Navigation Precis PDF

RESTRICTED PART 1 : NAVIGATION FIRST SEMESTER SECTION 1: BASICS OF NAVIGATION Chapter 1 : Air Navigation  Types of Air Navigation o Dead Reckoning o Astro o Contact / Visual o Radio o Radar Chapter 2 : Form of the Earth  The...

RESTRICTED PART 1 : NAVIGATION FIRST SEMESTER SECTION 1: BASICS OF NAVIGATION Chapter 1 : Air Navigation  Types of Air Navigation o Dead Reckoning o Astro o Contact / Visual o Radio o Radar Chapter 2 : Form of the Earth  The Shape of the Earth o Oblate Spheroid, Polar Diameter, Equatorial Diameter, Compression Ratio o Assumption of the Earth’s shape as a Sphere  The Rotation of the Earth o Axis of Rotation, The Poles, North, South, East and West o Cardinal and Quadrantal Points Chapter 3 : Representation of Various Lines on the Surface of Earth o The Great Circle, Small Circle, Rhumb Line, Equator, Meridian o Parallels of Latitude, Great and Small Circles, Rhumb Line o Latitude/ Longitude Change of Latitude/Longitude, Convergence Chapter 4 : Position Measurement o Latitude, Longitude, Recording of Position, o Change of Latitude, Change of Longitude o Problem Solving Change of Latitude / Longitude o Departure Chapter 5 : Angles and Distance Measurement o Angles, Distance and Speed Measurement. o Inter-Conversion of Units. Chapter 6 : Directions on the Earth o Direction --- True, Magnetic & Compass. o Variation, Isogonics, Agonic Lines, Compass direction, Deviation. o Heading – True, Magnetic and Compass. Chapter 7 : Elementary Definitions o Wind Speed – Direction (Wind Velocity) o Track ------ Track Required, Track Made Good, Track Error. o Drift, Airspeed, Ground Speed, Bearing -------- True, Magnetic and Relative. o Ground Position -- Pin Point, Fix and DR Position, Check Point o Height, Elevation, Altitude, Standard Symbols. 1 RESTRICTED  RESTRICTED Chapter 8 : Methods of Reporting Position o Place Name Method of Reporting Position. o Bearing and distance method. o Latitude and Longitude method. 2 RESTRICTED  RESTRICTED CHAPTER No 1 AIR NAVIGATION Objectives The students will understand:- (a) Air Navigation and its importance (b) Types of Air Navigation (i) Dead Reckoning (ii) Astro (iii) Contact / Visual (iv) Radio (v) Radar _____________________________________________________________________________________________ Air Navigation 1. Definition. It is the science, which deals with the safe conduct of flight from one place to another. 2. Aviators must have a thorough knowledge of the different techniques employed to navigate their airplanes. They must, also, keep abreast with the latest developments taking place in this field of science in order to keep their safety records ever high. Certain basic types of Air Navigation are discussed hereunder. Types of Air Navigation Types of Air Navigation Dead Contact/ Astro Radio Radar Reckoning Visual 3. Dead Reckoning. It is the name given to the art of navigating an airplane with the basic knowledge of its Heading, Airspeed and Time. This is basic navigating the airplane by calculations. The ever-changing flight conditions are not taken into consideration. It may not be very accurate but at times is the only method available. 4. Astro Navigation. In the beginning sailors used to navigate their ships by taking directions with the help of prominent stars. This technique was developed for finding out a fairly accurate position of the aircraft in addition to its direction with the help of Sun, Moon, prominent stars and planets. 3 RESTRICTED  RESTRICTED 5. Contact / Visual Navigation. The art of conducting a flight with the help of visual aids is known as Contact / Visual navigation. It is the most accurate and appropriate method for a single-seat aircraft. 6. Radio Navigation. It is the art of conducting a flight with the help of Radio Navigation aids, i.e., Radio Beacon (NDBs), VOR, and TACAN etc. 7. Radar Navigation. It is the art of conducting a flight with the help of Radars. There are two types of Radars, i.e., Ground Radars and Airborne Radars. The basic navigation technique remains the same. The range and bearing of fixed ground objects is determined instantaneously on the radar scope. It is a very good all-weather fixing technique. Other Types of Navigation 8. Certain other types of advanced navigation techniques are:- (a) Doppler Navigation (b) Global Positioning System. (GPS) (c) Inertial Navigation System (INS) 9. Some navigation techniques that are becoming obsolete are:- (a) Grid Navigation / Gyro Steering (b) Pressure Pattern Navigation 4 RESTRICTED  RESTRICTED CHAPTER No 2 FORM OF THE EARTH Objectives The students will understand:- (a) The shape of the Earth (i) Oblate Spheroid (ii) Polar Diameter (iii) Equatorial Diameter (iv) Compression Ratio (v) Assumption of the Earth’s shape as a Sphere (b)The rotation of the Earth (i) Axis of rotation (ii) The Poles (iii) North, South, East and West – Cardinal Points (iv) Quadrantal Points ______________________________________________________________ Shape of the Earth 1. Form of the Earth Early Greek theories about Earth’s shape ranged from a flat disc, a sphere, and a cylinder and even to a rectangle. For most of the navigational purposes, Earth’s shape has been assumed to be almost spherical, being slightly flattened at the poles. This shape is termed as an Oblate Spheroid. Earth’s flattening results from the fact that its polar diameter is approximately 27 statute miles shorter than its equatorial diameter. 2. Compression of the Earth. The ratio between this difference in (polar and equatorial) diameters and the equatorial diameter is termed as the Compression of the Earth. It indicates the amount of flattening. The Compression ratio is approximately 1 / 300. Compression Ratio = (Equatorial Dia. – Polar Dia) / Equatorial Dia Rotation of the Earth 3. The Poles. The extremities of the diameter about which the Earth is rotates are called Poles. 5 RESTRICTED  RESTRICTED 4. East and West. East is defined as the direction in which the Earth is rotating. This direction is anti clockwise to an observer looking down at the North Pole. West is the direction opposite to East. 5. North and South. The two poles are distinguished arbitrarily. The North Pole is said to be the pole, which lies to the left of an observer facing East. North is therefore that direction in which an observer would have to move in order to reach the North Pole. It is at right angles to East – West direction. 6. Cardinal Points. The directions North, South, East and West are known as Cardinal directions. North, South, East and West points are known as Cardinal points. 7. Quadrantal Points. The directions North-East, North-West, South-East, and South-West are known as Quadrantal directions. The four points North-East, North-West, South-East, and South-West are known as Quadrantal points. Cardinal Points Quadrantal Points Quadrantal Points Cardinal Cardinal Points Points Quadrantal Quadrantal Points Cardinal Points 6 Points RESTRICTED  RESTRICTED CHAPTER No 3 REPRESENTATION OF VARIOUS LINES ON THE SURFACE OF EARTH Objectives The students will understand :- (a) The Great Circle, Small Circle, Rhumb Line, Equator, Meridian (b) Parallels of Latitude, Great and Small Circles, Rhumb Line (c) Latitude/ Longitude Change of Latitude/Longitude, Convergence ______________________________________________________________ Introduction 1. Lines Drawn on the Earth. The shortest distance between two points is the length of the straight line joining them. It is, however, impossible to draw a straight line on a spherical surface. In other words, all lines drawn on the Earth are curved, some regularly and some irregularly. The regularly curved imaginary lines on the Earth, which are of interest to an aviator, are discussed hereunder. 2. Great Circle. A great circle is a circle on the surface of a sphere whose center and radius are those of the sphere itself. Only one great circle may be drawn through two points that are not diametrically opposed. The shortest distance between any two points on the surface of a sphere is the smaller arc of the great circle joining them. 7 RESTRICTED  RESTRICTED 3. Small Circle. A small circle is a circle on the surface of a sphere whose center and radius are not those of the sphere. All circles other than great circles on the surface of a sphere are small circles. 4. Equator. Equator is the great circle whose plane is perpendicular to the axis of rotation of the Earth. Every point on Equator is therefore equidistant from both the poles. Equator lies in an East-West direction and divides the Earth into Northern and Southern hemispheres. 5. Meridians. Meridians are semi-great circles joining the poles. Every meridian and its anti-meridian form a great circle joining the poles. All meridians indicate North-South direction. 6. Parallels of Latitude. Parallels of Latitude are small circles on the surface of the Earth whose planes are parallel to the plane of the Equator. They, therefore, lie in an East-West direction. 7. Rhumb Line. A rhumb line (Loxodrome) is a regularly curved line on Earth surface crossing every meridian at the same angle. Only one such line may be drawn through two points. Parallels of Latitude are rhumb lines as are the meridians and equator, though the latter two are special cases as they are the only examples of rhumb lines, which are also great circles. 8. Thus, when two places are situated elsewhere, than on the Equator or on the same meridian, the distance measured along the rhumb line joining them is not the shortest distance between them. However, the advantage of the rhumb line is that its direction is constant; therefore the rhumb line between any two points may be followed more conveniently than the great circle joining them. The direction of a great circle bearing changes continuously with reference to the meridians. 9. Earth Convergence. The meridians are only parallel to one another where they cross the equator. Elsewhere the angle of inclination between selected meridians increases towards the poles. This angle of inclination between selected meridians, at a particular latitude, is variously known as Earth Convergence, True Convergence, Meridian Convergence and Convergency. 8 RESTRICTED  RESTRICTED 10. At the poles its value is Ch Long, but it slowly reduces until, at the equator where the meridians are parallel to each other, its value is 0˚. If the earth is considered as a sphere its value is given by:- Earth Convergence = Ch Long (Mins) X Sin Mean Lat Where Mean Lat = (Lat A + Lat B) / 2 9 RESTRICTED  RESTRICTED CHAPTER No 4 POSITION MEASUREMENT Objectives The students will understand :- (a) Latitude, Longitude (b) Recording of Position (c) Change of Latitude, Change of Longitude (d) Problem Solving Change of Latitude / Longitude (e) Departure ______________________________________________________________ Introduction 1. On the Earth, position is normally defined by a reference system known as Latitude and Longitude. 2. Latitude. Latitude is defined as the angular distance from the Equator to a point, measured northwards or southwards, along the meridian through that point. It is expressed in degrees, minutes and seconds, and is annotated N or S, according to whether the point lies north or south of the equator. Equator Meridian of 180º N Pole West Greenwich Z A Longitude (E) B 10 East RESTRICTED  RESTRICTED 3. Longitude. The longitude of any point is the shorter angular distance, along the equator, between the prime meridian and the meridian through the point. It is expressed in degrees, minutes and seconds, and is annotated E or W, according to whether the point lies east or west of the prime meridian. As the plane of the Greenwich meridian bisects the plane of the Earth, longitude cannot be greater than 180º East or West. 4. Recording Position. In air navigation it is usually sufficient to express latitude and longitude in degrees and minutes only. By convention, the group of figures representing latitude is written first and is followed by the figures expressing longitude. To avoid ambiguity, figures below ten are preceded by the digit 0 (zero). The letters N, S, E and W are used to indicate the sense of the latitude and longitude coordinates. Thus the position of a point situated in latitude 33 degrees 36 minutes north and in longitude zero degrees 5 minutes east, is written as : 33 36 N 00 05 E. 5. Change of Latitude. The change of latitude (ch lat) between two points is the arc of a meridian intercepted between their parallels of latitude. It is annotated N or S according to the direction of the change from first point to the second. Change of Latitude 6. Change of Longitude. The change of longitude (ch long) between two points is the arc of the equator intercepted by the meridians through the two points. It is annotated E or W according to the direction of the change from first point to the second. 11 RESTRICTED Change of Longitude  RESTRICTED 7. Problem Solving. Classroom practice. Find out Ch Lat and Ch Long. (a) 33 36 N 00 05 E and 40 37 N 75 06 E (b) 23 30 S 171 15 W and 23 30 N 171 15 W (c) 89 30 S 16 13 W and 25 30 S 90 13 W 8. Departure. The distance between two given meridians, measured along a stated parallel and expressed in nautical miles, is called departure. In general terms, it is defined as the east-west component of the rhumb line distance between two points. The value of departure between two meridians varies with latitude, decreasing with increasing latitude; the change of longitude between these two points of course remains the same, irrespective of the latitude. 9. The departure between any two points is thus a function of their latitudes and the change of longitude, and the relationship is given by:- Departure (NMs) = Ch Long (Mins) X Cos Mean Lat Where Mean Lat = (Lat A + Lat B) / 2 12 RESTRICTED  RESTRICTED CHAPTER No 5 ANGLES AND DISTANCE MEASUREMENT Objectives The students will understand :- (a) Angular measurement. (b) Distance measurement. (c) Speed measurement. (d) Inter-conversion of units. _____________________________________________________________________________________________ Introduction 1. In order to state the direction of any object, a reference directional datum is necessary. The commonly chosen reference is the direction of the North Pole. The directions of the north and south poles and that of the heavenly bodies (Sun, Moon and stars) are the fundamental points of the compass. They are known as north, south, east and west. The directions halfway between these cardinal directions are called the Quadrantal directions. They are North East (NE), South East (SE), South West (SW), and North West (NW). 2. Angular Measurement. In navigation, the Sexagesimal System of measuring the angles and distances is universally employed. In this system, a Degree is defined as the angle subtended at the center of a circle by an arc equal to 360th part of the circumference. A right angle is divided into 90 degrees(º), each degree is further subdivided into 60 minutes ( ' ), and each minute into 60 seconds ( " ). The size of any angle may be expressed in terms of degrees, minutes and seconds. 3. Distance Measurement – Nautical Mile. Assuming the Earth to be a true sphere, a Nautical Mile is defined as the length of the arc of a great circle, which subtends an angle of one minute at the centre of the Earth. Thus the number of Nautical miles in the arc of any great circle equals the number of minutes subtended by that and at the centre of the Earth. The conversion of an angular measurement of spherical distance to linear units requires only the reduction of the angle to minutes of arc; the number of minutes is equal to the spherical distance in Nautical miles. 4. If AB, the arc of a great circle, subtends an angle at the Earth’s centre of 40o20’, AB is said to be 40o20’ in length. 40o20’ is equivalent to 2,420 minutes of arc which is equal to a length of 2,420 nautical miles. Because of the Earth’s uneven shape, the actual length of a nautical mile is not constant, but varies with latitude. It varies from 6046 feet at the equator to approximately 6108 feet at the poles. However, for the purpose of navigation a fixed unit of measurement is helpful, and the length of the nautical mile is taken to be 6080 feet. 13 RESTRICTED  RESTRICTED 5. Geographic Mile. The geographic mile is defined as being the length of one minute of arc of the Earth’s equator, and is approximately equal to 6987 feet. 6. Statute Mile. The other mile unit in common use is the statute mile (so called because its length is determined by law), this is 5,280 feet in length. It is a purely arbitrary unit of measurement and, unlike the Nautical Mile, is not readily converted into angular measurement. At one time the Statute Mile was used in navigation, but for many reasons, was found inconvenient. The Nautical mile has now been adopted as the unit of measurement in navigation. 7. Metric Units - Kilometer. The Kilometer is the length of 1/10,000 part of the average distance between the equator and either pole; it th is equivalent to 3,280 feet. 8. Conversion of Units. The following values must be memorized for converting one unit to another:- 66 NM = 76 SM 41 NM = 76 KM 61 SM = 66 KM 100 KM = 54 NM 7 SM = 6 NM 5 SM = 8 KM 9. Speed and its Measurement. Speed is the rate of change of position. It is usually expressed in linear units per hour. As there are three main linear units, there are three expressions of speed. (a) Knots, or Nautical miles per hour (kts) (b) Miles per hour (mph) (c) Kilometers per hour (km/hr) 14 RESTRICTED  RESTRICTED CHAPTER No 6 DIRECTIONS ON THE EARTH Objectives The students will understand :- (a) Direction --- True, Magnetic & Compass. (b) Variation, Isogonics, Agonic Lines. (c) Compass direction, Deviation. (d) Heading – True, Magnetic and Compass. ______________________________________________________________ 1. Introduction. In order to fly in a given direction an aviator must be able to refer to a datum line or fixed’ direction whose orientation he knows or can determine. The most convenient datum is the meridian through his own position, since it is the North-South line. By convention, direction is measured clockwise from North, to the nearest degree, i.e. from 000 o to 360o. Thus East is written 090o, and West 2700. 2. True Direction. Direction measurement with reference to True North, the direction of the North geographic pole, is said to be true direction (o T). True direction possesses a number of advantages, which commend its use to the pilot/navigator. (a) It is a constant directional reference (i.e. true direction about a point does not change). (b) It forms the basis of nearly all maps and charts. (c) It facilitates plotting. 3. Magnetic direction will, however, continue to be the basis of the majority of aircraft heading reference systems for some years yet, because magnetic systems are cheaper and simpler, and true direction can be derived quite easily from their outputs. 4. Magnetic Direction. The Earth acts as though it is a huge magnet whose field is strong enough to influence the alignment of a freely suspended magnetic needle anywhere in the world. The poles of this hypothetical magnet are known as the North and South magnetic poles and, like those of any magnet, they can be considered to be connected by lines of magnetic force. The North Magnetic Pole is located approximately at latitude 73º N and longitude 100º W on Prince of Wales Island. The South magnetic pole is located at latitude 68º S and longitude 144º E, on Antarctica. 5. Although, the magnetic and geographic poles are by no means coincident (the respective north poles are separated by approximately 1200 miles), the lines of force throughout the equatorial and temperate regions are roughly parallel to the Earth’s meridians. A freely suspended magnetic needle will take up the direction indicated by the Earth’s lines of force and thus assume a general north-south direction. The actual direction, in which it points assuming no other influences are acting upon it, is said to be Magnetic North. 15 RESTRICTED  RESTRICTED 6. With such datum available, it is possible to measure magnetic directions. Thus, knowing the angle by which the direction of magnetic north differs from true north at any given point (an angle which is accurately measured on the ground and displayed on plotting charts), the aviator is able to convert magnetic direction, which he can measure, to true direction which he requires. 7. Variation. The angular difference between the direction of true north and magnetic north at any given point, and therefore between all true directions and their corresponding magnetic directions at that point, is called variation. Variation is measured in degrees and is termed East (+) or West (-) according to whether the north-seeking end of a freely suspended magnetic needle, influenced only by the Earth’s field, lies to the East or West of True North at any given point. 8. The algebraic sign given to variation indicates how it is to be applied to magnetic direction to convert it to true direction. At any point, therefore, a navigator can determine true direction by measuring magnetic direction by application of local variation. A useful mnemonic is:- “Variation east, magnetic least, Variation west, magnetic best.” North (Magnetic) North (True) Var 10º E Direction magnetic 100o (M) Variation 10o E(+) Direction True 110o (T) 110º T 100º M North (Magnetic) North (True) Var 10º E Direction magnetic 100o (M) Variation 10oW (-) 090º T Direction true 090o (T) 100º M 9. Isogonals. Lines joining places of equal variation are known as isogonals. 16 RESTRICTED  RESTRICTED 10. Agonic Lines. Lines joining the places of zero variation are known as Agonic lines. 11. Compass Direction. When a freely suspended magnetic needle is influenced only by the Earth’s magnetic field, the direction it assumes is known as Magnetic North. If such a needle is placed in an aircraft, it is subject to a number of additional magnetic fields created by various electrical circuits and magnetized pieces of metal within the aircraft; consequently its north- seeking end deviates from the direction of magnetic north and indicates a direction known as compass north. 12. Deviation. The angular difference between the direction of Magnetic North and that of Compass North, and therefore all magnetic direction and their corresponding compass directions, are called deviation. Deviation is measured in degrees and is named East (+) or West (-) according to whether the north-seeking and of a compass needle, under various disturbing influences, lies to the East or West of Magnetic North. The algebraic sign given to deviation indicates how it is to be applied to compass direction to convert it to magnetic direction. 13. Deviation does not remain constant for a given compass; instead it varies with the heading of the aircraft. Deviation experienced by two different aircraft compasses may not be the same under identical conditions. In order to convert the directions registered by a particular compass to magnetic directions, an aviator requires a table of deviations of that compass found on various compass headings, usually in the form of a card, provided and placed near the compass to which it applies. 14. The deviation of a compass will change as its position in the aircraft is changed. Deviation will also change, over a period of time, due to changing magnetic fields within the aircraft. Moreover, as the aircraft flies great distances over the Earth, changes occur in deviation because of the Earth’s changing magnetic field. It is not sufficient, therefore, to prepare a deviation card and expect it to last indefinitely; the card must be renewed at regular intervals so that it deviation is recorded as accurately as possible. 15. Derivation of True Direction. It is possible therefore to express a direction with regard to a particular compass needle as true direction, provided deviation and variation are known. 16. NorthHeading. TheNorth heading represents the direction in which the nose of the aircraft is pointing. It is represented in degrees, (Compass) (Magnetic) North minutes, Var and seconds, North 22º W measured clockwise from the given datum to(Magnetic) (Compass) the fore and aft North axis of the (Compass) aircraft. The Dev three datums are:- North Dev 4º W Dev (Magnetic) 4º E 12º W North (a) Compass North : Compass Heading (Compass) (b) Magnetic North : Magnetic Heading (c) 104º (C) True North : True Heading 104º (M) 17. Direction of any place is normally calculated from a map. The direction 211º thus found 100º is the true direction. To fly in this direction 233º (M) (T) we depend on the (M) 100º (C) 245º (C) 17 RESTRICTED  RESTRICTED compass or the magnetic needle which points to Compass North and gives the compass heading of the aircraft. If the deviation and variation are known, the True heading may be calculated. The following method is utilized for interchanging directions from one to another. Compass Heading + E Deviation = Magnetic Heading. -W Magnetic Heading + E Variation = True Heading. -W 18 RESTRICTED  RESTRICTED CHAPTER No 7 ELEMENTARY DEFINITIONS Objectives The students will understand the elementary definitions of :- (a) Wind Speed – Direction (Wind Velocity) (b) Track ------ Track Required, Track Made Good, Track Error. (c) Drift (d) Airspeed, Ground Speed (e) Bearing -------- True, Magnetic and Relative. (f) Ground Position -- Pin Point, Fix and DR Position, Check Point (g) Height, Elevation, Altitude (h) Standard symbols. 1. Wind Velocity. It contains in it the wind speed and the wind direction. Wind speed is the speed at which the particular air mass moves. Like any other speed, wind speed may be in knots, mph, or kmph. The first unit is in common use. Wind direction is that direction from which the wind blows. It is expressed as three-figure group, in true direction. Thus westerly wind is one, which blows from the west; its direction is reported as 2700, meaning 2700 (T). 2. Track (TR). It is the direction of the path of an aircraft over the ground. (a) The direction, which an aircraft intends to follow, is known as its Track Required (TR). (b) The direction of the path, which the aircraft actually follows over the ground, is called its Track Made Good (TMG). (c) The angle between the Track Required (TR) and Track Made Good (TMG) is known as Track Error (TE). 3. Drift. The angular difference between Heading and the Track is known as the Drift. It is expressed Port (left) or Starboard (right) of the aircraft heading. An example maybe Drift 5º (P) or Drift 10º (SB). 4. Bearing. The direction of one point from another is called its Bearing. Like all directions, bearing may be expressed as true, magnetic or compass. The direction of the great circle joining two places is said to be great circle bearing. A rhumb line bearing is found by measuring the direction of rhumb line joining the two points. 5. Air speed. If the speed of the aircraft is measured in relation to the air through which it is moving, it is called Air speed. Airspeed is independent of wind and is the same regardless of whether the aircraft is flying upwind or downwind. 19 RESTRICTED  RESTRICTED 6. Ground Speed. Ground speed of an aircraft is the speed at which it moves over the ground. Ground speed of an aircraft is most commonly measured by using the distance between two positions on the ground over which the aircraft is observed to pass in a known time. It may be expressed in kts, mph. or kmph. 7. Ground Position. The position on the ground directly beneath an aircraft is known as its ground position. (a) Pin Point. A pinpoint is the ground position of the aircraft obtained by direct visual observation of the ground. (b) Fix. A fix is the position of the aircraft determined by methods other than direct visual means or it is the ground position obtained from the position lines. (c) DR Position.Determination of ground position with the help of calculations made with the available information of Heading, Time, Speed and Wind Velocity. 8. Check Point. It is the prominent point, place or feature with the help of which aircraft track, speed or ETA could be checked accurately. 9. Height. The vertical distance of a fixed point above ground level or some specified datum, other than the mean sea level. 10. Elevation. The vertical distance of a fixed point or a ground object above mean sea level. 11. Altitude. The vertical distance of a level, a point or an air object considered as a point, measured from the mean sea level. 12. Standard Symbols. The following symbols indicate different quantities:- Heading Track Wind Velocity Pin Point. Fix DR Position 20 RESTRICTED  RESTRICTED CHAPTER No 8 METHODS OF REPORTING POSITION Objectives The students will understand the following common methods:- (a) Place Name Method of Reporting Position. (b) Bearing and distance method. (c) Latitude and Longitude method. _____________________________________________________________________________________________ 1. Essentials of Reporting Position. When reporting position, the following essentials must be kept in mind:- (a) The reported position must be clearly and easily understood. (b) The desired accuracy must be achieved. (c) The method must ensure security if required (in war etc). Methods of Reporting Position 2. By Reference to Place Name. The position of an aircraft may be reported with reference to a particular place, i.e., if the aircraft is flying directly over the place. The limitations of reporting position by this method are that the place must be prominent, well known, and that the place should not cover a large area. 3. By Bearing and Distance to a Known Place. The position of an aircraft may be reported in relation to the direction (bearing) and distance from a particular place, if it is not flying directly above that place. An aircraft flying 5 NMs south of Risalpur would report position as 180º RS 5 miles. 4. The Latitude and Longitude Method. The latitude and longitude method of reporting position is the surest method of reporting position. In this method, the latitude and longitude of the place are given. The latitude is always reported first, followed by the longitude. The desired accuracy is achieved by reporting position in degrees, minutes, seconds and fraction of a second. (a) 34º N 74º E (b) 34º 03’ N 74º 58’ E (c) 34º 03’ 27” N 74º 58’ 31” E 5. Normally the aircraft position is reported only to the nearest minute. 21 RESTRICTED RESTRICTED 22 RESTRICTED RESTRICTED 23 RESTRICTED  RESTRICTED PART 1 : NAVIGATION FIRST SEMESTER SECTION 2 :PRESSURE INSTRUMENTS Chapter 9 : Airspeed Indicator  International Standard Atmosphere and ICAN Law.  Principle, construction and errors of the Airspeed Indicator.  Types of Airspeed, Mach Number. Chapter 10 : Vertical Velocity Indicator  Principle, Construction and Errors of Vertical Velocity Indicator. Chapter 11 : Simple Altimeter  Principle, Construction and Errors of a Simple Altimeter.  Altimeter Settings ------- QNH, QFE and QNE  Solution of Altimeter Problems. 24 RESTRICTED RESTRICTED 25 RESTRICTED  RESTRICTED CHAPTER No 9 AIRSPEED INDICATOR Objectives The students will understand:- (a) International Standard Atmosphere and ICAN Law. (b) Principle, construction and errors of the Airspeed Indicator. (c) Types of Airspeed, Mach Number. 1. International Standard Atmosphere. For the safe and universal application of the pressure instruments, such as Airspeed Indictor, Altimeter, and Vertical Velocity Indicator etc, International Standard Atmosphere has been created. The properties of this atmosphere are as follows:- (a) The air is dry and its chemical composition is the same at all altitudes. (b) The value of g is constant at 980.665 cm/sec2. (c) The temperature and pressure at mean sea level are + 15 0 C (590F) and 1013.25 Mbs or 29.92 inches Hg (d) The temperature lapse rate is 1.980C (or 20 approx.) per 1000 ft. upto a height of 36090 feet, above which the temperature is assumed to be constant at -56.50 C. (e) The pressure lapse rate maybe approximated to 1 millibar per 30 feet or 1 inch of mercury per 1000 feet. 2. The above formula has since been known as the ICAN Law. Airspeed Indicator 3. Purpose. The airspeed indicator shows the speed at which the aircraft is moving through the air. 4. Principle. In flight an aircraft experience a pressure on its leading edges owing to the impact of the airstreams. The pressure is proportional to the density of the air and the forward speed of the aircraft. This pressure is commonly known as the total pressure or pitot pressure. At any altitude the difference between the total or pitot pressure and the still air, or static pressure at the same altitude is known as the dynamic pressure and the ASI registers it on a scale graduated in units of speed. 5. Construction. ASI is a Pitot Tube sensitive differential pressure gauge operated by pressures picked up by Diaphragm a pressure head, which is mounted in a suitable position on the airframe. Air stream The simplest pressure head consists of an open ended tube, the pitot tube, aligned with the direction of 26 Static Tube RESTRICTED Casing  RESTRICTED flight, and a second tube, the static tube, which is closed and streamlined at the forward end but which has a series of small holes drilled radially along its length. 6. When moved through the air, the pitot tube picks up pitot pressure, made up of static pressure and dynamic pressure. The pitot pressure (p t) is led trough a pipeline to one side of a sealed chamber, divided by a thin flexible diaphragm. The static tube is unaffected by dynamic pressure as its end is closed, however, the small holes will pick up local static pressure (p). The static pressure is led through a second pipeline to the other side of the diaphragm. 7. The diaphragm is subjected to the two opposing pressures. However, the static pressure component of the pitot pressure is balanced by the static pressure on the other side of the diaphragm so that any diaphragm movement is determined solely by the dynamic, or pitot excess, pressure. Movement of the diaphragm is transmitted through a mechanical linkage to a pointer on the face of the ASI where the pitot excess pressure (pt – p) is indicated in terms of speed. 8. Errors of an ASI. The ASI is subject to the following errors:- (a) Pressure Error. Previously known as position error, it is caused by the effect of the movement of the aircraft on the static pressure, prevailing in the immediate vicinity of the aircraft. The magnitude of this error depends on the position of the static pressure source and the indicated airspeed of the aircraft. In order to minimize the pressure error, static pressure source is put in the fuselage of the aircraft in the shape of static vents instead of static tube. (b) Instrument Error. This error is caused by minute differences in construction. The extent of the error is determined by comparing individual instruments against a master ASI, which is also called master calibrator. The error is usually very small and is included in pressure error correction figures (PEC), sometimes displayed in the cockpit of the individual aircraft. This correction is termed as pressure and instrument error correction (PIEC). 27 RESTRICTED  RESTRICTED (c) Density Error. Pitot pressure varies not only with airspeed but also with the air density. The instrument is calibrated according to standard sea level density (0.002378 slugs per cubic cm.). Now as the density of the atmosphere decreases with altitude, pitot pressure for a given airspeed must also decrease with the increase of altitude. That is to say, in flight, an ASI operates in a less dense atmosphere than that for which it was calibrated and, therefore, indicates an airspeed lower than the true airspeed. Higher the altitude, greater is the discrepancy. Necessary correction is made by setting pressure altitude against corrected air temperature on the DR computer. (d) Compressibility Error. This error is prominent at higher speeds and also at higher altitudes. The air is a compressible fluid and will be compressed when brought to rest in a pitot tube. The higher pressure recorded in the ASI as a result of compressibility is interpreted by the instrument as a higher IAS. Thus CE causes the ASI to overhead and therefore compressibility error correction is always negative. Blocked or Leaking Pressure System 9. Blockages (a) Pitot Blockage. Blockages may occur if water in the pipe work freezes, or there are obstructions such as insects. The ASI will not react to changes of airspeed in level flight. However the casing may act as a barometer producing an indication increase in speed if the aircraft climbs or a decrease in speed if the aircraft descends. If the pitot tube contains a small bleed hole for drainage, partial blockage of nose of the tube (the most common effect of icing) will result in an under reading. More extensive icing will cause the reading to reduce to zero as the dynamic pressure leaks away through the bleed hole. (b) Static Tube Blockage. If the static tube is blocked, the ASI will over read at lower altitudes and under read at higher altitudes than that at which the blockage occurred. 10. Leakages (a) Pitot Leakage. A leak in the pitot tube causes the ASI to under read. (b) Static Port Leakage. A leak in the static tube, where the pressure outside the pipe is lower than static, will cause the ASI to over read. 11. Types of Airspeed. Based on the various errors encountered in the process of measuring the airspeed accurately or finding the True Airspeed 28 RESTRICTED  RESTRICTED (TAS), various intermediate airspeeds are defined, based on which of the errors have been catered for. Indicated Air Speed Pressure & Inst Error Correction Calibrated Airspeed Compressibility Error Correction Equivalent Airspeed Density Error Correction True Airspeed (a) Indicated air Speed (IAS). The air speed, which is indicated by the Airspeed Indicator, is termed as IAS. This is the uncorrected reading obtained from the airspeed indicator. (b) Calibrated Air Speed (CAS). CAS is the IAS corrected for pressure and instrument error of the airspeed indicator. (c) Equivalent Air Speed (EAS). EAS is the CAS corrected for compressibility error. (d) True air speed (TAS). TAS is the EAS corrected for density error. 12. Mach Number. It is the ratio of true airspeed to local sonic speed. nm Mach No. = TAS (V) / Local sonic speed (a) = V / a = V/ a ≈ (pt – p) / p where V = True airspeed; a = Local sonic speed; pt = Pitot pressure; p = Static pressure 29 RESTRICTED  RESTRICTED CHAPTER No 10 VERTICAL VELOCITY INDICATOR Objectives The students will understand the principle, construction and error of Vertical Velocity Indicator. ______________________________________________________________ Introduction 1. A vertical speed indicator (VSI), also known as a rate of climb and descent indicator (RCDI), is a sensitive differential pressure gauge, which displays a rate of change of atmospheric pressure in terms of a rate of climb or descent. Metering Unit Pointer Capsule Static Pressure Principle 2. The principle employed is that of measuring the difference of pressure between two chambers, one within the other. Static atmospheric pressure is fed directly to the inner chamber, or capsule, and through a metering unit to the outer chamber, which in effect forms the instrument case. The metering unit restricts the flow of air into and out of the case, whereas the flow to the inside of the capsule is unrestricted. Therefore, if the static pressure varies due to changing altitude, the pressure change in the case lags behind that in the capsule. The resultant differential pressure distorts the capsule and this movement is transmitted to the pointer by means of a mechanical linkage. A bleed valve is fitted in many VSIs to prevent damage and to improve the 30 RESTRICTED  RESTRICTED instrument’s reaction time (by reducing lag) when leveling off from a high- speed descent. 3. It is important that any given pressure difference between the inside and outside of the capsule should represent the same rate of climb or descent, regardless of the ambient atmospheric pressure and temperature variations with altitude. The function of the metering unit, in the manner in which it restricts the flow into the case, is to compensate for these changes in ambient conditions. 4. In level flight, pressure inside the capsule and the case are the same, and the pointer remains at the horizontal, zero, position. When the aircraft climbs, the static pressure decreases and the capsule collapses slightly, causing the pointer to indicate a rate of climb. The fall in pressure in the case lags behind that in the capsule until level flight is resumed and the pressures equalize. In a descent, the increase in pressure in the case lags behind the increase in static pressure in the capsule, and the capsule is expanded. Errors 5. The VVI can suffer from the following errors. (a) Pressure Error. If the static head or vent is subject to changing pressure error, the VSI may briefly indicate a wrong rate of climb or descent. (b) Instrument Error. Instrument error is the result of manufacturing tolerances and is usually insignificant. (c) Transonic Jump. Movement of a shock wave over the static vents results in a rapid change in static pressure, which briefly produces a false reading on the VSI. (d) Lag. Because of the time required for the pressure difference to develop, when an aircraft is rapidly maneuvered into a steady climb or descent there is a few seconds delay before the pointer settles at the appropriate rate of climb or descent. A similar delay in the pointer, indicating zero, occurs when the aircraft is leveled. (e) Static Line Blockage. If the static line or vent becomes blocked by ice or any other obstruction the VSI will be rendered unserviceable and the pointer will remain at zero regardless of the vertical speed. 31 RESTRICTED  RESTRICTED CHAPTER No 11 ALTIMETER Objectives The students will understand:- (a) Principle, Construction and Errors of an Altimeter. (b) Altimeter Settings ------- QNH, QFE and QNE (c) Solution of Altimeter Problems. ______________________________________________________________ 1. Purpose. The function of the altimeter is to indicate the height of the aircraft above a preset datum. 2. Principle. Pressure altimeters measure atmospheric pressure and register it against a height scale. They are, in fact Aneroid Barometers graduated to indicate against a height scale instead of a barometric scale. 3. As the aircraft climbs away from the earth’s surface, the height of the column of air above it, and therefore the weight and pressure exerted by that column, decreases. That is to say, atmospheric pressure decreases with height. Therefore if the atmospheric pressure at sea level and the rate of decrease of that pressure with height are known, knowledge of the pressure existing at any point above sea level enables the altitude above sea, level of that point to be established. In this connection, a practical approximation is that a decrease in pressure of one millibar is roughly equivalent to an increase in height of 30 feet. 32 RESTRICTED  RESTRICTED 4. Construction. The instrument consists of a thin corrugated metal capsule, which is partially evacuated, sealed, and prevented from collapsing completely by means of a leaf spring, or in some cases by its own rigidity. The capsule is mounted inside a case, which is fed with static pressure from the aircraft’s static tube or vent. As the aircraft climbs the static pressure in the case decreases allowing the spring to pull the capsule faces apart. Conversely a decrease in height compresses the capsule faces. This linear movement of the capsule face is magnified and transmitted via a system of gears and linkages to a pointer moving over a scale graduated in feet according to one of the standard atmospheres. 5. A simple altimeter will normally be calibrated according to the ICAN or ICAO atmosphere and will therefore normally be set to indicate height above the 1013.2 millibar pressure level. The dial-adjusting knob allows the indicator needle to be moved away from the normal datum. Thus, for example, the altimeter could be set on the ground to read airfield elevation so that it will thereafter indicate height above mean sea-level, providing that the prevailing sea-level pressure does not change. Alternatively by setting zero before take- off the altimeter will indicate height above the airfield, again providing that the surface pressure at the airfield remains constant. Pressure Altimeter Errors 6. Instrument and Installation Errors. Pressure altimeter errors may be considered under two categories; instrument or installation errors, and errors caused by non-standard atmospheric conditions. The errors inherent in the instrument and installation are:- (a) Instrument Error. Manufacturing tolerances causes instrument error. It is usually insignificant but if necessary a correction card can be provided. (b) Pressure Error. Pressure error occurs when true external static pressure is not accurately transmitted to the instrument. A false static pressure can be created by the effect of the airflow passing over the static vent. Although the error is generally negligible at low speeds and altitudes, it can become significant at high speeds, or when services such as flaps, airbrakes, or gear are operated. A voidance or reduction of the effect is accomplished by careful probe or vent design and location. Residual error is calibrated for each aircraft type and detailed in the Aircrew Manual or ODM, or automatically in an Air Data Computer or Pressure Error Corrector Unit (PECU). Large transient errors can be caused by shock waves passing over the vent during accelerations or decelerations. (c) Lag Error. Since the response of the capsule and linkage is not instantaneous, the altimeter needle lags whenever height is changed rapidly causing an under-read on climbs and an over-read on descents. Clearly the latter situation could be dangerous and should be 33 RESTRICTED  RESTRICTED allowed for in rapid descents. The amount of lag varies with the rate of change of height. Time lag is virtually eliminated in servo-assisted altimeters and may be reduced in others by the fitting of a vibration mechanism. (d) Hysteresis Loss. A capsule under stress has imperfect elastic properties and will settle to give a different reading after leveling from a climb compared to that obtained after leveling from a descent. (e) Blockages and Leaks. Blockages and leaks are unusual occurrences. Blockages may occur if water in the pipe work freezes, or there are obstructions such as insects. The effect is to increase altimeter lag or, with complete blockage, to make the instrument stick at the read when the blockage occurred. The effect of leaks varies with the size and location of the leak; leaks in pressurized compartments cause under-reading, while leaks in unpressurized compartments usually produce over-reading. 7. Atmospheric Errors. Variations from International standard atmosphere (ISA) conditions may be brought about by the development of weather systems, and local geographic effects. The resulting errors in ISA- calibrated altimeters are:- (a) Barometric Error. Barometric error occurs when the actual datum pressure differs from that to which the altimeter has been set and can be overcome simply by the correct setting of the millibar scale. The effect of the error on an altimeter, which is not reset when flying from an area of high pressure to one of low pressure at a constant indicated height, is illustrated through an example. An aircraft flies from an area where MSL pressure is 1010 Mbs, but 1030 Mbs is retained on the altimeter. In effect the datum is lowered during the flight so that the altimeter reads high. Conversely if the flight was from an area of low pressure to one of high pressure, the altimeter would read 34 RESTRICTED  RESTRICTED low if not corrected. In summary, from HIGH to LOW the altimeter reads HIGH, and from LOW to HIGH the altimeter reads LOW. (b) Temperature Error. Temperature error arises when the atmospheric conditions differ from those assumed by the standard atmosphere used to calibrate the altimeter. The ICAO standard atmosphere assumes a temperature lapse rate of 1.980 C per 1,000 ft up to 36,090 ft, with constant temperature of -56.50 C above that. If the actual temperatures differ from the assumed ones, as they very often do, then the indicated height will be incorrect. In a cold air mass the density is greater than in a warm air mass, the pressure levels are more closely spaced and the altimeter will over-read – the error being zero at sea-level and increasing with attitude. The error is not easy to compensate for, since in order to do so it would be necessary to have knowledge of the temperature structure from the surface to the aircraft. The magnitude of the error is approximately 4ft/1,000ft for every 1 0 C that the air generally differs from ISA. Corrections can be made for low altitudes by use of the table in the Flight Information Handbook and this may be necessary, for example, when calculating decision heights in arctic conditions. 35 RESTRICTED  RESTRICTED (c) Orographic Error (Airflow Effect). When a current of air strikes a barrier of hills, there is a marked tendency of the large portion of the air parcel to sweep around the ends of the barrier, thereby avoiding the ascent. This creates areas of low pressure to the lee side of the barrier. The altimeter readings may, therefore be affected due to barometric error (as explained above). Also the temperature profile in affected area maybe significantly different from the unaffected air mass thereby inducing temperature error effect (as discussed above). Altimeter Settings 8. QNH It is the value of pressure for a particular aerodrome and for time, which, when set on the sub-scale of an altimeter, when the aircraft is on the aerodrome, will cause the altimeter to read the exact elevation of the aerodrome (plus the height of the altimeter above the aerodrome). It is the prevailing atmospheric pressure at an airfield reduced to mean sea level in accordance with the ICAN Law. 9. QFE. It is the value of the atmospheric pressure at a particular aerodrome and time. It is not corrected to mean seal level. When QFE is set in the sub-scale of an altimeter in an aircraft on the runway, the altimeter will read zero height. 10. QNE. It is the standard pressure setting of 29.92”/1013.25 Mbs which, when set into the sub scale of the altimeter, indicates the pressure altitude. This pressure setting is set at a prescribed height. 11. Aircraft flying above an aerodrome with QNH set in the sub scale of the altimeter will experience errors in altitude measurement as the difference in the aerodrome pressure setting and the prevailing pressure at the altitudes, through which the aircraft is climbing, becomes increasingly significant. In order to overcome this problem, QNE provides a standard pressure setting for all the aircraft flying above a prescribed altitude above the aerodrome elevation. Altimeter Problems 12. Problem 1. You take off from London Heathrow where the QNH setting is standard 1013 Mbs for Manchester, which is in a low-pressure area and its QNH is 997 Mbs. The cruising altitude is 3000 ft. If you did not reset the altimeter setting enroute, then overhead Manchester with 3000 ft indicated on the altimeter, the aircraft would actually be flying at 16 x 30 ft less than 3000ft. Around Manchester on route is the Peak District of Derbyshire 36 RESTRICTED  RESTRICTED covered today in cloud some peaks are at 2800, AMSL. You can now appreciate how dangerous this is. Your altimeter would show you at 3000ft. You would be at 2520 ft with a hill in cloud at 2800ft in front of you. 13. Problem 2. An aircraft sets course for Sargodha over Risalpur at 5500 ft. Altimeter is set to 1015 Mbs (QNH). What height will be read in the altimeter, on landing at Sargodha if the elevation of Sargodha airfield is 600 ft. and QNH at Sargodha is 1010 Mbs and not set in the altimeter? (b) What pressure setting will you set in the altimeter to make the altimeter read 600 ft. on landing at Sargodha? (c) What will be the QFE at Sargodha? 14. Problem 3. An aircraft sets course over point ‘A’ at a height of 7500 ft. indicated in the altimeter. QNH at ‘A’ is 1015 Mbs, which is set in the altimeter. The aircraft is to over-fly a hill whose height is 7000 ft. and the QNH at the hill is 1000 Mbs. (a) Will the aircraft clear the mountain? (b) If the QNH at the hill reduces to 990 Mbs, will the aircraft still clear the hill? 37 RESTRICTED  RESTRICTED PART 1 : NAVIGATION FIRST SEMESTER SECTION 3 :NAV COMPUTER MB-9 Chapter 12 Navigation Computer MB-9  Time, Speed and Distance Problems.  Inter - conversion of Distance Units.  Multiplication and Division Problems.  Fuel Consumption Problems.  True Airspeed and Mach No. Problems  Altitude Problems.  Wind, Heading, Drift and Ground Speed Problems 38 RESTRICTED RESTRICTED 39 RESTRICTED  RESTRICTED CHAPTER No 12 NAVIGATION COMPUTER MB-9 Objectives The students will understand and practice the solution of the following on the manual navigation computer MB-9:- (a) Time, Speed and Distance Problems. (b) Inter - conversion of Distance Units. (c) Multiplication and Division Problems. (d) Fuel Consumption Problems. (e) True Airspeed and Mach No. Problems (f) Altitude Problems. (g) Wind, Heading, Drift and Ground Speed Problems _____________________________________________________________________________________________ Introduction 1. All manual navigation computers are based on the principle of a slide rule (logarithmic scale). The Slide part is used to compute time, speed and distance problems; fuel consumption; finding true airspeed; finding true altitude; multiplication, division and proportion problems of all types. Additional scales are used to compute Density Altitude, True Airspeed from Mach No and vice versa, and to solve wind correction factors. 2. Two circular scales are identically calibrated in logarithmic progression with the INNER SCALE having an additional overlay calibration in “hours” to simplify computations of over 60 min. The stationary OUTER SCALE is called “Miles Scale”. The miles scale is also used to determine TAS, Distance 40 RESTRICTED  RESTRICTED conversions, and Fuel consumption. The inner scale is also called the “Minute” scale. It is also used for other computations. 3. Each scale has a reference mark. The “10” in rectangular black box is called the “Index”. The inner rotating scale has an arrowhead at 60 minutes or 1-hour point. This reference point is used in conjunction with time and called, “Speed Index” or “Rate Arrow”. Time, Distance and Speed Problems 4. Most calculations for time, speed, and distance are set up on manual navigation computer as proportions. Figures on outer (miles) scale and inner (minutes) scale are considered as the lower and upper parts of a simple proportion. Known values are selected on the computer and unknown values are automatically given by the computer scale. 5. Time Problems. A plane traveled 80 NMs in 14 min. How many minutes are required to fly 120 NMs? 80 : 14 : 120 or 80 = 120 14 ? 6. In the latter form the problem maybe set on computer exactly as it appears. Place 80 on the outer “Miles Scale” opposite the inner “Minutes Scale”. Opposite 120 on the outer scale, read the answer 21 on the inner scale. Note that the “Arrow Head” or “Rate Arrow” indicates the speed of a/c (343). This is the basis of all time – distance computations. 7. Distance Problems (a) Given:- Speed 350 Kts; Dist:- 280 NMs; Time to fly ??? (b) Solution :- Place the Rate Arrow on the inner scale opposite the ground speed of 350 kts on the outer scale. Opposite the distance of 280 NMs on the outer scale, read the time on the inner scale (48 minutes). 8. Speed Problems (a) Given :- Dist:- 266 NMs; Time to fly:- 1:25; Speed ??? Kts; (b) Solution :- Place time (1:25) on the inner scale opposite the distance (266) on the outer scale. Opposite the Rate Arrow, read the ground speed (188 kts). 9. Conversion of Distance Units. Use Arrow heads. Multiplication and Division Problems 10. The “10” index is used instead of Rate Arrow. The calculations are approximate. However, care must be exercised in placing the decimal point correctly. A common sense mental check of the problem prevents errors. (a) Given:- Multiply 14 X 46 41 RESTRICTED  RESTRICTED (b) Solution:- Place the “10” index on the inner scale opposite either of the two numbers to be multiplied (46). Opposite, the other number to be multiplied (14), on the inner scale, read the product (644) on the outer scale. 11. Fuel Consumption Problems. The solution is same as Time/Speed Problems. The Outer Scale is now used for fuel quantity units instead of miles. The Rate Arrow indicates rate of fuel consumption instead of speed. (a) Given:- Fuel Consumed : 140 gal; Time:- 40 min; Fuel Flow ? (b) Solution:- Place time flown (40 min) on the inner scale against fuel consumed (140 gal) on the outer scale. Opposite the Rate Arrow, read fuel flow in gph on outer scale (210 gph). 12. Amount of Fuel Required (a) Given:- Fuel Flow : 320 gph; Time:- 40 min; Fuel Consumed ? (b) Solution:- Place the Rate Arrow opposite the fuel flow (320 gph) on the outer scale. Opposite the time (7:30) on the inner scale, read total fuel required for the flight on the outer scale (2400 gph). 13. Hours of Fuel Available (Endurance) (a) Given:- Fuel Flow : 185 gph; Fuel Available : 400 gal; Time:- ? (b) Solution:- Place the rate arrow opposite fuel flow (185 gph) on the outer scale. (c) Opposite the amount of fuel available (400 gal) on the outer scale, read the remaining flight time available (2:08) on the inner scale. True Airspeed Problems Indicated Air Speed Pressure & Inst Error Correction Calibrated Airspeed Compressibility Error Correction Equivalent Airspeed Density Error Correction True Airspeed 14. When solving for TAS, set the “10” index on the outer and inner scales opposite each other. The scale of the computer is now visible in the window marked, “For DEN. ALT. AND T.A.S. COMP.”. 42 RESTRICTED  RESTRICTED (a) Given Press Alt: 10,000’; Free Air Temp: -5ºC; EAS: 250 kts TAS? (b) Solution :- Set the Free Air Temp (-5ºC) opposite Pressure Altitude (10,000’) in the window marked, “For DEN. ALT. AND T.A.S. COMP.”. Opposite the EAS (250 kts), on inner scale, read the TAS (292 kts) on the outer scale. Conversion of TAS to Mach No and Vice Versa 15. TAS can be converted to Mach No and vice versa by using Mach No Index and Free Air Temperature of Standard Atmospheric Altitude. The Mach No Index appears to the right of Pressure Altitude Scale in Pressure Altitude Window. (a) Given :- True Free Air Temp: -50º C; Mach No : 0.80; TAS ? (b) Solution :- Set Mach No Index opposite true free air temperature (-50º C). Opposite the Mach No. on the minutes scale, read the TAS in kts on the miles scale (465.3 kts). Altitude Problems 16. Indicated Altitude. Altitude read from the altimeter with the correct altimeter setting. 17. Calibrated Altitude. Indicated Altitude corrected for instrument error. 18. Pressure Altitude. Calibrated Altitude corrected for variations in pressure conditions. This is the height above the standard datum (the theoretical point where pressure is 29.92” Hg and temp. +15ºC). 19. Density Altitude. Pressure Altitude corrected for temperature variations. 20. Problem. Altimeter gives correct altitude under standard conditions, which seldom exist. Corrections can be on the navigation computer. (a) Given: Press Alt: 20000’; Indicated Altitude: 18,500’; Free Air Temp: -10ºC; True Altitude??? (b) Solution :- In the “For Altitude Computations” window, place the free air temp (-10ºC) opposite Flight Level Press Altitude (20,000’). Opposite the calibrated or indicated altitude (18,500’) on the inner scale, read the True Altitude on the outer scale (19,600’). Calculation of Drift, Heading and Ground Speed 21. In order to determine drift and ground speed, the Relative Wind Angle (RWA) must be determined by using the “Compass Rose” (stationary) scale and the “Relative Wind” scale. A visual presentation of the wind is given on the computer by considering the course index to be the nose of the aircraft. Thus the wind is from the rear and right. 43 RESTRICTED  RESTRICTED (a) Given. Course 040º; Wind Direction 160º. Find RWA. (b) Solution. Set the Course Index against the desired course (040º) on the “compass rose. Opposite the wind direction (160º), on the compass rose, read the RWA on the relative wind scale (60º). Drift and Ground Speed 22. Determine the RWA. Place the cursor over TAS on the “Miles Scale”. Rotate center disc until RWA is read under the cursor on the “Wind Scale”. Opposite Wind Velocity on “Miles Scale”, read drift angle on “Wind Scale”. It maybe convenient to use the Cursor for proper alignment. 23. Re-align the cursor with TAS on “Miles Scale”. If the RWA indicates a tail wind component, the drift angle is added to the preset RWA to determine the ground speed and vice versa for a head wind component. 24. This is accomplished by holding the concentric disc in place and moving the cursor index so as to read the sum (for tail wind) or the difference (for head wind) of the relative wind and drift angles. 25. Example 1. TAS 500 kts; Course:050º (T) Wind Velocity: 070º/160 kts. Find RWA, Drift, Heading and Ground Speed. 26. Solution. Set “Course Index” of relative rose to the desired Course, 050º(T) on the compass rose. Opposite wind direction (070º), on the compass rose, read RWA on the relative wind scale (20º). Note that the wind will provide a head wind component and a drift angle to the left (port). (a) Preset the cursor to TAS (500 kts) on “Miles Scale”. (b) Rotate the inner disc to align RWA (20º) on the “Wind Scale”, with the preset cursor. (c) Opposite the wind velocity (160) on the “Miles Scale”, read the drift angle (6.3º) on the “Wind Scale”. (d) As the wind has a head wind component, 6.3º must be subtracted from RWA for the ground speed solution. 20º – 6.3º = 13.7º. (e) Holding the center disc stationary, move the cursor counter clockwise (CCW) by the amount of drift angle (6.3º) or to 13.7º on the ”Wind Scale”. (f) Read Ground Speed (347 kts) on the “Miles Scale”. (g) Since drift is left (port), the drift component will be added to the true course of the aircraft. 050º + 6.3º = 056.3º(T). Note If sum of relative wind and drift angle exceeds 90º, subtract the total angle in excess of 90º, from 90º and read appropriate ground 44 speed at final cursor setting. For example: If drift angle RESTRICTED = 9º and RWA = 85º, the total angle = 94º. Therefore ground speed is read with final cursor setting at 90º - 4º = 86º. RESTRICTED 45 RESTRICTED RESTRICTED 46 RESTRICTED  RESTRICTED PART 1 : NAVIGATION FIRST SEMESTER SECTION 4 :MAP PROJECTIONS & THEIR USES Chapter 13 : Map Projections  Maps & Charts o Graticule, Map Scale, Map Construction Stages o Ideal Map Properties, Scale Factor, Perspective, Conformal Projections  Types of Projections o Conical, Cylindrical and Azimuthal o Properties of IMP (Million Map) o Scale of Charts used in the PAF (TPC, ONC, JNC, ¼ Inch Map) Chapter 14 : Map Reading  Relief and its Representation on the Surface of the Earth  Scale Representation (3 Methods), Relative Values of Ground Features on Map  Map Reading technique for Day, Night & Poor Visibility Flights  Map Reading technique for High Level, Low Level Flights Chapter 15 : Douglas Protractor  Introduction, Use and Practice of Bearing Measurement through Douglas Protractor 47 RESTRICTED RESTRICTED 48 RESTRICTED  RESTRICTED CHAPTER No 13 MAP PROJECTIONS Objectives The students will be familiarized with:- (a) Map Projections, Graticule (b) Properties of an Ideal Map (c) Stages in Map Construction (d) Perspective and Non Perspective Projections (e) Classifications of the Map Projections (i) Conformal / Orthomorphic Projection (f) Types of Projections – Conical, Cylindrical and Azimuthal (g) Introduction to Lambert’s Conformal, IMP,(PAF Chart) & JNCs. _____________________________________________________________________________________________ Introduction 1. Earth is an irregularly shaped solid figure whose surface is largely water, out of which the various land masses rise. A map or chart is a representation of this surface at some convenient size on a flat sheet; the term map is generally taken to be a representation of land areas while chart is traditionally reserved for sea area representation. An aviator is not always concerned with this distinction and the air charts cover both. Other terms used are plan, to describe a bird’s eye view of a small area, and graphic, to describe maps which vividly portray topography. 2. Graticule. The network of parallels of latitude and longitudes (meridians) on a flat sheet of paper meant to prepare a projection is called graticule. 3. Map Projection. A map projection is a systematic laying down of the meridians and parallels onto a flat sheet in such a way that the picture displays certain of the features of the actual surface. They can be drawn in any way, but obviously we choose a particular method, which is useful to us. 4. Classification of Projections. Map Projections can be broadly categorized into two basic types, depending upon the method of projection:- (a) Perspective Projections. These projections are the actual projections of the graticule of the reduced earth onto a developable surface. They are simple drawings of the shadows, which would be cast by the meridians, and parallels on a transparent model earth onto a plane surface. (b) Non – Perspective Projections. When the relationship is such that simple geometric construction is impossible, the projection is designated Non – Perspective. The majority of projections are non- perspective, but every non – perspective projection can be thought of as a perspective projection, which has been adjusted in some way. 49 RESTRICTED  RESTRICTED Perspective Projection Scale of Topographical Maps 5. The scale of a map is the ratio between a given length on the map and the actual distance this length represents on the earth’s surface. Scale = Map Length Earth Distance Scale Factor 6. In map projections, a reduced earth model (globe for example) is used as the basis of a given projection; somewhere on each projection a point or line will exist with the same scale as the reduced earth model. This is the scale usually printed on maps and charts. Scale at other points is determined with the aid of a ratio known as scale Factor. Scale Factor is defined as :- Scale Factor = Chart Length Reduced Earth Length Scale Deviation 7. The stated scale of a chart is usually the reduced earth scale, hence at a point where stated scale is correct, Scale Factor = 1. At other places the Scale Factor will be other than unity; it may be more if the scale has expanded, or less if there has been compression. The difference between Scale Factor and unity describes the Scale Deviation or error. Scale Deviation = Scale Factor – 1 8. Properties of an Ideal Map. A perfect map is the one, which reproduces the earth’s entire surface onto a flat sheet of paper without distortion, and will thereafter have the following properties: - (a) Scale is constant and correct. (b) Shapes are correct. (c) Areas are correct. (d) Bearings are correct. (e) Great circle is a straight line. (f) Rhumb line is a straight line. 50 RESTRICTED  RESTRICTED (g) Adjacent sheets fit together perfectly. (h) World wide coverage. 9. A spherical surface cannot be made into a flat surface without some kind of distortion. Therefore it is impossible to have an ideal map on a flat surface. The best that can be done is to incorporate only those properties, which will fulfill the purpose for which, a particular map or chart in prepared. 10. Design Parameters of Map Projections. Map projections are constructed with one or two basic requirements in mind. No compromise is made on these requirements, however, other lesser important requirements maybe ignored or achieved partially. (a) Conformal / Orthomorphic Projection. Conformality means correct representation of angles i.e., angles between intersecting curves on the Earth will be preserved on the chart. For a map to be conformal, parallels and meridians must intersect at right angles. Additionally, scale or scale expansion must be same along the meridian as it is along the parallel. Scale on a conformal map will vary from point to point, but provided, it is the same in all directions at any point, the requirement is met. If a projection has parallels and meridians intersecting at right angles, and the scale at any given point is the same in all directions, even though it varies from point to point, the projection is then called Orthomorphic. 11. Stages in Map Construction (a) The spherical Earth is presumed mathematically to be a perfect sphere. (b) This sphere is then reduced to a chosen scale, reduced earth. (c) The graticule (the network of meridians and parallels) is drawn by some geometrical or mathematical method on to a flat surface. (d) The positions of the earth’s features, etc, are determined by accurate survey, and drawn on the map, using graticule as a reference. Types of Projections 12. Conical Projections. A cone is placed tangential to the parallel, which is named as the standard parallel. The point of projection is at the centre of reduced earth. This projection is known as simple conic projection. Conical Projection 51 RESTRICTED  RESTRICTED 13. Constant of the Cone. When the cone is developed the angle at the centre of the sector, x, represents 360o of longitude. The ratio is known the constant of the cone (or cone constant) and is denoted by n. 14. Properties of Conical Projections (a) The scale is correct along all the parallels. (b) The scale is also correct along the central meridian. (c) Meridians (except the central meridian) are smooth curves. (d) Sheets fit N-S but not E-W. Maps / Charts Commonly Used in the PAF 15. The majority of the maps and charts commonly used in the PAF are based on the Conical Projection. It is, therefore, imperative that the following conical projections be understood for selecting the right kind of map / chart relative to a particular mission / sortie. Lambert’s Conformal 52 RESTRICTED  RESTRICTED 16. Lambert’s Conformal Conic Projection. Lambert’s Conformal Conic is a non-perspective projection with two standard parallels. It is obtained by simply declaring the scale of the projection to be correct i.e., equal to reduced earth scale, along two parallels. These two parallels will be approximately equally spaced about the original standard. Scale factor is at a minimum at the original parallel, which is about the mean of the two standard parallels. The projection is not conformal at the poles and scale factor is very large near the poles. Sheets will join only if they are based on the same standard parallels and are at the same scale. 17. Global Navigation Chart (GNC). The Global Navigation Chart (GNC) is based, in lower and middle latitudes, on the Lambert’s Conformal projections. The scale is 1:5,000,0000. They are used for general planning purposes on a global scale. The actual conduct of the missions is mostly accomplished in the PAF with the help of various other conical projections. 18. Jet Navigation Chart (JNC). The Jet Navigation Chart (JNC), scale 1:2,000,000, series of topographical charts comprises 122 charts, providing worldwide coverage to satisfy en-route navigation requirements of aircraft, capable of high speed, high altitude and long range performance. They are basically sections cut from the 1:5,000,000 GNC series, expanded to a scale of 1:2,000,000. The design characteristics of the JNC’s satisfy radar navigation/bombing by strategic aircraft, celestial and visual navigation, pre- flight mission planning, operational planning and intelligence briefings. 19. Operational Navigation Chart (ONC). The Operational Navigation Chart (ONC), scale 1:1,000,000, is designed to satisfy enroute visual and radar requirements of pilots/navigators flying at medium altitudes (2,000 – 25,000 feet above ground level) and low altitude (500 – 2,000 feet above ground level) or low altitude-high speed operations. 20. Tactical Pilotage Chart. The Tactical Pilotage Chart (TPC), scale 1:500,000, is designed to provide an intermediate scale translation of cultural and terrain features for pilots / navigators flying at very low altitudes through medium altitudes or low altitude-high speed operations. Complete coverage of Pakistan territory and its neighbours is available. 21. International Modified Polyconic Projection. A non-perspective conical projection that is neither conformal nor equal area. In this projection all parallels are standard. This is achieved by putting a series of cones at successive parallels of latitudes. The arrangement resembles the picture of a person wearing various hats of different sizes. All meridians are straight, and there are two meridians that are made true to scale. 53 RESTRICTED  RESTRICTED (a) Distortion. Adjacent map sheets fit exactly together not only North to South but also East to West. (b) Usage. It is used as the basis for the 1:1,000,000-scale International Map of the World (IMW) Series. It is used extensively in the PAF as the standard sheet for map reading in training and routine flights. It is also termed in the PAF as the PAF Chart. Cylindrical Projections 22. Cylindrical projections are those in which the apex angle of the cone is zero; the cone becomes a cylinder tangential to the reduced earth along a great circle and the meridians and parallels are projected onto it. When developed, the great circle of tangency is shown as a straight line. The poles of the projection, those points removed 90o from the great circle of tangency, cannot be shown on most projections of this type. 23. When the great circle of tangency is along the equator, the projection is known as Normal Cylindrical; when it is other than the equator, it is named as a Skew Cylindrical Projection. Mercator’s Projection 24. Types of Cylindrical Projections 54 RESTRICTED  RESTRICTED (a) Geometric Cylindrical Projection (b) Equidistant Cylindrical Projection (c) Mercator’s Cylindrical Projection Azimuthal Projection 25. Another limiting case of the conic projection is the Azimuthal (or Zenithal) projection. Unless otherwise specified, the earth is treated as a sphere for simplicity. In this case the apex angle of the cone is 180 o, i.e. the projection is one to a plane tangential at a point to the reduced earth. All projections of this type have the property that bearings from point of tangency are correctly represented. Three types of Azimuthal projections are :- (a) The Gnomonic Projection. This is a perspective non- conformal projection which great circles are straight lines. (b) The Stereographic Projection. This projection is conformal and perspective. (c) The Azimuthal Equidistant. This is a non-conformal, non- perspective projection on which distances from the point of tangency are represented at a constant scale. 26. Summary of Map Projection Selection. Three traditional rules for choosing a map projection are: - (a) For low-latitude areas (12N - 12S) – Cylindrical (Mercator). (b) For middle-latitude areas (12N/S - 74N/S) - Conicals. (c) For Polar Regions (74N/S - 90N/S) - Azimuthal (Polar Stereographic). 55 RESTRICTED RESTRICTED 56 RESTRICTED  RESTRICTED CHAPTER No 14 MAP READING Objectives The students will understand:- (a) Relief on the earth’s surface. (b) Scale and its Representation. (c) Conventional signs on the IMP and Lambert’s Conformal. (d) Relative values of ground features on the map. (e) Map Reading Techniques. _____________________________________________________________________________________________ 1. Relief. The height of the ground over which the aircraft has to fly is of vital importance to the aircrew because high ground can be both a feature from which position may be established and a dangerous barrier to flight. Information as to the height of the ground is indicated on the map in the following way:- (a) Contours and Form Lines (b) Spot Heights (c) Layer Tinting (d) Hachuring (e) Hill Shading 57 RESTRICTED  RESTRICTED 2. Contours and Form Lines. Contours are lines drawn on maps, joining places of equal elevation. Where there has been no accurate survey and the contours have therefore, only approximate values, they are called “Form Lines”, and are usually shown as broken (dashed) lines. 3. The interval of height between successive contour lines is known as the vertical interval. The horizontal distance between successive contours is known as the horizontal equivalent. The height interval between adjacent contours may be standardized for a particular map series, but are not necessarily constant. The height interval between adjacent contours is dependent upon :- (a) The range of elevations depicted on the individual map sheet. (b) The scale of the map sheet. 4. Small changes of ground elevation in a plane area may produce a significant hill feature, and supplementary contours at smaller intervals may therefore be introduced. It is evident that for a given vertical interval, the smaller the horizontal equivalent (and therefore the closer the contours), the steeper is the average slope. The elevation level of each contour is stated wherever practicable at some point along its length. 5. Spot Elevations. The highest point on a hill is not distinguishable from the surrounding contours in the plan view. This difficulty is overcome by stating in figures the elevation of highest spot in the locality. These figures are called the spot elevations. Spot elevations are also used to indicate the height of airfields above sea level. Spot elevation may also be expressed in meters. 6. Layer Tinting. The height of landmarks is of vital importance. Contours are, therefore, often emphasized by tinting the area between each pair of adjacent contours. Shades of color chosen for this purpose, become deeper with increase of height. This system, known as Layer Tinting, enables an aviator to form a mental picture of a hilly or mountainous area at a glance...1943 2149 58 RESTRICTED Hachures  RESTRICTED 7. Hachures. Hachures are short tapered lines drawn on map, radiating from peaks and high grounds. They are used on topographical maps of incompletely surveyed areas and also used extensively on plotting charts, where contours are not marked to utilize the maximum space of the chart for plotting purposes. Spot elevations are usually associated with hachuring. 8. Hill Shading. Hill shading is the simulation of the shadows that would be produced if the high ground were actually standing out I relief on the map, and a light were shining across the map surface. The effect is to give an appearance of depth to the map – usually more effective when the map is viewed from a distance. Relative Values of Features 9. Knowing the amount of detail to be expected on maps of different scales and the conventional sings, the map reader is in a position to appreciate the relative values of features as seen on the ground. The following will help to indicate the type of features, which are of value to the map-reader. (a) Coast Lines. Coast lines are most valuable by day and stretch of coast in an area merely by its appearance, a satisfactory degree of certainty can often be obtained by taking a bearing of the general direction. (b) Water Features. Water features show up well by day and night. Rivers, canals and lakes are the main water features in order of importance. The season of the year must be taken into account. (c) Mountains and Hills. As an aircraft’s height above the ground increases, the countryside below appears to flatten out. Very high mountains frequently protrude above low-lying clouds and provide landmarks when all other features are obscured. In the case of low- level map reading even small hills assume great importance and help in fixing position. (d) Towns and Villages. Built up areas when used in conjunction with other features such as rivers, roads and railways are easily identified and help in fixing the position. (e) Railways. In countries with few railways, a railways line is a feature of absolute value. (f) Roads. As with railways, the value of roads depends upon the extent to which the area has been developed. (g) Woods. Woods make good landmarks, being clearly marked on maps, usually depicted by green areas representing their shape and size. Representation of Scale 59 RESTRICTED  RESTRICTED 10. Scale may be indicated on a map in one of three ways:- (a) Plain Statement. Scale may be indicated by a statement in words e.g. ¼ inch to a mile. This statement indicates that one mile on the earth is represented by ¼ inch on the map. (b) Representative Fraction. A representative fraction e.g., 1 : 500,000 indicates that the ratio of the map length to the corresponding earth distance is 1:500,000. (c) Graduated Scale. On most topographical maps a scale is constructed for the particular sheet in the margin. The distances are usually expressed in statute miles, nautical miles and kilometers. Conventional Signs 11. The details on topographical maps are shown by symbols of conventional signs. Some of these, e.g. roads and railways are pictorial in nature whilst other, e.g. obstructions and golf courses are purely symbolic. In either case it is of utmost importance that map-readers should be able to recognize the symbols and consult the map legend for clarity. 60 RESTRICTED  RESTRICTED 12. Map Reading. Skill and efficiency in map reading varies according to one’s natural aptitude and the amount of hard work an aviator puts into it. Various techniques may be employed for map reading in different conditions. Map Reading by Day 13. Orientation. The first action in map reading is to orientate the map by aligning the track drawn on the map with the approximate track over the ground. The aviator shall then by able to easily correlate what he sees on the map to what he sees on the ground. 14. Position Fixing by Map Reading.