Elements of-aeronautics

KIT – KALAIGNAR KARUNANIDHI
INSTITUTE OF TECHNOLOGY
( Approved by AICTE, Affiliated to Anna University, Chennai )
KANNAMPALAYAM, COIMBATORE – 641 402.
Department of Aeronautical engineering
Course Material
AE 6302 – ELEMENTS OF AERONAUTICS

UNIT – I
Historical Evaluation
1. Biplanes:
Type of airplane in which two wings are placed one above the other to increase the lift
produced with minimum speed. (e.g) Wright Flyer – I
2. Monoplanes
Type of airplane in which only one wings will be there placed along the lateral axis of
aircraft.(e.g) most modern air crafts are monoplanes.
3. Biplane interference:
The condition in a biplane in which the high pressure on under surface of upper wing low
pressure on upper surface of lower using, results in interference between two wings. Thus lift is
reduced.
4. An ornithopter:-
The concepts of wings flapped up and down by various mechanical mechanisms, powered by
some type of human arm, leg or lady movement was given by Leonardo da vinci in late 15th
century. This is termed as ornithopter.
5. Triplane:
Type of airplane in which three wings are placed one above the other. The wings are called
as low wing, mid wing and shoulder wing.
6. Differentiate between Monoplanes and Biplanes.
Monoplanes Biplanes
a) Only one wing is present.
b) Lift produced will be loss compared to
biplane
c) Biplane interference will not occur
Two wings placed one above other. They are
a) Upper wing and
b) Lower wing lift produced will be high but
not exactly double the monoplane
Biplane interference will occur
7. Differentiate between Lighter than Aeroplanes and Heavier than Aeroplanes.
Lighter than Aeroplanes Heavier than Aeroplanes
Based on Archimedes principles.
Pay load is very less control and manocurve is
tedius
Based on lift produced by a moving body.
Payload is very high control and manocurve is
simple.

Engines are not used for propulsion Engines are used for propulsion.
8. What is the difference between Airmen and Chauffeurs?
Airmen Chauffeurs
a) Air man are those who recognized the need
to get up in the air, fly around with gliders
and obtain the feel of an airplane before
engine was used for powered flight.
b) They are interested in flight control in air
a) Chauffeurs are those who just makes
engine and fix, in air frame and gets into air.
b) They interested in thrust and light.
9. Whirling arm apparatus.
Whirling arm apparatus is the one which is used by cay by to test air foils. This is nothing
but a airfoil mounted on the end of a long rod, which was rotated at some speed to generate a flow
of air over airfoil, which allowed the measurement of aerodynamic forces and centre of pressure
on lifting surface.
10. Glider:
Gliders are un powered airframes, which has very large lift producing surfaces and less weight.
11. Four forces acting on an aero plane.
i) lift - Perpendicular to direction of relative wind
ii) Drag - Parallel to direction of relative wind
iii) Thrust - produces forward motion
iv) Weight - force of gravity
12. Lift:
A force on airplane which is perpendicular to the direction of relative wind and opposite in
the direction of weight in level flight.
13. Drag:
A force acting on aero plan, which is parallel to the direction of relative wind a opposite
to thrust direction under level flight.
14. Composition of aluminum alloy used in modern aircraft.
i) Duralumin ii) Jn Bocing 747
Al-93.5%
Cu-4.4%
Mn-1.5%
Mg-0.6%
Al-80%
Steel-17%
Titanium-3%
15. How aircrafts propelled during early days?
Some basic propulsion methods are
i) Paddle wheel mechanism

ii) Steam engine
iii) Flapper using type
iv) Reciprocating engine, etc.
PART - B
DEVELOPMENTS IN PROPULSION AND MATERIALS:-
Human effort to fly literally got off the ground on November 21, 1783, when a balloon
carrying Pilatre de Rozier and Marquis d‟ Arlandes ascended into the air and drifted 5 miles across
Paris. The balloon was inflated and buoyed up by hot air from an open fire burning in a large
wicker basket underneath. It was the first time humans had been lifted off the ground for a
sustained period of time.
In 1799, Sir George Cay by used a paddle wheel mechanism for the propulsion of his aero
plane. He also stated that lift is generated by a region of low pressure on the upper surface of
using.
In 1810, the first successful airship, propelled by a steam engine was built.
In 1849, he built and tested a full – size airplane of trip lane type called “The Boy carrier”
and the vertical and horizontal fail surfaces are made and propulsive mechanism is flapper wing
type.
William Samuel Hendon (1812-1888) was contemporary of cay by. In April 1843, he
published in England a design for a fixed using airplane powered by steam engine driving two
propelled called the aerial steam carriage. In this type the engine is inside a closed fuselage,
driving two propellers.
In 1857, Felix Du Temple made the first successful powered model airplane in monoplane
type swept. Forward wings and was powered by lock work.
In 1874, In Temple achieved the world first powered take off by a piloted, full size airplane;
it was powered by some type of hot air engined.
In 1884 Alexander F. Mozhaiski designed a steam powered monoplane,
In 1893, lilienthal build a powered machine; however, the prime mover was carbonic acid
gas motor that twisted six states at each using tip, obviously an ornithoptes type ideal to mimic the
natural mode of propulsion for birds.
In 1897, Hawk was designed with 4hp engine weighing about 40lt, driving a 5-ft diameter
propeller by pitcher.
In 1905 samuel Pierpont Langley designed and builded a series of powered aircraft which
finally culminated in two attempted piloted flights.

Cay lay build a large whirling arm, powered by a steam engine, with which he made force
test on airfoils. He then build nearly 100 different types of rubber – band – powered model
airplanes, graduating to steam – powered models in 1892.
It had two propellers between the wings, powered by a 1-hp steam engines of langley‟s own
design.
Departing from his earlier use of steam Langley correctly decided that the gasoline fueled
engine was the proper prime mover for air craft. The first commissioned Stephan Balzer of New
York to produce such an engine. The resulting engine produced 52.4 hp and yet weighted only
208 lt.
Using 1.5-hp gasoline fueled engine he made successful flight with quarter scale size.
In 1903, Willbar‟s build theirs own engine of 12 hp and 200 lp weight.
In Wright flyer I, the spectacular gasoline fueled Wright engine, driving two pushes
propellers. By means of bicycle type chains.
In 1905, the advanced propellers are used in flyer III
During 1905 to 1908, wright‟s atleast would have designed six new engines.
In 1909, the European designers were quick to adopt the long, slender shape wright‟s
propeller, different from wide paddle like shape
The efficiency of propeller used to 76%
DEVELOPMENTS IN STRUCTURE OVER THE YEARS:-
The idea of flying come to human from birds. The early greek myth of daedalus and his son
I carus. Imprisoned on the Island of crete. Daedalus and his son made flying model both escaped
from prison.
Leonards da vinci have designed many or nithopters during 15th
century it is a human
powered flight by flapping wing.
George cayley in 1799 gave concept of fixed using for generating lift, a paddles for a
propulsion and combined horizontal and vertical (cruciform) tail for stability. In 1804, he built a
whirling – arm apparatus for testing air foils similar to wind tunnels and also designed a model
glider. He represented first modern – configuration of air plane with a fixed wing and horizontal
and vertical tail.
In 1809 cayley explained that when surface inclined at some angle to the direction of
motion will generate lift and that a cambered surface will do this more efficiently than a flat surface.
For first time in history that lift is generated by a region of low pressure on the upper surface of the
using.

The first successful air ship, propelled by a steam by a steam engine, was built by Henri Gifford
in Paris in 1852 in 1849, he built and tested a full – size airplane.
The modulation are
i) A main using at an angle of incidence for lift, with a dihedral for lateral stability
ii) An adjustable cruciform tail for longitudinal directional stability.
iii) A pilot – operated elevator and rudder
iv) A fuselage in the form of a car, with a pilot‟s seat and three – wheel under carriage
v) A tubular beam and box beam construction.
vi) Tricycle landing gear
In 1857, Felix Du temple made a monoplane with swept- forward wings and in 1884 he made
steam powered plane
In 1866, Francis H. wenhem published paper, in that most of the lift of a wing was obtained
from the portion near the leading edge and using with high aspect ratio was the most efficient for
producing lift.
In 1891, otto lilienthal designed and flow the first successful controlled gliders in history with
birdlike platform of the using lilienthal used cambered (carried) airfoil shaped on the using and
incorporated vertical and horizontal tail planes in the back for stability.
In 1896, Chanute designed a hang gliders and biplane glider which introduced by the effective
platt truss method of structural rigging.
In 1903, Langley stepped directly to the full size airplane. He mounted this on tandem winged
aircraft on a catapult to provide an assisted take off.
In willur‟s model the use of using twist to control airplane in lateral (rolling) motion and aibrons
are used on modern airplanes for this purpose, willur wined the term using warping and led to their
first aircraft, a trip lane kite with using span of 5 ft in 1899.
A full size biplane glider was ready by September 1900, it had 17 ft using span and a horizontal
elevator in front of the wings, and was usually flows on strings from the ground.
In 1901, Glider 2 was made of larger using span of 22-ft using span.
In 1902, they made about 200 different airfoil shapes.
In September 20, 1902 number 3 glider of biplane type flow with wing span of 32-ft 1- inch, with
modification in vertical rudder behind the wings.
In 1903, they made wright flyer I of using span 40 feet 4 inch and used double rubber behind
the wings and a double elevator in front of the wings.

In 1904, wright flyer II made with a smaller using camber (airfoil curvature) and a more
powerful and efficient engine.
In 1905, with more progress flyer III with slightly lower using area, increased airfoil camber,
large biplane elevator, double rubber and improved propellers was made.
In 1909, Henri Farman III introduced flap like ailerons at the trailing edge near wing tips,
ailerons quickly became the favored mechanical means for lateral control, continuing to present
day.
Thus the structure of air craft have attained several stages of improvements and made into a
fine structure with high rigid strength and very less drag for effective airborne of air craft.
MATERIALS:
Some of the materials commonly used in flight structures.
Aluminium:
It is the most widely used material in aircraft structures. Modern commercial transports such
as Boeing 749 use aluminum for about 80% of the structure. Al in reality formed and machined
has reasonable cost is corrosion – resistant, and has an excellent strength – to – weight ratio. In
its pure from Al in two self for aircraft use. Therefore alloys of Al are used, the most common being
Al 2024, an alloy consisting of 93.5%. Al, 4.4% cu, 1.5% Mn and 0.6% Mg. this alloy is also called
duralumin. The first metal covered airplanes were designed by Miyo Junkens. In 1914. He finet
used all steel, which proved to be too heavy, In 1915, he turned to the use of duralumin.
Steel:-
For a typical commercial transport, steel makes up about 17% of the structure. If in used in
those areas requiring very high strength, such as wing attachment fittings, landing gears, engines
fittings, and flap tracks steel in an alloy of iron and carbon, typical steel alloys have about 1%
carbon. Stainless steel is an alloy of steel and chromium that has good corrosion resistant
properties.
Titanium:
Titanium has a better strength- to – weight ratio than aluminum and retains its strength at
higher temperatures however it is hard to form and machine and in expensive, costing about 5 to
10 times more than Al. But some supersonic air craft have to use titanium because of the high skin
temperatures due to aerodynamic heating.
High temperature Nickel alloys:
The hypersonic airplanes require advanced, high – temperature materials to withstand the
high rates of aerodynamic heating at hypersonic speeds. Some nickel – based alloys are capable
of withstanding the temperatures associated with moderate hypersonic speeds.

The hypersonic aircraft X-15 made by usage of inconel, a nickel – based alloy.
Composites:
Composites materials can yield at least a 25% reduction in weight. Composites are quite
different from metals, in both their composition and physical properties.
Generally composites mean “made up of distinct components”.
For example, the nockhead – martin F-22 has 28% of its structure made up of composite
material with 33% Al, 24% Ti, 5% steel and 10% miscellaneous.
Biplanes:
Biplanes is plane using two aerofoils one placed above other. It is naturally come from birds
but the biplane idea seems to be a purely man made invention, though some naturalists claim that
there are biplane insects. At any rate of, the first plane to fly was a biplane, so the idea is at least
as old as the history of flight.
A very large wing areas are required for flight, and advantage of the biplane was that this
large area could arranged in a more compact fashion, making the finished aeroplane more
convenient to handle both on the ground and in the air. The biplane structure seemed more suited
than the monoplane to give as what we most required. Strength without weight so far the biplane
seemed to have all the advantages why then, has it proved the loser in the long run.
It is as a wing, as an aerofoil, that the monoplane has always been superior. Remembering
how the pressure is distributed round a wing section let us put two such section let us put two such
sections together, one above the other, and observe the effect. The increase pressure on the
under surface of the upper wing is not to so effective as it was when it was alone – still less is the
decreased pressure. Above the lower wing so effective; thus both upper and lower wings suffer.
There is in fact, an interference between the two wings and this is called bipolar interference.
Another way of thinking of it is to consider the induced drag, which is greater on a biplane – with
its four wing tips-than on a monoplane of the same wing area and so the overall lift 1 drag ratio of
the monoplane is better than that of the bipolar.

Fig.
The biplane enthusiasts full of confidence owing to the structural superiority of the bipolar
persistently endeavored to minimize this disadvantage.
To eliminate the interference by staggering the planes. That is separating them horizontally
rather than vertically.
 When the leading edge of the upper plane was infront of the leading edge of the lower
plane it was called forward (or) positive stagger.
 When behind it, it was called back ward (or) Negative stagger.
Wright Brothers contribution and their development in obtaining their successful flight
Willur and orille wright – Inventors of the first practical airplane they are called the premier
aeronautical engineers of history.
Willur look up the study of bird flight as a guide on the path toward mechanical flight. Willur
wrote to smithronian institution in May 1899 for papers and books on aeronautics in turn her
received a brief bibliography of flying. This led to their first air craft, a biplane kite with a using
spane of 5 ft in August 1899.
A full size biplane glider was ready by September 1900 and was flown in October of that year
at kity Hawk. It had a 17-ft using span and a horizontal elevator in front of the wings and was
usually flown on strings from the ground.
Willur and orbille preceded to build their number 2 glider moving their base of operations to kill
Devils Hills, 4 miles south of kitty Hawk, they tested number 2 during July and August of 1901.
This new glider was somewhat larger, with a 22-ft wing span. As with all wright machines, it has a
horizontal elevator in front of the wings.
The wrights were not loose to being satisfied with their results when they returned to Dayton
after their 1901 tests with the number 2 glider, both brothers began to suspect the existing data
that appeared in the aeronautical literature.
Between September 1901 and August 1902 the wrights under took a major program of
aeronautical research. They built a wind tunnel in their bicycle shop in Dayton and tested more
than 200 different airfoil shapes. They designed a force balance to measure accurately the lift a
drag.
The papers of Wilbur and orvile wright in 1901 led to their number 3 glider, which was flown in
1902. It was so successful. It first flew at kill Devil Hills on September 20, 1902. It was a biplane
glider with a 32 ft 1-inch wing span, the largest of wright gliders to data.
After several modifications, the wrightor added a vertical ladder behind the wings. During 1902,
they made more than 1000 perfect flights. They set a distance record of 622.5 ft and a duration

record of 26s. In the process, both Wilbur and orville become highly skilled and proficient pilots,
something‟s that would later be envied world wide.
They designed and burst their own engine during the winter months of 1903 It produced 12hp
and weighed about 200lt. moreover, they conducted their own research which allowed them to
design an effective propeller.
Wilbur and orville built their flyer I from scratch during the summer of 1903. After orville‟s first
flight on that December 17, three more flight were made during the morning, the last covering 852
if an remaining in the air for 59s the In may 1904, their second powered machine, the Wright flyer
II was ready this air craft had a smaller wing camber and more powerful and efficient engine. More
progress was made in 1905. The Wright flyer III was ready by June. The wing area was slightly
smaller than that of the flyer II, the airfoil camber was increased back to what it had been in 1903.
biplane elevators was made larger and was placed.
Composites and advanced materials in aircraft
The Lockheed F-22 uses composites for the atleast a third of its structure.
For many years, aircraft designers could propose theoretical designs that they could not
build because the materials needed to construct them did not exist (The term “unobtainium” is
sometimes used to identify materials that are desired but not yet available.) For instance, large
spaceplanes like the Space Shuttle would have proven extremely difficult, if not impossible, to
build without heat – resistant ceramic tiles to protect them during re – entry. And high – speed
forward-swept-wing airplanes like Grumman‟s experimental X-29 or the Russian Sukhoi S-27
Berkut would not have been possible without the development of composite materials to keep their
wings from bending out of shape.
Composites are the most important materials to be adapted for aviation since the use of
aluminium in the 1920s. composites are materials that are combinations of two or more organic or
inorganic components. One material serves as a “matrix,” which is the material that holds
everything together, while the other materials serves as a reinformcement, in the form of fibres
embedded in the matrix. until recently, the most common matrix materials were ”thermosetting”
materials such as epoxy, bismaleimide, or polymide. The reinforcing materials can be glass fibre,
boron fibre, carbon fibre, or other more exoitic mixtures.

Fiberglas is the most common composite material, and consists of glass fibres embedded
in a resin matrix. Fiberglas was first used widely in the 1950s for boats and automobiles, and
today most cars have fiberglass bumpers covering a steel frame Fiberglas was first used in the
boeing 707 passenger jet in the 1950s, where it comprised about two percent of the structure. By
the 1960s, other composite materials became available, in particular boron fibre and graphite,
embedded in epoxy resins. The U.S. Air Force and U.S. Navy began research into using these
materials for aircraft control surfaces like ailerons and rudders. The first major military production
use of boron fibre was for the horizontal stabilizers on the Navy‟s F-14 Tomcat interceptor. By
1981, the British Aerospace-McDonnell Douglas AV-8B Harrier flew with over 25 percent of its
structure made of composite materials.
Making composite structures is more complex than manufacturing most metal structures.
To make a composite structure, the composite material, in tape or fabric form, is laid out and put in
a mould under heat and pressure. The resin matrix material flows and when the heat is removed, it
solidifies. It can be formed into various shapes. In some cases, the fibres are wound tightly to
increase strength. One useful feature of composites is that they can be layered, with the fibres in
each layer running in a different direction. This allows materials engineers to design structures that
behave in certain ways. For instance, they can design a structure that will bend in one direction,
but not another. The designers of the Grumman X-29 experimental plane used this attribute of
composite materials to design forward – step wings that did not bend up at the tips like metal
wings of the same shape would have bent in flight.
The greatest value of composite materials is that they can be both lightweight and strong.
The heavier an aircraft weighs, the more fuel it burns, so reducing weight is important to
aeronautical engineers.
Despite their strength and low weight, composites have not been a miracle solution for
aircraft structures. Composites are hard to inspect for flaws. Some of them absorb moisture. Most
importantly, they can be expensive, primarily because they are labour intensive and often require
complex and expensive fabrication machines. Aluminium, by contrast, is easy to manufacture and
repair. Anyone who has ever gotten into a minor car accident has learned that dented metal can
be hammered back into shape, but a crunched fiberglass bumper has to be completely replaced.
The same is true for many composite materials used in aviation.
Modern airliners use significant amounts of composites to achieve lighter weight. About ten
percent of the structural weight of the Boeing 777, for instance, is composite material. Modern
military aircraft, such as the F-22, use composites for at least a third of their structures, and some
experts have predicted that future military aircraft will be more than two – thirds composite
materials. But for now, military aircraft use substantially greater percentages of composite
materials than commercial passenger aircraft primarily because of the different ways that
commercial and military aircraft are maintained.
Aluminum is a very tolerant material and can take a great deal of punishment before it fails.
It can be dented or punctured and still hold together. Composites are not like this. If they are
damaged, they require immediate repair, which is difficult and expensive. An airplane made
entirely from aluminium can be repaired almost anywhere. This is not the case for composite
materials, particularly as they use different and more exotic materials. Because of this, composites

will probably always be used more in military aircraft, which are constantly being maintained, than
in commercial aircraft, which have to require less maintenance.
Thermoplastics are a relatively new material that is replacing thermosets as the matrix
material for composites. They hold much promise for aviation applications. One of their big
advantages is that they are easy to produce. They are also more durable and tougher than
thermosets, particularly for light impacts, such as when a wrench dropped on a wing accidentally.
The wrench could easily crack a thermoset material but would bounce off a thermoplastic
composite material.
In addition to composites, other advance materials are under development for aviation.
During the 1980s, many aircraft designers became enthusiastic about ceramics, which seemed
particularly promising for lightweight jet engines, because they could tolerate hotter temperatures
than conventional metals. But their brittleness and difficulty to manufacture ewer major draw
backs, and research on ceramics for many aviation applications decreased by the 1990s.
Many modern light aircraft are constructed in composite material such as this Glasair
Aluminium still remains a remarkably useful material for aircraft structures and metallurgists
have worked hard to develop better aluminium alloys (a mixture of aluminium and other materials).
In particular, aluminium-lithium is the most successful of these alloys. It is approximately ten
percent lighter than standard aluminium. Beginning in the later 1990s it was used for the Space
Shuttle‟s large External Tank in order to reduce weight and enable the shuttle to carry more
payload. Its adoption by commercial aircraft manufacturers has been slower, however, due to the
expense of lithium and the greater difficulty of using aluminium lithium (in particular, it requires

much care during welding). But it is likely that aluminium lithium will eventually become a widely
used material for both commercial and military aircraft.
Aircraft Structural Design
Introduction
Although the major focus of structural design in the early development of aircraft was on
strength, now structural designers also deal with fail – safety, fatigue, corrosion, maintenance and
inspectablility, and producability.
EARLY DEVELOPMENTS IN AERODYNAMICS
Aerodynamics, literally “air in motion,” is the branch of the larger field of fluid dynamics that
deals with the motion of air and other gaseous fluids. It concerns the forces that these gaseous
fluids, and particularly air, exert on bodies moving through it. Without the science of
aerodynamics, modem flight would be impossible.
The word “aerodynamics” itself was not officially documented until 1837. However, the
observation of fluids and their effect on objects can be traced back to the Greek philosopher.
Aristotle in 350 B.C. Aristotle conceived the notion air has weight and observed that a body
moving through a fluid encounters resistance.
Archimedes another Greek philosopher, also has a place in the history of aerodynamics. A
hundred years later, in 250 B.C, her presented his law of floating bodies that formed a basic
principle of lighter-than-air vehicles. He stated that a fluid –either in liquid or a gaseous form – is
continuous, basically restating Aristotle‟s theory of a hundred years earlier. He comprehended that
every point on the surface of a body immersed in a fluid was subject to some force due to the fluid.
He stated that, in a fluid, “each part is always pressed by the whole weight of the column
perpendicularly above it. “He observed that the pressure exerted on an object immersed in a fluid
is directly proportional to its depth in the fluid. In other words, the deeper the objects is in the fluid,
the greater the pressure on it. Deep-sea divers, who have to accustom themselves to changes in
pressure both on the way does into the sea and again on the way up to the surface, directly
experience this phenomenon.
Leonardo da vinci sketched various flow fields over objects in a flowing stream.

A direct proportional relationship means that it one part increases, the other will increase by
the same factor. Physicists and mathematicians use the Greek letter alpha ( ) to denote such a
relationship. Applied to pressure and depth, if the depth of an object is doubled, the pressure
exerted on the object would double as well (Depth Pressure). The opposite would also be true.
As altitude increases (negative depth), pressure decreases. Archimedes also demonstrated that,
in order to set a stagnant fluid in motion, the pressure on the fluid must be increased or
decreased. The resultant movement will take place in the direction of the decreasing pressure.
The next contribution to aerodynamics did not occur until the end of the 1400s. In 1490, the
Italian painter, sculptor, and thinker Leonardo da vinci began documenting his aerodynamic
theories and ideas for flying machines in personal notebooks. An avid observer of birds and
nature, he first believed the birds fly by flapping their wings, and thought that this motion would
have to occur for manmade aircraft to rise. He later correctly concluded that the flapping of the
wings created forward motion, and this forward motion allowed air to pass across the bird‟s wings
to create lift. It was the movement of the wing relative to the air and the resulting reaction that
produced the lift necessary to fly. As a result of his studies, he designed several ornithopters –
machines that were intended to copy the action of a bird‟s wing with the muscle power being
supplied by man. But these designs did not leave the drawing board. His other designs included
those for the first helicopter and a parachute.
Leonardo da Vinci’s ornithoptger design
Leonardo noticed another phenomenon that would prove useful in the study of
aerodynamics. He noticed that water in a river moved faster- at a greater velocity- where the river
narrowed. In numerical terms, the area of a cross section of a river multiplied by the velocity of the
water flowing through that section equals the same number at any point in the river. This is known
as the law of continuity (Area Velocity=constant or AV=constant). The law of continuity
demonstrates the conservation of mass, which is a fundamental principal in modem
aerodynamics. He also observed the different ways in which a fluid flowed around and object-
called a flow field.
Leonardo also stated that the aerodynamic results are the same if an object moves through
the fluid at a given velocity or if the fluid flows past the object at rest at the same velocity. This
became known as the “wind tunnel principal.” For example, the results are the same
aerodynamically whether a runner moves at 10 miles per hour in calm air and if the wind is
blowing at 10 miles per hour past a stationary person. He also determined that drag on an object

is directly proportional to the area of the object. The greater the area of an object, the greater the
drag. Further, Leonardo pointed out the benefits of streamlining as a way to reduce an object‟s
drag.
However, Leonardo‟s notebooks were not discovered until centuries later, and his ideas
remained unknown until the 19th
century.
Scientists working in the 17th
century contributed several theories relating to drag. The
Italian mathematician and inventor Galileo Galilel built on Archimedes‟ work and discovered that
the drag exerted on a body from a moving fluid is directly proportional to density of the fluid.
Density describes the mass or an object per unit volume. A very dense fluid produces more drag
on objects passing through it than a less dense fluid. The density of air (a fluid) changes with its
distance from the Earth‟s surface, becoming less dense the farther it is above the Earth‟s surface
and, as such, exerting less pressure. Thus, an object passing through air high above the Earth‟s
surface will encounter less drag than the same object passing through air close to the Earth‟s
surface.
In 1673, the French scientist Edme Manotte demonstrated that drag is proportional to the
square of the velocity of an object (D V2
). Dutch mathematician Christiaan Huygens had been
testing this theory since 1669 and published his results with the same conclusion in 1690. The
English scientist and mathematician Sir Isaag Newton presented a derivation of the drag equation
of a body in 1687: Drag SV2
(where is density and S is cross – sectional area of the body.)
In 1738, the Dutch scientist Daniel Bemouli published his findings on the relationship
between pressure and velocity in flowing fluids. Other scientists used his research as a foundation
for further research. The French scientist Jean le Rond d‟Alembert, an associate of Benmouli‟s,
introduced a model for fluid flows and an equation for the principle of the conservation of mass. He
further presented the idea that velocity and acceleration can vary between different points in fluid
flow. (Remember that air is a fluid).
Benjamin Robins, the British mathematician, proved that air resistance was a critical factor
in the flight of projectiles in 1746. His apparatus consisted of a whirling arm device in which
weight (M) turned a drum and rotated the test object (P).
Swis mathematician Leonha.d Euler, also an associate of Bernoulli, derived equations from
Bemouili‟s and d‟Alembert‟s principles. The most famous of these became known us “Bemoulli‟s
Principle.” It states that, in a flowing fluid, as velocity increases, pressure decreases. This became

a key concept for understanding how lift is created. Euler also introduced equations for fluid flow,
though at the time they could not be solved and applied.
Italian mathematician Joseph Lagrange and French mathematician Pierre-Simon Laplace
studied Euler‟s findings and tried to solve his equations. In 1788, Lagrange introduced a new
model for fluid flow as well as new equations for calculating velocity and pressure. In 1789,
Laplace developed an equation that would help solve Euler‟s equations. It is still used in modem
aerodynamics and physics. Laplace also successfully calculated the speed of sound.
In addition to these theoretical advancements, experiments in aerodynamics were also
producing more practical results. In 1732, the French chemist Henri Pilot invented the Pilot tube, a
device that enables the calculation of velocity at a point in a flowing fluid. This would help explain
the behavior of fluid flow. The English engineer Benjamin Robins performed experiments in 1746
using a whirling arm device and a pendulum to measure drag at low and high speeds.
In 1759, the English engineer John Snmeaton also used a whirling arm device to measure
the drag exerted on a surface by moving air. He proposed the equation D=kSV2
, where D is the
drag, S is the surface area, V is the air velocity, and k is a constant, which Smeaton claimed was
necessary in the equation. This constant became known as Smeatorn‟s coefficient, and the value
of this constant was debated for years. Those making the first attempts at flight, including the
Wright brothers, used this coefficient. The French scientist Jean-charies Borda published the
results of his own whirling arm experiments in 1763. Borda verified and proposed modifications to
current aerodynamic theories and was able to show the effect that the movement of one object
had on another nearby object.
Sir George Cayley of England is generally recognized at the father of modem
aerodynamics. He understood the basic forces acting on a wing and built a glider with awing and a
tail unit that new successfully, he realized the importance of the wing angle of attack and that
curved surfaces (camber) would produced more limit than flat one. Stability in his designs came
with the use of dihedral – an important concept still used today He first made public the notion that
a fixed-wing aircraft was possible in 1804 in his major publication, “On Aerial Navigation,” which
described the theoretical problems of flight.
The contributions of all of these thinkers, mathematicians, and scientists are part of the
foundation of the science of aerodynamics. They paved the way for the aerodynamic
developments that would occur during the nineteenth century, as well as for those who would
eventually achieve heavier than air flight.

UNIT – II
Aircraft and Rocket Configurations
1. List out the different classifications of flight vehicles.
2. Differentiate between a gyroplane and a helicopter.
Helicopter Gyroplane
Rotor power driven Rotor not power driven
3. Explain how an airship or balloon is kept in the air.
By Archimedes principle, when a body is immersed in a fluid, a force acts upwards upon if
helping to support its weight, and this upwards force is equal to the weight of the fluid which is
displaced by body.
4. State the two kinds of aircraft.
5. What are the basic instruments of flying?
1. Altimeter
AIRCRAFT
LIGATER – THAN – AIR HEAVIER – THAN – AIR
Power – Driven Non-power – Driven Man-power – Driven
AIRCRAFT
LIGHTER – THAN – AIR HEAVIER – THAN – AIR

2. Air speed indicator
3. Mach Indicator
4. Turn and slip indicator
5. Artificial horizon.
6. What are the three main control surfaces used in an aircraft?
Elevator
Rudder
Aileron
7. What is the purpose of elevator?
The elevators are control surfaces that control the nose up – and – down pitching motion.
When the deflected downward the cost on the tail is increased, pulling the tail up and the nose of
the airplane down.
8. Name the secondary control surfaces used in an aircraft.
 Slats
 Flaps
 Spoilers
 Trim tab
9. What is the purpose of rudder and ailerons?
Rudder:
The rudder is a control surface that control surface that can turn the nose of the airplane to
the right or left (called yawing).
Ailerons:
The ailerons are control surfaces that control the rolling motion of the airplane around the
fuselage.
Example:
When left aileron is deflected downward and the right aileron is deflect upwards, lift is
increased on the left wing and decreased on the right wing, causing the airplane to roll to the rich.
Auxiliary airfoil surface, mounted forward of a main airfoil, to maintain a smooth airflow over
the main airfoil upper surface.
10. What are called Slats and what is its function?
Auxiliary air foil surface, mounted forward of a main air foil, to maintain a smooth air flow
over the main air foil upper surface.

Briefly explain about the Altimeter and air speed indicator.
The Altimeter
The word “altimeter” means “height measurer.” Would that the instrument were true to its
name! The so-called altimeter which is used in aero planes is nothing more or less than an
aneroid barometer, such as is used to measure the pressure of the atmosphere for the purpose of
forecasting the weather. The only real modification is that the dial is marked in thousands of feet
instead of in inches or millimeters of mercury, and this makes it just about as capable of
measuring the height as the barometer is of foretelling the weather. What it does do is to record
the pressure. As we go up, the pressure goes down, because there is less weight of air on top of
us; but unfortunately the rate at which the pressure goes down varies from day to day, depending
chiefly on the temperature and other effects, which also vary from day to day. Thus it is
impossible to mark off or calibrate the scale of an altimeter so that each pressure corresponds to a
definite height; the best that can be done is to assume some average set of conditions of
temperature and pressure, to mark the scale of the instrument to suit these conditions, and then
correct the readings for any large departure from such standard conditions.
This set of average conditions has been laid down, and, as mentioned in Section 4, is
called the International Standard Atmosphere (fig). When an aeroplane makes a test flight, or
some attempt on an altitude record, the height which counts is not the height reached according to
the altimeter, nor is it the actual height above the ground; it is the height which we estimate it
would have reached had the conditions of the atmosphere all the way up corresponded to those of
the Standard Atmosphere. It is not a very satisfactory state of affairs, but we cannot do any better
until we can devise an instrument which will really measure height, instead of just pressure.
Not only does an altimeter fail to record the correct height when flying, but it does not
necessarily read zero when at sea level, since the atmospheric pressure varies considerably from
time to the at the earth‟s surface. After all, that is how a bareometer works, and the altimeter is
only a barometer. For this reason, altimeters are fitted with an adjustment so that they can be
made to read zero (or the height of the aerodrome) before starting on a flight. It does onto by any
means follow that they will read zero on return to earth. In a flight of a few hours there may be
considerable change in atmospheric pressure, and there is also a certain amount of lag in the
instrument. For these reasons it is very important when flying over high ground or mountainous
districts in foggy weather not to put too much faith in the altimeter. Although this is usually
impressed upon pilots, accidents have occurred from this cause.
Modern altimeters are very much more sensitive than the old types. Some of them have
three hands, one making a complete revolution every 1,000 ft, the next one every 10,000 it, and
the third in 100, 000 ft. There is hardly any lag in such an instrument; in fact, such sensitivity
would be of no advantage if there were any serious lag. Another refinement is that, instead of
turning the dial to set the zero, the pointers are moved, and when they read zero a little window at

the bottom of the instrument gives the reading of the barometer. A great advantage of this method
is that if one can find out, by radio or other means, the reading of the barometer at any aerodrome
at which one wishes to land, one has only to set this reading on the altimeter and, one has only to
set this reading on the altimeter and, whatever may be the altitude of the aerodrome, the hands
will all point to zero or, by an alternative setting, to the correct height of the airfield, when the
aircraft touches the ground. This is a great help in instrument flying.
But, however sensitive the barometric type of altimeter may be, it still cannot measure true
height in the atmosphere, except under a very unlikely set of standardized conditions.
Is it possible, then, to measure the true height of an aircraft above sea level? In certain
instances it can be done by taking three simultaneous sight from the ground, or by various radio
and radar devices, or by some echo system such as is used for submarines.
But, for most purposes, the altimeter, the aneroid barometer, with all its faults still holds its
own, and though we never know how high we are flying we can either assume ignorance and
hope that the altimeter is right, or we can try to be very clever and work out how high we ought to
be. Special “computers” are provided for this purpose.
The Air-Speed Indicator
Throughout the book we have talked of air speed, and we have repeatedly noticed the
close connection with angle of attack. In taking off, climbing, straight and level flight, turning,
gliding, and landing, there is a best speed for each, while for the purpose of flying from one place
to another the navigator must known both the air speed of the aeroplane and the velocity of the
wind. It is true that he would prefer to know the ground speed, but no instrument can be devised
to measure this directly, and the pilot much prefers to know his air speed.
The usual type of air-speed indicator consists of a thin corrugated metal box very like that
used in an aneroid barometer. At some convenient place on the aeorplane, where it will be
exposed to the wind yet not affected by slipstream or other interference, is placed the pitoot-static
head Fig.
Figure: Pilot-static head
This consists of two tubes, one of which has an open end facing the air flow-called a pilot
tube. The other is closed at the end, but along the sides are several small holes which allow the

atmospheric pressure to enter, and this tube is called the static tube. In modern types the two
tubes are often combined into one, the static tube concentric with the pitot tube, and outside it
(fig).
Figure: Concentric pitot-static tube
Sometimes the pressure near the pitot tube is by no means atmospheric, and the static
pressure is taken from some other part of the aeroplane altogether. But wherever the pitot head,
and the static vent, may be, metal tubing is used to communicate the pressures to the instrument
in the pilot‟s cockpit, the pitot tube being connected to one side of the metal box and the static to
the other. When the aeroplane is at rest relative to the air, the ordinary atmospheric pressure will
be communicated by the tubes to both sides of the box and the instrument needle will be at “o”,
but when traveling through the air the pitot, or open, tube will record a higher pressure, depending
on the air speed, while the static tube will still record the atmospheric pressure. The instrument
then reads the difference between these two pressure which is automatically translated by the dial
into miles per hour or knots.
The pressure on the pitoto tube, just like all air resistances, will go up in proportion to the
square of the speed, e.g. at twice the speed to pressure will be four times as much, and thus we
can understand why the numbers round the dial of the instrument, 50, 60, 70, m.p.h., and so on,
are not equally spaced.
When we fly higher, the density of the air will become less, and since the difference
between the two pressures depends on the density as well as on the air speed, the indicator will
read incorrectly, we call the speed recorded by the instrument the indicated air speed, and the
real air speed the true air speed. The error is quite appreciable; for instance, when the indicator
reads 100 m.p.h. at 30,000 ft, the true air speed is about 160 m.p.h., and at 40,000 ft a reading of
100 m.p.h. on the instrument means that we are really traveling at more than 200 m.p.h.
There is, however, rather an interesting point about this incorrect reading of the air-speed
indicator at height. Just in the same proportion as the pressure on the metal box is reduced by the
smaller air density, so is the lift on the wings correspondingly reduced, and thus a higher speed is
necessary to support the aeroplane in flight. Therefore the stalling speed of the aeroplane will
increase with height, but at this increased speed the air-speed indicator will continue to read, when
the aeroplane is about to stall, the same stalling speed as when near the ground. The error, in
other words, has a distinct advantage from the pilot‟s point of view in that, whatever the height the
aeroplane stalls at the same indicated speed. Other speeds of flight, such as the speed for
maximum range, are affected in the same way.

True air speed can be measured by a system of rotating vanes or cups called an
anemometer. This instrument is used at meteorological stations for measuring wind velocity, but it
is not very satisfactory for use on aircraft. For navigational purposes elaborate instruments have
been devised for measuring true speed, but they are outside the scope of this book.
Describe about the primary control surface in detail.
There are three basic control on an airplane ailerons, elevator and rudder
These are hinged surfaces usually at the trailing edge of the wings and tail that can be
rotated up and down.
Ailerons and Elevators:
Figure:
The ailerons are control surfaces that control of the rolling motion of airplane around the
fuselage
Example:
When left aileron is deflected downward the right aileron is deflected upward, lift is
increased on the left wing deflected upward, lift is increased on the left wing decreased on the
right wing causing the airplane to roll to the right.
The elevators are control surfaces that controls nose up and down pitching motion.
Aileron
Elevator

When a elevator is deflected down wards the lift on the tail is increased, pulling the tail up and
nose of airplane down.
Rudder:
Figure:
Rudder is control surface can turn nose of airplane to the right or left. It is called yawing
1. 215 & 218
3. 114
Write short notes on Lateral control and longitudinal control.
Lateral control
The usual method of obtaining lateral control is by means of ailerons hinged at the rear of
each main plane near the wing tips.
Figure:

Plate 5: Here seen with landing gear extended, the Boeing YC-14 was the first to large aircraft to
use USB (uperr-surface blowing), one of the most potent forms of powered lift. The two 25-tonne
thrust turbofans blow their jets across the top of the wing. The Coanda effect keeps the transonic
jets attached to the metal surface, so with flaps depressed (as here) they end up deflected sharply
down, enormously increasing lift. The huge tail is needed for control at the very speeds that can
safely be reached.
Figure:
Plate 6: Here seen in service with the Royal Thai Navy, the Canadair CL-215 proves that large
piston-engined aircraft are not obsolete! Powered by 2,500-hp Pratt&Whitney R-2800 engines, this
amphibian is used mainly as a water bomber to fight forest fires, having the ability to scoop up
fresh loads many times in a single mission. Other mission include anti-smuggling patrols, air-sea
rescue, medevac and utility transport.
The ailerons are connected to the control column by a complete system of control wires
(figure) by a rigid system of rods, by torque tubes inside the wings, or again by some power-
operated system. This time it is a sideways movement of the control column which moves the
ailerons and does so in such a way that once again the control is instinctive, i.e. if the control
column is moved to the left the right-hand ailerons will go down, increasing the lift on the right-
hand wings, thus banking the aeroplane to the left; at the same time the left ailerons will have
been raised, decreasing the lift on the left wing and thus adding to the effect.

Figure: Lateral control-general arrangement
Sometimes the control column has no sideways movement, and lateral control is effected
by a type of handlebars, or by a wheel similar to the steering wheel on a car.
Longitudinal Control
Longitudinal control of an aeroplane is nearly always provided by elevators attached to the
rear of the tail plane. The principle is best illustrated by the old-fashioned system in which the
elevators were connected by control wires and levers to the control column in the pilot‟s cockpit.
The control is instinctive, i.e. when the column is pushed forward, the elevators are lowered and
the upward force on the tail is increased, thus causing the nose of the aeroplane to drop Fig.
Figure: Longitudinal control-direction of movements
In order to achieve this result it will be seen that in an ordinary simple control system the
wires must be crossed between the control column and the elevators. In modern practice,
however, instead of employing two wires which will tend to become slack, causing a certain
amount of backlash in the system, more positive controls are nearly always used; these may take
the form of a rigid rod serving both to push and to pull the elevators from top or bottom only, or
they may rely simply on the torsion of a rod or tube, or the whole control system may be power-
operated, hydraulic, pneumatic or electric.

Explain with a neat sketch components of an aero plane and their functions.

Figure: Basic components of an aircraft
Fuselage:
The fuselage is that portion of the aircraft that usually contains the crew and payload, either
passengers, cargo, or weapons. Most fuselages are long, cylindrical tubes or sometimes
rectangular box shapes. All of the other major components of the aircraft are attached to the
fuselage. Empennage is another term sometimes used to refer to the aft portion of the fuselage
plus the horizontal and vertical tails.
Wing:
The wing is the most important part of an aircraft since it produces the lift that allows a
plane to fly. The wing is made up of two halves, left and right, when viewed from behind. These
halves are connected to each other by means of the fuselage. A wing produces lift because of its
special shape, a shape called an airfoil. If we were to cult through a wing and look at its cross –
section, as illustrated below, we would see that a traditional airfoil has a rounded leading edge and
a sharp trailing edge.

Figure: Definition of an airfoil
Engine:
The other key component that makes an airplane go is its engine, or engines. Aircraft use
several different kinds of engines, but they can all be classified in two major categories. Early
aircraft from the Wright Flyer until World War II used propeller – driven piston engines, and these
are still common today on light general aviation planes. But most modern aircraft now use some
form of a jet engine. Many aircraft house the engine(s) within the fuselage itself. Most larger
planes, however, have their engines mounted in separate pods hanging below the wing or
sometimes attached to the fuselage. These pods are called nacelles.
Horizontal stabilizer:
If an aircraft consists of only a wing or a wing and fuselage, it is inherently unstable.
Stability is defined as the tendency of an aircraft to return to its initial state following a disturbance
from that state. The horizontal stabilizer, also known as the horizontal tail, performs this function
when an aircraft is disturbed in pitch. In other words, if some disturbance forces the nose up or
down, the horizontal stabilizer produces a counteracting force to push the nose in the opposite
direction and restore equilibrium. When in equilibrium, we say that an aircraft is in its trim
condition. The horizontal tail is essentially a miniature wing since it is also made up of an airfoil
cross – section. The tail produces a force similar to lift that balances out the lift of the wing to keep
the plane in equilibrium. To do so, the tail usually needs to produce a force pointed downward, a
quantity called down force.

Vertical stabilizer:
The vertical stabilizer, or vertical tail, functions in the same way as the horizontal tail, except
that it provides stability for a disturbance in yaw. Yaw is the side – to – side motion of the nose, so
if a disturbance causes the nose to deflect to one side, the vertical tail produces a counteracting
force that pushes the nose in the opposite direction to restore equilibrium. The vertical tail is also
made of an airfoil cross – section and produces forces just like a wing or horizontal tail. The
difference is that a wing or horizontal tail produces lift or down force, forces that are pointed up or
down from the aircraft. Mean while the vertical tail produces a force pointed to one side of the
aircraft. This force is called side – force.
Basic control surfaces:
In addition to the wing and tail surfaces, aircraft need some additional components that give
the pilot the ability to control the direction of the plane. we call these items control surfaces.
Figure: Aircraft control surfaces and axes of motion
Elevator:
The elevator is located on the horizontal stabilizer. It can be deflected up or down to
produce a change in the down force produced by the horizontal tail. The angle of deflection is
considered positive when the trailing edge of the elevator is deflected upward. Such a deflection
increases the down force produced by the horizontal tail causing the nose to pitch upward.

Rudder:
The rudder is located on the vertical stabilizer. It can be deflected to either side to produce
a change in the side – force produced by the vertical tail. The angle of deflection is usually
considered positive when the trailing edge of the rudder is deflected towards the right wing. Such
a deflection creates a side – force to the left which causes the nose to yaw to the right.
Aileron:
Ailerons are located on the tips of each wing. They are deflected in opposite direction (one
goes trailing edge up, the other trailing edge down) to produce a change in the lift produced by
each wing. On the wing with the aileron deflected down ward, the lift increases whereas the lift
decreases on the other wing whose aileron is deflected upward. The wing with more lift rolls
upward causing the aircraft to go into a bank. The angle of deflection is usually considered
positive when the aileron on the left wing deflects downward and that on the right wing deflects
upward. The greater lift generated on the left wing causes the aircraft to roll to the right.
The effects of these control surfaces and the conventions for positive deflection angles are
summarized in the following diagram.
Figure: Aircraft control surfaces and positive deflection angles
3. Additional components:
We‟ve already seen the major parts of a typical plane, but a few important items were left
out for simplicity. Let‟s go back and discuss a few of these items.

Figure: Components of an aircraft
Flap:
Flaps are usually located along the trailing edge of both the left and right wing, typically
inboard of the ailerons and close to the fuselage. Flaps are similar to ailerons in that they affect
the amount of lift created by the wings. However, flaps only deflect down ward to increase the lift
produced by both wings simultaneously. Flaps are most often used during takeoff and landing to
increase the lift the wings generate at a given speed. This effect allows a plane to takeoff or land
at a slower speed than would be possible with out the flaps. In addition to flaps on the trailing
edge of a wing, a second major category is flaps on the leading edge. These leading – edge flaps,
more often called slats, are also used to increase life. More information on slats and flaps is
available here.

Cabin & cockpit:
Sometimes these two terms are used synonymously, but most of the time the term cockpit
is applied to a compartment at the front of the fuselage where the pilots and flight crew sit. This
compartment contains the control yolks (or sticks) and equipment the crew use to sent commands
to the control surfaces and engines as well as to monitor the operation of the vehicle. Meanwhile,
a cabin is typically a compartment within the fuselage where passengers are seated.
Nose & main gear:
The landing gear is used during takeoff, landing, and to taxi on the ground. Most planes
today use what is called a tricycle landing gear arrangement. This system has two large main
gear units located near the middle of the plane and a single smaller nose gear unit near the nose
of the aircraft.
Trim tab:
The above diagram illustrates a “trim tab” located on the elevator. These control tabs may
be located on other surfaces as well, such as a rudder control tab or a balance tab on the aileron.
Nonetheless, the purpose of all these tabs is the same. In the previous section, we discussed that
the horizontal stabilizer and elevator are used to provide stability and control in pitch. In order to
keep a plane in a steady, level orientation, the elevator usually has to be deflected by some small
amount. Since it would be very tiring for a pilot to physically hold the control stick in position to
keep the elevator at that deflection angle for an entire flight, the elevator is fitted with a small “tab”
that creates that elevator deflection automatically. The trim tab can be through of almost as a
“mini – elevator”. By deflecting the tab up or down, it increases or decreases the down force
created by the elevator and forces the elevator to a certain position. The pilot can set the
deflection of the trim tab which will cause the elevator to remain at the deflection required to
remain trimmed.
Summary:
This discussion has provided an overview of the basic parts and control surfaces of a
typical aircraft. Yet there are still many more features related to control surfaces that we have not
seen. In a future installment, we will add further detail and complexity to illustrate the complex
nature of modern control surfaces.

How the air planes are classified? Discuss about various types of flight vehicles with
schematic sketches wherever possible.
Lighter than air aircraft:
The name itself indicates, that the aircraft is lighter than air. These depend for their lift on a
well – known scientific fact usually called „Archimedes principle‟. The principles states that „when
a body is immersed in a fluid, a force acts upwards upon it., helping to support its weight and this
upward fore is equal to the weight of the fluid which is displaced by the body.
Air ships, free balloons or kite balloons obtains its lift in precisely the same way (ie) By
Archimedes Principle.
Airship:
A power driven aircraft that is light than air. An airship can carry a maximum up to 2 to 3
persons.
Free balloons:
Free balloons are also comes under this category that means the balloons one flown in the
air with the help of gases such as a helium, hydrogen etc.,
Aircraft
Lighter than air Heavier than air
Airships Free balloons Captive balloons Power driven Non - Power driven Man - Power
driven
Gliders Kites
Sailplanes
Aero plane Rotorcraft Ornithopter
Land plane Sea plane Amphibian Helicopter
(rotor power
driven )
Gyroplane
(rotor not
power driven)
Cyclogyro
(paddle – wheel
type motor)
Float plane Flying boat

Heavier than air aircraft:
Here in the aircraft solid metals are used. So that it could not fly in air without any definite
shape. In order to fly such aircraft, aerofoil shapes should be maintained for such aircrafts. Since,
there is steady flow of air over such aircrafts, these types of aircrafts are found to be airborne (ie, it
can stay in air for a long time).
Power driven:
Under the heavier than aircrafts, power driven aircrafts play a dominant role today. Power
driven aircrafts are nothing but aircrafts which are provided with external power supply. (ie) the
aircraft can be flown with the help of certain factors like engines, etc.,
Aero plane:
The aero plane must be given some power, so that it can fly. So as in aero plane, the
power is provided mainly by engines and as well as propulsion systems.
Figure:
Rotor craft:
Here, the power provided to the craft is by means of rotor (ie) a rotating member that can
take off the aircraft to a specified height and it can be flown.
The rotor craft designs are
1. Helicopter
2. Gyroplane
3. Cyclogyro

Helicopter:
Here in the helicopter, the power is driven by a rotor, which is having blades that rotates up
to a certain speed, that makes the helicopter to lift up and so it can fly.
Ornithopter
Here in the ornithopters, the power is given mainly by the mechanism of flapping wings up
and down.
Figure: Orinithopler
Non – Power driven:
Non – power driven aircrafts are those crafts which can flown without the help of any
external power supply (ie) there is no presence of engines.
Gliders:
Gliders are those aircrafts which comes under non – power driven such that it can fly
without engines and also it should be start to fly from some elevated places like maintains etc.

Hydraulic Actuator and Electronic actuator system:
Brief summary of the invention:
[0014] According to principles of the present invention, a backup system is provided that
has a local electric motor and pump for some or all of the hydraulic actuators. A local back up
hydraulic actuator (LBHA) has two power sources, central hydraulic as primary and electrical as
backup. During normal operation, the hydraulic actuator receives pressurized fluid from one of the
central hydraulic systems and the fluid flow to the chambers is controlled by a servo valve. Failure
of the hydraulic system is detected by the local electronic controller that monitors the output signal
of a pressure sensor. When this observed pressure falls below a certain threshold, the local
electronic controller determines that this central hydraulic system has failed and t urns on the
electrical motor, which powers the local hydraulic pump to provide high pressure hydraulic fluid to
the hydraulic actuator via the servo value. The local electronic controller also uses the pressure
reading for closed – loop feedback control, and the pressure is maintained at the normal level.
Other types of monitoring and control schemes may also be used instead. In this manner, the
LBHA remains functional with electrical power following a partial or complete failure of the central
hydraulic system.
[0015] By coupling the LBHAs to appropriate flight control surfaces, the airplane remains
controllable with loss of all central hydraulic systems; therefore, the number of central hydraulic
systems can be reduced compared to using only conventional hydraulic actuators.
[0016] As explained in the background of the invention, some prior art approaches provide
a reduction in the number of hydraulic systems, namely EHA and EBHA, for example. A major
advantage that the LBHA offers over these prior art actuators is that it enables this reduction in the
central hydraulic system for airplanes with flight control surfaces which are controlled in an active
– active fashion. This is accomplished by overcoming both of the two major difficulties that have
been cited herein for the electric and hybrid actuators of the prior art, namely that of reduced
reliability and force fight.
[0017] The LBHA overcomes the reduced reliability problem by using the low – reliability
components only as backup following the failure of a central hydraulic system or during specific
phases of flight. The electrical part of the LBHA can be switched of during much of flight so the life
of the motor and pump is greatly extended. Therefore, even when the LBHA is used continuously
during normal operation, such as on an active- active surface, the operation is more reliable and
the life of the motor and pump are extended.
[0018] The force fight problem associated with coupling dissimilar actuators on a surface
and using them in an active – active fashion is resolved according to this invention by continuously
controlling the actuator in the same manner as a conventional hydraulic actuator and providing as
backup only alternate power source. The local motor and pump are upstream of the servo valve
and in parallel with the central hydraulic lines. A common servo value for the hydraulic actuator is
used under a unified electrical control system for both the central hydraulic system and the backup
system. This ensures that there is no substantial force fight when LBHA is used in an active –
active fashion with a hydraulic actuator or another LBHA on the same surface. This is because
during normal operation and operation following the failure of the central hydraulic system, the

LBHA is controlled in the same manner through the servo valve, with the only difference being the
source of hydraulic power, central or local.
[0019] In addition to enabling the reduction of hydraulic systems and resolving the problems
associated with applying electric or hybrid actuators of prior art in an active – active fashion, the
LBHA also offers other advantages. With the LBHA, the local pump can be a one – way pump
rather than a two – way pump, which, together with the motor and controller, is lower in weight and
cost, while having higher reliability. The local pump‟s role is to provide increased local pressure,
rather than also provide servo control of the system, thus simplifying the motor, the motor driver
and control device, and increasing the reliability of operation.
[0020] The inventive system also provides the advantage that during critical flight phases,
such as takeoff and landing, both the main system and the backup system can be in operation. In
the event of failure of the main system, the backup; system is already under power and is assisting
in the operation, so that there is no time lost for control while the backup system comes on. Check
values are provided between the central hydraulic system and the local backup system, permitting
both to operate at the same time when appropriate.
[0021] A further advantage is that the backup system has a separate power source, namely
electric power, so that increased availability of power is provided to the actuator. Because of this,
providing one LBHA in conjunction with at least one hydraulic actuator for a particular surface is
able to ensure that the likelihood of a complete loss of the power to position the surface correctly
is negligible. This may, for example, enable reduction in the number of actuators coupled to a
surface compared to only using conventional hydraulic actuators, while achieving and equivalent
or better level of safety. This may also enable smaller, lighter, and simpler individual actuators
than otherwise would have been possible.
Flight instruments:
From Wikipedia, the free encyclopedia
Most aircraft are equipped with a standard set of flight instruments which give the pilot information
about the aircraft‟s attitude, airspeed and altitude.
Figure: Six basic instruments in a light twin – engine airplane arranged in the basic – T.
From top left airspeed indicator, attitude indicator, altimeter, turn coordinator, beading
indicator, and vertical speed indicator.

Most aircraft have these seven basic flight instruments:
Figure:
Altimeter:
Gives the aircraft‟s height (usually in feet or meters) above some reference level (usually
sea – level) by measuring the local air pressure. It is adjustable for local barometric pressure
(referenced to sea level) which must be set correctly to obtain accurate altitude readings.
Figure: Attitude indicator (also known as an artificial horizon)
Shows the aircraft‟s relative to the horizon. From this the pilot can tell whether are level
and if the aircraft nose is pointing above or below the horizon. This is a primary instrument flight
and is also useful in conditions of poor visibility. Pilots are trained to use other instruments in
combination should this instrument or its power fail.
Figure: Airspeed indicator
Shows the aircraft‟s speed (usually in knots) relative to the surrounding air. It works by
measuring the ram – air pressure in the aircraft‟s pitot tube. The indicated airspeed must be
corrected for air density (which varies with altitude, temperature and humidity) in order to obtain
the true airspeed, and for wind conditions in order to obtain the speed over the ground.

Figure: The flight instruments of a Slings by T – 67 Firefly two – seat light airplane. The
basic T is present on the left side primary pilot station.
Magnetic compass:
Shows the aircraft‟s heading relative to magnetic north. While reliable in steady level flight
it can give confusion indications when turning, climbing, descending, or accelerating due to the
inclination of the earth‟s magnetic field. For this reason, the heading indicator is also used for
aircraft operation. For purposes of navigation it may be necessary to correct the direction
indicated (which points to a magnetic pole) in order to obtain direction of true north or south (which
points to the earth‟s axis of rotation).
Figure: Heading indicator
Also know as the directional gyro, or DG. Sometimes also called the gyrocompass, though
usually not in aviation applications. Displays the aircraft‟s heading with respect to magnetic north.
Principle of operation is a spinning gyroscope, and is therefore subject to drift errors (called
precession) which must be periodically corrected by calibrating the instrument to the magnetic
compass. In many advanced aircraft, the heading indicator is replaced by a Horizontal Situation
Indicator (HIS) which provides the same heading information, but also assists with navigation.

Figure: Turn and bank indicator or turn coordinator
The turn and bank indicator, also called the turn and slip indicator, displays of turn and rate
of turn. Internally mounted inclinometer displays „quality‟ of turn, i.e. whether the turn is correctly
coordinated, as opposed to an uncoordinated turn, where in the aircraft would be in either a slip or
a skid. Replaced in the late sixties and early seventies by the newer turn coordinator, the turn and
bank is typically only seen in aircraft manufactured prior to that time, or in Gliders manufactured in
Europe.
A turn coordinator displays rate and direction of roll while the aircraft is rolling; displays rate
and direction of turn while the aircraft is not rolling. Internally mounted inclinometer also displays
quality of turn. Replaced the older turn and bank indicator.
Figure: Vertical speed indicator
Also sometimes called a variometer Senses changing air pressure and displays that
information to the pilot as a rate of climb or descent, usually in feet per minute or meters per
second.

Figure: Schempp – Hirth Janus – C glider Instrument panel equipped for “cloud flying”.
The turn and bank indicator is top center. The heading indicator is replaced by a GPS –
driven computer with wind and glide data, driving two electronic variometer displays to the
right.
Arrangement in instrument panel:
Most aircraft built since about 1953 have four of the flight instruments located in a
standardized arrangement known as the “basic T”. The attitude indicator is in top center, airspeed
to the left, altitude to the right and heading indicator under the attitude indicator. The other two,
turn – coordinator and vertical – speed, are usually found under the airspeed and altitude, but are
given more latitude in placement. The magnetic compass will be above the instrument panel,
often on the windscreen center post. In newer aircraft with glass cockpit instruments the layout of
the displays conform to the basic T arrangement.
Flight instrument
Pitot – static instrument: Altimeter: Airspeed indicator – Machmeter – Vertical speed indicator
Gyroscople instruments: Attitude indicator – Heading indicator – Horizontal Situation Indicator –
Turn and back indicator – Turn coordinator
Navigation: Horizontal Situation Indicator – Course Deviation Indicator – Inertial Navigation
System – GPS Other magnetic compass – Yaw string.
Figure: Tabs fitted on elevators and rudder of an old Catalina flying boat
Powered servo controls:
Powered controls may take two forms, servo – assisted, or fully power operated. In the
former type, hydraulic pressure is transmitted via pipes to a servo – actuator which helps the

mechanical linkage to move the surface. The mechanical linkage can be used to operate the
control surface, even if power is lost, although the controls will then feel very heavy. The system is
similar to the servo – assisted steering and braking system of car.
Power control, fly – by – wire and fly – by – light:
In pure power operation, no mechanical override is provided. Control signals may be
transmitted hydraulically, directly from valves attached to the control column, or electrically to
actuators, which move the control surfaces. The latter system is known as fly – by – wire. The
actuators are electrically or hydraulically operated rams motors.
As an alternative to electrical signal transmission, modulated light signals may be
transmitted along optical fibres. This system is known as fly – by – light and over comes problems
due to electromagnetic interference. The detonation of nuclear weapons would cause very strong
electromagnetic signals capable of upsetting, if not destroying, conventional electronic circuits.
The deliberate jamming of electronic circuitry by means of powerful electromagnetic beams is also
a possibility, and some military aircraft have been found to be very vulnerable in this respect.
Once control by electrical signals is accepted, it becomes convenient to incorporate
sophisticate electronic processing into the circuit, with increasing emphasis on digital systems.
Such processing can be used to alter the response to control inputs, and can follow for
manoeuvres such as flying in a stalled or an unstable condition, or approaching very close to the
stall on landing.
Fly – by – wire can thus dramatically improve the performance, efficiency and even safety
of aircraft. It also allows for coordinated control surface movement that would be too complex for
a pilot to manage unaided. Such systems have demonstrated a high level of reliability and are
being increasingly used. On military aircraft, the flight control, autostabilisation, navigation, radar
ad weapons control system are all integrated in varying degrees.
Feedback or feel:
One problem with power – operated controls is that the pilot has no direct feel for the
amount of force that the control surface is producing. Therefore, some form of artificial feel has to
be introduced.
Generally, mechanical controls feed heavier the further they are pulled, so a crude form of
feel could be provided by attaching springs to the control column. This system is inadequate,
however, because the control loads should also increase as the flight speed increase.
The force actually required at the control surface, depends on the dynamic pressure
2
1
V
2
, rather than just the speed. At constant altitude, the controls will, for example, require
sixteen times more force to operate them at 800 km /h than at 200 km/h. To over come this
problem, also –called q – feel device can be added. (q is the symbol conventionally used to denote
dynamic pressure). The q – feel unit is a device which is attached to the mechanical control
linkage to increase its stiffness in proportion to increases n dynamic pressure. Nowadays, much

more sophisticated feedback systems are used, in which the force required to move the control
surface is sensed, and the force required to move the pilot‟s control stick is increased
appropriately.
By using the electronic processing of the feedback signal, it is possible to make a small
aircraft feel and handle like a large one. Reversing the procedure might be unwise, as trying to
throw a 747 around like a Pitts Special could cause problems. The handling of new untested
aircraft types is often simulated by artificially modifying the control of an existing different aircraft
type.
Early aircraft and small modern types use a direct mechanical linkage between the control
surface and the pilot control stick. The linkage normally consists of an arrangement of multi –
stranded wires and pulleys. Figure shows the complex system used on an executive jet. The
rudder actuating wire may just be seen under the tailplane on the Auster shown in figure.
Alternatively push – pull rods and twisting torque – tubes may be used, and are in some ways
preferred, since they produce a stiffer system, less prone to vibration problems.
As the speed and size of aircraft increased, so did the control forces required, and some
considerable ingenuity went into devising means of reducing these loads. The position of the
hinge line can be arranged so that the resultant force acts just behind it, thus producing only a
small moment. A typical arrangement, used on many aircraft up to the 1950s, is seen in figure.
The top of the rudder projects forward, in front of the hinge line, thereby moving the centre of
pressure of the rudder forwards, towards the hinge line.
Unfortunately, the position of the resultant force changes with angle of attack, speed, and
deflection angle, so that it is difficult to devise an arrangement that produces small forces under all
conditions. It is particularly important that the resultant force should not be in front of the hinge
line, as this would cause the control surface to be unstable, and run away in the direction of the
ever – increasing force.
In addition to such aerodynamic balancing the control surface mass should also be
balanced so that gravity forces do not pull it down in level flight, and inertia does not cause it to
move relative to the aircraft during manoeuvres. A rather crude external form of mass balancing
may be seen figure. As described later, masses may also be added to the control surfaces to alter
the natural frequency of oscillation.
Servo – tabs and trim tabs:
Another means of reducing the load required is to use a servo – tab, as illustrated in figure.
Deflection of the tab downwards causes the trailing edge of the surface of lift, producing a large
turning moment in the primary control surface. Various means of coupling the tab and primary
surface were devised, but such arrangements are now largely obsolete. Kermode (1996)
describes the historical development of tabs.
Nowadays tabs are normally used primarily for trimming the control surfaces; that is, setting
them so that the control surface produces just the right amount of force to keep the aircraft flying
steadily, hands – off. Such trim tabs are controlled by a separate trim wheel in the cockpit or flight
deck, and are actuated independently of the main surface actuating system.

Figure: External mass balance weights were used on the tail of the Venom
Figure: A servo – tab
Downward deflection of the tab increases the lift on the main control surface causing it to deflect
upwards
The force required to operate the tab is considerably less than that which would be needed to
operate the main control surface directly
Trim tabs allow an aircraft to be flown virtually, or even literally, hands – off, for much of the time.
Tabs may be seen in figure. Fixed trim tabs, in the form of small strips of metal affixed to the
trailing edge, may sometimes be used, their purpose being to „tune‟ the control surfaces to give a
good balance.
Movable trim tabs can provide restricted emergency control in the case of a failure in the
primary control surface system. On recent aircraft designs, they may provide the only manual
means of control.
Cockpit Instruments:
Altimeter

The word “altimeter” means “height measurer.” Would that the instrument were true to its
name! The so-called altimeter which is used in aero planes is nothing more or less than an
aneroid barometer, such as is used to measure the pressure of the atmosphere for the purpose of
forecasting the weather. The only real modification is that the dial is marked in thousands of feet
instead of in inches or millimeters of mercury, and this makes it just about as capable of
measuring the height as the barometer is of foretelling the weather. What it does do is to record
the pressure. As we go up, the pressure goes down, because there is less weight of air on top of
us; but unfortunately the rate at which the pressure goes down varies from day to day, depending
chiefly on the temperature and other effects, which also vary from day to day. Thus it is
impossible to mark off or calibrate the scale of an altimeter so that each pressure corresponds to a
definite height; the best that can be done is to assume some average set of conditions of
temperature and pressure, to mark the scale of the instrument to suit these conditions, and then
correct the readings for any large departure from such standard conditions.
This set of average conditions has been laid down, and, as mentioned in Section 4, is
called the International Standard Atmosphere (fig). When an aeroplane makes a test flight, or
some attempt on an altitude record, the height which counts is not the height reached according to
the altimeter, nor is it the actual height above the ground; it is the height which we estimate it
would have reached had the conditions of the atmosphere all the way up corresponded to those of
the Standard Atmosphere. It is not a very satisfactory state of affairs, but we cannot do any better
until we can devise an instrument which will really measure height, instead of just pressure.
Not only does an altimeter fail to record the correct height when flying, but it does not
necessarily read zero when at sea level, since the atmospheric pressure varies considerably from
time to the at the earth‟s surface. After all, that is how a bareometer works, and the altimeter is
only a barometer. For this reason, altimeters are fitted with an adjustment so that they can be
made to read zero (or the height of the aerodrome) before starting on a flight. It does onto by any
means follow that they will read zero on return to earth. In a flight of a few hours there may be
considerable change in atmospheric pressure, and there is also a certain amount of lag in the
instrument. For these reasons it is very important when flying over high ground or mountainous
districts in foggy weather not to put too much faith in the altimeter. Although this is usually
impressed upon pilots, accidents have occurred from this cause.
Modern altimeters are very much more sensitive than the old types. Some of them have
three hands, one making a complete revolution every 1,000 ft, the next one every 10,000 it, and
the third in 100, 000 ft. There is hardly any lag in such an instrument; in fact, such sensitivity
would be of no advantage if there were any serious lag. Another refinement is that, instead of
turning the dial to set the zero, the pointers are moved, and when they read zero a little window at
the bottom of the instrument gives the reading of the barometer. A great advantage of this method
is that if one can find out, by radio or other means, the reading of the barometer at any aerodrome
at which one wishes to land, one has only to set this reading on the altimeter and, one has only to
set this reading on the altimeter and, whatever may be the altitude of the aerodrome, the hands
will all point to zero or, by an alternative setting, to the correct height of the airfield, when the
aircraft touches the ground. This is a great help in instrument flying.
But, however sensitive the barometric type of altimeter may be, it still cannot measure true
height in the atmosphere, except under a very unlikely set of standardized conditions.

Is it possible, then, to measure the true height of an aircraft above sea level? In certain
instances it can be done by taking three simultaneous sight from the ground, or by various radio
and radar devices, or by some echo system such as is used for submarines.
But, for most purposes, the altimeter, the aneroid barometer, with all its faults still holds its
own, and though we never know how high we are flying we can either assume ignorance and
hope that the altimeter is right, or we can try to be very clever and work out how high we ought to
be. Special “computers” are provided for this purpose.
Air Speed Indicator
Throughout the book we have talked of air speed, and we have repeatedly noticed the
close connection with angle of attack. In taking off, climbing, straight and level flight, turning,
gliding, and landing, there is a best speed for each, while for the purpose of flying from one place
to another the navigator must known both the air speed of the aeroplane and the velocity of the
wind. It is true that he would prefer to know the ground speed, but no instrument can be devised
to measure this directly, and the pilot much prefers to know his air speed.
The usual type of air-speed indicator consists of a thin corrugated metal box very like that
used in an aneroid barometer. At some convenient place on the aeorplane, where it will be
exposed to the wind yet not affected by slipstream or other interference, is placed the pitoot-static
head Fig.
Figure: Pilot-static head
This consists of two tubes, one of which has an open end facing the air flow-called a pilot
tube. The other is closed at the end, but along the sides are several small holes which allow the
atmospheric pressure to enter, and this tube is called the static tube. In modern types the two
tubes are often combined into one, the static tube concentric with the pitot tube, and outside it
(fig).

Figure: Concentric pitot-static tube
Sometimes the pressure near the pitot tube is by no means atmospheric, and the static
pressure is taken from some other part of the aeroplane altogether. But wherever the pitot head,
and the static vent, may be, metal tubing is used to communicate the pressures to the instrument
in the pilot‟s cockpit, the pitot tube being connected to one side of the metal box and the static to
the other. When the aeroplane is at rest relative to the air, the ordinary atmospheric pressure will
be communicated by the tubes to both sides of the box and the instrument needle will be at “o”,
but when traveling through the air the pitot, or open, tube will record a higher pressure, depending
on the air speed, while the static tube will still record the atmospheric pressure. The instrument
then reads the difference between these two pressure which is automatically translated by the dial
into miles per hour or knots.
The pressure on the pitoto tube, just like all air resistances, will go up in proportion to the
square of the speed, e.g. at twice the speed to pressure will be four times as much, and thus we
can understand why the numbers round the dial of the instrument, 50, 60, 70, m.p.h., and so on,
are not equally spaced.
When we fly higher, the density of the air will become less, and since the difference
between the two pressures depends on the density as well as on the air speed, the indicator will
read incorrectly, we call the speed recorded by the instrument the indicated air speed, and the
real air speed the true air speed. The error is quite appreciable; for instance, when the indicator
reads 100 m.p.h. at 30,000 ft, the true air speed is about 160 m.p.h., and at 40,000 ft a reading of
100 m.p.h. on the instrument means that we are really traveling at more than 200 m.p.h.
There is, however, rather an interesting point about this incorrect reading of the air-speed
indicator at height. Just in the same proportion as the pressure on the metal box is reduced by the
smaller air density, so is the lift on the wings correspondingly reduced, and thus a higher speed is
necessary to support the aeroplane in flight. Therefore the stalling speed of the aeroplane will
increase with height, but at this increased speed the air-speed indicator will continue to read, when
the aeroplane is about to stall, the same stalling speed as when near the ground. The error, in
other words, has a distinct advantage from the pilot‟s point of view in that, whatever the height the
aeroplane stalls at the same indicated speed. Other speeds of flight, such as the speed for
maximum range, are affected in the same way.

True air speed can be measured by a system of rotating vanes or cups called an
anemometer. This instrument is used at meteorological stations for measuring wind velocity, but it
is not very satisfactory for use on aircraft. For navigational purposes elaborate instruments have
been devised for measuring true speed, but they are outside the scope of this book.
Mach Numbers
Since the speed of sound is so important it is sometimes convenient to speak of the speed
of aeroplanes in relation to the speed of sound and to say that they are traveling at half, or three-
quarters, or nine-tenths of the speed of sound, or even at the speed of sound itself or at two or
three times that speed. This is expressed in terms of Mach numbers, a Mach number of 0.5
simply meaning that the aeoplane is traveling at half the speed of sound. Thus the Mach numbers
in the examples given above would be, respectively, 0.5, 0.75, 0.9, 1, 2 and 3. Here, at least, is a
highbrow term which anyone can understand. It is so simple, in fact, that the reader may well ask
why it is necessary at all-if the speed of sound is 760 m.p.h., we know that when an aeroplane is
traveling at 380 m.p.h. it is traveling at half the speed of sound; why wrap the thing in mystery by
saying that it is traveling at a Mach number of 0.5?
Well, as it happens, it ins‟t-in this case-just an attempt to blind people with science. An
observant reader-especially if he has already fallen into some of our traps-may have noticed that
we have been rather careful throughout this argument not to give the actual speeds of rifle bullets
and so on, but just to compare them with the speed of sound-and that when we first said that the
speed of sound, was as near as matters, 760 m.p.h., we specified under normal atmospheric
conditions. That is the clue. The rate at which sound travels in air depends on the temperature is
the controlling factors); the lower the temperature the lower the speed of sound. Thus at the
temperature of ground level conditions of the International Standard Atmosphere (conditions which
rarely apply in practice) the speed of sound is about 760 m.p.h.; while at the temperature of the
stratosphere an aeroplane may be traveling below the speed of sound, at the speed of sound, or
above the speed of sound, according to the temperature at the time. What matters is not that it is
going at 700 m.p.h. but at what fraction of the particular speed of sound it is traveling-in other
words what matters is, not its speed, but its Mach number.
When there is no need to specify the actual Mach number and we only wish to indicate that
a body, or the air flow, is traveling at less than the speed of sound, at the speed of sound or above
it, it is usual and convenient to use the Latin words and to speak of subsonic, sonic, and
supersonic speeds.
As we shall soon se, it isn‟t just at the speed of sound that curious things happen, but over
quite a range of speeds which include that speed, and it is useful, therefore, to introduce the word
transonic. Our subject then falls into there quite distinct parts, i.e. flight at subsonic speeds which
is what we have so far considered, flight at transonic speeds which ahs problems all of its own,
and flight at supersonic speeds in which we are in a new world altogether and all the rules are so
much the opposite from what we have already learnt that it reminds us of Alice Through the
Looking-glass.

Turn and slip indicator
These two instruments together-the artificial horizon and the directional gyro-are the basis
of “George,” the robot or automatic pilot, which not only detects any tendency of the aeroplane to
yaw, pitch or roll but, having done so, moves the controls until it is once more flying correctly. That
sounds wonderful indeed; but it is no longer fantastic to imagine that in the future aeroplanes will
be flying about, carrying and dropping bombs, and perhaps even fighting each other, without any
pilots at all-indeed guided missiles are already doing just this.
This third gyroscopic instrument in common use is the turn and side-slip indicator, which
has already been mentioned. The lower needle on this indicates the rate of turn and is worked by
the precession of a gyroscope; the upper needle indicates side-slip and is worked by a pendulum.
There are not many other instruments concerned with the actual flight of the aeroplene.
The air temperature is needed for various corrections to speed, height, and so on in record or test
flights, and for this purpose an ordinary thermometer may be fitted on some exposed part. A rate-
of-climb indicator or, to be more exact, an instrument which shows either rate of ascent or rate of
descent, is usually fitted to modern aircraft, and, like so many of these modern luxury instruments,
is of great value in instrument flying. A machmeter, which will be mentioned in the following
paragraphs, is indispensable in high-speed aircraft.
Apart from the aircraft itself the engine or engine will need revolution indicators, oil-pressure
gauges, oil-temperature gauges, air-pressure gauges, fuel-pressure gauges, boost gauges for
superchargers, water thermometers for water cooled engines, fuel flowmeters, fuel-contents
gauges, and so on.
On the electrical side there may be anything varying from the simple switch used for the
engine ignition to a complete system of lighting and heating, dynamos and motors, and full radio
and radar installation with all its attendant instruments.
For high flying, oxygen apparatus must be installed, and this needs special instruments all
to itself as does the pressurization of cabins.
Incidentally, we must not forget what is perhaps the most useful of all man-made
instruments-the clock or watch. For any kind of serious flying it is indispensable.
Artificial horizon
An instrument panel in a modern aeroplane may contain at least three instruments which
depend on gyroscopes. They are usually driven by suction from an engine-driven pump or from
double venture tubes exposed to the air stream, and may revolve at 10,000 r.p.m.
Perhaps the most striking of all such instruments is the artificial horizon, which shows the
position of a small model aeroplane relative to a horizon marked on the instrument. If the nose of
the real aeroplane goes down, the model goes below the horizon; if the nose goes up, the model
moves above the horizon. If the aeroplane banks to right or left, so does the model. even if the
pilot cannot see the real horizon at all, if he is flying on the darkest on the darkest of nights, or

“under the hood”, he can always tell the attitude of his aeroplane. Only those who have tried to fly
“blind” can possibly conceive the value of such an instrument. It is worked by a gyroscope which
is so mounted that its axis does not move even though the aeroplane (and with it the case of the
instrument) may pitch or roll.
Simpler in principle, but no less useful in practice, is the directional gyro. This detects any
turn of the aeroplane, just as the artificial horizon shows pitch or roll. It is very like a compass
except that, instead of possessing the property of pointing towards the north, it will remain in any
position in which the pilot likes to set it. Actually it is marked off in degrees just like a compass,
and the pilot usually sets it to correspond to the compass course. The reader may well ask what
its justification may be, seeing that it seems to act like a compass, though lacking the chief
attribute of the latter. The answer is simple. The directional gyro responds more quickly to the
slights turn, it settle down at once after at turn, it is unaffected by acceleration and the various
magnetic errors of the compass.
Controls:
a) Longitudinal control
b) Lateral control and
c) Directional control
Longitudinal control
Longitudinal control of an aeroplane is nearly always provided by elevators attached to the
rear of the tail plane. The principle is best illustrated by the old-fashioned system in which the
elevators were connected by control wires and levers to the control column in the pilot‟s cockpit.
The control is instinctive, i.e. when the column is pushed forward, the elevators are lowered and
the upward force on the tail is increased, thus causing the nose of the aeroplane to drop Fig.
Figure: Longitudinal control-direction of movements
In order to achieve this result it will be seen that in an ordinary simple control system the
wires must be crossed between the control column and the elevators. In modern practice,
however, instead of employing two wires which will tend to become slack, causing a certain
amount of backlash in the system, more positive controls are nearly always used; these may take
the form of a rigid rod serving both to push and to pull the elevators from top or bottom only, or

they may rely simply on the torsion of a rod or tube, or the whole control system may be power-
operated, hydraulic, pneumatic or electric.
Lateral control
The usual method of obtaining lateral control is by means of ailerons hinged at the rear of
each main plane near the wing tips.
Figure:
Plate 5: Here seen with landing gear extended, the Boeing YC-14 was the first to large aircraft to
use USB (upper-surface blowing), one of the most potent forms of powered lift. The two 25-tonne
thrust turbofans blow their jets across the top of the wing. The Coanda effect keeps the transonic
jets attached to the metal surface, so with flaps depressed (as here) they end up deflected sharply
down, enormously increasing lift. The huge tail is needed for control at the very speeds that can
safely be reached.

Figure:
Plate 6: Here seen in service with the Royal Thai Navy, the Canadair CL-215 proves that large
piston-engined aircraft are not obsolete! Powered by 2,500-hp Pratt&Whitney R-2800 engines, this
amphibian is used mainly as a water bomber to fight forest fires, having the ability to scoop up
fresh loads many times in a single mission. Other mission include anti-smuggling patrols, air-sea
rescue, medevac and utility transport.
The ailerons are connected to the control column by a complete system of control wires
(figure) by a rigid system of rods, by torque tubes inside the wings, or again by some power-
operated system. This time it is a sideways movement of the control column which moves the
ailerons and does so in such a way that once again the control is instinctive, i.e. if the control
column is moved to the left the right-hand ailerons will go down, increasing the lift on the right-
hand wings, thus banking the aeroplane to the left; at the same time the left ailerons will have
been raised, decreasing the lift on the left wing and thus adding to the effect.
Figure: Lateral control-general arrangement

Sometimes the control column has no sideways movement, and lateral control is effected
by a type of handlebars, or by a wheel similar to the steering wheel on a car.
Directional control
Directional control is by rudder, which has very much the same effect as on a ship. The
rudder is connected by wires or rods or by a power-operated system to a rudder bar or rudder
pedals on the floor of the cockpit (Fig.) . In this instance it is not wise to stress the point that the
control movement is instinctive, because some people claim that it works the wrong way and
should be altered to make it instinctive. If the left foot is pushed forward, the rudder moves to the
left (the wires not being crossed) and the aeorplane turns to the left. It all sounds instinctive
enough, but it is exactly the opposite to what happens on a bicycle when the handlebars are
moved in the same way as the rudder bar.
Figure: Directional control-general arrangement
Rocket Engines
The gas turbine and reciprocating internal combustion engines are both air-breathing power
plants. They ingest air from the surrounding atmosphere and use the oxygen in the air as the
oxidizer for the chemical burning process that extracts the heat energy from the fuel. Only the fuel
is carried aboard the vehicle. A rocket is a device that burns fuel and an oxidizer, both of which
are carried by the vehicle. The forward thrust is obtained by applying a rearward momentum to
the products of combustion, the mass of which is clearly limited by the weight-carrying capacity of
the vehicle. Therefore, to obtain as large a thrust as possible with a given mass flow, the rearward
velocity must be as large as possible. A rocket is the only means of obtaining thrust in a vacuum
or near vacuum such as exists outside or neat the outer edge of the atmosphere.

There are two basic types of rockets, liquid propellant rockets and solid propellant rockets.
Liquid propellant rockets employ liquid propellants that are fed under pressure from tanks into the
combustion chamber. A schematic diagram of a liquid propellant system is shown in figure. The
propellants consist of a liquid oxidizer, such as liquid oxygen, red fuming nitric acid, or hydrogen
peroxide, and a liquid fuel (e.g., gasoline, ammonia, or liquid hydrogen).
In the combustion chamber the propellants react to form hot gases at high pressure, which
in turn are accelerated and ejected at a high velocity through a nozzle. The momentum imparted
to the gases per unit times equal to the thrust developed by the rocket.

Figure: Simplified schematic diagram of a liquid, propellant rocket system. From Sutton
and Ross, Rocket Propulsion Elements, 1976. Reprinted by permission of John Wiley &
Sons, New York.
A liquid rocket propulsion system is relatively complicated since it requires several precision
valves, a complex fed mechanism with propellant pumps and turbines, or a propellant
p[pressurizing device.
Solid propellant rockets contain all the propellant within the combustion chamber. This type
of rocket is simple since a feed system, valves or pumps are not required. Solid rockets are
usually limited to short-duration firing (1/10 to 25 s). Long-duration solid rockets require
excessively large and heavy combustion chambers. Solid propellant rockets have been widely
used for jet-assisted takeoff (JATO) purposes for aircraft with marginal takeoff performance, as
well as for the initial launch and acceleration of missiles and spacecraft. Figure shows a cross
section of a solid propellant rocket motor.
The solid propellant charge contains all the chemical elements necessary for complete
combustion. The propellants usually have a plastic like caked appearance and burn on their
exposed surfaces to form hot exhaust gases at a nearly constant rate. The body of the propellant
is called the grain. The grain may be a heterogeneous mixture of several chemicals, for example
a mixture of oxidizing crystals of per chlorate in a matrix of an organic, plastic like fuel such as
asphalt. It may be a homogeneous charge special chemicals, such as modified nitrocellulose-type
gun powder.

Figure: Sectional view of typical solid propellant rocket motor.
The shape, size, and exposed burning surface of the grain influence the burning
characteristics of the rocket and largely determine the operating pressure in the combustion
chamber, the thrust, and the duration.
Rocket motor performance
Consider a rocket in flight as shown in Figure. Assume that the rocket is operating in a
vacuum without gravitational forces. The only forces acting on the rocket are the reaction to the
exhaust gases being expelled through the rocket nozzle and the nozzle exit pressure acting over
the exit area, Se.
From Newton‟s second law, the time rate of change of linear momentum of a body, in this
case the exhaust gases, is proportional to the force acting on it. Therefore, the force on the
exhaust gases is
1 e
dm
F V
dt
where
F1 = force, N (lb)
dm/dt = mass flow rate of the exhaust gases, kg/s (slugs/s)
Ve = exhaust gas velocity relative to the rocket, m/s (ft/s)
Since a rocket is designed to maintain essentially constant temperature and pressure in the
combustion chamber or reservoir, the flow is similar to the supersonic wind tunnel flow discussed
in Chapter 7.
Figure: Rocket in flight.

The combustion chamber pressure is always high enough to obtain sonic velocity at the
throat or minimum section of the nozzle. The equation of Chapter 7 apply, and for a given exit
area the exit velocity is constant.
From Newton‟s third law, the force imposed on the exhaust gas by the rocket engine is
equal to the force exerted on the engine by the exhaust gases. The later is the major part of the
thrust. The other component is the pressure term given by peSe, so the total thrust, in a vacuum,
is
e e e
dm
F V p S
dt
If the rocket motor were immersed in the atmosphere at V0 = 0 and with zero thrust (Ve = 0),
atmospheric pressure p0 would act on all surfaces and the net pressure effect would be zero. If
the rocket is then ignited, all the pressures remain the same except at the nozzle exit, where the
pressure will be determined by the throat area, the exit area Se, and the combustion chamber
(reservoir) pressure in accordance with the one-dimensional compressible fluid equations in
Chapter 7. The additional force due to pressure is then
e 0 e
F p p S
and the total thrust is
e ee 0 e
dm
F V p p S
dt
Because of the relationship between Se, Ve, and pe, maximum thrust is obtained when the
exhaust pressure is equal to the atmospheric pressure. A rocket nozzle design that permits the
expansion of the propellant products to the pressure of the surrounding fluid is said to have an
optimum expansion ratio. An exit area differing from the optimum area will result in less rocket
thrust, although the loss is small for quite large deviations from the optimum area. Since most
rockets experience very large variations in atmospheric pressure along their flight path, exit area is
designed for an intermediate altitude that produces the most efficient overall performance for the
rocket powered vehicle.
The effective exhaust velocity is defined by the equation
e
F
C
dm/ dt
The effective exhaust velocity is a fractious velocity equal to the actual exhaust velocity plus
the increment in exhaust velocity that would produce the thrust increment actually contributed by
the pressure term (pe-p0)Se.ce is equal to the actual exhaust velocity when pe = p0.

An important performance parameter for rockets is specific impulse or specific thrust. It can
be defined as the thrust that can be obtained with a propellant weight flow of 1 unit per second. It
is the reciprocal of specific fuel consumption. Thus
sp
F
specific impulse I
dm/ dt g
Since, from equation, e
F c dm/dt ,
e
sp
C
I
g
The total impulse It is the Integral of thrust F over the operating duration t.
t t
t sp
0 0
dm
I F dt I g dt
dt
For constant thrust,
t sp sp p
dm
I Ft I gt I W
dt
where Wp is the total weight of propellant, N (lb).
Thus the performance of a rocket depends primarily on specific impulse, which, in turn, is
proportional to the effective exhaust velocity ce. The magnitude of ce for chemical rockets ranges
from 2000 m/s (6562 ft/s) to 4000 m/s (13,123 ft/s), with a typical value of about 3048 m/s (10,000
ft/s).
The exhaust velocity for a particular rocket can be determined from equation.
2
e
p e 0 T
V
c T c T
2
so
e
e p T e p T
T
T
V 2c T T 2c T 1
T
Since
1
e T e T p
T /T p /p equation , and c R/ 1 equation .

1 /
e
T
e
T
p
2 RT
V 1
1 p
From equation, we can see that the exhaust velocity is a function of TT, pe/pT, and the
constants R and . TT is a function of the chemical reaction of the fuel and the oxidizer. Any fuel-
oxidizer combination at a particular pressure will burn at a particular temperature determined by
the heat of reaction and called the adiabatic flame temperature. Thus TT depends primarily on the
propellant mixture. PT is dependent on the nozzle throat area and the mass flow rate at which the
rocket fuel and oxidizer are consumed. This, in turn, is determined by the rate at which the pumps
drive fuel into a liquid rocket engine combustion chamber or by the burning surface area in a solid
propellant rocket combustion chamber. The exit pressure pe is determined by the rocket exit area,
which is usually designed to bring the exit pressure equal to the ambient pressure at the average
height during the burning phase of the rocket flight path.
The other two factors in equation are the constants R and . Unfortunately, the values we
have been using so far for R and are applicable only to a particular gas, air. The gas constant R
is more generally defined as the universal gas constant R divided by the molecular weight of the
gas, M. Thus
R
R
M
where R, the universal gas constant = 8314 J/K-kg mole.
The molecular weight of air is 28.96. is not really a constant at all, because the
composition and temperature of the gas are changing as the gas flows through the rocket motor.
However, for preliminary design of rockets, is often taken as some average between 1.2 and
1.35.
Table 17.1 shows the combustion chamber temperature, the molecular weight of the
products of combustion, the exhaust velocity, the resulting specific impulse, and for several
rocket fuel-oxidizer combinations. We can see from equation that a fuel-oxidizer combination with
a high value of R, which results from a low molecular-weight M, and a high TT will increase the
exhaust velocity and therefore will be more efficient. Other factors must also be considered.
Hydrogen-fluorine, for example, suffers from being extremely corrosive and toxic. The choice of a
rocket fuel must be made not only on the basis of its performance but also after consideration of
the difficultly of designing the storage tanks, the pumps and piping that bring the fuel the difficulty
of designing the storage tanks, the pumps and piping that bring the fuel to the motor, the motor
itself, and the threat to personnel handling the equipment.
Note that the specific impulse as calculated for Table is simply Ve/g. this is because the
assumed rocket has been designed so that the exit pressure is equal to the ambient pressure (i.e.,
pe = p0 in equation). Also, the ratio of pT to pe has been taken as 68.03. this corresponds to a

combustion chamber pressure of 1000 lb/in2
. at sea level, a combination widely used to compare
rocket engine performance.
The use of equation to determine rocket motor performance is shown in the following
example.
Example:
A rock motor using liquid hydrogen and liquid oxygen as the fuel and oxidizer has a
combustion chamber temperature and pressure of 2700 K and 25 atm, respectively. The rocket
motor throat area is 0.07 m2
. The exit area is designed for a standard pressure altitude of 17 km.
may be assumed as 1.26.. The exit molecular weight of the combustion products is 9.5.
Table: Typical properties of several liquid rocket propellants
Fuel-
oxidizer
combination
Combustion
chamber
temperature
K
Molecular
weight of
combustion
products
Ve, m/s Isp, s
Kerosene-
oxygen
3555 21.9 2788 28.5 1.24
Hydrogen-
fluorine
3869 11.8 3774 385 1.33
Hydrogen-
oxygen
2689 8.9 3760 384 1.26
apT/pe = 68.03; sea level, pe = po.
At the design altitude of 17 km, calculate the exit velocity, specific impulse, and the thrust of
the engine. Also determine the Mach number and the area at the exit.
Solution: Since the rocket is designed for an altitude of 17 km, the nozzle exit area will be
designed to give an exit pressure equal to the ambient pressure at 17 km. From Table A.1. this
pressure is, by interpolation, 8852 N/m2
.
The chamber pressure is 25 atm (i.e.. 25 times the sea-level standard pressure). Thus pT =
25 x 101, 325 = 2.533, 125 N/m2
. the given problem is then

From equation,
1 /
e
e T
t
p
V 2 RT 1
1 p
R 8314
R 875.2 and =1.26
9.5
M
Then
1.26 1 /1.26
e
1.26 8852
V 2 875.2 2700 1
1.26 1 2.533,125
3971.79m/ s
Since the nozzle is designed with pe = p0, Isp is from equation, where ce = Ve.
e
sp
V 3971.79
I 405.29s
g 9.8
From equation.
/ 1 1 /
e e e e
T t T T
p T T p
so that
p T T p
and
1.26 1 /1.26
e
8852
T 2700 840.3K
2,533,125
Then the speed of sound at the nozzle exit is
e e
a RT 1.26 875.2 840.3 962.62m/s
and
e
e
e
V 3971.79
M 4.126
a 962.62

The area of the exit is found from equation. Note that figure is not applicable since we are
not working with air and is not.
2 1 / 1
2
e
e
* 2
l e
2.26 / 0.26
2
2
S 1 2 1
1 M
S M 1 2
1 2 0.26
1 4.126 517.5
2.26 2
4.126
and
* 2
e l
S S 517.5 0.07 22.75 1.592m
Thrust = Ve (dm/dt), so we must find dm/dt, the mass flow rate.
e e e
3
e
e
e
dm
p S V
dt
p 8852
p 0.0121kg kg/m
RT 875.2 840.3
Then
dm
0.0121 1.592 3971.79
dt
= 76.51 kg/s
and
thrust 3971.79 76.51
303,879N
68,318lb
Propulsion-Airframe integration
Propulsion-airframe integration is the process of locating the power plants and designing
their installation to meat many operating requirements while minimizing drag and weight penalties.
The arrangement of the propulsive units influences aircraft safety, structural weight, flutter, drag,
control, maximum lift, propulsive efficiency, maintainability, and aircraft growth potential.
For prop-driven aircraft, the propeller requirements almost always place the engines on the
wing or, for single-engine airplanes, at the fuselage nose. An unusual design used in converting a
small piston-engine-powered commuter airplane from a twin-engine configuration to a trimotor was
to place the center engine on the vertical tail. A recent trend in turboprop executive aircraft has

been to place the engines on the rear portion of the wing. The pusher propellers, at the rear of the
engines, are behind the aft bulkhead of the passenger cabin. The latter is actually the
fundamental design objective because it reduces the noise and vibration in the cabin caused by
the propellers. Because the engines are so far aft, the center of gravity is also far aft, and the
moment arm of the horizontal tail is small. For this reason, longitudinal control.
A Canadian division of Part & Whitney, United Technologies, is Prat & Whitney Canada
(PWC). Figure summarizes the PWC product line. This company produces several engines, all of
which are also discussed in this chapter.
General Electric Axial compressor Engines
Another major manufacturer of both large and small axial-flow gas turbines in this country is
the General Electric Company. One of their most highly produced machines is the J79 series Fig.
currently used in the McDonnel Douglas F-4 and formerly used on the General Dynamics B-58
and other aircraft. A commercial version of this engine was called the CJ805-3, and an affan
counterpart, the CJ805-23 Fig. was used in the Convair 880 and the Convair 990, respectively, but
it was never widely accepted. Three points worth noting about thee engine are the ariable-angle
inlet guide vanes, the variable-angle first six stator stages in the compressor (see chap. 5) and the
location and method of driving the fan in the CJ805-23 engine. The fan, located in the rear, is “gas
coupled” to the primary engine as opposed to the mechanical coupling used in many of the Pratt &
Whitney designs and others. Placing the fan in the rear and having it gas coupled is claimed to
compromise basic engine performance to a lesser degree. In addition, the engine can be
accelerated faster, and the aft-fan blades are automatically anti-iced by thermal conduction.
Forward fan designers claim fewer problems resulting from foreign-object damage, since most of
the foreign material will be thrown radically outward and not passed through the rest of the engine.
Furthermore, they claim that the forward fan in the cold section of the engine for highest durability
and reliability and minimum sealing problems.
As an interesting aside, General Electric‟s venture into the ultra-high-bypass-ratio propfan
area is based on their aft-fan concept. A General Electric F404 engine was modified by placing a
multistage, free-power turbine at the rear of the engine; this turbine was then attached to counter
rotating, wide-chord, carbon/epoxy composite fan blades. The engine, called Unducted Fan
(UDF), was never put into production but remains a viable competitor among propfan designs.
In addition to its aft-fan designs, General Electric also produces a high-bypass-ratio,
forward-fan engine called the TF39 Fig., which powers the Lockheed C5A and B Galaxy, one of
the largest airplanes in the world.
From the TF39, General electric has developed a series of engines using the same basic
gas generator (core) portion of the engine, but it has changed the fan and the number of turbines
needed to drive the fan. The CF6 series is installed in the McDonnell Douglas DC-10 and MD-11,
the Airbus Industrie A-300 and A-310, and the Boeing 747 and 767. The Rockwell International B-
1 Bomber uses the General electric F101, a medium-bypass turbofan. A low-bypass General
Electric turbofan engine is the F404, used in the McDonnell Douglas/Northrop F-18 Fig, while the
General Electric F110 (fig) is installed in the General Dynamics F-16. A no afterburning derivative

of the General Electric F110, the F18-GE-100, powers the Northrop B-2, and the General Electric
90B1 Fig. is slated for the Boeing 777.
Like Pratt & Whitney, General Electric manufactures a series of smaller gas turbine
engines. The CJ610, or J85 Fig. is used in the early Gates Lear Jet, Northrop Talon T38 (F5), and
the early Jet Commander. The Jet Commander, now made in Israel, is called the West wind 1124
and Astra 1125 and is powered by the Allied Signal Garrett TFE731 engine Fig. As might be
expected, General Electric has developed an aft-fan version of the CJ610 called the CF700 (fig),
two of which are installed on many models of the Falcon fanjet.
In addition to the turbojet and turbofan engines, General Electric manufactures the T58 (fig)
and the T64 Fig. Both are free-power turbine engines, a major difference being the location of the
power take-off shaft, and are used to power a variety of Sikorsky and Boeing helicopters.
The TF34 Fig is one of General Electric‟s small turbofan engines, driving the Lockheed S-
3A and the Fairchild Republic A-10 aircraft.
Other Axial Compressor Engines
Still other examples of axial-flow machines are the Allison Engine Company J71 Fig. which
powered the Douglas B-66, and the Allison Engine Company 501 series or T56 engine Fig., used
in the Lockheed Hercules and Electra, Grumman Hawkeye, Convair 580 Conversion, Lockheed C-
130, Lockheed P-3, and Grumman E-2C. Since the 501 is a turboprop, the compressor and the
load of the propeller require the use of many turbine wheels, a requirement typical of all
turboprop/turbofan designs. Although it was never put into production, the Allison Engine
Company has also designed an axial-flow turboprop engine incorporating a fixed regenerator.
British manufacturers have com up with some interesting variations of the axial-flow engine.
For example, the Fig. all three-spool turbofan engines. The RB211, in particular, has found wide
acceptance in this country and is used in the Lockheed L-1011; the Boeing 747, 757, 767, and
777; and the Airbus Industrie A330. The Rolls-Royce spey Fig, which powers the DeHavilland
Trident, British Aerospace Corporation (B.A.C) One-Eleven, and engine with a mixed exhaust.
The Rolls Royce Tyne Fig. is a two-spool turboprop engine with an integral gearbox for use in the
Caadair 44. Rolls-royce, in collaboration with SNECMA of France, also builds the Olympus 593,
one of the few afterburning commercial engines, for use in the supersonic British Aerospace
Aerospatiale Concorde.
The Oryx manufactured by D. Napier and Son Ltd., is another unusual design of British
manufacture. The power produced by the gas-generator section of the engine is used to drive
another axial-flow compressor. The airflow from both the gas generator and the air pump is mixed
together, resulting in an extremely high-volume airflow. The engine is specifically designed to
drive helicopter rotor blades by a jet reaction at the tips.
The Rolls-Royce/Bristol Produce is another form of engine designed to produce high-
volume airflows. Fan air and primary airflow are both vectored (directed) in an appropriate
direction in order to achieve the desired line of thrust. The engine is installed in the V/STOL
Hawker Harrier.

Axial-Centrifugal Compressor Engines
As a group, the axial-centrifugal-flow engines exhibit the greatest variability and design
innovation. The AlliedSignal Garrett ATF3 is a perfect example Fig. All of the various
permutations and combinations of compressor design, number of spools, type of combustion
chamber, single-shaft versus free-power turbine, location of the power-takeoff shaft, etc., can be
found on these engines.
An important producer of axial-centrifugal engines in this country is AlliedSignal Lycoming
Fig. their T53 and T55 series engines Fig, in their several versions, have been designed for wide
application in both conventional and rotary wing aircraft. Both engines use the same basic
concept and arrangement of parts; the main difference is in the number of compressor and free-
power turbine stages. The mechanically independent free-power turbine drives a coaxial through-
shaft to provide cold, front-end power extraction. A feature of these engines is the reverse-flow
combustion chamber design mentioned previously.
Two later engines developed by AlliedSignal Lycoming are the LTS/LTP (fig) series of small
turboshaft/turboprop engines and the ALF502 (Fig). At the time of this writing, most turbofan
engine fans are either coupled to one of the compressors or to a group of turbines independent of
the gas-generator compressor turbine(s). Either case requires a compromise, since the best
number of revolutions per minute (rpm) for the fan is, in most cases, lower than the best rpm for
the gas-generator compressor (core engine) or any turbine wheel. In the ALF502, the fan is
geared down, like the propeller on many piston engines, so the low pressure turbine and high-
bypass-ratio fan can each turn at an appropriate rpm.
The highly produced and used Pratt & Whitney Canada (PWC) PT6A engine also uses a
reverse-flow combustion chamber. On this machine, the air enters toward the rear and flows
forward, with the power takeoff at the front. It is currently in use on many twin engine aircraft in
business and commuter operation, including the Beech Starship, Beech King Air, Shorts 360, the
Piper Aircraft Corp. Cheyenne, Cessna Conquest, a few Bell helicopters, and several foreign
aircraft. The engine has also been used to power the STP Special at the Indianapolis 500 race.
Another interesting design from PWC, also incorporation a reverse-flow combustion chamber to
keep the engine short, is the JT15d fig. used on the Cessna Citation. As can be seen in this
chapter, many other engine manufacturers use the reverse-flow burner concept in their designs.
Allison Engine Company‟s bid for the small turbine market, the T63 (model 250) fig. has an
axial-centrifugal compressor (some variations of this engine use only a centrifugal compressor)
and incorporates many unusual design features. For example, it can be disassembled in minutes
with ordinary hand tools, contains a single combustion chamber, and has an interchangeable
gearbox. The axial part of the compressor is only about 4.5 inch (in) diameter, and the engine
weighs about 140 lb [64 kilograms (kg)] yet produces over 400 hp [298 kw] in some versions. The
turbo shaft variation of this engine is installed in the Hughes OH-6 Light Observation Helicopter
(LOH), the Bell Jet Ranger helicopter, and others. Figures 2-87 and 2-86 show two small
turbofans, with an axial-and centrifugal-style compressor: the Williams International FJ-44, which
powers the Cessna CitationJet, and the F107 Wr-400 used in the cruise missile.

Most small gas turbines use the free-power turbine method of driving the load, and the
driving the load, and the Boeing engine in Fig. 2-26 is no exception. Air is compressed by a single
axial stage, followed by a single centrifugal stage. The compressed air is mixed with fuel and
ignited in twin combustors. Hot gases then expand through the single-stage, gas-producer and
power turbines and exhaust through either a single-or double-exhaust nozzle.
GE is now producing an axial-centrifugal engine called the T700 (commercial version CT7)
Fig. This engine is designed to be installed in the Sikorsky Utility Tactical Transport Aircraft
(UTTAS) UH60A, the model 214 Bell helicopter, and the McDonnell Douglas Army Attack
Helicopter (AAH) AH64. It is sometimes fitted with an integral inlet particle separator located at
the forward end.
An engine that shows great promise, and combines many of the design innovations
discussed at the beginning of the section on the axial-centrifugal compressor, is to AlliedSignal
Garrett TFE731 Fig. This machine is a medium-bypass, two-spool engine, with the geared front
fan coupled through a planetary gearbox to the low-pressure axial spool. The centrifugal-
compressor, high-pressure spool is driven by a single turbine. Reverse-flow combustion
chambers are also used. The engine will be found on late model Lear Jerts, the I.A.I. 124
Westwind, and other aircraft.
Once again, British designers and manufacturers have produced an unusual axial-
centrifugal flow engine. The Bristol Proteus Fig. incorporates a reverse-flow, axial-centrifugal
compressor and a two-stage, free-power turbine driving the propeller output shaft through a series
of reduction gears. The engine is used in the Britannia aircraft.
Mixed-Flow Compressor Engine
The mixed-flow compressor does not fall into any of the three main categories. The mixed-
flow design is similar in appearance to the single-entry centrifugal compressor, but The mixed-flow
compressor does not fall into any of the three main categories. The mixed-flow design is similar in
appearance to the single-entry centrifugal compressor, but the blade arrangement provides a
different type of airflow. The compressor receives its air axially, as do many other types, but it
discharges this air at some angle between the straight-though flow of the axial compressor and the
radial flow of the centrifugal compressor. The Fairchild J44 engine Fig. used this design.

UNIT – III
Introduction to Principles of Flight
2. ISA:- (International standard Atmosphere)
It is the Atmospheric manual containing the mean values of the temp, pressure, density etc
existing throughout the world.
3. How drag disaffected by air density?
From the formula for relative drag produced on the body
2
d F d
1
R C PV .S C coeff as drag
2
P-density
R is disectly proportional to p V-Velocity
thus drag increases F
as pineseases S Prontal area
In other means, As the P increases the mass of air p molecules striking the wing increases
which in turn increases the energy to be supplied to displace the air molecules hitting the mane/it
absorbs energy: R increases with p.
4. Absolute attitude:
Absolute attitude is defined as the attitude of the plane from the centre of the earth. It is p
represented by ha.
Ha = ha + r (m)
ha
r
hG

Figure:
10. Pressure distribution over an aerofoil:-
Figure:
11. What do you mean by lift & drag?
Figure:
Lift is the force component on the wing/plane which is responsible for the up & down
movement drag is the unwanted force component on the plane which resists motion and always
lie opp to the direction of motion.
12. How pressure and density varies with attitude?
Pressure decreases with the increase in attitude, density also decrease with the increase in
attitude.
These are verified with the eqn.

Figure:
o
o R
2 1
T
o
o
2 1
T
g
g
.h h d
R
2 2
1
g
1
g
.h h aR
R
2 2
1
P T
e
P
isothermal region gradient region
p T
e
p
isothermal region gradient region
where
a – lapse rate - dT
dh
go – all due to glave in the rea level
PART – B
Short notes on ISA:-
The most aggravating feature of the atmosphere is its changeability- it is never the same
from day to day, from hour to hour. For this reason we have been forced to adopt an average set
of conditions (as shown in figure) called the International Standard Atmosphere. Although there
may never be a day when the conditions of the atmosphere all the way up are exactly the same as
those average conditions, they do serve as a standard for comparing the performances of aircraft.
For instance, when a height record is attempted, the height allowed is not the height actually
achieved but the height allowed is not the height actually achieved but the height which, according

to calculation, would have been achieved if the conditions had been those of the International
Standard Atmosphere. So it is no good choosing a lucky day!.
It is not easy to say how far the atmosphere actually extends, for the simple reason that the
change from atmosphere to space is so gradual it is impossible to decide on a definite dividing
line; of this reason it is hardly surprising to find that estimates of the maximum height vary from 50
to 250 miles or more –rather a wide range. So far as aircraft are concerned, the higher we get, the
more difficult does it become to go any higher. At record breaking heights we already have to
pump air into the engine, enclose the pilot in air-tight suit, supply him with oxygen and heat his
clothing artificially, while the aircraft itself can hardly get sufficient support in air that not got one-
quarter the thickness of the air near the ground.

Fig: The International Standard Atmosphere

Nor is it surprising that estimates of temperature in even higher regions of the atmosphere
vary very considerably-between temperatures both above and below anything known on earth-
when the air is so thin it isn‟t the temperature of the air that matters so much as the temperature of
the outer surfaces of the aircraft.
But in these days of missiles, satellites, and spaceships, we have become very interested,
no only in the upper reaches of the atmosphere, but in the space beyond it. These may not be
aircraft (as we have defined the term), and although they may not even fly (according to our
definition), no book on flight, with or without formulae, can any longer leave them out of
consideration; we shall have more to say about them towards the end of the book.
Derive an expression for the speed of sound:-
Consider an aircraft is flying at a certain velocity, IT is producing sound and the sound is
traveling at an velocity of a m/s.
Figure:
P, e, p + dp,
V p + dp,
V + dv.
Let us examine the wave in focus, speaking with respect to the wave, the air molecules
approaches the wave at a velocity vend at pressure p and density p and leaves the wave at an a
velocity vtdvat pressure p+2p and density p+dp applying continuity eqn, we have
PVA p dp v dv A
PV p dp v dv
PV pdV dpV dpdV dpdv o
O=pdv+dpv
dpv=pdv - 1

(A cannot change since area of the steam tube remains same before & after the wave)

From the culer‟s momentum eqn
dp vdv
dP
dv 2
v


sub (2) in (1)
2
vd dp
p pv
dp
v
dp
dp
v 3
dp

Zn this sound transmission there is no heat transfer in the process and also there is no
friction and so it is an isentropic flow process.
and therefore
aft bef
bef aft
aft
bef
aft
bef
af
P V m
m-mass
P V m
x Pr operty after the wave
x Pr operty before he wave
p
p
P t bef
aft bef
P P
Constnat =C= 4
P p
P
P
C P=Cp
p
and
1
d cp
dp C p
c 5
d d


   
sub (5) in (3)

vp
V
V RT PV=mRT
V
P RT
m
P RT


By substuting the values of an ideal gas
V = 340.29 m/s
UNIT – IV
Introduction to Aerodynamics and Propulsion
1. Define AR & Camber.
Aspect ratio:-
It is defined as the ratio of the wing span to the chord of the wing if it has a constant chord.
Otherwise it is the ratio of the wing span to the plan area of the wing
b
AR
c
S – Plan area
2
b
AR
S
Figure:
Camber:
b
n
b
S

Camber is defined as the max distance between the chord and the mean camber line
Figure:
2. Mach number:- (M)
It is defined as the ratio of the velocity of the aircraft (or) air (or) an object(v) to the velocity
of sound (a)
V
M no units
a
3. Airfoil:-
Airfoil is the cross section of the wing whose upper surface is more bulged than surface to
produce tight.
4. Aerodynamic centre:-
It is a point on the chord of the aerofoil where these is no change in the moment.
5. Types of drag:
(i) Form drag (or) pressurizing
(ii) Skin fiction (or) surface friction drag
(iii) Boundary layer drag
6. Centre of pressure:-
it is a point where the total pressure force acts on the aerofoil.
PART-B
The Turbojet Engine
Chord
Mean camber line
Chamber

Which deals with engine theory, points out that a turbojet derives its thrust by highly
accelerating a small mass of air, all of which goes through the engine. Since a high “jet” velocity is
required to obtain an acceptable amount of thrust, the turbine of a turbojet is designed to extract
only enough power from the hot gas stream to drive the compressor and accessories. All of the
propulsive force produced by a jet engine is derived from the imbalance of forces within the engine
itself Fig.
The turbojet characteristics and uses are as follows:
1. Low thrust at low forward speeds
2. Relatively high, thrust-specific fuel consumption (TSFC) at low altitudes and airspeeds, a
disadvantage that decreases as altitude and airspeed increase
3. Long takeoff roll
4. Small frontal area, resulting in low drag and reduced ground-clearance problems
5. Lightest specific weight (weight per pound of thrust produced)
6. Ability to take advantage of high ram-pressure ratios
These characteristics suggest that the turbojet engine would be best for high-speed, high-
altitude, long-distance flights.
The Turboprop Engine
Propulsion in a turboprop engine is accomplished by the conversion of the majority of the
gas-steam energy into mechanical power to drive the compressor, accessories, and the propeller
load. Only a small amount (approximately 10 percent of “jet” thrust is available in the relatively
low-pressure, low-velocity gas stream created by the additional turbine stages needed to drive the
extra load of the propeller.
The turboprop characteristics and uses are as follows:
1. High propulsive efficiency at low airspeeds, which results in shorter takeoff rolls but falls off
rapidly as develop high thrust at low airspeeds because the propeller can accelerate large
quantities of air at zero forward velocity of the airplane. A discussion of propulsive
efficiency follows in the next chapter.
2. More complicated design and heavier weight than a turbojet
3. Lowest TSFC
4. Large frontal area of propeller and engine combination that necessitates longer landing
gears for low-wing airplanes but does not necessarily increase parasitic drag
5. Possibility of efficient reverse thrust
These characteristics show that turboprop engines are superior for lifting heavy loads off
short and medium-length runways. Turboprops are currently limited in speeds to approximately
500 mph [805 km/h], since propeller efficiencies fall off rapidly with increasing airspeeds because
of shock wave formations. However, researchers in the Hamilton Standard division of United
Technologies Corporation and others are trying to overcome, or extend, this limitation by
experimenting with small diameter, multibladed, wide-chord propellers, said to be more efficient
than the high-bypass-ratio turbofan, with a 20 percent reduction in thrust-specific fuel

consumption. Aluminum blades large enough to deliver sufficient thrust and absorb high engine
power and of the right shape are also too heavy and flexible to resist straightening out from a
curved and tapered aluminum spar bonded to a fiberglass, airfoil-shaped shell filled with a plastic
like foam material. This composite construction produces a more rigid blade one-half the weight of
a comparable conventional aluminum blade. The obvious advantage is that the propeller hub and
the pitch-changing mechanism located within can be lighter and the blade will more closely
maintain its correct aerodynamic position.
The Turbofan Engine
The turbofan engine has a duct-enclosed fan mounted at the front or rear of the engine and
driven either mechanically geared down or at the same speed as the compressor, or by an
independent turbine located to the rear of the compressor drive turbine. Also illustrate two
methods of handling the fan air. Either the fan air can exit separately from the primary engine air
(short duct), or it can be ducted back to mix with the primary engine‟s air at the rear (long duct).
On some long duct engines the primary and secondary airflow may be mixed internally and then
exit from a common nozzle, or the two gas streams may be kept separate for the entire length of
the engine. If the fan air is ducted to the rear, the total fan pressure must be higher than the static
gas pressure in the primary engine‟s exhaust, or air will not flow. By the same token, the static fan
discharge pressure must be less than the total pressure in the primary engine‟s exhaust, or the
turbine will not be able to extract the energy required to drive the compressor and fan. By closing
down the area of flow of the fan duct, the static pressure can be reduced and the dynamic
pressure increased. For a discussion of static, dynamic, and total pressure.
The efficiency of the fan engine is increased over that of the pure jet by converting more of
the fuel energy into pressure energy rather than the kinetic (dynamic) energy of a high-velocity
exhaust gas stream. As shown in chapter 3, pressure times the area equals a force. The fan
produces this additional force or thrust without increasing fuel flow. As in the turboprop, primary
engine exhaust gas velocities and pressures are low because of the extra turbine stages needed
to drive the fan, and as a result the turbofan engine is much quieter. One fundamental difference
between he turbofan and turboprop engine is that the airflow through the fan is controlled by
design so that the air velocity relative to the fan blades is unaffected by the aircraft‟s speed. This
design eliminates the loss in operational efficiency at high airspeeds that limits the maximum
airspeed of propeller-driven aircraft.
The first generation of turbofan designs, such as the Pratt & Whitney JT3D engine series,
had a bypass ratio of approximately 1:1; that is, about 50 percent of the air went through the
engine core as primary airflow, and about 50 percent went through the fan as secondary airflow.
Second generation turbofans like the General Electric CF6 (fig), the Pratt & Whitney JT9D (Fig.)
and the Rolls Royce RB211 Fig have bypass rations on the order of 5:1 or 6:1. the fan thus
provides a greater percentage of the total thrust produced by the engine.
In terms of actual airflow, Table shows the fan, or cold stream, airflow and the core, or hot
stream, airflow for an engine with a total airflow of 1000 lb/s at several different bypass ratios.
Other engines with different airflows will have different fan and core airflows for similar bypass
ratios. For example, for a 500 lb/s airflow engine, divide each fan and core airflow in half for a
given bypass ratio.

Emphasis on the use and development of the turbofan engine in recent years is due largely
to the development of the transonic blade. The large-diameter fan would require a much lower
rpm to keep the blade tips below the speed of sound, development that would not be conducive to
good gas turbine design.
Fan engines show a definite superiority over the pure jet engines at speed below Mach 1,
the speed of present-day commercial aircraft, which, of course, require small frontal areas. At
high speeds, the increased drag offered by the fan more than offsets the greater net thrust
produced. The disadvantage of the fan for high-speed aircraft can be offset at least partially by
burning fuel in the fan discharge air.
Table: Fan and core airflow for different bypass ratios.
Bypass Ratio Fan Airflow lb/s Core Airflow lb/s
6.00 858 143
5.00 834 167
4.00 800 200
3.00 750 750
2.00 667 333
1.00 500 500
0.75 429 572
0.50 333 667
This process expands the gas, and, in order to keep the fan discharge air at the same
pressure, the are fan jet nozzle is increased. This action results in increased gross thrust due to
an increase in pressure times an area, and increased thrust-specific fuel consumption. Very-low-
bypass-ratio turbofan engines (less than one) are being used on some fighter aircraft capable of
supersonic speeds.
The turbofan characteristics and uses are as follows:
1. Increased thrust at forward speeds similar to a turboprop results in a relatively short
takeoff. However, unlike the turboprop, the turbofan thrust is not penalized with increasing
airspeed, up to approximately Mach 1 with current fan designs.
2. Weight falls between the turbojet and turboprop.
3. Ground clearances are less than turboprop but not as good as turbojet.
4. TSFC and specific weight fall between turbojet and turboprop, resulting in increased
operating economy and aircraft range over the turbojet.
5. Considerable noise level reduction of 10 to 20 percent over the turbojet reduces acoustic
fatigue in surrounding aircraft parts and is less objectionable to people on the ground.
Also, no noise suppressor is needed. On newer fan engines, such as the General Electric
CF6 and Pratt & Whitney 4000 series shown in Figs. Others, the inlet guide vanes have

been eliminated to reduce the fan noise, which is considered to be a large problem for
high-bypass-ratio fan engines. The noise level is reduced by the elimination by the fan
blades cutting through the wakes behind the vanes. Other fan-noise-reducing features are
also incorporated.
6. The turbofan is superior to the turbojet in “hot day” performance.
7. Two thrust reversers are required if the fan air and primary engine air exit through separate
fan nozzles, the advantage of which is the short fan duct with corresponding low duct loss.
Jet Propulsion
It is the propulsion of jet aircraft or other missiles by the reaction of jet coming out with a
high velocity. The term jet propulsion is used where the oxygen is obtained from the surrounding
atmosphere. It consists of air plus combustion products. The principle of jet propulsion is
obtained from the application of Newton‟s law of motion. It is nothing but reaction principle. Since
all the air craft engines breaths air from the surrounding atmosphere hence it is called air –
breathing engines. The air breathing engines are classified as:
(i) Turbojet engine
(ii) Turbo prop engine
(iii) Pulse jet (or) flying bomb and
(iv) Ram jet engine
Turbo Jet Engine
It is a most common type of air breathing engine whose essential features are shown in
figure.

Figure: Components of Turbo Jet Engines
This engine consists of inlet diffuser, compressor, combustion chamber, turbine and an
exhaust nozzle. The function of the diffuser is to convert the kinetic energy of the entering air into
a static pressure rise. After this air enters to the compressor, (axial or centrifugal) which further
compresses the air to a very high pressure and delivers it to the combustion chamber. Then fuel
nozzle supplies fuel continuously and continuous combustion takes place at constant pressure.
The high pressure and high temperature gases then enters the turbine, where they expand
partially to provide drive power for the turbine. The turbine is directly connected the compressor
and all the power developed by the turbine is to drive the compressor and the auxiliary devices.
After the gases leave the turbine, they expand further in the exhaust nozzle and are ejected with a
very high velocity than the flight velocity to produce a thrust for propulsion.
The T – S diagram or ideal and actual cycle is shown in figure
Figure:
i – 1 Inlet diffuser
1 – 2 Air
compressor
2 – 3 Combustion chamber
3 – 4 Turbine
4 – e Nozzle or tail pipe
Advantages:
1. Lower frontal area due to the absence of fan. Therefore the drag is less
2. Suitable for long distance flights at higher altitudes and speeds.

3. Since this engine has a compressor it is capable of operating under static conditions.
4. Reheat can be possible to increase the thrust.
5. Lower weight per unit thrust at design speed and altitude.
6. Since a diffuser is at the inlet, part of the compression is done by it without any work input.
Disadvantages:
1. Propulsive efficiency and thrust are lower at lower speeds
2. Thrust specific fuel consumption is high at low speeds and altitudes.
3. It is not economical for short distance flights.
4. Long runway is required due to slower acceleration.
5. Sudden decrease of speed is difficult to achieve.
Applications:
Turbo jet engines are used in military aircrafts, guided missiles and piloted aircrafts, etc,
Turbo Prop Engine:
It is very similar to turbo jet engine , the major difference being that the turbine is designed
so that it develops shaft power for deriving a propeller to provide most of the propulsive thrust
(90%), and only a small amount jet thrust is produced in the nozzle is shown in figure.
Figure: Components of Turbo – Prop Engine
The engine consists of a diffuser, compressor, combustion chamber, turbine, exhaust
nozzle, reduction gear and a propeller. The diffuser, compressor and combustion chamber
functions are as same as the turbo jet engine. However, in the turbo prop engine, the turbine
extracts much more power than the turbo – jet engine, because the turbine provides power for
both the compressor and the propeller. When all of this energy is extracted from the high
temperature gases, only little energy is left out for producing jet thrust. Thus the turbo – prop
engine drives most of its propulsive thrust from the propeller and drives only a small portion (10 to
25%) from the exhaust nozzle.

Since the shaft rotation speed of gas turbine engine is very high, a reduction gear must be
placed between the turbine shaft and the propeller to enable the propeller to operate efficiently.
Advantages:
1. Propulsive efficiency is very high.
2. The TSFC based on thrust is low
3. High acceleration at lower speed enables to a shorter run way.
4. Thrust reversal is possible by varying the blade angle, this gives the advantage of
decreasing the speed drastically.
5. Used for shorter distance travels. ( C < 600 Kmph)
Disadvantages:
1. Heavier propeller, compressor and turbine decreases pay load capacity.
2. A reduction gear is required to transmit the power from the turbine shaft to the propeller
shaft.
3. If the speed of the engine increases above 600 Kmph, the efficiency drastically decreases.
4. The frontal area is being blocked on account of large diameter propeller which increases
the co – efficient of drag.
5. Engine is heavier and more complicated.
Ram Jet Engine:
The simplest types of air – breathing engine is the Ram jet engine which is shown in figure.
The engine consists of a supersonic diffuser, subsonic diffuser section, combustion chamber and
a discharge nozzle section. The function of a supersonic and subsonic diffuser is to convert the
kinetic energy of the entering air into a pressure rise, called the “ram pressure”.
Air from the atmosphere enters the supersonic diffuser where in its static pressure
increased and the velocity of air is reduced. Then the air enters the subsonic diffuser it is
compressed further. The air then flows into the combustion chamber, where the fuel burners are
located and here the air is heated to a high temperature (16000
C to 20000
C) by the continuous
combustion of fuel. The highly heated products of combustion are then allowed to expand in the
exhaust nozzle section and are discharged from the engine with a speed greater than that of
entering air. Because of the rate of increase in momentum of the working fluid flowing through the
engine, a thrust „F‟ is developed in the direction of flight.

Figure: Components of Ram Jet Engine
The cycle pressure ratio of ram jet engine depends upon its flight velocity; the higher the
flight velocity, the larger the ram pressure and consequently larger the thrust. Since the flight
speed is very high, the pressure rise in the diffuser (ram pressure) is very high and this eliminates
the compressor. Consequently the turbine is also eliminated, because, the function of a turbine in
just to run the compressor. Since the rum jet engine cannot operate under static conditions as
there will be no pressure rise in the diffuser, it is not self – operating at zero flight velocity.
Therefore to attain the required flight speed some kind of starting device must be required such as
launching rockets.
Advantages:
1. Pay load capacity is very high due to the absence of fan, compressor and turbine.
2. Its fuel consumption decreases with flight speed and approaches reasonable values when
the flight Mach number is between 2 to 4, and therefore, it is suitable for propelling
supersonic missiles.
3. Since the frontal area is less, the co – efficient of drag is low.
4. It increases the mechanical efficiency due to the absence of sliding and moving parts.
5. High temperature and pressure can be employed.
Disadvantages:
1. A starting device is required to propel ram jet up to supersonic speed.
2. Altitude limitation is there.
3. It has low thermal efficiency and high TSFC.
4. Due to high temperature of gas coming out from the nozzle, erosion occurs at the exit of the
nozzle.
Applications:
Uses as guided missiles and high supersonic speed aircrafts.
Pulse Jet or Flying Bomb:
Figure a pulse jet engine which consists of a inlet diffuser, valve grid (contains springs that
close on their own spring pressure), combustion chamber, spark plug and a discharge nozzle.

Figure: Components of Pulse Jet Engine
The function of a diffuser is to change the kinetic energy of the entering air into static
pressure rise by slowing down the air velocity. When a certain pressure drop exits across the
valve grid, the valves will open and allow the fresh air to enter the combustion chamber, where
fuel is injected and mixed with air. Hence combustion takes place with spark ignition. There is a
rapid increase in pressure, which causes the valve to close rapidly and surges the products of
combustion rearward into the nozzle, where they expand and escape with higher velocity than the
entrance velocity. Thus the thrust is produced at the nozzle exit.
Since firing in the combustor is intermittent and therefore intermittent thrust is produced.
The pulse – jet engine is a simple, cheap for subsonic flights and well adopted to pilot less aircraft.
Advantages:
1. It gives higher pay load capacity due to the absence of compressor, propeller and turbine.
2. It is simple in construction and cheap. It is suitable for subsonic flights.
3. Drag co – efficient is less due to smaller frontal area.
4. Due to the absence of sliding and moving parts mechanical efficiency is very high.
Disadvantages:
1. Limited flight speed and altitude.
2. Severe vibrations and high intensity of noise due to intermittent combustion.
3. Nozzle erosion occurs, due to the high temperature of gases coming out from the nozzle.
Thrust:

The force which propels the aircraft forward at a given speed is called propulsive force or
thrust. This propulsive force is mainly depends on the velocity of gases at the exit of the nozzle in
turbo jet engines and from the propeller in turbo prop engines.
Jet Thrust (Turbo Jet Engine)
The two section 1 – 1 and 2 – 2 of an imaginary control surface for a turbo jet engine is
shown in figure. The flow of air (internal and external) is separated by the solid boundaries of the
engine casing.
Figure: Flow of Gases in Turbo Jet Engine
Ambient air enters the jet engine at a pressure Pa and velocity „u‟ and after expansion hot
gases leave from the nozzle at a pressure Pe and high velocity Ce. If Pe = Pa the expansion is
complete i.e., Ce = Cj (Jet velocity).
Mass flow rate at inlet of the engine is a
.
m and the mass flow rate at exit is a f
. .
m m
Kg/sec. Part of the air flow at section 1 – 1 is swallowed by the jet engine and experiences
change in momentum flux, the remaining flows through the engine without any change in the
momentum flux.
The net thrust on the engine = momentum thrust + pressure thrust
F = Fmom + Fpr
Momentum thrust Fmom = a f
. .
m m Ce - a
.
m u

Pressure thrust Fpr = (Pe – Pa ) Ae
Net thrust F = a f
. .
m m Ce - a
.
m u + Ae (Pe – Pa)
Propeller Thrust:
Figure shows the air flow takes place across the propeller of a turbo prop engine. The air
flow pattern before and after the propeller is shown in figure. A flow boundary similar to the walls
of a duct which separates the fluid at rest and fluid in motion.
Figure: Flow through a Turbo – Prop Engine
The pressure at section 1 – 1 and outside the boundary is ambient. Therefore, the thrust
on the propeller and the aircraft is due to the change in momentum flux between inlet and outlet
section.
The thrust on the propeller F = a
.
m (Cj – u)
Where Cj = Jet velocity and
u = flight speed
The flight to jet velocity ratio or effective speed ratio
j
u
C
Therefore, a j
j
. u
F m C 1
C
= a
.
m Cj [ 1 - ]

Propulsive, Thermal and Overall Efficiencies
The performance of an aircraft population system can be analyzed by various efficiencies.
Figure shows the utilization of power of the fuel in a turbo jet engine.
Figure: Utilization of Power in Aircraft Propulsion
Power input to the engine (Fuel power) =
.
f f
m Q
Power output from the engine =
.
2 2
j
1
m C u
2
Propulsive power (or) Thrust power F u = (Pout – Pin)
Propulsive Efficiency ( p)
Propulsive power (or) Thrust power
Propulsive efficiency=
Power output of the engine
.
m j
.
C u u
1
m
2
j
2 2
j
2 C u
C u j j
u
C u C u
p
j
2u
C u
Divide both Nr. and Dr. by „Cj‟ the above equation becomes

p
p
j
2
1
2 2
1 C
1 1
u
Case (a): When the speed of air craft u = 0, the propulsive efficiency p = 0, but the specific thrust
is maximum. Maximum thrust is needed during take – off period.
Case (b): When the speed of aircraft equals to the speed of jet i.e., u = Cj, p = 100%, but the
specific thrust is zero. Therefore „Cj‟ must be always greater than „u‟ when the aircraft is flying. In
normal conditions when the speed ratio ( ) increases, the propulsive efficiency ( p) will also
increases. The propulsive efficiency can be increased by increasing the jet velocity close to the
flight speed where as the thrust power can be increased by increasing the mass flow rate of air or
gas through the propulsive device. The propulsive efficiency versus speed ratio for turbo jet and
turbo prop engine is shown in figure.
Figure: Comparison of Turbo Jet Engines
Characteristics, Applications, comparisons, and evaluation of the turbojet, turboprop,
turbofan, and propfan engines
By converting the shaft horsepower of the turboprop into pounds of thrust and the fuel
consumption per horsepower into fuel consumption per pound of thrust, a comparison between the
various engine forms can be made. Assuming that the engines have equivalent compressor ratios
and internal temperatures and that they are installed in equal-sized aircraft best suited to the type
of engine used, Fig. shows how the various engines compare in thrust and thrust specific fuel
consumption versus airspeed. As the graphs indicate, each engine type has its advantages and
limitations. Summaries of these characteristics and uses follow.

Thermal Efficiency ( th)
th
.
2 2
J
.
f f
Power output of the engine
Power input to the engine through fuel
1
m C u
2
=
m Q
Overall efficiency ( 0)
th
.
j
.
f f
Propulsive power
Power input to the engine through fuel
m C u u
=
m Q
Multiply both Nr. and Dr. by
.
2 2
J
1
m C u
2
, the above equation becomes,
.
. 2 2
J
j
.
.
2 2
f f
J
1
m C u
m C u u 2
1
m Q
m C u
2
0 p th
Specific Fuel consumption:
It is the ratio between fuel consumption rate per unit thrust. Since the output is in the form
of thrust, a thrust fuel consumption is
.
f
m
TSFC
F
It is an important parameter to compare the engine performance of different types of aircraft
propulsion systems.
Substituting equation we get,
0 . .
f f
f f
.
j
u u
m m
Q Q
F
m C u

f
u
=
TSFC Q
Specific Thrust:
It is defined as the thrust produced per unit mass flow rate through the propulsive device.
sp .
F
F
m
It is an another useful parameter for comparing the different types of propulsion devices.
Specific Impulse:
It is defined as the thrust produced per unit weight flow rate through the propulsive device.
It is also an another useful performance parameter in aircraft propulsion devices.
.
j
sp . .
j
m C u
F
I
W mg
C
u
= 1
g u
u 1
=
g
Effect of Forward Speed:
The forward speed of the aircraft affects the compressor inlet pressure and temperature.
As flight velocity increases, inlet drag will be more and the net specific thrust is reduced using the
normal values of cycle variables. Therefore, propulsive efficiency is decreased.
Effect of Altitude:
At higher altitude, the ambient temperature and pressure is very less. This ambient air is
not sufficient to propel the aircraft engines. Therefore, the flight must fly at a designed altitude.
Thrust Augmentation:
To achieve better take – off performance, higher rates of climb and increased performance
at altitude during combat manoeuvres, there has been a demand for increasing the thrust output of
aircraft power plant for short intervals of time. The following methods of thrust augmentation for
turbo jet engines are:
(a) After - burning:

Burning additional fuel in the tail pipe between the turbine exhaust section and entrance
section of the exhaust nozzle is shown in figure.
Figure: After Burner
This method of thrust augmentation increases the enthalpy of air entering the nozzle. Thus
the jet velocity at the nozzle exit is increased, resulting in increased thrust.
(b) Injecting Refrigerants:
Injecting refrigerants, water or water – alcohol mixture at some point between inlet and exit
sections of the air compressor. This method of thrust augmentation increases the mass flow rate
of air and decreases the compressor work.
UNIT-V
Introduction to Airplane Structures and Materials
1. What are the functions of ribs and spars?
Spars:-
The wing spars which are large I-beams that run most of the span of wing, with heights that
reach from the bottom to the top surface of the wing. The spars are basically cantilever beams
extending from the fuselage carry through structure.
Ribs:-
The spars the run along the span of the wing, and the airfoil section that help to form the
shape of the wing, these airfoil shapes are called the wing ribs.
2. Differentiate between monocoque and semi-monocoque construction.

Monocoque:-
A structure in which the outer skin carries the primary stresses and is free of internal
bracing.
Semi-monocoque:-
An aircraft structure in which the outer skin in inadequate to carry the primary stresses, and
is reinforced by frames, formers and longerons.
3. State the uses of titanium in aircraft industries.
Titanium has a better strength-to-weight ratio than aluminium and retains its strength at
higher temperatures.
Supersonic aircraft have to use titanium because of the skin temperatures due to
aerodynamic heating.
4. Enumerate the composite materials.
Composite materials are bringing about a revolution in aircraft structures because for the
same load the composite structure can yield at least a 25% reduction in weight. Composite
materials are quite different from metals in both their composition and physical properties.
5. State the uses of aluminium alloys in aircraft industry.
 Aluminium is readily formed and machined, reasonable cost, corrosion resistant, and has
an excellent strength to weight ratio.
 It is pure form, aluminium is too short for aircraft use.
6. What are the different types of fuselage structure?
1. Monocoque shell
2. Geodetic construction
3. D-Spar construction
4. Box-Spar construction
5. Semi-monocoque
7. What is box truss structure?

A box truss is a structure composed of three or more chords connected by transverse
and/or diagonal structural elements.
Box trusses are commonly used in certain types of electric power pylons, large ratio
antennas, and many bridge structures.
8. What is monocoque shell?
Monocoque is a construction technique that supports structural load using an object‟s
external skin. This stands in contrast with using an internal framework (or truss) that is then
covered with a non-load-bearing skin. Monocoque construction was first widely used in aircraft,
starting in the 1930s.
1. Types, characteristics, and uses of Titanium and its alloys.
Titanium and titanium alloys are used chiefly for parts that require good corrosion
resistance, moderate strength up to 600o
F, and lightweight.
Types, Characteristics, and uses
Titanium alloys are being used in quantity for jet engine compressor wheels, compressor
blades, spacer rings, housing compartments, and airframe parts such as engine pads, ducting,
wing surfaces, fire walls, fuselage skin adjacent to the engine outlet, and armor plate. In view of
titanium‟s high melting temperature, approximately 3,300o
F, its high-temperature properties are
disappointing. The ultimate and yield strengths of titanium drop fast above 800o
F. In applications
where the declines might be tolerated, the absorption of oxygen and nitrogen from the air at
temperatures above 1,000o
F makes the metal so brittle on long exposure that it soon becomes
worthless. Titanium has some merit for short-time exposure up to 2,000o
F where strength is not
important, as in aircraft fire walls. Sharp tools are essential in machining techniques because
titanium has a tendency to resist or back away from the cutting edge of tools. It is readily welded,
but the tendency of the metal to absorb oxygen, nitrogen, and hydrogen must never be ignored.
Machine welding with an inert gas atmosphere has proven most successful. Both commercially
pure and alloy titanium can absorb large amounts of cold-work without cracking. Practically
anything that can be deep drawn in low-carbon steel can be duplicated in commercially pure
titanium, although the titanium may require more intermediate anneals.

Identification of Titanium:-
Titanium metal, pure or alloyed, is easily identified. When touched with a grinding wheel, it
makes white spark traces that end in brilliant white bursts. When rubbed with a piece of glass,
moistened titanium will leave a dark line similar in appearance to a pencil mark.
2. Write a short note on composite material.
Composites are materials consisting of a combination of high-strength stiff fibers embedded
in a common matrix (binder) material; for example, graphite fibers and epoxy resin. Composite
structures are made of a number of fiber and epoxy resin laminates. These laminates can number
from 2 to greater than 50, and are generally bonded to a substructure such as aluminum or
nonmetallic honeycomb. The much stiffer fibers of graphite, boron, and Kevlar® epoxies have
given composite materials structural properties superior to the metal alloys they have replaced.
The use of composites is not new. Fiber glass, for example, has been used for some time
in various aircraft components. However, the term application for naval aircraft.
Composite materials are replacing and supplementing metallic materials in various aircraft
structural components. The first materials were used with laminated fiber glass radomes and
helicopter rotor blades. In recent years, the replacement of metallic materials with more advanced
composite materials has rapidly accelerated. This has become particularly evident with the advent
of the F/A-18, AV-8B, SH-60B, and CH-53E aircraft; and it is anticipated that composite materials
will continue to comprise much of the structure in future aircraft. As a result, there is a growing
requirement to train you in the use of advanced composite materials.
There are numerous combinations of composite materials being studied in laboratories and
a number of types currently used in the production of aircraft components. Examples of composite
materials are as follows: graphite/epoxy, Kevlar®/epoxy, boron poly-amide, graphite polyamide,
boron-coated boron aluminum, coated boron titanium, boron graphite epoxy hybrid, and
boron/epoxy. The trend is toward minimum use of boron/epoxy because of the cost when
compared to current generation of graphite/epoxy composites. Composites are attractive
structural materials because they provide a high strength/weight ratio and offer design flexibility.
In contrast to traditional materials of construction, the properties of these materials can be
adjusted to more efficiently match the requirements of specific applications.

Figure: Sandwich construction
However, these materials are highly susceptible to impact damage, and the extent of the
damage is difficult to determine visually. Nondestructive inspection (NDI) is required to analyze
the extent of damage that the effectiveness of repairs. In addition, repair differs from traditional
metallic repair techniques.
3. Discuss the monocoque and semi-monocoque construction.
There are two general types of fuselage construction-welded steel truss and monocoque
designs. The welded steel truss was used in smaller Navy aircraft, and it is still being used in
some helicopters. The monocoque design relies largely on the strength of the skin, or covering, to
carry various loads. The monocoque design may be divided into three classes-monocoque,
semimonocoque, and reinforced shell ! The true monocoque construction uses formers, frame
assemblies, and bulkheads to give shape to the fuselage. However, the skin carries the primary
stresses. Since no bracing members are present, the skin must be strong enough to keep the
fuselage rigid. The biggest problem in monocoque construction is maintaining enough strength
while keeping the weight within limits. ! Semimonocoque design overcomes the strength-to-weight
problem of monocoque construction. In addition to having formers, frame assemblies, and
bulkheads, the semimonocoque construction has the skin reinforced by longitudinal members. !
The reinforced shell has the skin reinforced by a complete framework of structural members.
Different portions of the same fuselage may belong to any one of the three classes. Most are
considered to be of semimonocoque-type construction. The semimonocoque fuselagies
constructed primarily of aluminimum alloy, although steel and titanium are found in high-
temperature areas. Primary bending loads are taken by the longerons, which usually extend
across several points of support. The longerons are supplemented by other longitudinal members
known as stringers.
Stringers are more numerous and lightweight than longerons. The vertical structural
members are referred to as bulkheads, frames, and formers. The heavier vertical members are
located at intervals to allow for concentrated loads. These members are also found at points
where fittings are used to attach other units, such as the wings and stabilizers. The stringers are
smaller and lighter than longerons and serve as fill-ins. They have some rigidity but are chiefly
used for giving shape and for attachment of skin. The strong, heavy longerons hold the bulkheads
and formers. The bulkheads and formers hold the stringers. All of these join together to form a
rigid fuselage framework. Stringers and longerons prevent tension and compression stresses from
bending the fuselage. The fuselage skin thickness varies with the load carried and the stresses
sustained at particular location.

4. Write a short note on wings structure.
Wings develop the major portion of the lift of a heavier-than-air aircraft. Wing structures
carry some of the heavier loads found in the aircraft structure. The particular design of a wing
depends on many factors, such as the size, weight, speed, rate of climb, and use of the aircraft.
The wing must be constructed so that it holds its aerodynamics shape under the extreme stresses
of combat maneuvers or wing loading. Wing construction is similar in most modern aircraft. In its
simplest form, the wing is a framework made up of spars and ribs and covered with metal. The
construction of an aircraft wing is shown in figure. Spars are the main structural members of the
wing. They extend from the fuselage to the tip of the wing. All the load carried by the wing is
taken up by the spars. The spars are designed to have great bending strength. Ribs give the
wing section its shape, and they transmit the air load from the wing covering to the spars. Ribs
extend from the leading edge to the trailing edge of the wing. In addition to the main spars, some
wings have a false spar to support the ailerons and flaps. Most aircraft wings have a removable
tip, which streamlines the outer end of the wing. Most NAVY aircraft are designed with a wing a
wing referred to as a wet wing. This term describes the wing that is constructed so it can be used
as a fuel cell. The wet wing is sealed with a fuel-resistant compound as it is built. The wing holds
fuel without the usual rubber cells or tanks. The wings of most naval aircraft are of all metal, full
cantilever construction. Often, they may be folded for carrier use. A full cantilever wing structure
is very strong. The wing can be fastened to the fuselage without the use of external bracing, such
as wires or struts. A complete wing assembly consists of the surface providing lift for the support
of the aircraft. It also provides the necessary flight control surface.
Note: The flight control surfaces on a simple wing may include only ailerons and trailing edge
flaps. The more complex aircraft may have a variety of devices, such as leading edge flaps, slats,
spoilers, and speed brakes. Various points on the wing are located by wing station numbers (fig).
Wing station (WS) 0 is located at the centerline of the fuselage, and all wing stations are
measured (right or left) from this point (in inches).

Figure:
1. Types, characteristics, and uses of aluminium and its alloys.
Commercially pure aluminum is a white, lustrous metal, light in weight and corrosion
resistant. Aluminum combined with various percentages of other metals (generally copper,
manganese, magnesium, and chromium) form the alloys that are used in aircraft construction.
Aluminum alloys in which the principal alloying ingredients are either manganese, magnesium, or
chromium, or magnesium and silicon, show little attack in corrosive environments. On the other
hand, those alloys in which substantial percentages of copper are used are more susceptible to
corrosive action. The total percentage of alloying elements is seldom more than 6 or 7 percent in
the wrought aluminum alloys.
Types, characteristics, and uses
Aluminium is one of the most widely used metals in modern aircraft construction. It is vital
to the aviation industry because of its high strength/weight ratio, its corrosion-resisting qualities,
and its comparative ease of fabrication. The outstanding characteristic of aluminum is its light
weight. In color, aluminium resembles silver, although it possesses a characteristic bluish tinge of
its own. Commercially pure aluminum melts at the comparatively low temperature of 1,216o
F. It is
nonmagnetic, and is an excellent conductor of electricity.

Commercially pure aluminum has a tensile strength of about 13,000 psi, but by rolling or
other cold-working processes, its strength may be approximately doubled. By alloying with other
metals, together with the use of heat-treating processes, the tensile strength may be raised to as
high as 96,000 psi, or to well within the strength range of structural steel.
Aluminum alloy material, although strong, is easily worked, for it is very malleable and
ductile. It may be rolled into sheets as thin as 0.0017 inch or drawn into wire 0.004 inch in
diameter. Most aluminum alloy sheet stock used in aircraft construction ranges from 0.016 to
0.096 inch in thickness; however, some of the larger aircraft use sheet stock that may be as thick
as 0.0356 inch.
One disadvantage of aluminum maybe divided into two classes-casing alloys (those
suitable for casting in sand, permanent mold, and die castings) and the wrought alloys (those that
may be shaped by rolling, drawing, or forging). Of the two, the wrought alloys are the most widely
used in aircraft construction, being used for stringers, bulkheads, skin, rivets, and extruded
sections. Casting alloys are not extensively used in aircraft.
Wrought Alloys:-
Wrought alloys are divided into two classes-nonheat treatable and heat treatable. In the
nonheat-treatable class, strain hardening (cold-working) is the only means of increasing the tensile
strength. Heat-treatable alloys may be hardened by heat treatment, by cold-working, or by the
application of both processes. Aluminum products are identified by a universally used designation
system. Under this arrangement, wrought aluminum and wrought aluminum alloys are designated
by a four-digit index system.
The first digit of the designation indicates the major alloying element or alloy group, as
shown in table. The lxxx indicates aluminum of 99.00 percent or greater; 2xxx indicates an
aluminum ally in which copper is the major alloying element; 3xxx indicates an aluminum alloy with
manganese as the major alloying element; etc. Although most aluminum alloys contain several
alloying elements, only one group (6xxx) designates more than one alloying element.
In the 1xxx group, the second digit in the designation indicates modifications in impurity
limits. If the second digit is zero, it indicates that there is no special control on individual
impurities. The last two of the four digits indicate the minimum aluminum percentage. Thus, alloy
1030 indicates 99.30 percent aluminum without special control on impurities. Alloys 1130, 1230,
1330, etc., indicate the same aluminum purity with special control on one or more impurities.
Likewise, 1075, 1175, 1275, etc., indicate 99.75 percent aluminum.
Table:
Aluminum – 99.00 percent minimum and greater …………………… 1xxx
Aluminum alloys, grouped by major alloying element:
Copper ………………………………………………………………………2xxx

Manganese ………………………………………………..……………… 3xxx
Silicon ……………………………………………………………………… 4xxx
Magnesium ……………………………………………………………… 5xxx
Magnesium and silicon ……………………………………………………6xxx
Zinc ………………………………………………………………………… 7xxx
Other elements …………………………………………………………… 8xxx
In the 2xxx through 8xxx groups, the second digit indicates alloy modifications. If the
second digit in the designation is zero, it indicates the original alloy, while numbers 1 through 9,
assigned consecutively, indicate alloy modifications. The last two of the four digits have no special
significance, but serve only to identify the different alloys in the group.
The temper designation follows the alloy designation and shows the actual condition of the
metal. It is always separated from the alloy designation by a dash.
The letter F following the alloy designation indicates the “as fabricated condition, in which
no effort has been made to control the mechanical properties of the metal,
The letter O indicates dead soft, or annealed, condition.
The letter W indicates solution heat treated. Solution heat treatment consists of heating the
metal to a high temperature followed by a rapid quench in cold water,
This in an unstable temper, applicable only to those alloys that spontaneously age at room
temperature. Alloy 7075 may be ordered in the W condition.
The letter H indicates strain hardened, cold-worked, hand-drawn, or rolled. Additional digits
are added to the H to indicate the degree of strain hardening. Alloys in this group cannot be
strengthened by heat treatment, hence the term nonheat-treatabel.
The letter T indicates fully heat treated. Digits are added to the T to indicate certain
variations in treatment.
Greater strength is obtainable in the heat-treatable alloys. They are often used in aircraft in
preference to the nonheat-treatable alloys. Heat-treatable alloys commonly used in aircraft
construction ( in order of increasing strength) are 6061, 6062, 6063, 2017, 2024, 2014, 7075, and
7178.
Alloys 6061, 6062, and 6063 are sometimes used for oxygen and hydraulic lines and in
some applications as extrusions and sheet metal.
Alloy 2017 is used for rivets, stressed-skin covering, and other structural members.
Alloys 2024 is used for airfoil covering and fitting. It may be used wherever 2017 is
specified, since it is stronger.

Alloy 2014 is used for extruded shapes and forgings. This alloy is similar to 2017 and 2024
in that it contains a high percentage of copper. It is used where more strength is required than
that obtainable from 2017 or 2024.
Alloy 7178 is used where highest strength is necessary, Alloy 7178 contains a small
amount of chromium as a stabilizing agent, as does alloy 7075.
Nonheat-treatable alloys used in aircraft construction are 1100, 3003, and 505. These do
not respond to any heat treatment other than a softening, annealing effect. They may be
hardened only by cold-working.
Alloy 1100 is used where strength is not an important factor, but where weight, economy,
and corrosion resistance are desirable. This alloy is used for fuel tanks, fairings, oil tanks, and for
the repair of wing tips and tanks.
Alloy 3003 is similar to 1100 and is generally used for the same purposes. It contains a
small percentage of manganese and is stronger and harder than 1100, but retains enough work
ability that it is usually preferred over 1100 in most applications.
Alloy 5052 is used for fuel lines, hydraulic lines, fuel tanks, and wing tips. Substantially
higher strength without too much sacrifice of workability can be obtained in 5052. it is preferred
over 1100 and 3003 in many applications.
Alclad is the name given to standard aluminum alloys that have been coated on both sides
with a thin layer of pure aluminum. Alclad has very good corrosion-resisting qualities and is used
exclusively for exterior surfaces of aircraft. Alclade sheets are available in all tempers of 2014,
2017, 7075, and 7178.
2. Explain in detail the main group of materials used in aircraft construction.
Titanium and Titanium Alloys
Titanium and titanium alloys are used chiefly for parts that require good corrosion
resistance, moderate strength up to 600o
F, and lightweight.
Types, characteristics, and uses
Titanium alloys are being used in quantity for jet engine compressor wheels, compressor
blades, spacer rings, housing compartments, and airframe parts such as engine pads, ducting,
wing surfaces, fire walls, fuselage skin adjacent to the engine outlet, and armor plate. In view of
titanium‟s high melting temperature, approximately 3,300o
F, its high-temperature properties are
disappointing. The ultimate and yield strengths of titanium drop fast above 800o
F. In applications
where the declines might be tolerated, the absorption of oxygen and nitrogen from the air at
temperatures above 1,000o
F makes the metal so brittle on long exposure that it soon becomes
worthless. Titanium has some merit of short-time exposure up to 2,000o
F where strength is not
important, as in aircraft fire walls. Sharp tools are essential in machining techniques because
titanium has a tendency to resist or back away from the cutting edge of tools. It is readily welded,

but the tendency of the metal to absorb oxygen, nitrogen, and hydrogen must never be ignored.
Machine welding with an inert gas atmosphere has proven most successful. Both commercially
pure and alloy titanium can absorb large amounts of cold-work without cracking. Practically
anything that can be deep drawn in low-carbon steel can be duplicated in commercially pure
titanium, although the titanium may require more intermediate anneals.
Identification of Titanium:
Titanium metal, pure or alloyed, is easily identified. When touched with a grinding wheel, it
makes white spark traces that end in brilliant white bursts. When rubbed with a piece of glass,
moistened titanium will leave a dark line similar in appearance to a pencil mark with an inert gas
atmosphere has proven most successful. Both commercially pure and alloy titanium can absorb
large amounts of cold-work without cracking. Practically anything that can be deep drawn in low-
carbon steel can be duplicated in commercially pure titanium, although the titanium may require
more intermediate anneals.
Copper and Copper Alloys
Most commercial copper is refined to a purity of 99.9 percent minimum copper plus silver.
It is the only reddish-colored metal, and it is second only to silver in electrical conductivity. Its use
as a structural material is limited because of its great weight. However, some of its outstanding
characteristics, such as its high electrical and heat conductivity, in many cases overbalance the
weight factor. Because it is very malleable and ductile, copper is ideal for making wire. In aircraft,
copper is used primarily for the electrical system and for instrument tubing and bonding. It is
corroded by salt water, but is not affected by fresh water. The ultimate tensile strength of copper
varies greatly. For cast copper, the tensile strength is about 25, 000 psi; and when cold-rolled or
cold-drawn, its tensile strength increases, ranging from 40,000 to 67,000 psi.
BRASS.-
Brass is copper alloy containing zinc and small amounts of aluminum, iron, lead,
manganese, magnesium, nickel, phosphorous, and tin. Brass with a zinc content of 30 to 35
percent is very ductile, while that containing 45 percent has relatively high strength. “Muntz metal”
is a brass composed of 60 percent copper and 40 percent zinc. It has excellent corrosion-
resistant qualities when in contact with saltwater. Its strength can be increased by heat treatment.
As cast, this metal has an ultimate tensile strength of 50, 000 psi and can be elongated 18
percent. It is used in making bolts and nuts, as well as parts that come in contact with salt water.
“Red brass,” sometimes termed bronze because of its tin content, is used in fuel and oil line
fittings. This metal has good casting and finishing properties and machines freely.
Bronzes.-
Bronzes are copper alloys containing tin. The true bronzes have up to 25 percent tin, but
those below 11 percent are most useful, especially for such items as tube fittings in aircraft.
Among the copper alloys are the copper aluminum alloys, of which the aluminum bronzes rank
very high in aircraft usage. They would find greater usefulness in structures if it were not for their
strength/weight ratio as compared with alloy steels. Wrought aluminum bronzes are almost as

strong and ductile as medium-carbon steel, and posses a high degree of resistance to corrosion
by air, salt water, and chemicals. They are readily forged, hot-or cold-rolled, and some react to
heat treatment. These copper-based alloys contain up to 16 percent of aluminum (usually 5 to 11
percent) to which other metals such as iron, nickel, or manganese maybe added. Aluminum
bronzes have good tearing qualities, great strength, hardness, and resistance to both shock and
fatigue. Because of these properties, they are used for diaphragms and gears, air pumps,
condenser bolts, and slide linears. Aluminum bronzes are available in rods, bars, plates, sheets,
strips, and forgings. Cast aluminum bronzes, using about 89 percent copper, 9 percent aluminum,
and 2 percent of other elements, have high strength combined with ductility, and are resistant to
corrosion, shock, and fatigue. Because of these properties, cast aluminum bronze is used in gun
mounts, bearings, and pump parts. These alloys are useful in areas exposed to salt water and
corrosive gases. Manganese bronze is an exceptionally high-strength, tough, corrosion-resistant
copper zinc alloy containing aluminum, manganese, iron, and occasionally nickel or tin. This
metal can be formed, extruded, drawn, or rolled to any desired shape. In rod form, it is generally
used for machined parts. Otherwise it is used in catapults, landing gears, and brackets. Silicon
bronze is composed of abut 95 percent copper, 3 percent silicon, and 2 percent mixture of
manganese, zinc, iron, tin, and aluminum. Although not a bronze in the true sense of the word
because of its small tin content, silicon bronze has high strength and great corrosion resistance
and is used variably.
Beryllium Copper
Beryllium copper is one of the most successful of all the copper-based alloys. It is a
recently developed alloy containing about 97 percent copper, 2 percent beryllium, and sufficient
nickel to increase the percentage of elongation. The most valuable feature of this metal is that the
physical properties can be greatly stepped up by heat 1-33 treatment-the tensile strength rising
from 70,000 psi in the annealed state to 200,000 psi in the heat-treated state. The resistance of
beryllium copper to fatigue and wear makes it suitable for diaphragms, precision bearings and
bushings, ball cages, spring washers, and nonsparking tools.
Monel
Monel, the leading high-nickel alloy, combines the properties of high strength and excellent
corrosion resistnace. This metal consists of 67 percent nickel, 30 percent copper, 1.4 percent
iron, 1 percent manganese, and 0.15 percent carbon. It cannot be hardened by heat treatment; it
responds only ot cold-working. Monel, adaptable to castings and hot- or cold- working, can be
successfully welded and ahs working properties similar to those of steel. It has a tensile strength
of 65, 000 psi that, by means of cold-working, may be increased to 160, 000 psi, thus entitling this
metal to classification among the tough alloys. Monel has been successfully used for gears and
chains, for operating retractable landing gears, and for structural parts subject to corrosion. In
aircraft, Monel has been used for parts demanding both strength and high resistance to corrosion,
such as exhaust manifolds and carburetor needle valves and sleeves.
K-Monel

K-Monel is a nonferrous alloy containing mainly nickel, copper, and aluminum. It is
produced by adding a small amount of aluminum to the Monel formula. It is corrosion resistant
and capable of hardening by heat treatment. K-Monel has been successfully used for gears,
chains, and structural members in aircraft that are subjected to corrosive attacks. This alloy is
nonmagnetic at all temperatures. K-Monel can be successfully welded.
Magnesium and Magnesium Alloys
Magnesium, the world‟s lightest structural metal, is a silvery-white material weighing only
two-thirds as much as aluminum. Magnesium does not possess sufficient strength in its pure state
for structural uses; but when ti is alloyed with zinc, aluminum, and manganese, it produces an
alloy having the highest strength/weight ratio. Magnesium is probably more widely distributed in
nature than any other metal. It can be obtained from such ores as dolomite and magnetite, from
underground brines, from waste liquors of potash, and from seawater, With about 10 million
pounds of magnesium in 1 cubic mile of seawater, there is no danger of a dwindling Supply.
Magnesium is used extensively in the manufacture of helicopters. Its low resistance to corrosion
has been a factor in reducing its use in conventional aircraft. The machining characteristics of
magnesium alloys are excellent. Usually the maximum speeds of machine tools can be used with
heavy cuts and high feed rates. Power requirements for magnesium alloys are about one-sixth of
those for mild steel. An excellent surface finish can be produced, and, in most cases, grinding is
not essential. Standard machine operations can be performed to tolerances of a few ten-
thousandths of an inch. There is no tendency of the metal to tear or drag. Magnesium alloy
sheets can be worked in much the same manner as other sheet metal with one exception-the
metal must be worked while hot.
The structure of magnesium is such that the alloys work harden rapidly at room
temperatures. The work is usually done at temperatures ranging from 450o
F, which is a
disadvantage.
However, compensations are offered by the fact that in the ranges used, magnesium is
more easily formed than other materials. Sheets can be sheared in much the same way as other
metals, except that a rough flaky fracture is produced on sheets thicker than about 0.064 inch. A
better edge will result on a sheet over 0.064 inch thick if it is sheared hot. Annealed sheet can be
heated to 600o
F, but heard-rolled sheet should not be heated above 275o
F. A straight bend with a
short radius can be made by the Guerin process, as shown in figure 1-24, or by press or leaf
brakes. The Guerin process is the most widely used method for forming and shallow drawing,
employing a rubber pad as the female die, which bends the work to the Sharpe of the male die.
Magnesium alloys possess good casting characteristics. Their properties compare favorably with
those of cast aluminum. In forging, hydraulic presses are ordinarily used; although, under certain
conditions, forging can be accomplished in mechanical presses or with drop hammers.
Magnesium embodies fire hazards of an unpredictable nature. When in large sections, its high
thermal conductivity makes it difficult to ignite and prevents its burning. It will not burn until the
melting point is reached, which is approximately 1,200o
F, However, magnesium dust and fine
chips are ignited.
3. Write a note on types of fuselage structure.

1) Box truss structure
The structural elements resemble those of a bridge, with emphasis on using linked
triangular elements. The aerodynamic shape is completed by additional elements called formers
and stringers and is then covered with fabric and painted. Most early aircraft used this technique
with wood and wire trusses and this type of structure is still in use in many lightweight aircraft
using welded steel tube trusses. This method is especially suitable for amateur-build aircraft kits,
where a complete welded truss structure is delivered with the fitting of other components,
covering, and finishing completed by the user, as it ensures that a robust, uniform load bearing
structure is within the completed aircraft.
2) Geodetic construction
Airframe geodetic fuselage structure exposed by battle damage
Geodetic structural elements were used by Barnes Wallis for British Vickers between the
wars and into World War II to form the whole of the fuselage, including its aerodynamic shape. 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 hand
the advantage of being made almost entirely of wood. A similar construction using aluminum alloy
was used in the Vickers Warwick with less materials than would be required for other structural
types. The geodesic structure is also redundant and so can survive localized damage without
catastrophic failure. A fabric covering over the structure completed the aerodynamic shell (see the
Vickers Wellington for an example of a large warplane which uses this process). 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 below.
3. Monocoque shell
In this method, the exterior surface of the fuselage is also the primary structure. A typical
early form of this (see the Lockheed Vega) was built using molded plywood, where the layers of
plywood are formed over a “plug” or within a mold. A later form of this structure uses fiberglass
cloth impregnated with polyester or epoxy resin, instead of plywood, as the skin. A simple form of
this used in some amateur-built aircraft uses rigid expanded foam plastic as the core, with a
fiberglass covering, eliminating the necessity of fabricating molds, but requiring more effort in
finishing (see the Rutan VariEze). An example of a larger molded plywood aircraft is the de
Havilland Mosquito fighter/light bomber of World War II . It should be noted that no plywood-skin
fuselage is truly monocoque, since stiffening elements are incorporated into the structure to carry
concentrated loads that would otherwise buckle the thin skin. The use of molded fiberglass using
negative (“female”) molds (which give a nearly finished product) is prevalent in the series
production of many modern sailplanes. The use of molded composites for fuselage structures is
being extended to large passenger aircraft such as the Boeing 787 Dreamliner (using pressure
molding on female molds).
Semi-monocoque
This is the preferred method of constructing an all-aluminum fuselage. First, a series of
frame in the shape of the fuselage cross sections are held in position on a rigid fixture, or jig.
These frames are then joined with lightweight longitudinal elements called stringers. These are in
turn covered with a skin of sheet aluminum, attached by riveting or by bonding with special
adhesives. The fixture is then disassembled and removed from the completed fuselage shell,
which is then fitted out with wiring, controls, and interior equipment such as seats and luggage
bins. Most modern large aircraft are built using this technique, but use several large sections
constructed in this fashion which are then joined with fasteners to form the complete fuselage. As
the accuracy of the final product is determined largely by the costly fixture, this form is suitable for
series production, where a large number of identical aircraft are to be produced. Early examples
of this type include the Douglass Aircraft DC-2 and DC-3 civil aircraft and the Boeing B-17 Flying
Fortress. Most metal light aircraft are constructed using this process.
Both monocoque and semi-monocoque are referred to as “stressed skin” structures as all
or a portion of the external load (i.e. from wings and empennage, and from discrete masses such
as the engine) is taken by the surface covering. In addition, all the load from internal
pressurization is carried (as skin tension) by the external skin

Figure: Construction of the wing for the Dc-10. (McDonnell Douglas Corp.)

Figure: The internal structure of a modern transport wing. (Lockheed California Co).
Stops the yaw.

Control surfaces
1. Winglet
2. Low-Speed Aileron
3. High-Speed Aileron
4. Flap track fairing
5. Kruger flaps
6. Slats
7. Three slotted inner flaps
8. Three slotted outer flaps
9. Spoilers
10.Spoilers-Air brakes

Elements of-aeronautics

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