空中领航学(E-01).ppt

1、,空中领航学,Air Navigation,课件制作 课程讲授,王惠民,北京航空航天大学,飞 行 学 院,Flight, or air navigation is the means by which pilots reach their destination and find their exact location at any time.,空中领航学是引领飞机航行的一门应用学科，它以地球作为参照系来研究飞机相对于地球的运动及其导航方法。,空中领航学所要解决的三大基本问题，是确定： 飞机位置 飞机航向 飞行时间,空中领航学研究的主要内容： 领航基础及元素； 领航原理和方法； 领航设备工作

2、原理和使用； 领航误差及修正原理； 领航准备和实施。,学 科 交 叉,师 生 互 动,本课件 (共九章) 系根据西澳教材An Aviation Theory Centre Manual - Meteorology and Navigation ， 即 The Pilots Manual 系列丛书第二册制作，仅供课堂教学使用。特此申明，谨向该书编者致谢。,Chapter 1 Fundamentals of Air Navigation,Basic Principles,The basic principles of air navigation apply to all aircraft, fr

3、om the simplest trainers to the most sophisticated passenger jets. When flying cross-country, you are the pilot, the navigator and the radio operator.,你既是驾驶员, 也是领航员， 又是无线电通信员。,Basic Principles,As a pilot, you must aviate, navigate and communicate.,Types of Navigation,The basic method of navigation i

4、n VFR (day) operations is map reading, which is visual-contact navigation. It requires more or less continuous visual reference to the ground and is therefore of limited value in poor visibility conditions or when navigating above extensive cloud cover.,Types of Navigation,The basic method of naviga

5、tion in VFR (day) operations is map reading, which is visual-contact navigation. It requires more or less continuous visual reference to the ground and is therefore of limited value in poor visibility conditions or when navigating above extensive cloud cover.,Types of Navigation,To assist us with ou

6、r visual navigation procedures, we can use any radio navigation equipment installed in our aeroplane to obtain information from ground-based radio beacons.,To support visual navigation procedures, we use dead reckoning (DR) to deduce our position.,To assist us with our visual navigation procedures,

7、we can use any radio navigation equipment installed in our aeroplane to obtain information from ground-based radio beacons.,To support visual navigation procedures, we use dead reckoning (DR) to deduce our position.,Form of the Earth,All air navigation is done with reference to the surface of the ea

8、rth.,For practical purpose the earth can be treated as a perfect sphere with an average diameter of R = 6 371.004 km.,Shape and Size,地球半径：,R,Rotation of the Earth,Polar axis,True south,True north,The earth rotates toward the east.,极 轴,6633,Imaginary Lines on the Earths Surface,Great Circles 大圆,A gre

9、at circle (GC) drawn on the earths surface has a plane which passes through the centre of the sphere (earth). 大圆以地球的球心为其圆心。,经 线,赤 道,无,线,电,信,号,Great circle,Small circle,大圆具有如下特点： 大圆是在球体表面上所能画出的最大的圆； 在球体表面两点之间的最短距离是大圆的弧； 除了像地球的地理两极（径向相反）的两点以 外，在球体表面上两点之间只能画出一个大圆。,Small Circles 小圆,A small circle is any

10、 circle on the surface of a sphere that is not a great circle; that is, the centre of a small circle is not at the centre of the earth. 在地球表面上除大圆以外的圆，其圆心不是球心。,The plane of a small circle does not pass through the centre of a sphere. 小圆平面不通过球心。,球心,圆心,Latitude 纬度,南极,北极,赤道,Latitude,纬 度,Longitude 经度,南极,

11、北极,本初子午线,( 0经线 ),英国伦敦格林威治,皇家天文台,Longitude,经 度,Position on the Earth,The usual method of specifying the exact position of any point on earth is by reference to imaginary lines of forming the latitude and longitude grid on the surface of the earth. 参照地球表面的纬度和经度网格, 可为地球上任何一点精确定位。,例如: 北京 3957N, 11628E,T

12、he more commonly methods to pass position information by radio include the following: Stating a position as over(过) or abeam(切) a landmark or a navigation aid; and Stating the distance(距离) and bearing(方位) of an aircraft from a landmark or a navigation aid.,Alternative methods for specifying aircraft

13、 position.,Direction,Direction is the angular position of one point to another without reference to the distance between them. To measure direction, the full circle is divided into 360.,It is usual to refer to direction as a three-figure group to prevent any misunderstanding.,Beechcraft BE-55,Piper

14、P28A,Cessna C150,The most fundamental reference from which angles are measured is that of true north, from 000T through 090T, 180T, 270T to 360T.,NM, A great circle crosses successive meridians at a gradually changing angle. A rhumb line crosses all meridians longitude at the same angle.,In practica

15、l terms, the great-circle direction and the rhumb-line direction may be considered to be the same over short distances, say less than 200 nm.,True Direction,When we measure direction by reference to the local meridian, we are using the north geographic pole or true north as the reference. This direc

16、tion is referred to as true direction.,Direction is measured from a meridian.,Magnetic Direction,The actual direction shown by a freely suspended magnet is called magnetic north, and this is the datum we use to measure magnetic direction.,The earths magnetic field.,Variation 磁差,Variation is the angu

17、lar difference between true north and magnetic north. Variation east, magnetic least; variation west, magnetic best.,地 球 磁 场,磁 差,Isogonals and the agonic line.,Airport PERTH JANDAKOT 32551S 1155252E Mag Var: 1.483W,U.S.A.,Australia,Relative Bearings 相对方位角,The relative bearing of an object from an ae

18、roplane is its angular distance from the aircrafts heading measured clockwise from the nose of the aeroplane from 000REL through to 360REL.,RB = 035,Conversions 换算,A Relative Bearing A Magnetic Bearing,Aircraft magnetic heading,+,Relative bearing of object from aircraft,=,Magnetic bearing of object

19、from aircraft,飞机航向角+相对方位角=磁方位角,NM,Aircraft magnetic heading,Relative bearing of object from aircraft,Distance,For navigation purposes, the unit of measurement of horizontal distance is the nautical mile (nm). For other aviation uses, such as visibility, horizontal distance from cloud and runway leng

20、ths, the unit is either the kilometer or meter.,Units of Measurement,The Nautical Mile 海里,The nautical mile has its origin in its relationship to the size of the earth, where 1 min of latitude is equal to 1nm.,1 nm = 1, 852 m,A nautical mile is absolutely not an Imperial measurement, although many t

21、hink it is.,10 nm,10 min,Speed,Airspeed and Groundspeed,Because of the effect of the wind, the speed of an aeroplane can be expressed in two ways: It is measured in relation to the ground, ground speed. It is measured relative to the air mass through which it is moving, airspeed.,The effect of the w

22、ind on the speed of an aeroplane.,BAS（基本表速） - shown by ASI IAS （指示空速） CAS （校正空速） EAS （当量空速） TAS （真空速） - actual speed through the air,空速表机械误差修正,空气动力误差修正,空气压缩性修正,空气密度修正,Airspeed Indicator,True Airspeed (TAS),For navigation purposes we need to know our true airspeed (TAS) or actual speed through the ai

23、r.,TAS =,CAS,/ 0,Where, / 0 is the air density ratio.,/ 0,For the same IAS, warmer air increases TAS.,For the same TAS, the aircraft in less dense air has lower IAS.,TAS 80 kt,IAS 80 kt,TAS 93 kt,IAS 80 kt,Movement in an Air Mass,Velocity,The velocity is a rate of change of position in a given direc

24、tion and is therefore a combination of both speed and direction.,Movement in an Air Mass,Velocity,Wind Velocity 风速向量,The wind velocity is nearly always expressed as a five- or six-figure group; the first three figures are the direction from which the wind blows, and the last two or three indicate th

25、e speed of the wind.,Ground Velocity 地速向量,The result due to the wind velocity effect is that the aeroplane has another velocity in addition to that described by its heading and TAS, and this is the ground velocity, or its track and groundspeed.,TR/GS vectors.,Vector Addition 向量加法,The Triangle of Vel

26、ocities 航行速度三角形,HDG/TAS + W/V = TR/GS,航向 /真速 + 风向量 = 航迹 /地速,W/V,TR/GS,HDG/TAS,The Triangle of Velocities 航行速度三角形,HDG/TAS + W/V = TR/GS,The wind side of a typical navigation computer.,Altimetry (Vertical Navigation),Vertical Measurement,Altitude (高度) is the vertical distance of a level, a point, or a

27、n object considered as a point, measured from mean sea level (MSL).,Flight Level (高度层) is a surface of constant atmospheric pressure that is related to a specified pressure datum, 1, 013.2 hPa, and is separated from other such surfaces by specified pressure intervals.,Height (高) is the vertical dist

28、ance of a level, a point, or an object considered as a point, measured from a specified datum.,A pressure altimeter calibrated in accordance with the International Standard Atmosphere has the following properties:,When set to a QNH altimeter setting, it will indicate altitude;,When set to a pressure

29、 of 1,013.2 hPa, it may be used to indicate flight level.,Note. QFE settings are not used in Australia.,Altimeter Settings,When set to a QFE altimeter setting, it will indicate height above the QFE reference datum;,The actual MSL pressure at any one place is called QNH, and an altimeter set to QNH (

30、with the altimeter subscale set to the actual MSL) will indicate altitude.,QNH Setting,QNH Setting,Variations in Mean Sea Level Pressure,The actual MSL pressure differs most of the time from that under ISA conditions,and it also varies from day to day, and even from hour to hour, as the various pres

31、sure systems move across the country.,The charts we use for navigation show the height above mean sea level of all high ground and obstacles. Therefore, with the altimeter set to QNH, we will have an immediate indication of our vertical separation from the ground beneath us (terrain clearance).,Effe

32、ct of Variation in the MSL Pressure,Plan and profile views of synoptic situation.,The constant variation of MSL pressure has the potential to cause two significant operational problems.,If corrections are not made to the QNH setting the following will occur: Terrain Clearance（离地高度） when flying from

33、high pressure to low pressure, the altimeter will over-read. when flying from low pressure to high pressure, the altimeter will under-read.,From high to low, beware below.,从高(压区)飞往低(压区) ， 当心高度低。,Traffic Separation（空中交通间隔）,Safe traffic separation requires all aircraft in the same vicinity to use the

34、same QNH altimeter setting.,Area QNH,To ensure a proper vertical separation , all aircraft operating in the same general vicinity must use the same altimeter subscale setting, the area QNH. Area QNH settings are used by all aircraft operating at or below 10,000 ft AMSL (transition altitude). The are

35、a QNH is a forecast value that is valid for a period of 3 hr and normally applies throughout an area QNH zone. Before flight, the area QNH will be available through the AVFAX system. In flight, the area QNH will be available from ATS.,Accuracy of Area QNH Setting,Area QNH values are required to be a

36、ccurate to within 5 hPa of the actual QNH at any low-level point (below 10,000 ft AMSL) within, or on, the boundary of their respective AQZs during the period of validity of the forecast. The indicated altitude will be within 150 ft of the actual altitude anywhere in the associated AQZ.,Accuracy of

37、Area QNH Setting,Area QNH values are required to be accurate to within 5 hPa of the actual QNH at any low-level point (below 10,000 ft AMSL) within, or on, the boundary of their respective AQZs during the period of validity of the forecast. The indicated altitude will be within 150 ft of the actual

38、altitude anywhere in the associated AQZ.,Flight Levels,Above 10,000 ft (the transition altitude) we select the standard MSL pressure of 1,013 hPa, and with the altimeter set to this, we fly at flight levels.,Cruising Flight Levels,Cruising Altitudes,Pressure Height (Pressure Altitude),There are two

39、methods of determining pressure altitude: we can set 1,013 hPa on the altimeter subscale and read off directly the value of the pressure height; or we can make a simple calculation as shown below, using our knowledge that up to 5,000 ft, the approximate rate of fall of pressure is 1 hPa per 30 ft.,How to find pressure height.,Example:,When 1,013 is greater than QNH, pressure height is greater than elevation.,How to find pressure height.,Example:,When 1,013 is less than QNH, pressure height is less than elevation.,Altimeter Setting Rules （高度表拨正规则）,You