RMIT飞行训练课件－ADF Operations ADF操作
**** Hidden Message ***** RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 1<BR>ADF OPERATIONS<BR>Aim: To learn the principles behind the operation of the ADF navigation system.<BR>Application:<BR>- orientation (where am I?).<BR>- supplementary navigation information.<BR>Definitions:<BR> NDB<BR>- Non-Directional Beacon, is the ground radio transmitter that radiates<BR>energy in all directions.<BR> ADF<BR>- Automatic Direction Finder, is the airborne receiver which when tuned,<BR>indicates the direction TO the NDB.<BR> Locator<BR>- Low powered NDB used for approaches in conjunction with an ILS.<BR>Principles:<BR> NDB<BR>- Operates on frequencies between 200Hz and 500 KHz (LF to MF radio<BR>range).<BR>- Primarily short distance navigation aids of usually < 200Nm.<BR>- Transmitter power is between 100 and 3000W with majority in the 100 to<BR>500W range.<BR>- Greater the transmitter power, the greater the range.<BR>- Details found in ERSA and ERC charts; VTC, TAC and VNC.<BR>- The emitted wave has a Morse code identifier superimposed upon it, of 2<BR>to 3 letters.<BR>- The carrier wave may Also contain voice/ ATIS information.<BR> ADF<BR>- airborne equipment consists of three main components:<BR>1. Antennae<BR>- loop antenna aligns itself perpendicular to the direction of the received<BR>signal. As it is a loop, two nulls are received - one removed 180 from the<BR>other.<BR>- to resolve the ambiguity the signal from the sense antenna is combined,<BR>to drive the loop (and hence the pointer) in the correct direction.<BR>RMIT Flight Training ADF Operations<BR>Brief 18<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 2<BR>2. Receiver<BR>- the receiver and associated control panel are used to tune the ADF to the<BR>required NDB.<BR> OFF = switch ADF off<BR> ADF = normal position for bearing information<BR> ANT = only sense antenna is used. No bearing information but enhanced<BR>audio reception<BR> BFO = beat frequency oscillator, rarely used in Australia<BR> TEST = deflects needle to right wing. Pressing ADF again points needle<BR>to NDB<BR>3. Cockpit Display<BR>- the needle always points directly TO the station.<BR>4. Fixed-Card ADF<BR>- the needle indicates relative bearing of the station from the aircraft<BR> Rotatable-Card ADF<BR>- the needle indicates a magnetic bearing TO the station. Any change in<BR>HDG requires re-alignment of the ADF card.<BR> Radio Magnetic Indicator (RMI)<BR>- is a gyro-stabilised ADF which automatically aligns the card, and indicates<BR>magnetic bearings.<BR>RMIT Flight Training ADF Operations<BR>Brief 18<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 3<BR>Considerations:<BR> Limitations<BR>- various limitations effect the readings of the ADF:<BR>a) Coastal Refraction<BR>- when passing from land to sea at an oblique angle, NDB radio waves may<BR>be refracted (bent) due to different conducting and reflecting properties of<BR>land and water. Always refracts towards the land (away from the normal).<BR>b) Co-Channel Interference<BR>- signals received from other NDBs operating on the same frequency, may<BR>give false bearing information. (eg: SHT and BNS) Generally NDBs of<BR>similar frequencies are spaced well apart geographically.<BR>c) Thunderstorm Effect<BR>- thunderstorms generate a lot of radio energy, and the ADF needle may<BR>point towards it; a poor mans weather radar.<BR>d) Terrain Effect<BR>- radio signals have greater range over water than over sandy or<BR>mountainous country where the range is considerably reduced.<BR>Brief 18<BR>RMIT Flight Training ADF Operations<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 4<BR>e) Mountain Effect<BR>- fluctuating bearings may result from the mixing of radio waves reflected<BR>from the surfaces of mountains.<BR>- higher frequencies minimise this effect.<BR>f) Night Effect<BR>- radio waves take two paths; ground waves (along the Earth’s surface) and<BR>sky waves.<BR>- during the day the sky waves are absorbed by the lower ionosphere. At<BR>night the ionosphere reflects the sky wave back, mixing with the ground<BR>wave, causing errors.<BR>g) Quadrantal Error<BR>- results from the metal construction of the aircraft. Needle of ADF will align<BR>itself to the cardinal points of aircraft. (ie: N, E, S, W) when station in<BR>between these quadrants.<BR>Brief 18<BR>RMIT Flight Training ADF Operations<BR>RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 5<BR>Air Exercise:<BR>T - Tune to NDB using receiver<BR>I - Identify using Morse code<BR>T - Test by depressing TEST switch<BR>Airmanship:<BR>- Always use NDB within it’s rated coverage<BR>- TIT checks before use<BR>- AM stations not to be used for navigation<BR>- Instrument taxi checks to be completed<BR>Brief 18<BR>RMIT Flight Training ADF Operations 感谢楼主万分感谢感谢万分 谢谢楼主，我正准备去RMIT读书
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