儀表飛行員地面課程Lesson3課件

1、Sierra Academy of Aeronautics IR GroundLesson 3ADF Nondirectional Radio Beacons (NDBs)NDBs transmit in the low/medium frequency range between 190 to 535 kHzNDBs are not limited to line of sightNDB signals travel both as ground waves that penetrate obstacles and as sky waves that are refracted by the

2、 ionosphereNondirectional Radio Beacons (NDBs)Ground waves & Sky wavesNDBs are grouped into 4 classesNDB aircraft components2 antennas: Sense and LoopAutomatic direction Finder (ADF) uses both antennas to determine relative position to NDBNDB aircraft components cont.Loop AntennaThe loop antenna sen

3、ses direction of the station but cannot determine whether the station is behind or ahead, or to the left or right.It breaks down all possibilities to 2.360 or 180270 or 90020 or 200Sense AntennaThe sense antenna solves the ambiguityNDB aircraft components cont.The ADF receiver may have several funct

4、ion switchesADF: Operates as automatic direction finder using both antennas (normal mode)REC/ANT: Receiver provides maximum sensitivity to radio signals for improved audio and identifying capabilitiesBFO:Beat Frequency Oscillator for positive navigating outside the USTest: Offsets bearing pointer to

5、 verify free movement (Needle should return)NDB aircraft components cont.Typical older SIU ADF Indicator & ReceiverNDB ground componentsOne variation of an NDB ground antennaADF LimitationsMountainous TerrainPrecipitation StaticThunderstormsTwilight Effect Shoreline EffectADF Limitations cont.Mounta

6、inous terrainThe signal can be reflected by irregular terrainADF Limitations cont.Precipitation StaticWhen flying in rain, snow or clouds a buildup of static electricity occurs on the aircraft. If buildup becomes significant enough, the ADF needle wanders aimlessly.ThunderstormsLightning radiates ra

7、dio waves in the L/MF band and causes the ADF indicator to momentarily point towards the area of electrical discharge.ADF Limitations cont.Twilight effectHeight of the ionosphere changes around sunset and sunrise. This can cause erratic ADF indications.Shoreline EffectThe NDB signal can be bent in a

8、reas where it crosses the shoreline.For Your InformationHow can you tell if you are receiving erroneous bearing information?Must be continuously monitored for identification and reliable signal.How can you tell when station passage occurs?As you pass the station the needle will swing from 0 to 180 o

9、n the indicatorADF cont.There are 2 types of ADF indicators Fixed Card Moveable CardADF terminologyBearingThe horizontal direction TO or FROM any point which is measured clockwise through 360 deg. from magnetic northRelative Bearing (RB)The number of degrees between the nose of the aircraft and the

10、station.Magnetic BearingCourse to or from the station“Course To” or “ Bearing From”ADF terminology (Bearings)The formulaMagnetic Heading+Relative Bearing=Magnetic BearingMH+RB=MBADF terminology (Bearings)ADF doing the mathWhat is the mag. bearing to the station? MH=010 RB=60 MH010+ RB + 060 MB070ADF

11、 doing the mathWhat is the mag. bearing to the station? MH=210 RB=300MH+RB=MB210+300=510510-360=150ADF doing the mathWhat is the mag. bearing FROM the station?MH+RB=MB330+110=440-360MBTo=080+180MBFrom=260The easier way in flightTranspose the ADF needle onto the DGADF OrientationWhat is your bearing

12、to the station?Where are you in relation to the station?ADF OrientationWhat is your bearing to the station?Where are you in relation to the station?More ADF OrientationMore ADF OrientationADF HomingHoming - Keeping the needle pointed on ZeroNDB Tracking/BracketingNDB InterceptsOn an NDB intercept yo

13、u are on course when the ADF needle deflection equals the angle of interceptNeedle deflection is in reference to nose when going TO the stationNeedle deflection is in reference to tail when going From the stationMore NDB OrientationMore NDB Orientation (Intercepts)ADF Orientation (more advanced)NDB ArcRadio Magne