lift augmentation devices for education purpose to understand and how its work to avoid the boundary layer separation thanks to royal air force and air cadets the next generation

1. SCIENCE OF AERONAUTICS
AND
ENGINEERING EDUCATIONAL TECHNICS
Presented by :-
CH. PURUSHOTHAM
Aeronautical Engineering
Lift Augmentation
or
High Lift Devices (Flaps)
Note : Download this file and see the slide show mode (F5)
for the better animation effects to under stand easily

2. Contents
Introduction -- High Lift Systems
Flaps
Trailingedge Devices
1. plainflap
2. split flap
3. Slottedflaps
4. Double-SlottedFowler Flap
5. Triple-slotted Flap
6. Fowlerflap
7. Zapflap
8. Junkersflap
9. Blownflaps
Leading edge Devices
SLATS AND SLOTS
Operation
Lift Augmentation Effects On CL

3. High Lift Systems -- Introduction
A wing designed for efficient high-speed flight is often quite different from one designed solely
for take-off and landing. Take-off and landing distances are strongly influenced by aircraft stalling
speed, with lower stall speeds requiring lower acceleration or deceleration and correspondingly
shorter field lengths. It is always possible to reduce stall speed by increasing wing area, but it is
not desirable to cruise with hundreds of square feet of extra wing area (and the associated weight
and drag), area that is only needed for a few minutes. Since the stalling speed is related to wing
parameters by:
It is also possible to reduce stalling speed by reducing weight, increasing air density, or increasing
wing CLmax . The latter parameter is the most interesting. One can design a wing airfoil that
compromises cruise efficiency to obtain a good CLmax , but it is usually more efficient to include
movable leading and/or trailing edges so that one may obtain good high speed performance while
achieving a high CLmax at take-off and landing. The primary goal of a high lift system is a high
CLmax; however, it may also be desirable to maintain low drag at take-off, or high drag on
approach. It is also necessary to do this with a system that has low weight and high reliability.
This is generally achieved by incorporating some form of trailing edge flap and perhaps a leading
edge device such as a slat.

4. Flaps
Trailingedge Devices
1. plain flap
2. split flap
3. Slotted flaps
4. Double-Slotted Fowler Flap
5. Fowler flap
6. Zap flap
7. Junkers flap
8. Blown flaps

5. 50% Increase CLMAX Critical Angle 12o
plain flap
The plain flap changes camber to
increase lift, but its effect is limited by
additional flow separation which occurs when it
is deflected. The additional separation occurs
because the upper surface of the deflected flap
experiences a stronger adverse pressure gradient

6. 60% Increase CLMAX Critical Angle 14o
SPLIT FLAP
split flap
The split flap deflects only the underside
of the trailing edge so that, while it creates a great
deal of pressure drag, it avoids the strong adverse
pressure gradient on its upper surface and
therefore keeps the flow attached slightly longer.
This gives the split flap slightly greater lift.

7. 65% Increase CLMAX Critical Angle 16o
SLOTTED FLAP
Slotted flaps
A Slotted flaps have a gap or slot in them
to allow faster-moving air from the lower surface
to flow over the upper surface. The higher-energy
air from the slot gives the boundary layer more
energy to fight the adverse pressure gradient and
delay separation

8. Double-Slotted Fowler Flap
Modern high lift systems are often quite
complex with many elements and multi-bar linkages.
Here is a double-slotted flap system as used on a DC-
8. For some time Douglas resisted the temptation to
use tracks and resorted to such elaborate 4-bar
linkages. The idea was that these would be more
reliable. In practice, it seems both schemes are very
reliable. Current practice has been to simplify the
flap system and double (or even single) slotted
systems are often preferred.

9. Triple-slotted Flap
A type of trailing-edge wing flap used on
some of the larger, high-performance airplanes.
Triple-slotted flaps extend from the trailing edge of a
wing in three sections. The trailing edge of one
section forms a duct with the leading edge of the
section behind it to force air down over the top of the
flap. Triple-slotted flaps prevent the airflow from
separating from the surface of the flap when they are
fully extended.

10. FOWLER FLAP
90% Increase CLMAX Critical Angle 15o
Fowler flap
The Fowler flap moves aft to increase
the wing area before deflecting downward to
increase camber. Fowler flaps usually have
one or more slots to increase their
effectiveness.

11. Zap FLAP
Zap flap
The leading edge of the flap is
mounted on a track, while a point at mid chord
on the flap is connected via an arm to a pivot
just above the track. When the flap's leading
edge moves aft along the track, the triangle
formed by the track, the shaft and the surface
of the flap (fixed at the pivot) gets narrower
and deeper, forcing the flap down.

12. Junkers flap
A slotted plain flap where the flap is
fixed below the trailing edge of the wing, rotating
about its forward edge, and usually part of the
Junkers Doppelflügel, or "double-wing" style of
wing trailing edge control surfaces (including the
ailerons), which hung just below and behind the
wing's fixed trailing edge. When not in use, it has
more drag than other types, but is more effective at
creating additional lift than a plain or split flap,
while retaining their mechanical simplicity.

13. THE BLOWN FLAP
80% Increase CLMAX Critical Angle 16o
Blown flaps
Blown flaps also known as Boundary Layer Control
Systems, are systems that blow engine air over the
upper surface of any of the previously mentioned
types of flap to improve lift characteristics.
Two types exist - the original type blew air out of
channels or holes in the surface of the flap, while
newer systems simply blow engine exhaust over the
top of the flap. These require ample reserves of power
and are maintenance intensive thus limiting their use,
but they provide lots of lift at low airspeeds.

14. SLATS AND SLOTS
Leading edge Devices

15. SLOTS AND SLATS
Slats: are auxiliary airfoils fitted to the leading edge
of the wing. At high angles of attack, they
automatically move out ahead of the wing. The
angle of attack of the slat being less than that of the
main plane, there is a smooth airflow over the slat
which tends to smooth out the eddies forming over
the wing. Slats are usually fitted to the leading edge
near the wing tips to improve lateral control.
Slots: are passageways built into the wing a short
distance from the leading edge in such a way that, at
high angles of attack, the air flows through the slot
and over the wing, tending to smooth out the
turbulence due to eddies.

16. AUTOMATIC SLAT
70% Increase CLMAX Critical Angle 25o
Automatic Slat
The slat lies flush with the
wing leading edge until reduced
aerodynamic forces allow it to extend by
way of aerodynamics when needed.
Sometimes referred to as Handley-Page
slats

17. Fixed Slat
Fixed Slat
The slat is permanently extended.
This is sometimes used on specialist low-
speed aircraft (these are referred to as slots)
or when simplicity takes precedence over
speed.

18. 40% Increase CLMAX Critical Angle 20o
SLOT
A leading edge slot is a fixed aerodynamic
feature of the wing of some aircraft to
reduce the stall speed and promote good
low-speed handling qualities. A leading
edge slot is a span-wise gap in each wing,
allowing air to flow from below the wing to
its upper surface. In this manner they allow
flight at higher angles of attack and thus
reduce the stall speed.

19. “DROOP SNOOT”
FLAP
50% ? Increase CLMAX Critical Angle 20o
droop or droop nose
A droop or droop nose is a type of high-
lift device found on the wings of some aircraft.
Droops are similar to leading-edge slats, but with
the difference that the entire leading edge section
rotates downwards, whereas a slat is a panel that
moves away from a wing leading edge when it is
deployed.

20. Krueger flaps
Krueger flaps are lift enhancement
devices that may be fitted to the leading edge of an
aircraft wing. Unlike slats or drooped leading
edges, the main wing upper surface and its nose is
not changed. Instead, a portion of the lower wing is
rotated out in front of the main wing leading edge.
KRUGER FLAP
50% Increase CLMAX Critical Angle 25o
•To increase lift at low speed
•Increase camber  increase lift

21. Operation
The chord of the slat is typically only a few percent of the
wing chord. The slats may extend over the outer third of the wing, or they
may cover the entire leading edge. Many early aerodynamicists, including
Ludwig Prandtl believed that slats work by inducing a high energy stream to
the flow of the main airfoil thus re-energizing its boundary layer and
delaying stall . In reality, the slat does not give the air in the slot high
velocity (it actually reduces its velocity) and also it cannot be called high-
energy air since all the air outside the actual boundary layers has the same
total heat.

22. boundary layer separation on bluff body

23. boundary layer separation on blunt body

24. To avoid the boundary layer separation Due to High lift
devices

25. LIFT AUGMENTATION EFFECTS ONCL

26. Relative Airflow
Basic ‘Clean’ Situation
α
EFFECT OF FLAP

27. Relative Airflow
Flap Lowered
α
Basic ‘Clean’ Situation
Effective Increase in AoA
EFFECT OF FLAP

28. EFFECT OF FLAP
Flap Lowered
α
Maintaining the Same Lift
Effective Increase in AoA
To obtain the same CL the Attitude is Lowered
to Reduce the AoA

29. Cl Max
AT STALL: WEIGHT = LIFT = CLMAX ½ρ V2
STALL S
Critical Angle
Without Flap
AoA
CL
EFFECT OF FLAP

30. AT STALL: WEIGHT = LIFT = CLMAX ½ρ V2
STALL S
IF THIS IS THIS IS
CONSTANT
MORE LESS
Critical Angle
With FlapCl Max More
AoA
CL
Nose
lower
at
Stall
Without Flap
Cl Max
EFFECT OF FLAP

31. EFFECTS ON CL
α
CL
BASIC AEROFOIL SECTION
BASIC AEROFOIL SECTION

32. α
CL
BASIC AEROFOIL SECTION
TRAILING EDGE FLAP
TRAILING EDGE FLAP
EFFECTS ON CL

33. α
CL
BASIC AEROFOIL SECTION
LEADING EDGE FLAP
EFFECTS ON CL
LEADING EDGE FLAP

34. α
CL
BASIC AEROFOIL SECTION
SLAT OR SLOT
EFFECTS ON CL
SLAT

35. α
CL
BASIC AEROFOIL SECTION
TRAILING EDGE FLAP
LEADING EDGE FLAP
SLAT OR SLOT
EFFECTS ON CL

36. Adding flaps gives
higher CLmax
CLmax
Anderson, J. D., Introduction to Flight, 4th Edition, page 315

37. Flaps
But, what about Drag?
Flaps 30
o
Flaps 90
o
Flaps 60
o
Flap
30
o
60
o
90
o
Drag
Small Inc
Large Inc
V Large Inc
Lift
Large Inc
Small Inc
No Sig Inc

38. Conclusion
1. Clear understanding the High lift Devices and its operational
working principle
2. Several technology research and development efforts exist to
integrate the functions of flight control systems such
as ailerons, elevators, flaps, and flaperons into wings to perform
the aerodynamic purpose with the advantages of less: mass, cost,
drag, inertia (for faster, stronger control response), complexity
(mechanically simpler, fewer moving parts or surfaces, less
maintenance), and radar cross section for stealth.

39. To invent an airplane is nothing. To
build one is something. But to fly is
everything.
- Otto Lilienthal
Thank you..
SCIENCE OF AERONAUTICS
AND
ENGINEERING EDUCATION TECHNICS