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Flashcards in NDB And ADF Deck (29)
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Frequency range of ADF?

190 KHz - 1750 KHz


Primary method of signal propagation of ADF?

Surface waves


Range of ADF over land and water?

300 NM over land 600 NM over sea


What does the loop aerial do? What can’t it show by itself?

If the incoming wave from the ADF station is at any other angle other than at 90 degrees to the loop, an ac current will be induced in the loop as the phase of the wave will be different on each side. If the loop is rotated so that no ac is induced, the incoming wave must either be directly behind or in front of the loop. It cannot tell weather the signal is coming from behind or in front as there are two null points in the polar diagram


What does the sense aerial do? What is the name of the polar diagram produced when combined with loop aerial?

Receives signals from all directions and resolves the ambiguity of the two null points of loop aerial by combining reception characteristics Cardioid polar diagram


What is the most primitive form of ADF cockpit indicator called? (2 names)

Fixed card or RBI


What is the moving card ADF?

Aircraft heading can be manually set at the top of the instrument so the head of the needle indicates bearing to the station and the tail indicates the radial


What is an RMI?

Aircraft magnetic heading is automatically set on the instrument from a remote indicating compass and point of needle automatically displays bearing to station and tail indicates radial


If the heading info fed to an RMI is incorrect, will the bearing to the station be correct and will the relative bearing be correct?

Bearing to station will be wrong but relative bearing will be correct


What is the BFO for?

Used to make the A1A morse ident signal audible


ICAO requirement is accuracy of +/-... degrees with signal to noise ratio of no less than ...

6 degrees



what create the largest unpredictable errors in ADF and thus greatest navigational uncertainty?



What is night effect?

possible for weak sky waves to be returned at night when the ionosphere is less dense and attenuation least. These sky waves tend to strike the top of the loop aerial and induce a current flow where none would otherwise be present. The null is no longer sharply defined and the needle hunts, reducing bearing accuracy


night effect most likely when?

dawn or dusk


What is station interference?

a similar symptom to night effect but caused because the long ground waves of LF and MF bands occasionally overlap on similar frequencies. Does not cause errors during day time if the stations are only used in the protected range but can at night when returning sky waves cause rogue signals at considerable range. Problem detected the same as night effect and possible two idents audible


what is a bandpass switch?

reduces received bandwidth to reduce station interference ny listening to a sharper band


what is quadrantal error?

the wave front can be distorted by the EMF in the aircraft metallic structure as it approaches the aerial. Called Quadrantal because the effect is worst for signals arriving from 45 degrees and 135 degrees left and right of nose (the four quadrants). Error small and predictable and normally compensated for with any residual error recorded on Quadrantal error card kept near the instrument. Modern receivers completely remove it 


what is dip?

occurs when the sense aerial is masked by the loop aerial. It gives large bearing errors, only occurs in a turn and is greatest when the NDB is on a relative bearing of 45 and 135 left and right of the nose


protected range of a beacon highly unusual to be greater than ...



Max range of NDB over land formula =

2 x sqaure root of power


Max range of NDB over water formula =

3 x square root of power


Locator beacons usually located?



low powered beacons with a rated of coverage of between 10 and 25 NM and power output of 15 to 40 watts. Usually co-located with an ILS outer marker


ADF needle indicates what Q direction?



When NDB tracking allowing for drift, the angle between heading and the needle head shold be the same as...



Tail of an ADF needle indicates what Q direction?

QDR (beacon radial)


When NDB tracking If heading is out by more than drift, the effect is to...

push the head of the needle away from the heading bug


When tracking away from an NDB with wrong wind correction angle, the effect on the needle tail is...

pulls towards heading


To place the aircraft on a chosen bearing from/to a beacon, the rule is...

push the head and pull the tail


When flying an NDB approach the pilot has to fly the required bearing to an accuracy of +/- ... to be considered established on the bearing

5 degrees