSPEED
INDUCED
p
VELOCITY/AIRSPEED

19. ParasiticDrag Parasitic
Drag
•Theresistanceoftheairproducedbyanypartof
the
airplane
that
does
not
produce
lift
the
airplane
that
does
not
produce
lift
.
•Parasiticdragismadeupofviscouspressuredrag
(
form
drag
)
and
drag
due
to
surface
roughness
(
form
drag
)
,
and
drag
due
to
surface
roughness
(skinfrictiondrag).andinterferencedrag
•The
p
arasitic dra
g
is directl
y
p
ro
p
ortional to the
p
g
y
pp
size(S),thesquareofthespeed(V2),thedensity
(p)oftheair. •Parasite drag is directly proportional to the square
of the speed.

20. PARASITE DRAG PARASITE DRAG
•Increases rapidly with 
airs
p
eed.
PARASITE
POWER REQUIRED
p
DRAG/
PARASITE
DRAG/
 
POWER
VELOCITY/AIRSPEED

21. INTERFERENCE
DRAG
INTERFERENCE
DRAG
Ctd
b
th
lli i
f
it
•
C
rea
t
e
d
b
y
th
eco
lli
s
i
ono
f
a
i
rs
t
reams.
•Causes eddy currents, restrictions, and turbulence
t
th
fl
t
osmoo
th
fl
o
w
.
•Variesdirectlywiththeairspeed.

22. WaveDrag Wave
Drag
•Wavedragoccursinsupersonicflight,orflight
abo e
the
speed
of
so nd
Wa e
drag
is
a
form
abo
v
e
the
speed
of
so
u
nd
.
Wa
v
e
drag
is
a
form
ofpressuredrag.
h
if
bk
h
d
f
d
•W
h
enana
i
rcra
f
t
b
rea
k
st
h
espee
d
o
f
soun
d
,a
shock wave is created. A shock wave is a
h
il
stron
g
p
ressure wave t
h
at creates a v
i
o
l
ent
changeinpressure.
•High pressure pushes on the front of the
aircraft. This results in a large pressure drag
towar
d
therearoftheaircraft

23. Induced VsParasite Drag
The
distinction
between
induced
drag
and
The
distinction
between
induced
drag
and
parasitedragissignificant
•
In
the
low
airspeeds
most
of
the
drag
is
•
In
the
low
airspeeds
,
most
of
the
drag
is
induced drag. As you go slower and slower, induced
drag
increases
dramatically
and
induced
drag
increases
dramatically
and
parasitedragbecomesalmostnegligible. A
hi h
id
i
d
i
di
•
A
t
high
a
i
rspee
d
s,
p
aras
i
te
d
ra
g
i
s
d
om
i
nant
andinduceddragbecomesalmostnegligible.

24. •
Lift
and
drag
vary
directly
with
the
density
of
Lift
and
drag
vary
directly
with
the
density
of
theair.Asairdensityincreases,liftanddrag increase
and
as
air
density
decreases
lift
and
increase
and
as
air
density
decreases
,
lift
and
drag decrease. Thus, both lift and drag will decrease
at
higher
altitudes
decrease
at
higher
altitudes
.

26. •
Parasite
drag
is
the
mathematical
sum
of
Parasite
drag
is
the
mathematical
sum
of
formdragandskinfrictiondrag. Parasite Drag = Form Drag + Skin Friction Drag

27. •
The
total
drag
is
the
sum
of
parasite
and
The
total
drag
is
the
sum
of
parasite
and
induceddrag. TotalDrag=ParasiteDrag+InducedDrag