A SEMINAR REPORT ON

PRINCIPLE OF Aviation

by

Sakti Prasad mishraM.Sc. Applied Physics and Ballistics

CONTENTSTOPIC

IntroductionHistoryTypes of Air CraftJet PlanesControl SurfaceThrust Provider Types of Jet EnginesPrinciplesConclusion

INTRODUCTION

Aviation is the design, development, production,operation, and use of aircraft especially heavier- than –airaircraft. It is derived from the latten word “avis”, whichmeans bards. The human activity that surrounds theaircraft called aviation.

An aircraft is a vehicle which is able tofly by being supported by the air or in general, theatmosphere of a planet. An air craft counters the force ofgravity by using either static lift or by using the dynamiclift of an airfoil or in a few cases the downward thrust fromjet engines.

TYPES OF AIRCRAFTS

The aircrafts are manned aircraft i.e. those are flown by an onboard pilot. Again unmanned aerial vehicles which are remotely controlled or self controlled by onboard computers. Again aircraft can either be heavier-than-air or lighter- than –air. The lighter than aircraft are like balloons and airships etc. and heavier than aircraft including airplanes, autogiros, gliders, helicopters and ornithopters etc.

HISTORY

For centuries man has dreamed to soar with the birds. Famous inventors such as Leonardo da Vinci, John String and Lawrence Hardgrave have conjured up ideas of how to get some of the strangest machines to fly long before the Wright brothers.

The first form of an aircraft was the kite, designed in the 5th century BC. Later on in the 13th century, Roger Bacon, an English monk, performed studies which latter gave him the idea that air could support a craft just like water supports a boats. In 16th century, Leonardo da Vinci studied bird’s flight and latter produced the airscrew and the parachute. The Wright brothers Orville and Wilbur were the two Americans who are generally credited with inventing and building the world’s first successful air plane and making the first controlled, powered and sustended heavier-than –air human flight on 17th December 1903.The first jet engine was made by a German physicist Hans Joachim Von Ohian but sir Frank Whittles is known as the father of jet engine because turbojet powered the Gloster E 28/39 which first flew in 1941.

Now consider Aviation with jet planes.

JET PLANES

Emission of a high speed fluid from a container through a narrowopening by virtue of which the container can move in the oppositedirection called jet. The fundamental theory of jet propulsion isNewton’s third law of motion.

A jet plane can be classified in to two major components.

(a)Control surface (b) Thrust provider

Flight Control Surface

Aircraft flight control surface allows a pilot to adjust and control the aircraft’s flight altitude. The three major control surfaces are,

(a)Wing (b) Fin (c) ElevatorWing

Wing plays an important role in flying of an aircraft; also its shape isresponsible for lifting and landing of the air plane. Even if we stop the engineof the aero plane it can fly over some distances only due to the wing, becausewing gives stability to the plane. The wing is also placed that, unlike fin whatever may be the forces acts on the wing it also act on the same way.

AILERON (FLAP)The major component of the wing is responsible for giving up and downward motion to the plane is its flap. Flaps are normally hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft.

During takeoff just before leaving the run way the pilot bends the flapdownward and it separates the air in to two directions. One part of the air overthe wing which flows very faster and the other part below the wing which isequal to atmospheric pressure. But the pressure of air is lowered above thewing for which a pressure difference is created and due to this the plane getsupward lift.During landing the reverse happens.

FIN

Fin is also an important component of an aero plane which is responsible for changing the horizontal direction, i.e. to move left or right. It also helps in maintaining balance.

Rudder is an important component of the fin which is responsible for the changing of direction. It is a device to steer an air craft that moves through the medium (air).Rudder is a flat plane or sheet of material attached with hinges to the craft’s tail or after end. These are shaped so as to minimize aerodynamic drag.

ELEVATOR

An elevator is mounted on the trailing edge on each side of the fin in the tail. They move up and down together. When the pilot pulls the stick backward, the elevator goes up. Pushing the stick forward causes the elevator to go down. Raised down elevators push down on the tail and causeuse the nose to pitch up. This makes the wings fly at a higher angle of attack.

YAW, PITCH AND ROLL

An aircraft in flight is free to rotate in the three dimensions: pitch (nose up ordown about an axis running from wing to wing), yaw (nose left or right about anaxis running up and down) and roll (rotation about an axis running from nose totail).

The pitch axis is perpendicular to the yaw axis and is parallel to the body of thewings with its origin center at the center of gravity and directed towards the rightwing tip. Pitch changes the vertical direction of the aircraft’s nose.The elevators arethe primary control of pitch.

The yaw axis is defined to be perpendicular to the body of the wings with its originat the centre of gravity and directed towards the bottom of the aircraft. A yawmotion is a movement of the nose of the aircraft from side to side.Rudder is primarycontrol of yaw.

The roll axis is perpendicular to the pitch and yaw axes with its origin at the centerof gravity, and is directed towards the nose of the aircraft. Rotation of the axis iscalled bank or roll .Bank changes the orientation of the aircraft’s wings with respectto the downward gravity.The pilot changes the bank angle by increasing the lift onone wing and decreasing it on the other.

THRUSTN PROVIDERThe engine provides the required thrust to the aero plane.

FAN

The fan is the first component whose blades are made with titanium like material. The large spinning fan sucks in large quantities of air and then splits in to two parts. One part continues through the “core” or centre of the jet engine and other part bypasses the jet engine which produces much of the force that propels the airplane forward.

COMPRESSORThe Compressor is the component in the jet engine core made up of fan with many blades and that attached to a shaft. Compressor is generally two types.

Axial flow compressor

Axial compressor is rotating airfoil based in which the working fluid principally flows parallel to the axisof rotation. Axial flow compressor produce a continuous flow of compressed gas and large mass flowcapacity, particularly in relation to their crossection.It can raise the air pressure to about 30 times that ofout side air.

Centrifugal compressor

It can squeeze the air by taking it near the centre of rapidly spinning wheel and then throwing the air out towards the rim. The wheel of centrifugal compressor can not be arranging in rows like axial flow compressor. It can raise the air pressure to about 6 times that of the out side air.

COMBUSTOR

Here the air is mixed with fuel and then ignited. There are as many as 20 nozzles to spray fuel into the airstream. The mixture of air and fuel catches fire. This provides a high temperature, high energy flow. The fuel burns with the oxygen in the compressed air, producing hot expanding gases. The inside of the combustor made with ceramic materials to provide a heat resistant chamber. The heat can reach 27000F.

TURBINE

The high energy air flow coming out of the combustor goes in to the turbine causing theturbine blades to rotate. The turbine is linked by a shaft to turn the blades in the compressorand to spin the intake fan at the front. The gases produced in the combustion chamber movethrough the turbine and spin its blades. The turbines of the jet spin around thousands oftimes.

NOZZLE

The nozzle is the exhaust duct which produces the actual thrust. The energy depleted air flow thatpassed the turbine, and the colder air that bypassed the engine core, produces a force when exitingthe nozzle that acts to propel the engine and thus the air plane moves forward.

PRINCIPLE APPLIED TO AERODYAMICS

Bernoulli’s Principle

Bernoulli’s principle is the principle that allows wings to produced lift for planes to fly. It works on the idea thatas a wing passes through the air .Its shape makes the air travel more over the top of the wing than beneath it. Thiscreates high pressure beneath the wing than above it. This pressure difference cause the wing to push upwardsand lift is created.

When the faster the wing moves through the air the more air is forced over and under the wing which createsmore lift. Again the amount of lift is also created due to the density of the air. The denser the air is the more lift isproduced. This is why planes climb in winter, the colder air is denser.

Types of jet engine

Turbo jet Engine

It’s very simple. Air taken in front of the engine is compressed to 3 to 12 times its original pressure in thecompressor. Fuel is added to the air and burned in a combustion chamber to raise the temperature of the fluidmixture to about 11000F to 13000F.The resulting hot air is passed through the turbine, which drives thecompressor.

Turbo fan Engine

It has a large fan at front which sucks in air. Most of the air flows around the outside of the engine makingit quieter and giving it more thrust at the low speed.

Turbo shaft Engine

This is the another form of gas turbine engine which the rotor speed to be kept constant even when the speed of thegenerator is varied to modulate the amount of power produced. It is designed so that the speed of the helicopter rotor isindependent of the gas generator.

Turboprops Engine

This is the jet engine that attached to a propeller. The turbine at the back is turned by the hot gases, andthis turns a shaft that drives the propeller. Some small airlines and transport aircraft are powered byturboprops.

Ramjet Engine

The simplest jet engine Ha no moving parts .The speed of the jet engine “rams “or forces air in to the engine .Its essentially aturbojet in which rotating machinery has been omitted. Space vehicles use this type of jet. A ramjet engine provides a simple, light propulsion system for high speed flight.

ThrustThrust is the force which moves any aircraft through the air. Thrust is generated by the propulsion

system of the aircraft. Different propulsion systems develop thrust in different ways, but all thrust isgenerated through some application of Newton’s third law of motion. For every action there is anequal and opposite reaction.

Thrust supplied by jetThrust supplied by the jet. Let us now calculate the thrust supplied to an aircraft by the jet produced by

the power-unit inside it.Suppose we have an aircraft travelling with a speed ‘v’ and fitted with a power-unit which produces a

jet of fluid, of velocity ‘v’ relatives to the aircraft, where ‘u’ is higher than ‘v’, the velocity ‘u’ of the jetbeing measured at a point in it a little away from the nozzle, where the static pressure is the same asthat in the surrounding air. Then, if we impose a velocity ‘v’ on the aircraft in the opposite directionto its own, the aircraft comes to rest, with the air streaming past it with velocity ‘v’. So that, if ‘a’ bethe area of cross-section of the jet at the point where its velocity is ‘u’, the volume of the fluidflowing per second in the jet is dearly (a.u). If, therefore, ‘ρ’ be the density of the fluid, we have,

Mass-flow of the fluid per second in the jet=a.u.ρ=m (say).And, therefore, momentum of this fluid in the jet=m.u.If this mass ‘m’ of the fluid finally emerges out from the aircraft with a velocity ‘v’, its momentum is

clearly reduced to “mv”. It thus suffers a loss of momentum, equal to (mu-mv) or m (u-v) persecond, i.e. , its rate of change of momentum = m (u-v).

Therefore in accordance with Newton’s second law of motion, must be the force or the thrust Fsupplied to the aircraft by the jet in the direction of opposite. So that,

F = m (u-v) = a.u.ρ. (u-v).

Efficiency of the jetLet the aircraft is moving with velocity v , then the velocity of the final jet , moving in the opposite direction , clearly becomes (u-v) and therefore,

Kinetic Energy of the final jet = 2 = .

Again the aircraft does Fv amount of work per second against the air resistanceas it moves forwards. So that total energy that supplied by the power unit =

Thus the efficiency of the jet is defined as

The efficiency will be maximum value 1, when (u-v), i.e. when the initial jetvelocity is equal to the flight velocity of the aircraft for then, the energy wastedin the form of the final jet i.e. will become zero.

MACH NUMBER The ratio of the speed of the aircraft to the speed of the sound in the gas determines themagnitude of the compressibility effect. This ratio in aerodynamics is designated withthe special parameter called the Mach number in honor of the 19th century physicistErnst Mach. This Mach number is denoted by ‘M’.

The space shuttle may re enters the atmosphere at whichhypersonic speed of Mach value M ~ 25.The Mach numberdepends on the speed of sound in the gas and the speed of sounddepends on the type of gas and the temperature of the gas.

Low subsonic

subsonic Transonic Supersonic Highsupersonic Hypersonic

M<< 1 M<1 M=1 1<M<3 3<M<5 M>5

CONCLUSION

Aircrafts are most sophisticated and costly products of themodern age. These vehicles are used in many fields such astransport, war and in other fields. In future there will bemany other types of propulsion methods which will makethese machines more costly, powerful and technologicallyadvanced. The most important thing is that thesemachines can be used both for the welfare and destructionof mankind. So if these powerful machines are used for thewelfare of mankind then the future generation will be safeand more advanced.