UNIT 1Discuss the evolution process towards the modern day powered heavier than air manned aircraftThe first basic principle of flight heavier than air was first expressed by Sir George cayley of u.k in 1809 as follows:The solution of the flight heavier than air lies on application of power to overcome the resistance of air and fly at higher speeds .it also requires a wing surface which would allow to create a lift force more than weight of the aircraft, by virtue of its forward speed.STEAM ENGINES:Subsequently attempts to fly the aircraft with steam engines were attempted , notable among them areDu temple in France 1858Mozhaski in Russia 1884Ader in france 1890The flight with steam engine was then realised to be impossible due to weight and efficiency.PISTON ENGINE:The development of 4 stroke petrol internal combustion engine by otto of Germany was the first important milestone which is now termed as piston engine. By the beginning of 20th century improved piston engine of lighter weight and increased [power were developed by BENZ AND DAILMER of germany, Manly and wright brothers of USA and le varasseur of france. This type of engine were used for all powered flight till 1940, hence jet engine development took the role of powering.FIRST UNSUCCESSFUL FLIGHT:The monoplane designed by professor Langley of Smithsonian insitution over a considerable distance before it failed due to wing failure in torsion over river potamac in 1903. It was a monoplane.FIRST SUCCESSFUL FLIGHT FLYER 1:The wright brothers, who were bi cycle manufactures, took considerable interest in developing a flying machine .after reviewing the work done by previous pioneers of aviation attempted to design a powered aircraft, with engine and propellers. The biplane made a first successful flight for 12 seconds covering a distance of 120 feetAfter the success of flyer I aircraft, Wright brother attempted several improvements and flew continuously for 2 hours at an average speed of 53 kmph1) Early development in aerodynamics:Atmosphere:The compelling reason for study of atmosphere above the earth is to evaluate flight performance of a solid object when it moves through atmosphere air conditions .basically aerodynamics may be defined as atmospheric interaction with a object, when there is a relative motion between object and surrounding air.When a body moves in air and when relative velocity between them, an aerodynamic force develops which can alter the flight path of a rigid body. to evaluate these aerodynamic forces and hence flight path performance it is essential to understand.Variation of pressure and density at different altitutde Aerodynamic forces that develop on the body based on Mass is conserved continuity equationNewtons second lawEnergy is conservedWhen the above fundamental physics law is applied to aerodynamic flow, certain equations result, which for the basics for aerodynamics. Further since air is compressible, compressible of air is accounted while using above equationsIncompressible flow:Density of fluid flow is constant at every point in the flow region. In subsonic flow, it is assumed that fluid is incompressible which only means compressibility effect is low.Compressible flow:Density of air is not a constant but variable from point to point in the flow region. It is accounted while dealing with subsonic flow, supersonic flow, rocket engines2) Development n material technology in aerospace industry:The early aircraft of 1910-1920 were maximum speeds which were low and their strength requirement was not high. Consequently they were using wood, bamboos, plywood and fabrics.Wood was the main preferred material for early generation of aircrafts for load carrying members such as spars, ribs, fuselage, frames, and propellers. For this purpose spruce and balsa are used. Fabrics doped with water repellent treatment were used foreskinThin plies of wood glued together were used for external skins to make torsional boxes, webs, ribs as the speed requirements of aircraft grew, the required mechanical properties also increased both fro mechanical strength as well as stiffness requirements. Further to keep the weight of aircraft low, the density requirement were also stringent .hence the objective of the designer is to achieve structural integrity at minimum cost and weight. The mechanical properties which are needed to achieve this areStrength and rigiditySpecific properties ( w r t mass)Fatigue propertiesToughness and rate of crack propagationStress corrosionCost of workingThe second generation of aircraft from material point of view used aluminium alloys for load carrying members , the weight penalty of using materials instead of cloth were compensates by the advance in propulsion. As the speed of the aircraft grew, the loads proportional to speed increases phenomenally, hence major joints such as wing/fuselage attachment requires use of steel alloys.Aluminium alloys used in aircraft industry comes in various shapes for raw material such as sheets, plates, billets, extrusions, tubes , casting and forging which are machined to required size .currently the trend is t make by integral millingWith the speed of mach greater than one , very high skin temperatures are reached . Hence in order to have high mechanical, properties at elevated temperatures such as engines, titanium alloys are used.Further to have strength tailored to meet the need were developed in the form of composites. Composites are combination of 2 materials which are insoluble with each other.3)Development in structures:The structures at the earliest stage of aircraft design, during 1905-1920 were flying for very short distances at very low speed. Consequently the structures were made of wood, fabric, glue , some steel wires and fittingsThey were mainly truss type of work. The wing was not consisting of any aerofoil section but was single surface cambered aerofoils. The wings were braced by the pratt truss system. As such there was not any fuselage. The pilot lay prone on the upper surface of the lower wing by the side of engines. The aircraft had a pair of movable surfaces in the horizontal plane mounted ahead of wing. Similarly another pair of movable surfaces in the vertical plane. There was no aileron, and for rolling wing wrap was used. Wing warp of helical twist of wing using steel wires such that incidence of one wing is increased and incidence f one wing decreasedSubsequently the wings were made single unlike earlier bi plane sand the wing section was adapted to an aerofoil shape. The covering of skin was using thin aluminium sheets which were capable of giving torsional rigidity.Subsequent to the first two world wars, armed with knowledge gained in designing aircraft, modern aircraft as we see today were developed. Important features compared to earlier aircraft are listed below

Monoplane configuration with all metal constructionUse of stressed skin, retractable landing gearEngines with variable pitch propellers and jet enginesFull range of instruments, navigational aids, auto pilot systems t reduce pilot work loadHydraulic, pneumatic, electrical systems t operate various utilities such as landing gear, wheels, brakes, control surfaces etcHeating, ventilations cabin furnishings

4)Development in propulsion over yearsSince the beginning of powered flight , the evolution of both the aero vehicle and propulsion systems are strongly inter related and are governed by a few major thrust namelyDemand for improving reliabilityEndurance and life timeImprovement i n flight performanceUnder theses thrust the technology of aero vehicle and propulsion advanced continuouslyThe advancement in propulsion technology has occurred in the following type of engine1. Reciprocating engine2. Turbojet3. Turbofan4. TurbopropThe development of these four types of engine is historical and chronological thread. Beginning with propeller driven aircrafts, which powered earlier type of aircraft as the speed requirements were low. The need for higher thrust was met by the invention of jet engine in 1930. This jet engine makes powered flight in transonic and supersonic region. Even though propulsion technology has enabled the gradual growth of above four types of engine, they continue to be used even today. This anomaly is while designing the aircraft, a trade of study between thrust and efficiently have to be made, which make the requirement of engines to be anyone of the above.In between these engines, even attempts were made to fly the aircraft with steam engines, but later on realised to be impossible due to weight and efficiently

Biplane ,helicopter, mono plane

UNIT 2

Conventional Flight Control

Aircraft flight control systems are classified as primary and secondary. The primary control systems consist of those that are required to safely control an airplane during flight. These include the ailerons, elevator (or stabilator), and rudder. Secondary control systems improve the performance characteristics of the airplane, or relieve the pilot of excessive control forces. Examples of secondary control systems are wing flaps and trim systems. The axis system has been given below.An airplane moves in three dimensions called roll, pitch, and yaw. Roll is rotation about the longitudinal axis that goes down the center of the fuselage. The ailerons control rotation about the roll axis. Pitch is rotation about the lateral axis of rotation, which is an axis parallel to the long dimension of the wings. The elevators control the pitch of the airplane. By controlling the pitch of the airplane, the elevators also control the angle of attack of the wing. To increase the angle of attack, the entire airplane is rotated up. As we will see, this control or the angle of attack is key in the adjustment of the lift of the wings.Finally, yaw, which is controlled by the rudder, is rotation about the vertical axis,which is a line that goes vertically through the center of the wing. It is important to note that all three axes go through the center of gravity (often abbreviated c.g.) of the airplane. The center of gravity is the balance point of the airplane. Or, equivalently, all of the weight of the airplane can be considered to be at that one point.Primary Control Surfaces (question :functions of control surface)Ailerons:Ailerons control roll about the longitudinal axis. The ailerons are attached to the outboard trailing edge of each wing and move in the opposite direction from each other. Ailerons are connected by cables, bellcranks, pulleys or push-pull tubes to each other and to the control wheel.Moving the control wheel to the right causes the right aileron to deflect upward and the left aileron to deflect downward. The upward deflection of the right aileron decreases the camber resulting in decreased lift on the right wing. The corresponding downward deflection of the left aileron increases the camber resulting in increased lift on the left wing. Thus, the increased lift on the left wing and the decreased lift on the right wing causes the airplane to roll to the right.

Elevator:The elevator controls pitch about the lateral axis. Like the ailerons on small airplanes, the elevator is connected to the control column in the cockpit by a series of mechanical linkages. Aft movement of the control column deflects the trailing edge of the elevator surface up. This is usually referred to as up elevator. Moving the control column forward has the opposite effect. In this case, elevator camber increases, creating more lift (less tail-down force) on the horizontal stabilizer/elevator. This moves the tail upward and pitches the nose down.Rudder:The Rudder controls movement of the airplane about its vertical axis. This motion is called yaw. Like the other primary control surfaces, the rudder is a movable surface hinged to a fixed surface, in this case, to the vertical stabilizer, or fin. Moving the left or right rudder pedal controls the rudder. When the rudder is deflected into the airflow, a horizontal force is exerted in the opposite direction.Secondary control surfaces:Flaps:Flaps are the most common high-lift devices used on practically all airplanes. These surfaces, which are attached to the trailing edge of the wing, increase both lift and induced drag for any given angle of attack. Flaps allow a compromise between high cruising speed and low landing speed, because they may be extended when needed, and retracted into the wings structure when not needed.Leading edge flaps, like trailing edge flaps, are used to increase both Cl and the camber of the wings. There are four common types of flaps: plain, split, slotted, and Fowler flaps.

Slats and Slots:High-lift devices also can be applied to the leading edge of the airfoil. The most common types are fixed slots, movable slats, and leading edge flaps. Fixed slots direct airflow to the upper wing surface and delay airflow separation at higher angles of attack. Movable slats consist of leading edge segments, which move on tracks. Opening a slat allows the air below the wing to flow over the wings upper surface, delaying airflow separation.

Spoilers:On some airplanes, high-drag devices called spoilers are deployed from the wings to spoil the smooth airflow, reducing lift and increasing drag. Spoilers are used for roll control on some aircraft, one of the advantages being the elimination of adverse yaw.

Trim Tabs:The most common installation on small airplanes is a single trim tab attached to the trailing edge of the elevator. Most trim tabs are manually operated by a small, vertically mounted control wheel. However, a trim crank may be found in some airplanes. The cockpit control includes a tab position indicator.Anti servo Tabs:In addition to decreasing the sensitivity of the stabilator, an antiservo tab also functions as a trim device to relieve control pressure and maintain the stabilator in the desired position. The fixed end of the linkage is on the opposite side of the surface from the horn on the tab, and when the trailing edge of the stabilator moves up, the linkage forces the trailing edge of the tab up. When the stabilator moves down, the tab also moves down. This is different than trim tabs on elevators, which move opposite of the control surface.Balance Tabs:The control forces may be excessively high in some airplanes, and in order to decrease them, the manufacturer may use balance tabs. They look like trim tabs and are hinged in approximately the same places as trim tabs. The essential difference between the two is that the balancing tab iscoupled to the control surface rod so that when the primary control surface is moved in any direction, the tab automatically moves in the opposite direction.Ground Adjustable Tabs:Many small airplanes have a non-moveable metal trim tab on the rudder. This tab is bent in one direction or the other while on the ground to apply a trim force to the rudder. it is motor driven. The trimming effect and cockpit indications for an adjustable stabilizer are similar to those of a trim tab.

Plan form of conventional wings:Wing plan form - the shape of the wing as viewed from directly above - deals with airflow in three dimensions, and is very important to understanding wing performance and airplane flight characteristics.Aspect ratio, taper ratio, and sweepback are factors in plan form design that are very important to the overall aerodynamic characteristic of a wingTypes of planform:The shape of a wing greatly influences the performance of an airplane. The speed of an airplane, its maneuverability and its handling qualities are all very dependent on the shape of the wings. There are four basic wing shapes that are used on modern airplanes: straight, sweep (forward and back), delta and swing-wing.

The straight wing is found mostly on small, low-speed airplanes. General Aviation airplanes often have straight wings. These wings provide good lift at low speeds, but are not suited to high speeds. Since the wing is perpendicular to the airflow it has a tendency to create appreciable drag. However, the straight wing provides good, stable flight. It is cheaper and can be made lighter, too.

The sweepback wing is the wing of choice for most high-speed airplanes made today. Sweep wings create less drag, but are somewhat more unstable at low speeds. The high-sweep wing delays the formation of shock waves on the airplane as it nears the speed of sound. The amount of sweep of the wing depends on the purpose of the airplane. A commercial airliner has a moderate sweep. This results in less drag while maintaining stability at lower speeds. High speed airplanes (like fighters) have greater sweep. These airplanes are not very stable at low speeds. They take off and descend for landing at a high rate of speed.

The forward-sweep wing is a wing design that has yet to make it into mass production. An airplane (like the X-29) is highly maneuverable, but it is also highly unstable. A computer-based control system must be used in the X-29 to help the pilot fly.

Simple Delta Wing and Complex Delta WingA delta wing looks like a large triangle from above. Because of the high sweep, airplanes with this wing can reach high speeds - many supersonic airplanes have delta wings. Because of the high sweep, the landing speeds of airplanes with delta wings are very fast. This wing shape is found on the supersonic transport Concorde.

BALLOON:In aeronautics, a balloon is an unpowered aerostat, which remains aloft or floats due to its buoyancy. A balloon may be free, moving with the wind, or tethered to a fixed point. It is distinct from an airship, which is a powered aerostat that can propel itself through the air in a controlled manner.Principle: A balloon is conceptually the simplest of all flying machines. The balloon is a fabric envelope filled with a gas that is lighter than the surrounding atmosphere. As the entire balloon is less dense than its surroundings, it rises, taking along with it a basket, attached underneath, which carries passengers or payload. Although a balloon has no propulsion system, a degree of directional control is possible through making the balloon rise or sink in altitude to find favourable wind directions.There are three main types of balloon:

The hot air balloon or Montgolfire obtains its buoyancy by heating the air inside the balloon. It has become the most common type. The gas balloon or Charlire is inflated with a gas of lower molecular weight than the ambient atmosphere. Most gas balloons operate with the internal pressure of the gas the same as the pressure of the surrounding atmosphere. A superpressure balloon can operate with the lifting gas at pressure that exceeds that of the surrounding air, with the objective of limiting or eliminating the loss of gas from day-time heating. Gas balloons are filled with gases such as: hydrogen originally used extensively but since the Hindenburg disaster is now seldom used due to its high flammability. Coal gas - Although giving around half the lift of hydrodgen,[1] extensively used during the nineteenth and early twentieth century since it was cheaper than hydrogen and readily available. helium used today for all airships and most manned gas balloons.

Hot air balloon parts:EnvelopeModern hot air balloons are usually made of materials such as ripstop nylon or dacron (a polyester).A hot air balloon is inflated partially with cold air from a gas-powered fan, before the propane burners are used for final inflation.During the manufacturing process, the material is cut into panels and sewn together, along with structural load tapes that carry the weight of the gondola or basket. The individual sections, which extend from the throat to the crown (top) of the envelope, are known as gores or gore sections

VentsThe parachute vent at the top of an envelope, as seen from below through the mouth.The top of the balloon usually has a vent of some sort, enabling the pilot to release hot air to slow an ascent, start a descent, or increase the rate of descent, usually for landing. Some hot air balloons have turning vents, which are side vents that, when opened, cause the balloon to rotate. Such vents are particularly useful for balloons with rectangular baskets, to facilitate aligning the wider side of the basket for landing.BasketBaskets are commonly made of woven wicker or rattan. These materials have proven to be sufficiently light, strong, and durable for balloon flight. Such baskets are usually rectangular or triangular in shape. They vary in size from just big enough for two people to large enough to carry thirty. Larger baskets often have internal partitions for structural bracing and to compartmentalize the passengers. Small holes may be woven into the side of the basket to act as foot holds for passengers climbing in or out.Baskets may also be made of aluminium, especially a collapsible aluminium frame with a fabric skin, to reduce weight or increase portabilityBURNER:The burner unit gasifies liquid propane, mixes it with air, ignites the mixture, and directs the flame and exhaust into the mouth of the envelope. Burners vary in power output; each will generally produce 2 to 3 MW of heat (7 to 10 million BTUs per hour), with double, triple, or quadruple burner configurations installed where more power is needed.The pilot actuates a burner by opening a propane valve, known as a blast valve.Fuel tanksPropane fuel tanks are usually cylindrical pressure vessels made from aluminium, stainless steel, or titanium with a valve at one end to feed the burner and to refuel. They may have a fuel gauge and a pressure gauge.

Geometric properties of airfoil:

Chord:The chord of an airfoil is an imaginary straight line drawn through the airfoil from its leading edge to its trailing edgeWing tips: The ends of the wing are called the wing tips Span: The distance from one wing tip to the other is called the span.Wing area: The wing area, is the projected area of the plan form and is bounded by the leading and trailing edges and the wing tips.The wing area is not the total surface area of the wing. The total surface area includes both upper and lower surfaces. The wing area is a projected area and is almost half of the total surface area.Angle of attack: it is the angle between the relative wind and the chord line and is generally represented by a symbol Camber: The maximum distance between the two lines is called the camber, which is a measure of the curvature of the airfoil.Camber is the measure of the curvature of an airfoil as evaluated by the height of the mean camber line above or below the chord line.Center of pressure: center of pressure is a point on the chord of an airfoil through which all the aerodynamic forces act.The viscosity is an important fluid property when analyzing liquid behavior and fluid motion near solid boundaries. Viscosity of a fluid is a measure of its resistance to gradual deformation by shear stress or tensile stress. The shear resistance in a fluid is caused by intermolecular friction exerted when layers of fluid attempt to slide by one another.

viscosity is the measure of a fluid's resistance to flow

molasses is highly viscous water is medium viscous gas is low viscous

dynamic viscosity Absolute viscosity - coefficient of absolute viscosity - is a measure of internal resistance. Dynamic (absolute) viscosity is the tangential force per unit area required to move one horizontal plane with respect to an other plane - at an unit velocity - when maintaining an unit distance apart in the fluid = dc / dyNewtons Law of Friction.

compressibleWhen a fluid flow is compressible, the fluid density varies with its pressure. Compressible flows are usually high speed flows with Mach numbers greater than about 0.3.Incompressible flows do not have such a variation of density. The key differentiation between compressible and incompressible is the velocity of the flow. A fluid such as air that is moving slower than Mach 0.3 is considered incompressible, even though it is a gas. A gas that is run through a compressor is not truly considered compressible (in the thermodynamic sense) unless its velocity exceeds Mach 0.3Chord line: chord line is a straight line between the leading edge and the trailing edge of an airfoil.Mean camber line: mean camber line is the line described by points which are equidistant from the upper and lower surfaces of the airfoil.Maximum thickness: The maximum distance between the upper and lower surfaces is called the maximum thickness.Aerodynamic center: it is the point on the chord of an airfoil about which the moment coefficient is practically constant for all angles of attack.Reynolds number is used to check whether the flow is laminar or turbulent. It is denoted by Re. This number got by comparing inertial force with Viscous force.SYMMETRICAL AEROFOIL AND UNSYMMETRICAL AEROFOIL:The aerofoil for which loci of mid point of distance between upper and lower surface coincides with the chord is symmetrical aerofoilThe loci of mid point of distance between upper and lower surface does not coincide with chord.Stagnation point:Any point on the flow where v is zero is called stagnation pointMean camber line: it is the locus of midway between upper and lower surface of a unsymmetrical aerofoil.Centre of pressure of an aerofoil:Chord wise location of a point about which pitching moment is zero is called center of pressure.Mean aerodynamic chord:The chord of an imaginary regular aerofoil having the same force vector , under all conditions and throughout the flight range as those of an actual wing.Fuselage reference line:The straight line used as reference from which basic dimensions are laid out and major components are located.Biplane terms:Decalgae:Angular difference between upper and lower wings of a biplne.The decalage is said to be positive when the upper wing has a higher angle of incidence than lower positive declage results in greater lift from the upper wing to lower wing.In monoplanes:Aerodynamic decalage is the angular difference between wing mean aerodynamic zerolift line and horizontal surface mean aerodynamic zero lift lineGeometric decalage:It is the angular difference between wing chord (mac) and horizontal (mac) lines.Gap-chord ratio:The difference between upper and lower wing is the gap. Ratio of gap to chord greatly influences the lift decalage.

Stagger:The distance between leading edge of top and bottom wing. When the top surface is staggered forward, it can result in a small increase in lift

AIRFOIL: Cross section shape obtained by the intersection of wing with the plane perpendicular is called airfoilThe amount of lift produced by an airfoil depends upon many factors:

angle of attack the lift devices used (like flaps) the density of the air the area of the wing the shape of the wing the speed at which the wing is travelingDihedral angle: The angle that the wing makes with the local horizontal is called the dihedral angle. A negative dihedral angle is called anhedral.

ASPECT RATIO:Aspect ratio is a measure of how long and slender a wing is from tip to tip. The Aspect Ratio of a wing is defined to be the square of the span divided by the wing area.High aspect ratio wings have long spans (like high performance gliders), while low aspect ratio wings have either short spans (like the F-16 fighter) or thick chords (like the Space Shuttle). There is a component of the drag of an aircraft called induced drag which depends inversely on the aspect ratio. A higher aspect ratio wing has a lower drag and a slightly higher lift than a lower aspect ratio wing

Cl vs Cd for various value of aspect ratio

Cl vs angle of attack for various aspect ratio valuesFIGURES ARE TAKEN FROM THEORY OF FLIGHT(RICHARD VON MISES)There are several reasons why not all aircraft have high aspect wings:

Structural: A long wing has higher bending stress for a given load than a short one and therefore requires higher structural-design (architectural and/or material) specifications. Also, longer wings may have some torsion for a given load, and in some applications this torsion is undesirable (e.g. if the warped wing interferes with aileron effect).

Maneuverability: a low aspect-ratio wing will have a higher roll angular acceleration than one of high aspect ratio, because a high-aspect-ratio wing has a higher moment of inertia to overcome. In a steady roll, the longer wing gives a higher roll moment because of the longer moment arm of the aileron. Low aspect ratio wings are usually used on fighter aircraft, not only for the higher roll rates, but especially for longer chord and thinner airfoils involved in supersonic flight.

Parasitic drag: While high aspect wings create less induced drag, they have greater parasitic drag, (drag due to shape, frontal area, and surface friction). This is because, for an equal wing area, the average chord (length in the direction of wind travel over the wing) is smaller. Due to the effects of Reynolds number, the value of the section drag coefficient is an inverse logarithmic function of the characteristic length of the surface, which means that, even if two wings of the same area are flying at equal speeds and equal angles of attack, the section drag coefficient is slightly higher on the wing with the smaller chord. However, this variation is very small when compared to the variation in induced drag with changing wingspan.

Practicality: low aspect ratios have a greater useful internal volume, since the maximum thickness is greater, which can be used to house the fuel tanks, retractable landing gear and other systems.

Typical ARs High Performance Glider: 25 (long, thin) Prop Driven Trainer: 6 to 8 Jet Fighter 3.5 (short, stubby)

b = spans = wing area Nomenclature of airfoil:NACA Four-Digit Series:The first family of airfoils designed using this approach became known as the NACA Four-DigitSeries. The first digit specifies the maximum camber (m) in percentage of the chord (airfoil length),the second indicates the position of the maximum camber (p) in tenths of chord, and the last twonumbers provide the maximum thickness (t) of the airfoil in percentage of chord. For example, theNACA 2415 airfoil has a maximum thickness of 15% with a camber of 2% located 40% back fromthe airfoil leading edge (or 0.4c).

NACA Five-Digit Series:The NACA Five-Digit Series uses the same thickness forms as the Four-Digit Series but the meancamber line is defined differently and the naming convention is a bit more complex. The first digit,when multiplied by 3/2, yields the design lift coefficient (cl) in tenths. The next two digits, whendivided by 2, give the position of the maximum camber (p) in tenths of chord. The final two digitsagain indicate the maximum thickness (t) in percentage of chord. For example, the NACA 23012nhas a maximum thickness of 12%, a design lift coefficient of 0.3, and a maximum camber located15% back from the leading edge.NACA 1-Series or 16-Series:Unlike those airfoil families discussed so far, the 1-Series was developed based on airfoil theoryrather than on geometrical relationships. By the time these airfoils were designed during the late1930s, many advances had been made in inverse airfoil design methods. The basic concept behindthis design approach is to specify the desired pressure distribution over the airfoil (this distributiondictates the lift characteristics of the shape) and then derive the geometrical shape that producesthis pressure distribution. As a result, these airfoils were not generated using some set of analyticalexpressions like the Four- or Five-Digit Series. The 1-Series airfoils are identified by five digits, asexemplified by the NACA 16-212. The first digit, 1, indicates the series (this series was designed forairfoils with regions of barely supersonic flow). The 6 specifies the location of minimum pressure intenths of chord, i.e. 60% back from the leading edge in this case. Following a dash, the first digitindicates the design lift coefficient in tenths (0.2) and the final two digits specify the maximumthickness in tenths of chord (12%).

NACA 6-Series:Although NACA experimented with approximate theoretical methods that produced the 2-Seriesthrough the 5-Series, none of these approaches was found to accurately produce the desired airfoilbehavior. The 6-Series was derived using an improved theoretical method that, like the 1-Series,relied on specifying the desired pressure distribution and employed advanced mathematics toderive the required geometrical shape. The goal of this approach was to design airfoils thatmaximized the region over which the airflow remains laminar. In so doing, the drag over a smallrange of lift coefficients can be substantially reduced. The naming convention of the 6-Series is byfar the most confusing of any of the families discussed thus far, especially since many differentvariations exist. One of the more common examples is the NACA 641-212, a=0.6.In this example, 6 denote the series and indicates that this family is designed for greater laminarflow than the Four- or Five-Digit Series. The second digit, 4, is the location of the minimum pressurein tenths of chord (0.4c). The subscript 1 indicates that low drag is maintained at lift coefficients 0.1above and below the design lift coefficient (0.2) specified by the first digit after the dash in tenths.The final two digits specify the thickness in percentage of chord, 12%.NACA 7-Series:The 7-Series was a further attempt to maximize the regions of laminar flow over an airfoildifferentiating the locations of the minimum pressure on the upper and lower surfaces. An exampleis the NACA 747A315. The 7 denotes the series, the 4 provides the location of the minimumpressure on the upper surface in tenths of chord (40%), and the 7 provides the location of theminimum pressure on the lower surface in tenths of chord (70%). The fourth character, a letter,indicates the thickness distribution and mean line forms used. A series of standardized formsderived from earlier families are designated by different letters. Again, the fifth digit incidates thedesign lift coefficient in tenths (0.3) and the final two integers are the airfoil thickness in perecentageof chord (15%).NACA 8-Series:A final variation on the 6- and 7-Series methodology was the NACA 8-Series designed for flight atsupercritical speeds. Like the earlier airfoils, the goal was to maximize the extent of laminar flow onthe upper and lower surfaces independently. The naming convention is very similar to the 7-Series,an example being the NACA 835A216. The 8 designates the series, 3 is the location of minimumpressure on the upper surface in tenths of chord (0.3c), 5 is the location of minimum pressure onthe lower surface in tenths of chord (50%), the letter A distinguishes airfoils having different camberor thickness forms, 2 denotes the design lift coefficient in tenths (0.2), and 16 provides the airfoilthickness in percentage of chord (16%). ROLLING MOMENT, YAWING MOMENT, PITCHING MOMENTIn flight, the control surfaces of an aircraft produce aerodynamic forces. These forces are applied at the center of pressure of the control surfaces which are some distance from the aircraft cg and produce torques (or moments) about the principal axes. The torques cause the aircraft to rotate. The elevators produce a pitching moment, the rudder produces a yawing moment, and the ailerons produce a rolling moment. The ability to vary the amount of the force and the moment allows the pilot to maneuver or to trim the aircraft.Draw the variation of pressure distribution over an airfoil with change in angle of attack?From experiments conducted on wind tunnel models and on full size airplanes, it has been determined that as air flows along the surface of a wing at different angles of attack there are regions along the surface where the pressure is negative, or less than atmospheric, and regions where the pressure is positive, or greater than atmospheric. This negative pressure on the upper surface creates a relatively larger force on the wing than is caused by the positive pressure resulting from the air striking the lower wing surface. Figure 17-7 shows the pressure distribution along an airfoil at three different angles of attack. In general, at high angles of attack the center of pressure moves forward, while at low angles of attack the center of pressure moves aft. In the design of wing structures this center of pressure travel is very important, since it affects the position of the airloads imposed on the wing structure in low angle of attack conditions and high angle of attack conditions. The airplane's aerodynamic balance and controllability are governed by changes in the center of pressure.

The center of pressure is determined through calculation and wind tunnel tests by varying the airfoil's angle of attack through normal operating extremes. As the angle of attack is changed, so are the various pressure distribution characteristics (Fig. 17-7). Positive (+) and negative (-) pressure forces are totaled for each angle of attack and the resultant force is obtained. The total resultant pressure is represented by the resultant force vector shown in Fig. 17-8. The point of application of this force vector is termed the "center of pressure" (CP). For any given angle of attack, the center of pressure is the point where the resultant force crosses the chord line. This point is expressed as a percentage of the chord of the airfoil.

In the airplane's normal range of flight attitudes, if the angle of attack is increased, the center of pressure moves forward; and if decreased, it moves rearward. Since the center of gravity is fixed at one point, it is evident that as the angle of attack increases, the center of lift (CP) moves ahead of the center of gravity, creating a force which tends to raise the nose of the airplane or tends to increase the angle of attack still more. On the other hand, if the angle of attack is decreased, the center of lift (CP) moves aft and tends to decrease the angle a greater amount. It is seen then, that the ordinary airfoil is inherently unstable, and that an auxiliary device, such as the horizontal tail surface, must be added to make the airplane balance longitudinally.

Unit -3

(refer J.D ANDERSON INTRODUCTION TO FLIGHT for clear understanding of the derivation) WHICH INCLUDES HYDROSTATIC EQUATIONS.

Relations between height, pressure, density and temperature

g = Gravitational acceleration at a certain altitude (g0 = 9.81m/s2) (m/s2) ,r = Earth radius (6378km) hg = Height above the ground (Geometric height) (m)

ha = Height above the center of the earth (ha = hg + r) (m) h = Geopotential altitude (Geopotential height) (m)p = Pressure (Pa = N/m2) = Air density (kg/m3)

= = Specific volume (m3/kg)

T = Temperature (K)R = 287.05J/(kgK) = Gas constantPs = 1.01325 105N/m2 = Pressure at sea levels = 1.225kg/m3 = Air density at sea levelTs = 288.15K = Temperature at sea level

a == Temperature gradient (a = -0.0065K/m in the troposphere (lowest part) of the earth atmosphere) (K/m)

Relation between geopotential height and geometric height

Newtons gravitational law implicates:

g= g0(r/ha)2= g0(r/r+hg)2The hydrostatic equation is:

dp = gdhg

However, g is variable here for dierent heights. Since a variable gravitational acceleration is dicult to work with, the geopotential height h has been introduced such that:

dp = g0dh(2.1)

So this means that:

dh= (g/go )dhg = r2/(r+hg)2 dhg

And integration gives the general relationship between geopotential height and geometric height:

h= (r/r+hg) hg

1

Relations between pressure, density and height

The famous equation of state is:

p = RT(3.1)

Dividing the hydrostatic equation (2.1) by the equation of state (3.1) gives as results:

dp/p =-g0dh/RT =-(go/RT)dh

If we assume an isothermal environment (the temperature stays the same), then integration gives:

Solving this gives the following equation:

And combining this with the equation of state gives the following equation:

Relations between pressure, density and temperature expression for pressure and density variation in gradient layer (stratosphere)

We now again divide the hydrostatic equation (2.1) by the equation of state (3.1), but this time we dont assume an isothermal environment, but we substitute dh = in it, to get:

Integration gives:

Which is a nice formula. But by using the equation of state, we can also derive the following:

All those relations can be written in a simpler way:

These relations are the standard atmospheric relations in gradient layers.MACH NUMBER:

The speed of sound is the speed of transmission of a small disturbance through a medium.As an aircraft moves through the air, the air molecules near the aircraft are disturbed and move around the aircraft. If the aircraft passes at a low speed, typically less than 250 mph, thedensityof the air remains constant. But for higher speeds, some of the energy of the aircraft goes into compressing the air and locally changing the density of the air. This compressibility effectalters the amount of resulting force on the aircraft. Thus if a vehicle moves faster than the speed of sound ,the air ahead of it cannot move away there is no way for it to know the approaching object. This leads to the formation of shock waves ahead of the object,that affects both the lift and drag of an aircraft.Theratioof the speed of the aircraft to the speed of sound in the gas determines the magnitude of many of the compressibility effects. Because of the importance of this speed ratio, aerodynamicists have designated it with a special parameter called theMach number(definition of mach number)in honour ofErnst Mach, a late 19th century physicist who studied gas dynamics. The Mach numberMallows us to define flight regimes in which compressibility effects vary. If the mach number is 1 flow appear around the object. In case of an airfoil (such as an aircraft's wing), this typically happens above the wing. Supersonic flow can decelerate back to subsonic only in a normal shock; this typically happens before the trailing edgecritical Mach number (Mcr) of an aircraft is the lowest Mach number at which the airflow over some point of the aircraft reaches the speed of sound, but does not exceed it.

If the mach number isbetween 1.25.0, the flowspeed is higher than the speed of sound - and the speed issupersonic.As the speed increases, the zone of M > 1 flow increases towards both leading and trailing edges. As M = 1 is reached and passed, the normal shock reaches the trailing edge and becomes a weak oblique shock: the flow decelerates over the shock, but remains supersonic. A normal shock is created ahead of the object, and the only subsonic zone in the flow field is a small area around the object's leading edge

If the mach number is between5.010.0, the flowspeed is much higher than the speed of sound - and the speed ishypersonic.As the Mach number increases, so does the strength of the shock wave and the Mach cone becomes increasingly narrow. As the fluid flow crosses the shock wave, its speed is reduced and temperature, pressure, and density increase. The stronger the shock, the greater the changes. At high enough Mach numbers the temperature increases so much over the shock that ionization and dissociation of gas molecules behind the shock wave begin. Such flows are called hypersonic.

International Standard Atmosphere:The International Standard Atmosphere (ISA) is an atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations. It has been established to provide a common reference for temperature and pressure and consists of tables of values at various altitudes, plus some formulas by which those values were derived.

Altitudes:Three distinct kinds of "altitude" are commonly used when discussing the vertical heights of objects in the atmosphere above the Earth's surface. The first is simple geometric altitude, which is what would be measured by an ordinary tape measure. However, for many purposes we are more interested in the pressure altitude, which is actually an indication of the ambient pressure, expressed in terms of the altitude at which that pressure would exist on a "standard day". Finally, there is the so-called geopotential altitude, which is really a measure of the specific potential energy at the given height (relative to the Earth's surface), converted into a distance using the somewhat peculiar assumption that the acceleration of gravity is constant, equal to the value it has at the Earth's surface.

Indicated altitude is the reading on the altimeter when the altimeter is set to the local barometric pressure at Mean Sea Level.We use indicated altitude for 2 things, maintaining terrain/obstacle clearance and maintaining vertical separation between planes that pass over each other. For terrain/obstacle clearance, we're using indicated altitude as a substitute for true altitude, which we're usually not equipped to measure in our plane.Absolute altitude is the height of the aircraft above the terrain over which it is flyingTrue altitude is the actual elevation above mean sea level. It is Indicated Altitude corrected for non-standard temperature and pressure.This is your height above "mean sea level", a mostly arbitrary reference point. (By "mean" we mean "average", because sea levels do vary with the tides, and the wind causes waves, so mean sea level averages out all these effects to a single "mean" sea level). You're primarily interested in this because terrain and obstacles are charted with reference to MSL altitudes, and you want to make sure you're well above these when flying over them.Pressure altitude is the elevation above a standard datum air-pressure plane (typically, 1013.25 millibars or 29.92" Hg). Pressure altitude and indicated altitude are the same when the altimeter setting is 29.92" Hg or 1013.25 millibars.Density altitude is the altitude corrected for non-ISA International Standard Atmosphere atmospheric conditions. Aircraft performance depends on density altitude, which is affected by barometric pressure, humidity and temperature. On a very hot day, density altitude at an airport (especially one at a high elevation) may be so high as to preclude takeoff, particularly for helicopters or a heavily loaded aircraft.Density altitude is a yardstick by which we can reference the "density" of air. Air density is a measure of the number of gas molecules (nitrogen, oxygen, etc., whatever we've got in our atmosphere) within a given volume of space. We care about the density of air because our wings and prop use these air molecules to generate lift and thrust, and because our engine needs oxygen for combustion. As density decreases (i.e. density altitude increases), our engines generate less power because they have less oxygen to mix with fuel and burn, and our wings and prop generate less lift, so we accelerate slower and have higher stall speeds. This means longer takeoff and landing runs, and slower climbs.

2) Relation between temperature, pressure and temperature:a) Influence of temperature, pressure and density on aircraft:The effects of temperature changes:When air is warmer than average the airplane will be higher than the altimeter indicatesWhen air is colder than average the airplane will be lower than the altimeter indicatesWhen temperature lowers en route, the airplane is lower than the altimeter indicatesWhen temperature rises en route, the airplane is higher than the altimeter indicatesThe effects of pressure changes :Pilots can determine the correct pressure altitude from the on-board altimeter by setting the altimeter at the standard altitude reading of 29.92 inches (of mercury at sea level). The altimeter will then indicate the pressure altitude at which the aircraft is flyingFlying from a high pressure area to a low pressure area without adjusting the altimeter while maintaining a constant indicated altitude would result in a loss of true altitudeFlying from a low pressure area to a high pressure area without adjusting the altimeter while maintaining a constant indicated altitude would result in a gain of true altitude.The effects of density changes :Density altitude is perhaps the most critical to an airplane's performance during takeoff and landing. Results can be disastrous if the density altitude is incorrectly computed. Density altitude is a comparison between the air density at your aircraft's current altitude to the standard atmosphere where the air density is the same. Temperature, pressure and humidity determine air density. Pilots differentiate between high-density altitude and low-density altitude in terms of the performance of an airplane. Let's say that at an airplane's present flight location the day is hot. That means that the air has become thinner (fewer molecules in the air). When that hot location is compared to the standard atmosphere its density is the same as if the aircraft were located at a much higher altitude. That means that the airplane at its current location will act as if it is flying through air that is at a higher altitude. That means the airplane is flying in high-density altitude conditions.Now let's say that the present aircraft location is in very cold air. The air has now become heavier than before (more molecules in the air). When that cold location is compared to the standard atmosphere its density is the same as if the aircraft were located at a much lower altitude. That means that the airplane at its current flight location will act as if it is flying through air that is at a lower altitude or low-density altitude conditions. It is crucial for a pilot to know the density altitude of the airport at which takeoff and landings are planned.Knowing the performance specifications of one's airplane is also important. After computing all the necessary altitudes, the pilot needs to know if the airplane can perform safely under all these conditionEffects of density changes on an aircraft's performance:Flight ConditionsAltitude ConditionsAircraft performanceCharacteristics

High elevations, low atmospheric pressure, high temperatures, high humidity,High density altitude conditionsReduction in aircraft performance- Engine taking in less air so power is reduced;- Propellers and jet engines have less air to move so thrust is reduced;- Less molecules in the air, less force on the wings results in reduced lift;- Reduced thrust and lift means more takeoff runway length needed and more clearance area at the runways end needed because of a reduced climb rate.

Lower elevations, high atmospheric pressure, low temperatures, and low humidity are more indicative of low density altitudeLow-density altitude conditionsIncrease in aircraft performance- Greater thrust than normal due to a greater number of molecules in the air with which propellers and jet engines can interact;- Greater lift force as heavier air exerts more force on the wings;- Faster speed and faster climb rate as thrust and lift are increased.

Stability and control

Generally the stability of an aircraft is defined as the aircrafts ability to sustain a specific, prescribed flight condition. The concept of stability is closely related to the equilibrium of the aircraft. If the net forces and moments exerted on the aircraft is zero, the aircraft is in equilibrium, in that flight condition; i.e. the lift equals the weight, the thrust equals the drag, and no moment of force acting on the aircraft.Stability:It is the study of how an aircraft responds to small disturbance in flight and how it can designed so that it remains at a fixed incidence and speed without overworking the pilotControl: It refers to the ability to initiate and sustain changes in angle of attack.

What is Static Stability?

When an aircraft undergoes some turbulence (or some form of static imbalance) when in equilibrium flight, the nose tilts slightly up or down (an increase or decrease in the angle of attack), or there will be a slight change in flight attitude. There are additional forces acting on the aircraft, and it is no longer in the equilibrium condition.

If the aircraft continues to increase the orientation after disturbance, the aircraft is said to be statically unstable. If there are no further changes in flight attitude and if the aircraft retains the position, which means there are no net forces or moments acting on the aircraft in the new orientation too, then the aircraft is said to be statically neutral. If forces are generated on the aircraft in a way such that forces causing the disturbance are countered, and the aircraft attains its original position, then the aircraft is said to be statically stable.

In aircrafts, three types of dimensional stabilities are considered. Those are the longitudinal stability that concerns the pitching motion, the directional stability that concerns the yawing motion, and the lateral stability that concerns the rolling motion. Often the longitudinal stability and directional stability are closely interrelated.

What is Dynamic Stability?

If an aircraft is statically stable, it may undergo three types of oscillatory motion during flight. When imbalance occurs the airplane attempts to retain its position, and it reaches the equilibrium position through a series of decaying oscillations, and the aircraft is said to be dynamically stable.If the aircraft continues the oscillatory motion without decay in the magnitude, then the aircraft is said to be on dynamically neutral. If the magnitude oscillatory motion increases and the aircraft orientation start to change rapidly, then the aircraft is said to be dynamically unstable.

An aircraft that is both statically and dynamically stable can be flown hands off, unless the pilot desires to change the equilibrium condition of the aircraft.

What is the difference between Dynamic and Static Stability (of Aircrafts)?

Static stability of an aircraft describes the tendency of and aircraft to retain its original position when subjected to unbalanced forces or moments acting on the aircraft.

Dynamic stability describes the form of motion an aircraft in static stability undergoes when it tries to return to its original position.Lift and drag Drag is a component of the aerodynamic force, namely the projection onto the direction parallel to the relative wind. Lift is another component of the aerodynamic force, namely the projection onto the two directions perpendicular to the relative wind. Weight is the force of gravity. It is equal to the mass of the airplane times the local gravitational acceleration, i.e. the local gravitational field. You can measure the acceleration of gravity by observing the motion relative to your chosen reference frame of a freely falling object. This defines what we mean by downward. For present purposes, it is convenient to choose a reference frame attached to a nearby point on the earths surface, in which case the downward direction points approximately toward the center of the earth. Thrust is the force produced by the engine. It is directed forward along the axis of the engine.THEORY OF LIFT BY FUNDAMENTAL THEORIES:When a gas flows over an object, or when an object moves through a gas, the molecules of the gas are free to move about the object; they are not closely bound to one another as in a solid. Because the molecules move, there is a velocity associated with the gas. Within the gas, the velocity can have very different values at different places near the object. Bernoulli's equation, which was named for Daniel Bernoulli, relates the pressure in a gas to the local velocity; so as the velocity changes around the object, the pressure changes as well. Adding up (integrating) the pressure variation times the area around the entire body determines the aerodynamic force on the body. The lift is the component of the aerodynamic force which is perpendicular to the original flow direction of the gas. The drag is the component of the aerodynamic force which is parallel to the original flow direction of the gas. Now adding up the velocity variation around the object instead of the pressure variation also determines the aerodynamic force. The integrated velocity variation around the object produces a net turning of the gas flow. From Newton's third law of motion, a turning action of the flow will result in a re-action (aerodynamic force) on the object.. Integrating the effects of either the pressure or the velocity determines the aerodynamic force on an object. We can use equations developed by each of them to determine the magnitude and direction of the aerodynamic force.FURTHUR WE CAN EXPALIN LIFT WITH THE HELP OF EULER EQUATIONSCalculate the pressure temperature ,density, mach number of an aircraft flying at an altitude of 15000m height? flying with velocity 150m/s

Model:

=a

=1.4T=287

M=150/a

UNIT -5 STRUCTURES AND MATERIALS:MATERIALS:Broad classification of materials:(list of nonmetals and metals are given in page number 8 )There are thousands of materials available for use in engineering applications. Most materials fall into one of three classes that are based on the atomic bonding forces of a particular material. These three classifications are metallic, ceramic and polymeric. Additionally, different materials can be combined to create a composite material. Within each of these classifications, materials are often further organized into groups based on their chemical composition or certain physical or mechanical properties. Composite materials are often grouped by the types of materials combined or the way the materials are arranged together. Below is a list of some of the commonly classification of materials within these four general groups of materials.Metals Ferrous metals and alloys (irons, carbon steels, alloy steels, stainless steels, tool and die steels) Nonferrous metals and alloys (aluminum, copper, magnesium, nickel, titanium, precious metals, refractory metals, superalloys) Polymeric Thermoplastics plastics Thermoset plastics Elastomers

Ceramics Glasses Glass ceramics Graphite Diamond Composites Reinforced plastics Metal-matrix composites Ceramic-matrix composites Sandwich structures Concrete

MetalsMetals account for about two thirds of all the elements and about 24% of the mass of the planet. Metals have useful properties including strength, ductility, high melting points, thermal and electrical conductivity, and toughness. From the periodic table, it can be seen that a large number of the elements are classified as being a metal. A few of the common metals and their typical uses are presented below. Common Metallic Materials Iron/Steel - Steel alloys are used for strength critical applications Aluminum - Aluminum and its alloys are used because they are easy to form, readily available, inexpensive, and recyclable. Copper - Copper and copper alloys have a number of properties that make them useful, including high electrical and thermal conductivity, high ductility, and good corrosion resistance. Titanium - Titanium alloys are used for strength in higher temperature (~1000 F) application, when component weight is a concern, or when good corrosion resistance is required Nickel - Nickel alloys are used for still higher temperatures (~1500-2000 F) applications or when good corrosion resistance is required. Refractory materials are used for the highest temperature (> 2000 F) applications.

The key feature that distinguishes metals from non-metals is their bonding. Metallic materials have free electrons that are free to move easily from one atom to the next. The existence of these free electrons has a number of profound consequences for the properties of metallic materials. For example, metallic materials tend to be good electrical conductors because the free electrons can move around within the metal so freely. More on the structure of metals will be discussed later. CeramicsA ceramic has traditionally been defined as an inorganic, nonmetallic solid that is prepared from powdered materials, is fabricated into products through the application of heat, and displays such characteristic properties as hardness, strength, low electrical conductivity, and brittleness." The word ceramic comes the from Greek word "keramikos", which means "pottery." They are typically crystalline in nature and are compounds formed between metallic and nonmetallic elements such as aluminum and oxygen (alumina-Al2O3), calcium and oxygen (calcia - CaO), and silicon and nitrogen (silicon nitride-Si3N4).Depending on their method of formation, ceramics can be dense or lightweight. Typically, they will demonstrate excellent strength and hardness properties; however, they are often brittle in nature. Ceramics can also be formed to serve as electrically conductive materials or insulators. Some ceramics, like superconductors, also display magnetic properties. They are also more resistant to high temperatures and harsh environments than metals and polymers. Due to ceramic materials wide range of properties, they are used for a multitude of applications. The broad categories or segments that make up the ceramic industry can be classified as: Structural clay products (brick, sewer pipe, roofing and wall tile, flue linings, etc.) Whitewares (dinnerware, floor and wall tile, electrical porcelain, etc.) Refractories (brick and monolithic products used in metal, glass, cements, ceramics, energy conversion, petroleum, and chemicals industries) Glasses (flat glass (windows), container glass (bottles), pressed and blown glass (dinnerware), glass fibers (home insulation), and advanced/specialty glass (optical fibers)) Abrasives (natural (garnet, diamond, etc.) and synthetic (silicon carbide, diamond, fused alumina, etc.) abrasives are used for grinding, cutting, polishing, lapping, or pressure blasting of materials) Cements (for roads, bridges, buildings, dams, and etc.) Advanced ceramics Structural (wear parts, bioceramics, cutting tools, and engine components) Electrical (capacitors, insulators, substrates, integrated circuit packages, piezoelectrics, magnets and superconductors) Coatings (engine components, cutting tools, and industrial wear parts) Chemical and environmental (filters, membranes, catalysts, and catalyst supports)The atoms in ceramic materials are held together by a chemical bond which will be discussed a bit later. Briefly though, the two most common chemical bonds for ceramic materials are covalent and ionic. Covalent and ionic bonds are much stronger than in metallic bonds and, generally speaking, this is why ceramics are brittle and metals are ductile.POLYMER:A polymeric solid can be thought of as a material that contains many chemically bonded parts or units which themselves are bonded together to form a solid. The word polymer literally means "many parts." Two industrially important polymeric materials are plastics and elastomers. Plastics are a large and varied group of synthetic materials which are processed by forming or molding into shape. Just as there are many types of metals such as aluminum and copper, there are many types of plastics, such as polyethylene and nylon. Elastomers or rubbers can be elastically deformed a large amount when a force is applied to them and can return to their original shape (or almost) when the force is released.COMPOSITES(study entire thing)A composite is commonly defined as a combination of two or more distinct materials, each of which retains its own distinctive properties, to create a new material with properties that cannot be achieved by any of the components acting alone. Using this definition, it can be determined that a wide range of engineering materials fall into this categoryComposite materials are said to have two phases. The reinforcing phase is the fibers, sheets, or particles that are embedded in the matrix phase. The reinforcing material and the matrix material can be metal, ceramic, or polymer. Typically, reinforcing materials are strong with low densities while the matrix is usually a ductile, or tough, material. Some of the common classifications of composites are: Reinforced plastics Metal-matrix composites Ceramic-matrix composites Sandwich structures ConcreteComposite materials can take many forms but they can be separated into three categories based on the strengthening mechanism. These categories are dispersion strengthened, particle reinforced and fiber reinforced. Dispersion strengthened composites have a fine distribution of secondary particles in the matrix of the material. These particles impede the mechanisms that allow a material to deform. (These mechanisms include dislocation movement and slip, which will be discussed later). Many metal-matrix composites would fall into the dispersion strengthened composite category. Particle reinforced composites have a large volume fraction of particle dispersed in the matrix and the load is shared by the particles and the matrix. Most commercial ceramics and many filled polymers are particle-reinforced composites. In fiber-reinforced composites, the fiber is the primary load-bearing component. Fiberglass and carbon fiber composites are examples of fiber-reinforced composites. If the composite is designed and fabricated correctly, it combines the strength of the reinforcement with the toughness of the matrix to achieve a combination of desirable properties not available in any single conventional material. Some composites also offer the advantage of being tailorable so that properties, such as strength and stiffness, can easily be changed by changing amount or orientation of the reinforcement material. The downside is that such composites are often more expensive than conventional materialsWhat are the desirable characteristics considered in the choice material for aircraft use? Weight,strength, reliability are most important in selecting a material. Good strength to weight ratio Reliability (it should eliminate any possibility of dangerous) So, designer should have better knowledge in materials to determine the best material for any application.Things to be considered for selecting the best material ENGINEERING CONSIDERATION ECONOMIC CONSIDERATIONENGINEERING CONSIDERATION: STRENGHT STRENGTH TO WEIGHT TO RATIO CORROSION RESISTENT ECONOMIC CONSIDERATION: AVAILABILTIY COST SHOP EQUIPMENT REQUIRED STANDARDIZATION OF MATERIALS SUPPLEMENTARY OPERATION REQUIRED Mechanical parameters required in selecting a material :( just write basic things, dont write everything)Knowledge and understanding of the uses, strengths, limitations, and other characteristics of structural material s is vital to properly construct and maintain any equipment, especially airframes.Hardness:Hardness refers to the ability of a material to resist abrasion, penetration, cutting action, or permanent distortion.Strength:Strength is the ability of a material to resist deformation. Strength is also the ability of a material to resist stress without breakingDensity:Density is an important consideration when choosing a material to be used in the design of a part in order to maintain the proper weight and balance of the aircraft.

Malleability:A metal which can be hammered, rolled, or pressedinto various shapes without cracking, breaking, orleaving some other detrimental effect, is said to bemalleable. This property is necessary in sheet metal that is worked into curved shapes, such as cowlings, fairings, or wingtips. Copper is an example of a malleable metal.DuctilityDuctility is the property of a metal which permits it to be permanently drawn, bent, or twisted into various shapes without breaking. This property is essential for metals used in making wire and tubing. Ductile metals are greatly preferred for aircraft use because of their ease of forming and resistance to failure under shock loads. For this reason, aluminum alloys are used for cowl rings, fuselage and wing skin, and formed or extruded parts, such as ribs, spars, and bulkheads. Chrome molybdenum steel is also easily formed into desired shapes. Ductility is similar to malleability.ElasticityElasticity is that property that enables a metal to return to its original size and shape when the force which causes the change of shape is removed.In aircraft construction, members and parts are so designed thatthe maximum loads to which they are subjected will not stress them beyond their elastic limits. ToughnessA material which possesses toughness will withstand tearing or shearing and may be stretched or otherwise deformed without breaking. Toughness is a desirable property in aircraft metalsBrittlenessBrittleness is the property of a metal which allows little bending or deformation without shattering. A brittle metal is apt to break or crack without change of shape. Because structural metals are often subjected to shock loads, brittleness is not a very desirable property. Cast iron, cast aluminum, and very hard steel are examples of brittle metals.Titanium alloy:Better strength to weight ratio than aluminum and retains its strength at higher temperatures. Hard to form and manufacturing and expensive. 5 to 10 times expensive than aluminum.MATERIALS USED IN AIRCRAFT: Wood was used on most early airplanes and is now mainly used on homebuilt airplanes. Wood is lightweight and strong, but it also splinters and requires a lot of maintenance.Aluminum (blended with small quantities of other metals) is used on most types of aircraft because it is lightweight and strong. Aluminum alloys dont corrode as readily as steel. But because they lose their strength at high temperatures, they cannot be used for skin surfaces that become very hot on airplanes that fly faster than twice the speed of sound. Steel can be up to four times stronger and three times stiffer than aluminum, but it is also three times heavier. It is used for certain components like landing gear, where strength and hardness are especially important. It has also been used for the skin of some high-speed airplanes, because it holds its strength at higher temperatures better than aluminum. Graphite-epoxy is one of several types of composite materials that are becoming widely used for many aircraft structures and components. These materials typically consist of strong fibers embedded in a resin (in this case, graphite fibers embedded in epoxy). Thin sheets of the material can be stacked in various ways to meet specific strength or stiffness needs. Graphite-epoxy is about as strong as aluminum and weighs about half as much.TITANIUM (VERY IMPORTANT)Titanium is about as strong as steel and weighs less, though it is not as light as aluminum. It holds its strength at high temperatures and resists corrosion better than steel or aluminum. Though titanium is expensive, these characteristics have led to its greater use in modern aircraft.Aircraft construction requires the use of materials that can withstand the severe pressures of flight at high altitudes, as well as constant exposure to the elements. Traditionally, aircraft were constructed of steel, but lighter, more durable materials are now used to extend the life of aircraft and make them more energy efficient.

Facts About TitaniumTitanium is a classified as a metal with chemical element symbol of Ti and an atomic number of 22.Titanium has the highest weight-to-strength ratio of any metal, which makes it useful for a variety of industries in which parts must have superior strength but not add to the overall weight of the product. Titanium is as strong as steel but 45 percent lighter. It is also corrosion resistant, which makes it a preferred metal for a number of outdoor uses. Titanium can be made into an alloy with a number of metals, such as iron, aluminium, molybdenum and vanadium. Titanium was discovered in 1791 by Reverend William Gregor. It was named by Martin Heinrich Kaproth after the Titans of Greek mythology. Titanium can be found in abundance in the earth. It is always found bonded to other elements in its natural form. It must be extracted and purified through a number of processes.

Titanium AdvantagesTitanium can withstand long periods of exposure to salt water in marine atmospheres, as well, which makes it of particular value in coastal regions. It is also a very ductile material that can be worked into many shapes. Titaniums melting point is very high, at 3000 degrees Fahrenheit, which makes it able to bear high-heat environments. It is also nonmagnetic and does not conduct heat or electricity well. All of these qualities make it an especially good choice for aircraft parts. Welding of titanium requires special treatment to avoid intrusion of impurities into the weld, which can cause cracking and failure. Machining of titanium must also be done using specific processes to avoid softening and galling of the metal.

Use in Aircraft ConstructionTitanium is used in a variety of parts in aircraft construction, both on the exterior framework and in the engine. Titanium can be found on parts for landing gear, internal components of wings, propellers and other components. It can also be found within the aircraft engine, such as the housing, fan blades, pumps, screens and components that may be exposed to high temperatures. Steel and steel alloys are still used extensively in many aircraft because of cost considerations. Titanium is not only an expensive material, the costs involved in properly machining the metal often make it less feasible for widespread use throughout the aircraft. Titanium alloys are common in aircraft construction with complex compounds used to provide specific qualities for particular parts, such as with aluminium for hydraulic tubing and with tin and chromium for frames and engines.

Titanium is a desirable option for many aircraft parts because of its intrinsic qualities. As this metal becomes more widely used, the cost per unit is expected to drop, making it the metal of choice for the industry.CATEGORIES OF METAL:BASE METALA base metal may be distinguished by oxidizing or corroding relatively easily and reacting variably with diluted hydrochloric acid (HCl) to form hydrogen. Examples include iron, nickel, lead and zinc. Copper is also considered a base metal because it oxidizes relatively easily, although it does not react with HCl.In mining and economics, the term base metals refers to industrial non-ferrous metals excluding precious metals. These include copper, lead, nickel and zinc.The U.S. Customs and Border Protection is more inclusive in its definition. It includes, in addition to the four above, iron and steel, aluminum, tin, tungsten, molybdenum, tantalum, cobalt, bismuth, cadmium, titanium, zirconium, antimony, manganese, beryllium, chromium, germanium, vanadium, gallium, hafnium, indium, niobium, rhenium and thallium.FERROUS METAL Mild Steel Carbon content of 0.1 to 0.3% and Iron content of 99.7 99.9%. Used for engineering purposes and in general, none specialised metal products. Carbon steel Carbon content of 0.6 to 1.4% and Iron content of 98.6 to 99.4 %. Used to make cutting tools such as drill bits. Stainless Steel Made up of Iron, nickel and chromium. Resists staining and corrosion and is therefore used for the likes of cutlery and surgical instrumentation. See our infographic celebrating 100 years of stainless steel usage in buildings or the different types of stainless steel. Cast Iron carbon 2 6% and Iron at 94 to 98%. Very strong but brittle. Used to manufacture items such as engine blocks and manhole covers.Wrought Iron Composed of almost 100% iron. Used to make items such as ornamental gates and fencing. Has fallen out of use somewhat.NON FERROUS METALAluminium An alloy of aluminium, copper and manganese. Very lightweight and easily worked. Used in aircraft manufacture, window frames and some kitchen ware. Copper Copper is a natural occurring substance. The fact that it conducts heat and electricity means that it is used for wiring, tubing and pipe work. Brass A combination of copper and zinc, usually in the proportions of 65% to 35% respectively. Is used for ornamental purposes and within electrical fittings.Silver Mainly a natural substance, but mixing with copper creates sterling silver. Used for decorative impact in jewellery and ornaments, and also to solder different metals together. Lead Lead is a naturally occurring substance. It is heavy and very soft and is often used in roofing, in batteries and to make pipesNOBLE METALHere is a list of noble metals, which are metals that resist oxidation and corrosion.rutheniumrhodiumpalladiumsilverosmiumiridiumplatinumgoldNON METALS:The nonmetal elements occupy the upper righthand corner of the periodic table. These elements have similar chemical properties that differ from the elements considered metals.

The nonmetal element group is a subset of these elements. The nonmetal element group consists of hydrogen, carbon, nitrogen, oxygen, phosphorus, sulfur and selenium.Hydrogen acts as a nonmetal at normal temperatures and pressure and is generally accepted to be part of the nonmetal group.Properties of nonmetals include:dull, not shinypoor conductor of heatpoor conductor of electricityhigh ionization energieshigh electronegativitynot malleable or ductile, usually brittlelower density (when compared to metals)lower melting point and boiling points (when compared to metals)gains electrons in reactionsThis is a list of the nonmetal elements in order of increasing atomic number. NUMBER SYMBOLELEMENT1HHydrogen2HeHelium6CCarbon7NNitrogen8OOxygen9FFluorine10NeNeon15PPhosphorus16SSulfur17ClChlorine18ArArgon34SeSelenium35BrBromine36KrKrypton53IIodine54XeXenon85AtAstatine86RnRadon117UusUnunseptium118UuoUnunoctium

Draw stress-strain diagram pertaining to a typical metallic material used in aircraft structural build and mark important and regions. Compare it with that of a composite material

Aluminium is used here for our study , you can also explain steels strain stress graph also(19)

The region starts from origin to yield point or yield strength is termed as elastic region.The region starts from yield strength to ultimate tensile strength is termed as plastic region.Further we have strain hardening(strengthening of a metal by plastic deformation) and necking(Necking (engineering), the process by which a ductile material deforms under tension forming a thin neck)

Stress-strain graph for compositesFiber compositeWhen compared with the strain stress graph of conventional metal, composites have both the ductile property of resins and brittle property of fiber. So, if we employ fiber alone, it may give you high ultimate strength, but it will fail after (fracture) and if we employ material similar to the any ductile material (in here resin), then its ultimate strength will be less. So when combine both, both ductility and brittle properties are attained. When compared with aluminum stress strain graph , aluminum ultimate strength is 150-300 mpa ( includes alloys) and fiber has some high values( compare with the above table). But both have good duclity.

DIFFERENCES WITH OTHER MATERIALS

The basic difference of composite materials with by examples metals is that they have a An-Isotropic behavior, which means that the habits of the composite material or formed laminate are directional depended. Metals have in general an Isotropic behavior, which means that their habits are in all directions the same. Some other differences are:

End material is formed during production process, in most cases in the end form of the end product.

Materials habits are also determined by production/curing process

Fibrous composites are more versatile than metals and can be tailored to meet performance needs and complex design requirements.

Higher specific strength (material strength/density material). Aramide and Carbon Fiber reinforced epoxies have approx. 4 to 6 times higher spec. tensile strength than steel or aluminum

Great fatigue endurance especially for aramide and carbon reinforced epoxies, compared with metals.ADVANTAGES OF COMPOSITES

Very high specific strength. Which means very high strength and low weight

Great freedom of shape. Double curved and complex parts can be simple produced.

High degree of integration possible. Which means simple integration of stiffeners, inserts, cores*, and production of self-supporting structures in one or two production cycles.

Material can be tailored. Which means fit for the loads / performance the end product has to perform during its lifetime

Excellent fatigue endurance concerning number of load cycles (many times higher than with metals) and residual fatigue strength (aramide and carbon epoxy laminates retain more than 60% of their residual static strength, which is far more higher than is possible with metals.)

Excellent chemical resistance against acids, chemicals etc.

Excellent weather/water resistance. Material has almost no corrosion, takes on little water which leads to low maintenance cost especially on the long run.

Composites have excellent RAM features (Radar absorbing materials). It's also possible to make special laminates which are radar and sonar transparent.

Excellent impact habits

Excellent electrical habits, concerning isolation but also conduction, dielectric habits, EMS shielding etc. Structures can be tailored on RF transparency but can also be made RF reflecting. Great for telecom especially UMTS frequencies.

Great thermal isolation habits, fire retardancy habits, and high temperature performance.

TYPES OF COMPOSITES

The most known type of composites are the fiber reinforced plastics. However there are more types of composites, in which also metals are used !.

Types of composites are:

Fiber reinforced plastics

Fiber reinforced thermo set plastics (like polyester, vinlyester, epoxy, BMI/Polyimide, phenol, etc.)

Fiber reinforced thermoplastics (like PPS, PEEK, PEI, PAI, etc.)

Sandwich structures

FRP facings, aluminum facings, steel facings and foam (PUR, PIR, PVC etc.) and/or honeycomb (nomex, aluminum, carbon, etc.) core's

Fiber metal laminates (FML's like ARALL and GLARE)

Metal Matrix Composites (MMC's)

Glass matrix composites

Ceramic Matrix Composites

Ceramic Ceramic Composites

Carbon Carbon Composites

etc.

HIGH STRENGTH FIBERS (most known)

glass fiber (E-glass, S-glass, C-glass)

quartz fiber

organic fibers

aramide (Twaron / Kevlar)

zylon

polyethylene fiber (Dyneema / Spectra)

M5 fiber (under development at Magellan) http://www.m5fiber.com/

carbon fiber (HT and HM)

boron fiber

ceramic fibers, alumina, carbide and nitride fibers

MATRICES (most known)

Thermo set resins like:

polyester (ortho, isothr, bisphenol)

vinlyester

epoxy

phenol

BMI and Polyimide

etc.

Thermoplastics like

PPS

PEEK

PEI

PAI

etc.

Metals (aluminum, titanium etc.)

Glass

Ceramics

carbonized phenol (carbon/carbon applications)

PRODUCTION METHODS (most known) TOP

hand lay-up (thermo sets and prepregs)

spray up (thermo sets)

cold press (thermo sets)

GMT and BMT (SMC and BMC)

injection molding (thermoplastics)

vacuum infusion and vacuum injection (VI-RTM)

Resin Transfer Molding (RTM of thermo sets and ceramics, fiber preforms 3D woven and braiding )

compression molding (prepregs and thermoplastics, glass, ceramics and metals)

pultrusion (thermo set and thermoplastics)

filament winding (thermo set, thermoplastics and ceramics)

vacuum bagging (prepregs lay-up and cure in oven)

autoclave (cure under pressure and high temp, thermoplastic, thermo set, ceramics, MMC's, FML's)

or you can study the stress strain graph for mild steel

Stress strain curve is a behavior of material when it is subjected to load. In this diagram stresses are plotted along the vertical axis and as a result of these stresses, corresponding strains are plotted along the horizontal axis. As shown below in the stress strain curve.

Stress Strain Curve

From the diagram one can see the different mark points on the curve. It is because, when a ductile material like mild steel is subjected to tensile test, then it passes various stages before fracture.

These stages are;

Proportional Limit Elastic Limit Yield Point Ultimate Stress Point Breaking Point

Proportional Limit

Proportional limit is point on the curve up to which the value of stress and strain remains proportional. From the diagram point P is the called the proportional limit point or it can also be known as limit of proportionality. The stress up to this point can be also be known as proportional limit stress.

Hooks law of proportionality from diagram can be defined between point OP. It is so, because OP is a straight line which shows that Hooks law of stress strain is followed up to point P.

Elastic Limit

Elastic limit is the limiting value of stress up to which the material is perfectly elastic. From the curve, point E is the elastic limit point. Material will return back to its original position, If it is unloaded before the crossing of point E. This is so, because material is perfectly elastic up to point E.

Yield Stress Point

Yield stress is defined as the stress after which material extension takes place more quickly with no or little increase in load. Point Y is the yield point on the graph and stress associated with this point is known as yield stress.

Ultimate Stress Point

Ultimate stress point is the maximum strength that material have to bear stress before breaking. It can also be defined as the ultimate stress corresponding to the peak point on the stress strain graph. On the graph point U is the ultimate stress point. After point U material have very minute or zero strength to face further stress.

Breaking Stress (Point of Rupture)

Breaking point or breaking stress is point where strength of material breaks. The stress associates with this point known as breaking strength or rupture strength. On the stress strain curve, point B is the breaking stress point.

STRUCTURES (CONSTRUCTIONS):

METTALIC WING AND FUNCTION OF ITS PARTS:(OR REFER PDF IN UR MAIL)

SWings develop the major portion of the lift of aheavier-than-air aircraft.Wing structures carry some ofthe 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 4-8. 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 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 surfaces.

Construction of wings:( for brief description plz refer aircraft structure lalith gupta) Mass boom Box beam Multi spar

Mass boom: Advantage and disadvantage of mass boom

Box Beam:

MULTI SPAR :

fig 5fig 6

Fig 7

Continuation in next page.

Fuselage construction:

There are two general types of fuselage constructionwelded steel truss and monocoque designs. The welded steel truss was