modgshjsjsjsjsjsjnjdjdjjsjdjdjdjjdjdjjdn

Studocu is not sponsored or endorsed by any college or university
Module 1
Elements of Aeronautics (Dr. Ambedkar Institute of Technology)
Studocu is not sponsored or endorsed by any college or university
Module 1
Elements of Aeronautics (Dr. Ambedkar Institute of Technology)
Downloaded by KEERTHIPRIYA (k93010217@gmail.com)
lOMoARcPSD|35498426

Module -1
Introduction to Aircrafts
History of aviation; Atmosphere and its properties; Classification of aircrafts; Basic
components of an aircraft; structural members; aircraft axis system; aircraft motions;
control surfaces and high lift devices; classification of aircraft; conventional design
configurations; principle of operation of each major part; Helicopters, their parts and
functions.
Aircraft Structures and Materials:
Introduction; general types of construction; monocoque, semimonocoque and geodesic
structures; typical wing and fuselage structure; metallic and non-metallic materials for
aircraft application.
History of Aviation
1. Leonardo da Vinci conceives the ornithopter, drawn more than 500 sketches from 1486 to
1490.
2. The Montgolfier hot-air balloon floats over Paris on November 21, 1783.
3. A red-letter date in the progress of aeronautics is 1799. In this year, Sir George Cayley in
England engraves on a silver disk his concept of a fuselage, a fixed wing, and horizontal
and vertical tails. He is the first person to propose separate mechanisms for the generation
of lift and propulsion.
4. The first two powered hops in history are achieved by the Frenchman Felix Du Temple in
1874 and the Russian Alexandar F. Mozhaiski in 1884.
5. Otto Lilienthal designs the first fully successful gliders in history. During the period from
1891 to 1896, he achieves more than 2000 successful glider flights.
6. Samuel Piperpont Langley, secretary of the Smithsonian Institution, achieves the first
sustained heavier-than-air, unmanned, powered flight in history with his small-scale
Aerodrome in 1896. However, his attempts at manned flight are unsuccessful, the last one
lOMoARcPSD|35498426

failing on December 8, 1903 – just nine days before the Wright brothers’ stunning
success.
7. Another red-letter date in the history of aeronautics, indeed in the history of humanity, is
December 17, 1903. On that day, at Kill Devil Hills in North Carolina, Orville and
Wilbur Wright achieve the first controlled, sustained, powered, heavier-than-air, manned
flight in history.
8. The development of aeronautics takes off exponentially after the Wright brothers’ public
demonstrations in Europe and the United States in 1908.
Atmosphere and its properties
Aerospace vehicles can be divided into two basic categories: atmospheric vehicles such
as airplanes and helicopters, which always fly within the sensible atmosphere, and space vehicles
such as satellites, which operate outside the sensible atmosphere.
(i) Atmospheric Pressure
lOMoARcPSD|35498426

Atmospheric pressure at any level reflects the weight of the column of air above
that level. Thus the pressure at a point on the earth’s surface must be greater than the
pressure at any height above it. An increase in surface pressure denotes an increase in
mass of the column of air above the surface. Similarly a decrease in surface pressure
denotes a decrease in the mass. The gradient is the difference in pressure, both vertically
and horizontally. In a standard atmosphere, the rate of change of altitude with pressure is
as indicated in the following table:
Altitude Rate of Change of Altitude with Pressure
0 to 1500 m 112 mb per kilometer
(ii) Absolute and Standard Temperature
The absolute temperature of the melting point of ice under a pressure of 1.01325
X 105
N/m2
is 273.16o
K.
The standard temperature at sea level is 15o
C. In terms of absolute temperature
scale, the standard temperature at sea level is 288.16o
K.
(iii) Atmospheric Density
The air is assumed to obey the perfect gas law, 𝜌 = 𝑃/𝑅𝑇, where 𝜌 is the density
in kg/m3
, P is static air pressure in hectopascals, R is gas constant and T is absolute
temperature in o
K.
(iv) Atmospheric Moisture
lOMoARcPSD|35498426

If a gas or vapour is cooled so that molecular movements become relatively
sluggish, the attractive forces draw the molecules close together to form a liquid. This
process is called condensation. At the same temperature and pressure, the moist
atmosphere including water vapour is slightly less dense than the dry atmosphere. This is
due to the fact that the vapour displaces a corresponding amount of the other gases per
unit volume and the molecular weight ratio of water vapour to dry air is 0.62:1. Thus the
moist air is more buoyant than the surrounding dry air.
(v) Humidity
Atmospheric humidity is usually described as a percentage of saturation value.
Relative humidity is the ratio of the amount of water vapour content in air to the amount
that would be present at saturation point at the same temperature. It is usually expressed
as a percentage. Specific humidity is the mass of water vapour per unit mass of moist air
in grams per kg. Absolute humidity is the mass of water vapour per unit volume of air
expressed in grams per m3
. Wet bulb temperature is the lowest temperature to which air
(surrounding the thermometer bulb) can be cooled by the evaporation of water.
Standard Atmosphere
1. For flight tests, wind tunnel results, and general airplane design and performance to a
common reference required standard atmosphere.
2. The definitions of the standard atmospheric properties are based on a given temperature
variation with altitude, representing a mean of experimental data. In turn, the pressure
and density variations with altitude are obtained from this empirical temperature variation
by using the laws of physics. One of these laws is the hydrostatic equation:
𝑑𝑝 = −𝜌𝑔𝑑ℎ𝐺
3. In the isothermal regions of the standard atmosphere, the pressure and density variation
are given by,
𝑝
𝑝1
=
𝜌
𝜌1
= 𝑒−[𝑔𝑜 (𝑅𝑇)
⁄ ](ℎ−ℎ1)
lOMoARcPSD|35498426

4. In the gradient regions of the standard atmosphere, the pressure and density variations are
given by, respectively,
𝑝
𝑝1
= (
𝑇
𝑇1
)
−𝑔𝑜/(𝑎𝑅)
𝑝
𝑝1
= (
𝑇
𝑇1
)
−{[𝑔𝑜/(𝑎𝑅)]+1}
where, 𝑇 = 𝑇1 + 𝑎(ℎ − ℎ1) and a is the given lapse rate.
5. The pressure altitude is that altitude in the standard atmosphere that corresponds to the
actual ambient pressure encountered in flight or laboratory experiments.
Classification of airplanes according to configuration
This classification is based on the following features of the configuration.
a) Shape, number and position of wing.
b) Type of fuselage.
c) Location of horizontal tail.
d) Location and number of engines.
lOMoARcPSD|35498426

Fig. 1.1 Airplane Wing Configuration
lOMoARcPSD|35498426

i) Classifications of airplane based on wing configuration
Early airplanes had two or more wings e.g. the Wright airplane had two wings braced with
wires. Presently only single wing is used. These airplanes are called monoplanes. When the wing
is supported by struts the airplane is called semi-cantilever monoplane (Fig.1.1a). Depending on
the location of the wing on the fuselage, the airplane is called high wing, mid-wing and low wing
configuration (Fig.1.1b, c and d). Further, if the wing has no sweep the configuration is called
straight wing monoplane (Fig.1.1e). The swept wing and delta wing configurations are shown in
Figs.1.1f and g.
ii) Classification of airplanes based on fuselage
Generally airplanes have a single fuselage with wing and tail surfaces mounted on the
fuselage (Fig.1.1 h). In some cases the fuselage is in the form of a pod. In such a case, the
horizontal tail is placed between two booms emanating from the wings (Fig.1.1 i). These
airplanes generally have two vertical tails located on the booms. The booms provide required tail
arm for the tail surfaces. Some airplanes with twin fuselage had been designed in the past.
However, these configurations are not currently favored.
iii) Classification of airplanes based on horizontal stabilizer
In a conventional configuration, the horizontal stabilizer is located behind the wing (Fig.1.1
j). In some airplanes there is no horizontal stabilizer and the configuration is called tailless
design (Fig.1.1 k). In these airplanes, the functions of elevator and aileron are performed by
ailevons located near the wing tips. When both ailevons (on left and right wings) move in the
same direction, they function as elevators and when the two ailevons move in opposite direction,
they function as ailerons. In some airplanes, the control in pitch is obtained by a surface located
ahead of the wing. This configuration is called canard configuration (Fig.1.1 l). In conventional
lOMoARcPSD|35498426

configuration the horizontal tail has a negative lift and the total lift produced by the wing is more
than the weight of the airplane. In canard configuration, the lift on the canard is in the upward
direction and lift produced by the wing is less than the weight of the aircraft. However, the
canard has destabilizing contribution to the longitudinal stability.
iv) Classification of airplanes based on number of engines and their location
Airplanes with one, two, three or four engines have been designed. In rare cases, higher
number of engines are also used. The engine, when located in the fuselage, could be in the nose
or in the rear portion of the fuselage. When located outside the fuselage the engines are enclosed
in nacelles, which could be located on the wings or on the rear fuselage. In case of airplanes with
engine-propeller combination, there are two configurations – tractor propeller and pusher
propeller. In pusher configuration the propeller is behind the engine (Fig.1.1h).
Factors affecting the configuration
The configuration of an airplane is finalized after giving consideration to the following factors.
i. Aerodynamics
ii. Low structural weight
iii. Lay-out peculiarities
iv. Manufacturing procedures
v. Cost and operational economics
vi. Interaction between various features
Main Components of an Aircraft
lOMoARcPSD|35498426

The basic components of an aircraft and the nuances of flight.
 The fuselage or the body of the airplane, holds all of the pieces together. The pilots sit in
the cockpit at the front of the fuselage, while passengers and cargo are carried in the rear
of the Some aircraft carry fuel in the fuselage, while others carry fuel in the wings.
 The empennage is the tail of the aircraft and its main purpose is to give stability to the It
consists of two flight control surfaces, the elevator, and the rudder. The elevator steers up
or down and the rudder steers from right to left.
 The wings are the primary lifting surfaces for the aircraft. A wing is a type of fin with a
surface, which produces aerodynamic force for flight or propulsion through the
atmosphere. The airflow over the wing is what generates the vast majority of lifting force
necessary for flight. In the event that the wings are not functioning properly during the
aircraft’s pre-flight inspection, a skilled aircraft dispatcher will delay the flight until the
wing is properly fixed and functioning.
 The powerplant or the engine generates the power or thrust for the aircraft. Private jets
usually have two engines.
 The landing gear allows the aircraft to take off, land, and taxi, and also provides shock
absorbers to enable smooth landing and takeoff.
lOMoARcPSD|35498426

Structural Members
Structural members of an aircraft's fuselage include stringers, longerons, ribs,
bulkheads, and more. The main structural member in a wing is called the wing spar. The skin
of aircraft can also be made from a variety of materials, ranging from impregnated fabric to
plywood, aluminum, or composites.
Stringers - a longitudinal structural piece in a framework, especially that of a ship or
aircraft,
Longerons - a longitudinal structural component of an aircraft's fuselage,
Ribs - The ribs are the parts of a wing which support the covering and provide the airfoil
shape, Usually ribs incorporate the airfoil shape of the wing, and the skin adopts this shape when
stretched over the ribs,
Bulkheads - A it is an upright wall within the hull of a ship or within the fuselage of an
airplane,
Spars - In a fixed-wing aircraft, the spar is often the main structural member of the wing,
running spanwise at right angles (or thereabouts depending on wing sweep) to the fuselage. The
spar carries flight loads and the weight of the wings while on the ground.
Formers - A former is a structural member of an aircraft fuselage, of which a typical
fuselage has a series from the nose to the empennage, typically perpendicular to the longitudinal
axis of the aircraft.
Frames - A frame is a structural system that supports other components of a physical
construction.
Aircraft Axis System
lOMoARcPSD|35498426

 Normal axis, or yaw axis — an axis drawn from top to bottom, and perpendicular to the
other two axes. Parallel to the fuselage station.
 Lateral axis, transverse axis, or pitch axis — an axis running from the pilot's left to right
in piloted aircraft, and parallel to the wings of a winged aircraft.
 Longitudinal axis, or roll axis — an axis drawn through the body of the vehicle from tail
to nose in the normal direction of flight, or the direction the pilot faces.
Aircraft Motions
Pitch - nose up or down about an axis running from wing to wing.
Yaw - nose left or right about an axis running up and down.
Roll - rotation about an axis running from nose to tail.
Maintaining Control
 The Ailerons Control Roll
On the outer rear edge of each wing, the two ailerons move in opposite directions, up and
down, decreasing lift on one wing while increasing it on the other. This causes the
airplane to roll to the left or right. To turn the airplane, the pilot uses the ailerons to tilt
the wings in the desired direction.
lOMoARcPSD|35498426

 The Elevator Controls Pitch
On the horizontal tail surface, the elevator tilts up or down, decreasing or increasing lift
on the tail. This tilts the nose of the airplane up and down.
 The Rudder Controls Yaw
On the vertical tail fin, the rudder swivels from side to side, pushing the tail in a left or
right direction. A pilot usually uses the rudder along with the ailerons to turn the airplane.
Control surfaces and high lift devices
Flight control surfaces are hinged (movable) Airfoils designed to change the attitude of
the aircraft during flight. These surfaces are divided into three groups—primary, secondary, and
auxiliary.
The primary flight control surfaces on a fixed-wing aircraft include: ailerons, elevators,
and the rudder. The ailerons are attached to the trailing edge of both wings and when moved,
rotate the aircraft around the longitudinal axis. The elevator is attached to the trailing edge of the
horizontal stabilizer. When it is moved, it alters aircraft pitch, which is the attitude about the
horizontal or lateral axis. The rudder is hinged to the trailing edge of the vertical stabilizer. When
the rudder changes position, the aircraft rotates about the vertical axis (yaw).
lOMoARcPSD|35498426

lOMoARcPSD|35498426

High Lift Devices
Basically, increasing the lift of an airfoil can be accomplished by anyone or combination
of the following three methods:
 Increase in the wing area,
 Increase in the camber of a wing, and
 Delay the separation through some means of boundary layer control.
i. Trailing edge devices
The trailing edge flap is a small auxiliary airfoil located at the rear of the main
airfoil. When the flap is deflected, it changes the geometry of the airfoil i.e.
increase in camber and the aerodynamic characteristics. The flap deflection
reduces the zero lift incidence and the stalling speed. The reduction in stalling
speed is beneficial because it decreases the incidence during take-off and landing.
ii. Plain Flap
The simplest type of trailing edge flap is a plain flap. Its operating principle is
simple in that its extension causes a change in the overall section camber. This
brings about an increase in the amount of lift. In fact, the zero-lift incidence angle
is reduced with virtually no effect on the lift-curve slope. However, flap extension
does reduce the section stalling angle as separation will occur earlier over a more
highly cambered upper surface.
iii. Split Flap
A split flap is like a flat metal plate, which is hinged on the lower surface at its
forward edge. Like a plain flap, deflection of split flap also increases the effective
camber. However, this has a minor effect on the upper surface as compared to
plain flap, resulting in less reduction in the stall angle and a slightly higher
∆CLmax. The main advantage of split flaps is that they are structurally very strong
and as a result can be extended at high speeds.
iv. Slotted Flap
A slotted flap is similar to a plain flap except that a small slot opens up when the
flap is moved to the extended position. This causes high pressure air to move
from the lower surface through the gap to the upper surface, thus re-energising the
lOMoARcPSD|35498426

upper surface boundary layer and delaying the premature separation problem
associated with plain flaps. It also allows the use of flap upto around 45o
.
v. Fowler Flap
A Fowler flap is similar to a slotted flap. However, when deflected, it increases
the lift by increasing the wing area as well as by increasing the camber. In the
retracted position it looks just like the split flap, however, when it is extended it
lowers and translates aft, thus increasing the wing area and camber.
vi. Leading Edge Devices
There are two basic categories of leading edge high lift devices as indicated
below:
a. Slots/slats, and
A slot is basically a boundary layer control device since it takes high energy air
from the lower surface of the wing and ducts it through the wing into the low
energy boundary layer on the upper surface. In doing so, it delays separation and
allows higher lift coefficients to be developed. A slot is relatively ineffective at
low angles of attack, but becomes very effective at high angles thus improving the
high lift characteristics without significantly compromising the low lift
characteristics.
b. Leading edge flaps
The leading edge flaps and slats increase the wing area and the wing camber. This
increases lift to help improve the take-off and landing performance of an aircraft.
These surfaces extend during take-off to increase lift, which permits slower
speeds for aircraft rotation. During landing, the leading edge slats fully extend to
increase lift and help prevent a stall.
Helicopters
Main Rotor System
 Root: The inner end of the blade where the rotors connect to the blade grips.
 Blade Grips: Large attaching points where the rotor blade connects to the hub.
 Hub: Sits atop the mast, and connects the rotor blades to the control tubes.
lOMoARcPSD|35498426

 Mast: Rotating shaft from the transmission, which connects the rotor blades to the
helicopter.
 Control Tubes: Push Pull tubes that change the pitch of the rotor blades.
 Pitch Change Horn: The armature that converts control tube movement to blade pitch.
 Pitch: Increased or decreased angle of the rotor blades to raise, lower, or change the
direction of the rotors thrust force.
 Jesus Nut: Is the singular nut that holds the hub onto the mast. (If it fails, the next person
you see will be Jesus).
This type of rotor system pivots around the trunion to allow for blade flapping
Swash plate
lOMoARcPSD|35498426

The swash plate assembly has two primary roles:
 Under the direction of the collective control, the swash plate assembly can change the
angle of both blades simultaneously. Doing this increases or decreases the lift that the
main rotor supplies to the vehicle, allowing the helicopter to gain or lose altitude.
 Under the direction of the cyclic control, the swash plate assembly can change the angle
of the blades individually as they revolve. This allows the helicopter to move in any
direction around a 360-degree circle, including forward, backward, left and right.
 The swash plate assembly consists of two plates -- the fixed and the rotating swash plates
-- shown above in blue and red, respectively.
 The rotating swash plate rotates with the drive shaft (green) and the rotor's blades (grey)
because of the links (purple) that connect the rotating plate to the drive shaft.
The pitch control rods (orange) allow the rotating swash plate to change the pitch of the
rotor blades.
 The angle of the fixed swash plate is changed by the control rods (yellow) attached to the
fixed swash plate. The fixed plate's control rods are affected by the pilot's input to the
cyclic and collective controls. The fixed and rotating swash plates are connected with a
set of bearings between the two plates. These bearings allow the rotating swash plate to
spin on top of the fixed swash plate.
lOMoARcPSD|35498426

Controls
 Collective: The up and down control. It puts a collective control input into the rotor
system, meaning that it puts either "all up", or "all down" control inputs in at one time
through the swash plate. It is operated by the stick on the left side of the seat, called the
collective pitch control. It is operated by the pilots left hand.
The collective lets you change the angle of attack of the main rotor simultaneously on both
blades.
 Cyclic: The left and right, forward and aft control. It puts in one control input into the
rotor system at a time through the swash plate. It is also known as the "Stick". It comes
out of the centre of the floor of the cockpit, and sits between the pilots legs. It is operated
by the pilots right hand.
lOMoARcPSD|35498426

The cyclic changes the angle of attack of the main rotor's wings unevenly by tilting the swash
plate assembly. On one side of the helicopter, the angle of attack (and therefore the lift) is
greater.
 Pedals: These are not rudder pedals, although they are in the same place as rudder pedals
on an airplane. A single rotor helicopter has no real rudder. It has instead, an anti-torque
rotor (Also known as a tail rotor), which is responsible for directional control at a hover,
and aircraft trim in forward flight. The pedals are operated by the pilots feet, just like
airplane rudder pedals are. Tandem rotor helicopters also have these pedals, but they
operate both main rotor systems for directional control at a hover.
The Tail Rotor
The tail rotor is very important. If you spin a rotor using an engine, the rotor will rotate,
but the engine and the helicopter will try to rotate in the opposite direction. This is called
TORQUE REACTION.
The tail rotor is used like a small propeller, to pull against torque reaction and hold the
helicopter straight.
lOMoARcPSD|35498426

By applying more or less pitch (angle) to the tail rotor blades it can be used to make the
helicopter turn left or right, becoming a rudder. The tail rotor is connected to the main rotor
through a gearbox. When using the tail rotor trying to compensate the torque, the result is an
excess of force in the direction for which the tail rotor is meant to compensate, which will tend to
make the helicopter drift sideways. Pilots tend to compensate by applying a little cyclic pitch, but
designers also help the situation by setting up the control rigging to compensate. The result is
that many helicopters tend to lean to one side in the hover and often touchdown consistently on
one wheel first. On the other hand if you observe a hovering helicopter head-on you will often
note that the rotor is slightly tilted. All this is a manifestation of the drift phenomenon.
lOMoARcPSD|35498426

This picture illustrates how the helicopter moves when using the appropriate controls. Up
and Down movements are controlled by the "Collective". Side to Side and Forward and Back
motions are controlled by the "Cyclic". Lateral control (Also called directional control or "Yaw")
is achieved by using the "Foot Pedals".
Fuselage
Fuselage is the main body of an aircraft where all of the aircraft’s components are
attested and holds crew and passenger/ cargo. In single engine aircraft it contains an engine. The
fuselage also serves to position control and stabilization surfaces in specific relationships to
lifting surfaces, required for aircraft stability and maneuverability.
Types of Structures
Truss Structure
1. Truss Structure: The truss-type fuselage is constructed of steel or aluminum tubing. Strength
and rigidity is achieved by welding the tubing together into a series of triangular shapes, called
trusses.
Construction of the Warren truss features longerons, as well as diagonal and vertical web
members. To reduce weight, small airplanes generally utilize aluminum alloy tubing, which may
be riveted or bolted into one piece with cross-bracing members.
lOMoARcPSD|35498426

As technology progressed, aircraft designers began to enclose the truss members to streamline
the airplane and improve performance. This was originally accomplished with cloth fabric,
which eventually gave way to lightweight metals such as aluminum. In some cases, the outside
skin can support all or a major portion of the flight loads.
Geodesic Construction
2. Geodesic Construction: In this type of construction multiple flat strip stringers are wound
about the formers in opposite spiral directions, forming a basket-like appearance. This proved to
be light, strong, and rigid and had the advantage of being made almost entirely of wood. The
geodesic structure is also redundant and so can survive localized damage without catastrophic
failure. The logical evolution of this is the creation of fuselages using molded plywood, in which
multiple sheets are laid with the grain in differing directions to give the monocoque type.
3. Monocoque Shell: The monocoque design uses stressed skin to support almost all imposed
loads. This structure can be very strong but cannot tolerate dents or deformation of the surface.
This characteristic is easily demonstrated by a thin aluminum beverage can. You can exert
considerable force to the ends of the can without causing any damage.
lOMoARcPSD|35498426

Semi-monocoque and Monocoque
However, if the side of the can is dented only slightly, the can will collapse easily. The true
monocoque construction mainly consists of the skin, formers, and bulkheads. The formers and
bulkheads provide shape for the fuselage.
Since no bracing members are present, the skin must be strong enough to keep the fuselage rigid.
Thus, a significant problem involved in monocoque construction is maintaining enough strength
while keeping the weight within allowable limits. Due to the limitations of the monocoque
design, a semi-monocoque structure is used on many of today´s aircraft
4. Semi-monocoque: The semi-monocoque system uses a substructure to which the airplane´s
skin is attached. The substructure, which consists of bulkheads and/or formers of various sizes
and stringers, reinforces the stressed skin by taking some of the bending stress from the fuselage.
The main section of the fuselage also includes wing attachment points and a firewall.
lOMoARcPSD|35498426

On single-engine airplanes, the engine is usually attached to the front of the fuselage. There is a
fireproof partition between the rear of the engine and the cockpit or cabin to protect the pilot and
passengers from accidental engine fires. This partition is called a firewall and is usually made of
heat-resistant material such as stainless steel.
Wing Design
• Wings are airfoils that, when moved rapidly through the air, create lift. They are built in
many shapes and sizes.
• Wing design can vary to provide certain desirable flight characteristics. Control at
various operating speeds, the amount of lift generated, balance, and stability all change as
the shape of the wing is altered.
• Both the leading edge and the trailing edge of the wing may be straight or curved, or one
edge may be straight and the other curved.
• One or both edges may be tapered so that the wing is narrower at the tip than at the root
where it joins the fuselage. The wing tip may be square, rounded, or even pointed.
• The internal structures of most wings are made up of spars and stringers running
spanwise and ribs and formers or bulkheads running chordwise (leading edge to trailing
edge).
• The spars are the principle structural members of a wing. They support all distributed
loads, as well as concentrated weights such as the fuselage, landing gear and engines.
lOMoARcPSD|35498426

• The skin, which is attached to the wing structure, carries part of the loads imposed during
flight. It also transfers the stresses to the wing ribs. The ribs, in turn, transfer the loads to
the wing spars.
• In general, wing construction is based on one of three fundamental designs:
1. Monospar - The monospar wing incorporates only one main spanwise or longitudinal
member in its construction. Ribs or bulkheads supply the necessary contour or shape to
the airfoil.
2. Multispar - The multispar wing incorporates more than one main longitudinal member
in its construction. To give the wing contour, ribs or bulkheads are often included.
3. Box beam - The box beam type of wing construction uses two main longitudinal
members with connecting bulkheads to furnish additional strength and to give contour to
the wing
CONSTRUCTION MATERIALS
An aircraft must be constructed of materials that are both light and strong. Early aircraft
were made of wood. Lightweight metal alloys with a strength greater than wood were developed
and used on later aircraft. Materials currently used in aircraft construction are classified as either
metallic materials or nonmetallic materials.
METALLIC MATERIALS
The most common metals used in aircraft construction are aluminum, magnesium, titanium,
steel, and their alloys.
Alloys
An alloy is composed of two or more metals. The metal present in the alloy in the largest
amount is called the base metal. All other metals added to the base metal are called alloying
elements. Adding the alloying elements may result in a change in the properties of the base
metal. For example, pure aluminum is relatively soft and weak. However, adding small amounts
lOMoARcPSD|35498426

or copper, manganese, and magnesium will increase aluminum's strength many times. Heat
treatment can increase or decrease an alloy's strength and hardness. Alloys are important to the
aircraft industry. They provide materials with properties that pure metals do not possess.
Aluminum
Aluminum alloys are widely used in modern aircraft construction. Aluminum alloys are valuable
because they have a high strength-to-weight ratio. Aluminum alloys are corrosion resistant and
comparatively easy to fabricate. The outstanding characteristic of aluminum is its lightweight.
Magnesium
Magnesium is the world's lightest structural metal. It is a silvery-white material that
weighs two-thirds as much as aluminum. Magnesium is used to make helicopters. Magnesium's
low resistance to corrosion has limited its use in conventional aircraft.
Titanium
Titanium is a lightweight, strong, corrosion-resistant metal. Recent developments make
titanium ideal for applications where aluminum alloys are too weak and stainless steel is too
heavy. Additionally, titanium is unaffected by long exposure to seawater and marine atmosphere.
Steel Alloys
Alloy steels used in aircraft construction have great strength, more so than other fields of
engineering would require. These materials must withstand the forces that occur on today's
modern aircraft. These steels contain small percentages of carbon, nickel, chromium, vanadium,
and molybdenum. High-tensile steels will stand stress of 50 to 150 tons per square inch without
failing. Such steels are made into tubes, rods, and wires. Another type of steel used extensively is
stainless steel. Stainless steel resists corrosion and is particularly valuable for use in or near
water.
NONMETALLIC MATERIALS
lOMoARcPSD|35498426

In addition to metals, various types of plastic materials are found in aircraft construction. Some
of these plastics include transparent plastic, reinforced plastic, composite, and carbon-fiber
materials.
Transparent Plastic
Transparent plastic is used in canopies, windshields, and other transparent enclosures.
You need to handle transparent plastic surfaces carefully because they are relatively soft and
scratch easily. At approximately 225°F, transparent plastic becomes soft and pliable.
Reinforced Plastic
Reinforced plastic is used in the construction of radomes, wingtips, stabilizer tips,
antenna covers, and flight controls. Reinforced plastic has a high strength-to-weight ratio and is
resistant to mildew and rot. Because it is easy to fabricate, it is equally suitable for other parts of
the aircraft.
Composite and Carbon Fiber Materials
High-performance aircraft require an extra high strength-to-weight ratio material.
Fabrication of composite materials satisfies this special requirement. Composite materials are
constructed by using several layers of bonding materials (graphite epoxy or boron epoxy). These
materials are mechanically fastened to conventional substructures. Another type of composite
construction consists of thin graphite epoxy skins bonded to an aluminum honeycomb core.
Carbon fiber is extremely strong, thin fiber made by heating synthetic fibers, such as rayon, until
charred, and then layering in cross sections.
lOMoARcPSD|35498426

modgshjsjsjsjsjsjnjdjdjjsjdjdjdjjdjdjjdn

Recommended

Recommended

More Related Content

Similar to modgshjsjsjsjsjsjnjdjdjjsjdjdjdjjdjdjjdn

Similar to modgshjsjsjsjsjsjnjdjdjjsjdjdjdjjdjdjjdn (20)

Recently uploaded

Recently uploaded (20)

modgshjsjsjsjsjsjnjdjdjjsjdjdjdjjdjdjjdn