Contents
S .no Topic
page no
1. Introduction Of the wings 7
2.
Structure of the wing 9
3. Types of wing configuration 14
4.
Wing cross section
28
5.
Wing aerodynamics 30
6. Conceptual design calculations 33
7.
Specification
39
8. CAD modeling
42
9. Conclusion
43
10.
References
44
ABSTRACT
The basic
intent of this design project is to design an aircraft wing structure for a
high subsonic trainer aircraft for the maximum speed of 0.8 Mach (1000kph). By
identifying and studying the various types of wing structures, wing
configuration, NACA 4 and 5 digit airfoils, supercritical airfoils and its
performance parameters, the conceptual design is carried out. Therefore the
results from the design calculation are taken to take the right airfoil (NACA
4408) and the wing geometries and parameters are determined.
With the input
parameters, calculated results and necessary assumptions the CAD model of the
wing structure is constructed using CATIA V5 R20. The CAD modeling of the wing
structure constitutes the creation of individual structural members followed by
assembly of each and every individual part.
INTRODUCTION
THE WING
A wing is a surface that produces lift for flight through the atmosphere—or occasionally through another gaseous or fluid substance. An artificial wing is
called an airfoil,
which always have a distinctive cross-sectional shape.
A wing's aerodynamic quality is expressed as its lift-to-drag ratio. The lift of a wing
generates at a given speed and angle of
attack can be one to
two orders of magnitude greater than the total drag on the
wing. A high lift-to-drag ratio requires a significantly smaller thrust to propel the wings through the air at
sufficient lift.
The design and analysis of the wings
of aircraft is one of the principal applications of the science of aerodynamics
For a wing to produce
"lift", it must be oriented at a suitable angle of
attack relative to the
flow of air past the wing. When this occurs the wing deflects the airflow
downwards, "turning" the air as it passes the wing. Since the wing
exerts a force on the air to change its direction, the air must exert a force
on the wing, equal in size but opposite in direction. This force manifests
itself as differing air pressures at different points on the surface of the
wing.
A region of lower-than-normal air
pressure is generated over the top surface of the wing, with a higher pressure
existing on the bottom of the wing. These air pressure differences can be
either measured directly using instrumentation or they can be calculated from
the airspeed distribution using basic physical
principles, including Bernoulli's Principle which relates changes in air speed to
changes in air pressure.
The lower air pressure on the top of
the wing generates a smaller downward force on the top of the wing than the
upward force generated by the higher air pressure on the bottom of the wing.
Hence, a net upward force acts on the wing. This force is called the
"lift" generated by the wing.
The different velocities of the air
passing by the wing, the air pressure differences, the change in direction of
the airflow, and the lift on the wing are intrinsically one phenomenon. It is,
therefore, possible to calculate lift from any of the other three. For example,
the lift can be calculated from the pressure differences, or from different
velocities of the air above and below the wing, or from the total momentum
change of the deflected air. There are other approaches in fluid dynamics to
solving these problems. All of these approaches will result in the same answers if done correctly. Given a
particular wing and its velocity through the air, debates over which
mathematical approach is the most
convenient to use can be
misperceived by novices as differences of opinion about the basic principles of
flight
TYPES OF WING STRUCTURES:
Wing
construction is basically the same in all types of aircraft. Most modern
aircraft have all metal wings, but many older aircraft had wood and fabric
wings. Ailerons and flaps will be studied later in this chapter.
To
maintain its all-important aerodynamic shape, a wing must be designed and built
to hold its shape even under extreme stress. Basically, the wing is a framework composed chiefly of spars, ribs, and
(possibly) stringers.
Three systems are used to determine
how wings are attached to the aircraft fuselage depending on the strength of a
wing's internal structure. The strongest wing structure is the full cantilever
which is attached directly to the fuselage and does not have any type of
external, stress-bearing structures. The semi-cantilever usually has one, or
perhaps two, supporting wires or struts attached to each wing and the fuselage.
The externally braced wing is typical of the biplane (two wings placed one
above the other) with its struts and flying and landing wires.
Wing structure consists of the
following components: -
·
Spars
·
Ribs
·
Stringers
·
External structure
·
Upper skin
·
Lower skin
A Wing structure should posses the
following factors: -
·
Sufficient strength
·
Stiffness
·
Light weight
·
Minimum manufacturing
problems
SPARS
Spars are the main members of the wing.
They extend lengthwise of the wing (crosswise of the fuselage). The entire load
carried by the wing is ultimately taken by the spars. In flight, the force of
the air acts against the skin. From the skin, this force is transmitted to the
ribs and then to the spars.
Most
wing structures have two spars, the front spar and the rear spar. The front
spar is found near the leading edge while the rear spar is about two-thirds the
distance to the trailing edge. Depending on the design of the flight loads,
some of the all-metal wings have as many as five spars. In addition to the main
spars, there is a short structural member which is called an aileron spar.
·
Spars are of two types namely
o Shear web
o Truss type
RIBS
The ribs are
the parts of a wing which support the covering and provide the airfoil shape.
These ribs are called forming ribs. and their primary purpose is to provide
shape. Some may have an additional purpose of bearing flight stress, and these
are called compression ribs.
The most simple wing
structures will be found on light civilian aircraft. High-stress type of
military aircraft will have the most complex and strongest wing structure.
WING
SKIN PANEL
Wing skin panel gives the wing its shape.
Carries loads such as Bending and shear loads. It should
also carry torsion loads caused by
control surfaces and other features attached to the wing
It creates walls for the wing mounted fuel
tanks
LEADING
EDGE
Leading edge
consists of Ribs,
Slats, Skin, Plenum beam, Piccolo tube, Clips. The structural member running across the
leading edge is called as the nose cone.
STRINGERS
Stringers are
stiffening members in the wing which run from root to the tip. Stringers are
made from forming or extrusion.
EXTRUSION
TYPE FORMING TYPE
Wing configuration
Lifting body - Relies on air
flow over the fuselage to provide lift.
Powered lift - Relies on
downward thrust from the engines to stay airborne.
Monoplane – Means one wing. Most airplanes have been
monoplanes since before the Second World War. The wing may be mounted at
various heights relative to the fuselage:
Low wing - mounted on the
lower fuselage.
Mid wing - mounted
approximately half way up the fuselage.
High wing- mounted on the upper
fuselage.
Shoulder wing - a high wing
mounted on the upper part of the main fuselage (as opposed to mounting on the
cockpit fairing or similar).
Parasol wing - mounted on
"cabane" struts above the fuselage.
 Low wing |
 Mid wing |
|
Shoulder wing
High wing
A fixed wing aircraft
may have more than one wing plane, stacked one above another:
Biplane - two planes of approximately equal size
stacked one above the other. The most common type until the 1930s, when the
cantilever monoplane took over.
Sesquiplane - literally
"one-and-a-half planes" is a variant on the biplane in which the
lower wing is significantly smaller than the upper wing.
Inverted sesquiplane - has a
significantly smaller upper wing.
 Parasol wing |
 Biplane |
||
 |
 |
Sesquiplane Inverted sesquiplane
Classification by Wing support
To support itself a wing
has to be rigid and strong and consequently may be heavy. By adding external
bracing, the weight can be greatly reduced. Originally such bracing was always
present, but it causes a large amount of drag at higher speeds and has not been
used for faster designs since the early 1930s.
The types are:
Cantilevered – They are self-supporting.
All the structure is buried under the aerodynamic skin, giving a clean
appearance with low drag.
Braced: the wings are
supported by external structural members. Nearly all multi-plane designs are
braced. Some monoplanes, especially early designs such as the Fokker Eindecker,
are also braced to save weight. Braced wings are of two types:
Strut braced - one or more
stiff struts help to support the wing. A strut may act in compression or
tension at different points in the flight regime.
Wire braced - alone, or in
addition to struts, tension wires also help to support the wing. Unlike a
strut, a wire can act only in tension.
 Cantilever |
 Strut braced |
Wire braced |
Wings can also be characterized
as:
Rigid - stiff enough to
maintain the aerofoil profile in varying conditions of airflow.
Flexible - usually a thin
membrane. Requires external bracing or wind pressure to maintain the aerofoil shape.
Common types include Rogallo wings and kites.
Classification by Wing plan form
The wing plan form is
the silhouette of the wing when viewed from above or below.
Aspect ratio
The aspect ratio is
the span divided by the mean or average chord. It is a
measure of how long and slender the wing appears when seen from above or below.
Low aspect ratio - short and stubby
wing. More efficient structurally, more maneuverable and with less drag at high
speeds. They tend to be used by fighter aircraft, such as the Lockheed F-104 Starfighter,
and by very high-speed aircraft (e.g. North American X-15).
Moderate aspect ratio - general-purpose
wing (e.g. the Lockheed P-80 Shooting Star).
High aspect ratio - long and slender
wing. More efficient aerodynamically, having less drag, at low speeds. They
tend to be used by high-altitude subsonic aircraft (e.g. the Lockheed U-2),
subsonic airliners (e.g. the Bombardier Dash 8)
and by high-performance sailplanes (e.g. Glaser-Dirks DG-500).
 Low aspect ratio |
 Moderate aspect ratio |
 High aspect ratio |
Most Variable geometry configurations
vary the aspect ratio in some way, either deliberately or as a side effect.
Classification by Wing sweep
Wings may be swept
forwards or back for a variety of reasons. A small degree of sweep is sometimes
used to adjust the centre of lift when the wing cannot be attached in the ideal
position for some reason, such as a pilot's visibility from the cockpit. Other
uses are described below.
Straight – It extends at
right angles to the line of flight, the most efficient structurally, and common
for low-speed designs, such as the P-80 Shooting Star.
Swept back - (references to "swept" often
assume swept back). From the root, the wing angles backwards towards the tip.
In early tailless examples, such as the Dunne aircraft, this allowed the outer wing
section to act as a conventional tail empennage to
provide aerodynamic stability. At transonic speeds
swept wings have lower drag, but can handle badly in or near a stall and
require high stiffness to avoid aeroelasticity at
high speeds. Common on high-subsonic and supersonic designs e.g. the English Electric Lightning.
Forward swept - the wing angles
forwards from the root. Benefits are similar to backwards sweep, also at
significant angles of sweep it avoids the stall problems and has reduced tip
losses allowing a smaller wing, but requires even greater stiffness and for
this reason is not often used. A civil example is the HFB-320 Hansa Jet and
in military Sukhoi Su-47.
Swing-wing - also called
"variable sweep wing". The left and right hand wings vary their sweep
together, usually backwards. Seen in a few types of combat aircraft, the first
being the General Dynamics F-111. Another is the Grumman F-14.
Oblique wing - a single full-span
wing pivots about its midpoint, so that one side sweeps back and the other side
sweeps forward. Flown on the NASA AD-1 research
aircraft.
|
Straight |
 Swept |
 Forward swept |
|
|
Oblique wing
Swing wing
Classification by Plan form variation along span
The wing chord may be varied along the span of the
wing, for both structural and aerodynamic reasons.
Constant chord - leading &
trailing edges are parallel. Simple to make, and common where low cost is
important, e.g. in the Short Skyvan.
Elliptical - wing edges are
parallel at the root, and curve smoothly inwards to a rounded tip, with no
division between the edges and the tip. Aerodynamically the most efficient, but
difficult to make. Famously used on the super marine Spitfire.
Tapered - wing narrows
towards the tip, with straight edges. Structurally and aerodynamically more
efficient than a constant chord wing, and easier to make than the elliptical
type. One of the most common types of all, as on the Hawker Sea Hawk.
Reverse tapered - wing widens
towards the tip. Structurally very inefficient, leading to high weight. Flown
experimentally on the XF-91 Thunderceptor in an attempt to
overcome the stall problems of swept wings.
Compound tapered - taper reverses
towards the root, to increase visibility for the pilot. Typically needs to
be braced to maintain stiffness. The Westland Lysander was
an observation aircraft.
Trapezoidal - a low aspect
ratio tapered wing, having little or no sweep such that the leading edge sweeps
back and the trailing edge sweeps forwards. Used for example on the Lockheed F-22 Raptor.
 Constant chord |
 Elliptical |
Tapered |
 Reverse tapered |
 Compound tapered |
 Trapezoidal |
Delta - triangular planform with swept leading
edge and straight trailing edge. Offers the advantages of a swept wing, with
good structural efficiency. Variants are:
Tailless delta - a classic
high-speed design, used for example in the widely built Dassault Mirage III series.
Tailed delta - adds a
conventional tailplane, to improve handling. Popular on Soviet types such as
the Mikoyan-Gurevich MiG-21.
Cropped delta - tip is cut off.
This helps avoid tip drag at high angles of attack. At the extreme, merges into
the "tapered swept" configuration.
Compound delta or double delta - inner section has a
(usually) steeper leading edge sweep e.g. Saab Draken.
This improves the lift at high angles of attack and delays or prevents
stalling. They are seen in tailless form on the Tupolev Tu-144.
The HAL Tejas has
an inner section of reduced sweep.
Ogival delta - A smoothly blended
"wineglass" double-curve encompassing the leading edges and tip of a
cropped compound delta. They are seen in tailless form on the Concorde supersonic
transports.
 Tailless delta |
 Tailed delta |
 Cropped delta |
 Compound delta |
Ogival
delta
|
The
angle of sweep may also be varied, or cranked, along the span:
Cranked arrow - similar to a
compound delta, but with the trailing edge also kinked inwards. Trialed
experimentally on the General Dynamics F-16XL.
M-wing - the inner wing
section sweeps forward, and the outer section sweeps backwards. The idea has
been studied from time to time, but no example has ever been built.
W-wing - the inner wing
section sweeps back, and the outer section sweeps forwards. The reverse of the
M-wing. The idea has been studied even less than the M-wing and no example has
ever been built.
 Crescent |
 Cranked arrow |
|
|
|
 M-wing |
 W-wing |
Dihedral and Anhedral
Angling the wings up or
down span wise from root to tip can help to resolve various design issues, such
as stability and control in flight.
Dihedral - the tips are
higher than the root as on the Boeing 737,
giving a shallow 'V' shape when seen from the front. It adds lateral stability.
Anhedral - the tips are
lower than the root, as on the Ilyushin Il-76;
the opposite of dihedral. Used to reduce stability where some other feature
results in too much stability thus making maneuvering difficult. A popular
choice in modern fighters since the configuration makes them more agile in
battle. In level flight, computers assist the pilot in preventing the plane
from teetering about.
 Dihedral |
Anhedral
|
Some biplanes had
different angles of dihedral / anhedral on different wings; e.g. the
first Short Sporting Type, known as the Shrimp,
had a flat upper wing and a slight dihedral on the lower wing.
The dihedral angle may
vary along the span.
Gull wing - sharp dihedral on the wing root section,
little or none on the main section, as on the Göppingen 3 glider. Typically done to
raise wing-mounted engines higher above the ground or water.
Inverted gull - anhedral on the root section, dihedral
on the main section. The opposite of a gull wing. Typically done to reduce the
length and weight of wing-mounted undercarriage legs. Two well-known examples
of the inverted gull wing are World War II's
American F4U Corsair, and the German Junkers Ju 87 Stuka dive
bomber.
 Gull wing |
 Inverted gull wing |
Wings
vs. bodies
Some designs have no
clear join between wing and fuselage, or body. This may be because one or other
of these is missing, or because they merge into each other:
Flying wing - the aircraft has
no distinct fuselage or tail empennage (although fins and small pods, blisters,
etc. may be present); one example is the B-2 Spirit.
Blended body or blended wing-body -
smooth transition between wing and fuselage, with no hard dividing line.
Reduces wetted area and hence, if done correctly, aerodynamic
drag. The McDonnell XP-67 Bat was also designed to maintain the aerofoil
section across the entire aircraft profile.
Lifting body - the aircraft has
no significant wings, and relies on the fuselage to provide aerodynamic lift
i.e. X-24 .
  |
  |
Some proposed designs,
typically a sharply-swept delta planform having a deep centre section tapering
to a thin outer section, fall across these categories and may be interpreted in
different ways, for example as a lifting body with a broad fuselage, or as a
low-aspect-ratio flying wing with a deep center chord.
Variable chord
Variable incidence - the wing plane
can tilt upwards or downwards relative to the fuselage. Used on the
Vought F-8 Crusader to tilt the leading edge up by a small
amount for takeoff, to give STOL
performance. If powered prop rotors are fitted to the wing to allow vertical takeoff or STOVL performance,
merges into the powered lift category.
Variable camber - the leading and
trailing edge sections of the wing pivot and/or extend to increase the
effective camber and/or area of the wing. This increases lift at low angles of
attack, delays stalling at high angles of attack, and enhances maneuverability.
Variable thickness - the upper wing
centre section can be raised to increase wing thickness and camber for landing
and take-off, and lowered for high speed flight. Charles Rocheville modified
one or more aircraft in the course of his researches.
Minor aerodynamic
surfaces
Additional minor
aerodynamic surfaces may form part of the overall wing configuration:
Winglet - a small vertical fin at the wingtip
usually turned upwards. Reduces the size of vortices shed by the wingtip, and
hence also tip drag.
Chine - narrow extension
to the leading edge wing root, extending far along the forward fuselage. As
well as improving low speed (high angle of attack) handling, provides extra lift
at supersonic speeds for minimal increase in drag. Seen on the Lockheed SR-71 Blackbird.
Moustache - small
high-aspect-ratio canard surface having no movable control surface. Typically
is retractable for high speed flight. Deflects air downward onto the wing root,
to delay the stall. Seen on the Dassault Milan and Tupolev Tu-144.
Minor surface features
Additional minor
features may be applied to an existing aerodynamic surface such as the main
wing:
Leading edge extensions of various kinds.
Slot - a span wise gap
behind the leading edge section, which forms a small aerofoil or slat extending
along the leading edge of the wing. Air flowing through the slot is deflected
by the slat to flow over the wing, allowing the aircraft to fly at lower air
speeds. Leading edge slats are moveable extensions
which open and close the slot.
Flap - trailing-edge
(or leading-edge) wing section which may be angled downwards for low-speed
flight, especially when landing. Some types also extend backwards to increase
wing area.
Wing fence - a thin surface extending along the wing
chord and for a short distance vertically. Used to control spanwise airflow
over the wing.
Vortex generator - small triangular
protrusion on the upper leading wing surface; usually, several are spaced along
the span of the wing. The vortices are used to re-energize the boundary layer
and reduce drag.
Anti-shock body - a streamlined
"pod" shaped body added to the leading or trailing edge of an
aerodynamic surface, to delay the onset of shock stall and reduce transonic
wave drag. Examples include the Küchemann carrots on the wing
trailing edge of the Handley Page Victor B.2, and the tail
fairing on the Hawker Sea Hawk.
Fairings of various kinds,
such as blisters, pylons and wingtip pods, containing equipment which cannot
fit inside the wing, and whose only aerodynamic purpose is to reduce the drag
created by the equipment.
Wing skeleton
The wing skeleton is nothing but the arrangement of various
structural members in an orderly fashion in order the wing gets its aerodynamic
profile and most importantly the structural loading arrangement. The pictorial
representation of certain wing skeletons are shown as below.
WING CROSS SECTION:
Airfoil geometry can be characterized by the coordinates of the
upper and lower surface. It is often summarized by a few parameters such as:
maximum thickness, maximum camber, position of max thickness, position of max
camber, and nose radius. One can generate a reasonable airfoil section given
these parameters. This was done by Eastman Jacobs in the early 1930's to create
a family of airfoils known as the NACA Sections.
The NACA 4 digit and 5 digit airfoils were created by superimposing a simple mean line shape with a thickness distribution that was obtained by fitting a couple of popular airfoils of the time:
y = ±(t/0.2) * (.2969*x0.5 - .126*x - .3537*x2 + .2843*x3 - .1015*x4)
The camber line of 4-digit sections was defined as a parabola from the leading edge to the position of maximum camber, then another parabola back to the trailing edge.
NACA
4-Digit Series:
4 4 12
Max camber
Position max thickness
in % chord
of max camber in % of chord
In 1/10 of c
After the 4-digit sections came the 5-digit sections such as the
famous NACA 23012. These sections had the same thickness distribution, but used
a camberline with more curvature near the nose. A cubic was faired into a
straight line for the 5-digit sections.
NACA
5-Digit Series:
2 30 12
|
|
|
The 6-series of NACA airfoils departed from this
simply-defined family. These sections were generated from a more or less
prescribed pressure distribution and were meant to achieve some laminar flow.
NACA
6-Digit Series:
6 3, 2 - 2
1 2
Six- location half width ideal Cl max thickness
Series of min Cp
of low drag in tenths in % of chord
in 1/10 chord
bucket in 1/10 of Cl
After the six-series
sections, airfoil design became much more specialized for the particular
application. Airfoils with good transonic performance, good maximum lift capability,
very thick sections and very low drag sections are now designed for each use.
Often a wing design begins with the definition of several airfoil sections and
then the entire geometry is modified based on its 3-dimensional
characteristics.
WING AERODYNAMICS
SUPERCRITICAL AEROFOILS:
The supercritical airfoil, below,
maintains a lower Mach number over its upper surface than the conventional
airfoil, above, which induces a weaker shock.
A supercritical airfoil is
an airfoil designed, primarily, to delay
the onset of wave drag in the transonic speed range. Supercritical
airfoils are characterized by their flattened upper surface, highly cambered (curved) aft section, and
greater leading edge radius compared with
traditional airfoil shapes. The supercritical airfoils were designed in the
1960s, by then NASA engineer Richard Whitcomb, and were first tested on theTF-8A Crusader. While the design was initially developed
as part of the supersonic transport (SST) project at NASA, it has since been mainly applied
to increase the fuel efficiency of many high subsonic aircraft. The
supercritical airfoil shape is incorporated into the design of a supercritical
wing. Research in 1940 by Deutsche
Versuchsanstalt für Luftfahrt's K. A. Kawalki led to subsonic
profiles very similar to the supercritical profiles, which was the basis for
the objection in 1984 against the US-patent specification for the supercritical
airfoil.
Wing tip vortices
Wingtip vortices are tubes of circulating
air that are left behind a wing as it generates lift. One wingtip vortex trails from the tip of each wing. The cores of vortices
spin at very high speed and are regions of very low pressure. To first approximation, these low-pressure regions
form with little exchange of heat with the neighboring regions (i.e., adiabatically),
so the local temperature in the low-pressure regions drops, too. If it drops below the local dew point,
there results a condensation of water vapor present in the cores of wingtip
vortices, making them visible. The temperature may even drop below the local freezing point,
in which case ice crystals will form inside the cores.
Wingtip vortices are
associated with induced drag,
an unavoidable side-effect of the wing generating lift. Managing induced drag
and wingtip vortices by selecting the best wing planform for the mission is critically
important in aerospace engineering.
Downwash
There are many factors which influence the amount of
aerodynamic lift which a body generates. Lift depends
on the shape, size, inclination, and flow conditions of the air passing the object. For a
three dimensional wing, there is an additional effect on lift, called downwash, which will be
discussed on this page.
For a lifting wing, the air pressure on the top of the wing is lower than
the pressure below the wing. Near the tips of the wing, the air is free to move
from the region of high pressure into the region of low pressure. As the
aircraft moves to the lower left, a pair of counter-rotating vortices is formed
at the wing tips. The lines marking the center of the vortices are shown as
blue vortex lines leading from the wing tips. If the
atmosphere has very high humidity, you can sometimes see the vortex lines on an
airliner during landing as long thin "clouds" leaving the wing tips.
The wing tip vortices produce a downwash of air behind the wing which is very
strong near the wing tips and decreases toward the wing root. The local angle of attack of the wing is increased by the flow
induced by the downwash, giving an additional, downstream-facing, component to
the aerodynamic force acting over the entire wing. The downstream component of the force is called induced drag because it faces downstream and has
been "induced" by the action of the tip vortices. The lift near the
wing tips is defined to be perpendicular to the local flow. The local flow is
at a greater angle of attack than the free stream flow because of the induced
flow. Resolving the tip lift back to the free stream reference produces a reduction in the lift coefficient of the entire wing.
CONCEPTUAL
DESIGN CALCULATIONS:
General design procedure:
The general steps involved in the conceptual design
calculations are:
ü Finding maximum Lift co
efficient CL MAX
ü Finding Reynolds no
ü Selection of airfoil
ü Wing selection
1.
chord at the root section(c ROOT)
2.
chord at tip (c TIP)
3. mean aerodynamic centre
(ĉ)
4. aerodynamic
centre
5. distance
from mean aerodynamic centre chord from fuselage (Ŷ)
6. selection
of dihedral angle and wing incidence
7. wet
area calculation
8. Finding
drag co efficient (CD)
Step1:
Finding maximum Lift co efficient CL MAX
In order to find Lift force,
L
= C l max *.5 * ρ * s * (V stall)2 ---- (1)
Where,
ρ – Density
s – Wing area
V stall – stalling speed
And C l max – maximum lift co
efficient.
But for steady for flight condition,
L=W
------- (2)
Therefore the equation (1) becomes,
W=C
l max *.5*ρ*s* (V stall) 2
Therefore, to find C l max
C
l max= 2(w/s) / (ρ*Vstall2)
Where,
The wing loading, W/S= 265kg/m2
At an altitude of 9000m,
Density, ρ =.4663kg/m3,
Stalling speed,
The stalling speed shall not exceed
beyond 50knots for trainer aircrafts (Reference from the book aircraft design
by raymer)
(i.e)
V stall = 31.1m/s
Now substituting V stall on C
l max, we get,
C
l max = (265*2)/(.4663*31.12)
C l max = 1.21
STEP
2: REYNOLD NUMBER CALCULATION
We know that,
Re
= (ρ*v*l)/µ -------- (3)
Where, Density, ρ = .4663
V = 31.1 m/s
Chord, I = Span / Aspect ratio = 9.55 /
5.12 = 1.86m
Dynamic viscosity, µ= 14.35 * 10 -6
Kg / ms
Thus,
Re = (.4663*31.1*1.86) / (14.35*10-6)
Re
= 4.33*106
STEP
3: AEROFOIL SELECTION
From the obtained values of coefficient
of lift and Reynold’ s number, we can determine the type of aerofoil for the
design.
From the book THEORY OF WING SECTIONS BY ABBOT, Using the graph the aerofoil can
be selected. Thus the selection of aerofoil is,
NACA
4408
Performance parameters
WING
SELECTION
Wing is the part of the aircraft, which
produces lift force to the aircraft and in trainer aircrafts it provide for
fuel storage and landing gear alignments. Generally the tapered wing the chord
length of the aerofoil is not the same in root and tip.
STEP
1: CHORD AT THE ROOT SECTION(C root)
C
root = (2s) / [b*(1+λ)] -------- (4)
Where,
b - wing span
λ – taper ratio
S = w TO / (W/S) (w TO = Take off weight)
S = 4600 / 265 = 17.35 m2
b
= (Aspect ratio* span)1/2
b
= (9* 17.35).5 = 9.5 m
λ = 0.5 (For trainer aircrafts, )
Therefore,
C root = (2*17.35) / [9.5*(1+0.5)]
CROOT
= 2.12 m
Step
2: CHORD AT TIP (C tip)
C tip = c root * λ
------ (5)
C tip = 5.32 * 0.5
C
tip = 1.06 m
Step
3: MEAN AERODYNAMIC CENTRE (Ĉ)
Ĉ = (2/3) * C root * (1+λ +λ2)
/ (1+λ) -------- (6)
Ĉ = (2/3) * 2.12 * (1+0.5+0.25) /
(1+0.5)
Ĉ = 1.648 m
Step 4: AERODYNAMIC
CENTRE
A/D centre = 0.25 * Ĉ --------- (7)
A/D centre = 0.25 * 1.648m
A/D centre = 0.412 M
Step 5: DISTANCE FROM
MEAN AERODYNAMIC CENTRE CHORD FROM FUSELAGE (ŷ)
Ŷ
= [b * (1+2λ) *(1+ λ)] / 6 ------- (8)
Ŷ
= [9.5*(1+(2*0.5)) * (1+0.5)] / 6
Ŷ
= 4.75 m
Step
6: SELECTION OF DIHEDRAL ANGLE AND WING INCIDENCE
(1) The
dihedral angle = 5 degrees. (Dihedral angle is the
upward angle from horizontal of the wings or tail plane of a fixed-wing aircraft)
(2) Wing
incidence = 1 degree.
The above parameters can be assumed
(Reference from the book aircraft design by raymer)
Step
7: WET AREA CALCULATION
S
wet = S – S ref ----------
(9)
Where, S = 17.35 m2
S
ref = Root Chord * Fuselage Diameter = 2.12 * 1.2
S
ref = 2.54 m2
Thus, S wet = 17.35 – 2.54 =
14.806 m2
Where, (CL) 2 /
*(π *e* AR) ----------- (10)
Where,
Efficiency e = 0.8
AR = 5.12
CL = 1.21
Therefore,
(CL)
2 / *(π *e* AR) = (1.21)2 / (π *0.8*9)
=
0. 089
Thus,
CD
= CDO + [(CL) 2 / (π *e* AR)] ----------- (11)
=
0.0091 + 0.089
CD = 0.0981
Thus the drag is
calculated now,
D = (1/2) * ρ *
V2 * S * CD ----------- (12)
D = (1/2) *
.4663 * 31.12 * 17.35 * 0.0981
Therefore
the total drag, D = 387 N
SPECIFICATION OF THE
WING
|
WING
SPAN
|
9.5m
|
|
WING
AREA
|
17.45m2
|
|
C
L MAX
|
1.2
|
|
WING
PLANFORM
|
Tapered-slight
swept wing
|
|
STALLING
SPEED
|
31.1m/s
|
|
AIRFOIL
TYPE
|
NACA
4408
|
|
ASPECT
RATIO
|
5.12
|
|
SWEEP
ANGLE
|
5
DEGREES
|
With
the above derivatives the CAD modeling using CATIAV5 R20 can be done.
Some
of the tools used in the CATIA to create the CAD model are,
i)
Sketcher tools
ii)
Operations
iii)
Constraints
iv)
Sketch based features
v)
View, measure and
workbench
vi)
Reference elements
vii)
Surfaces etc.,
Also
different modules in CATIA like PART DESIGN, WIREFRAME AND SURFACE DESIGN and
ASSEMBLY DESIGN, DRAFTING are used.
Below
are some of the CAD modeled views of the wing structure.
ISOMETRIC VIEW
EXPLODED VIEW
Orthogonal view
CONCLUSION
Thus
the necessary literature survey on the wing structures and its types is learnt
and with the essential parameters and requirements the conceptual design is carried
out and the geometrical CAD model of the wing was drafted. The following table
gives the specification of the wing.
SPECIFICATION
OF THE WING
|
WING
SPAN
|
9.5m
|
|
WING
AREA
|
17.45m2
|
|
C
L MAX
|
1.2
|
|
WING
PLANFORM
|
Tapered-slight
swept wing
|
|
STALLING
SPEED
|
31.1m/s
|
|
AIRFOIL
TYPE
|
NACA
4408
|
|
ASPECT
RATIO
|
5.12
|
|
SWEEP
ANGLE
|
5
DEGREES
|
REFERENCES:
ü Aircraft
performance and design by J. Anderson
ü Aircraft
design by Raymer
ü Aircraft
design by Rosakkam
ü Theory
of wing sections by Abbott
ü www.Wikipedia.com
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