The NDB (14-05-18) Flashcards
What does an A/C need on board in order to use an NDB?
An automatic direction finder (ADF)
What frequency band do NDBs use?
LF/MF (190 - 1750kHz)
How far will a 10kW NDB transmit over a sea surface?
500nm
What are the 2 types of NDB?
Locator (2 letter ident) - 10 -25nm used near airfield
Enroute (3 letter ident) - 50nm or more
What facility is sometimes associated with an ILS and has a 2 letter ident?
A locator
What is the promulgated range?
The maximum range you can receive a transmission from an NDB and guarantee it won tbe affected by another NDB’s transmission.
What is the relationship between range and power for an NDB?
Range^2 prop Power
What is the range of an NDB over water and land?
NDB range over water = 3 x root(P)
NDB range over land = 2 x root(P)
What is the ICAO requirement for the accuracy of an NDB?
+/-5deg
What are the dimensions of the cone of confusion above an NDB?
40 deg cone from the vertical.
What is the principle of operation of an NDB/ADF?
A directional loop aerial seeks a null signal, of which there are 2, which points out the plane of NDB.
This is then combined with a sense aerial to pin point which direction the NDB is in.
What can be said about the compass card on a Relative Bearing Indicator (RBI)?
It is fixed
What can be said about the compass card on the Radio Magnetic Indicator (RMI)?
It rotates.
What does a Radio Magnetic Indicator (RMI) look like?
Rotating compass card, can show NDB or VOR station, most have 2 needles.
What is homing?
Nose pointing to the object you are wanting to go to.
What is tracking?
Heading directly to the object of interest, not necessarily pointing the nose at it (to counter wind deviation)
What are the errors associated with Automatic Direction Finding (ADF)?
Static from Precipitation & TSs
Night Effect
Station interference
Coastal refraction
Mountain effect
Quadrantal error
Dip error
How does static from precipitation and TSs affect ADF?
They both create a static potential which creates a magenetif field which turns the DF.
In the case of a TS it actually points towards the center of the TS
How does the night effect affect ADF?
MF/LF signals are not attenuated at night due to the disappearence of the D layer, thus they are refracted and return as sky waves causing destructive interference
How does station interference affect ADF?
The signal from a different NDB causes erroneous indication, therefore we need to use the NDB in its promulgated range.
How does coastal refraction affect ADF?
Signal bends at the coast, making the A/C think the NDB is in a certain direction when it actually isnt.
This effect is worse further inland.
How does mountain effect affect ADF?
Mountains cause reflection and defraction which causes multipath situation leading to destructive interference.
How does Quadrantal error affect ADF?
The electric field of the A/C itself bend the signal towards the electric axis (usually the longitudinal axis)
This is at a min at 360R, 270R, 180R & 090R
This is at a max at 045R, 135R, 225R & 315R
How does dip error affect ADF?
Caused by banking A/C inducing a current in the horizontal part of the loop antenna, leading to erroneous indications.
