The NDB (14-05-18)

Question 1

What does an A/C need on board in order to use an NDB?

Answer 1

An automatic direction finder (ADF)

Question 2

What frequency band do NDBs use?

Answer 2

LF/MF (190 - 1750kHz)

Question 3

How far will a 10kW NDB transmit over a sea surface?

Answer 3

500nm

Question 4

What are the 2 types of NDB?

Answer 4

Locator (2 letter ident) - 10 -25nm used near airfield

Enroute (3 letter ident) - 50nm or more

Question 5

What facility is sometimes associated with an ILS and has a 2 letter ident?

Answer 5

A locator

Question 6

What is the promulgated range?

Answer 6

The maximum range you can receive a transmission from an NDB and guarantee it won tbe affected by another NDB’s transmission.

Question 7

What is the relationship between range and power for an NDB?

Answer 7

Range^2 prop Power

Question 8

What is the range of an NDB over water and land?

Answer 8

NDB range over water = 3 x root(P)

NDB range over land = 2 x root(P)

Question 9

What is the ICAO requirement for the accuracy of an NDB?

Answer 9

+/-5deg

Question 10

What are the dimensions of the cone of confusion above an NDB?

Answer 10

40 deg cone from the vertical.

Question 11

What is the principle of operation of an NDB/ADF?

Answer 11

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.

Question 12

What can be said about the compass card on a Relative Bearing Indicator (RBI)?

Answer 12

It is fixed

Question 13

What can be said about the compass card on the Radio Magnetic Indicator (RMI)?

Answer 13

It rotates.

Question 14

What does a Radio Magnetic Indicator (RMI) look like?

Answer 14

Rotating compass card, can show NDB or VOR station, most have 2 needles.

Question 15

What is homing?

Answer 15

Nose pointing to the object you are wanting to go to.

Question 16

What is tracking?

Answer 16

Heading directly to the object of interest, not necessarily pointing the nose at it (to counter wind deviation)

Question 17

What are the errors associated with Automatic Direction Finding (ADF)?

Answer 17

Static from Precipitation & TSs

Night Effect

Station interference

Coastal refraction

Mountain effect

Quadrantal error

Dip error

Question 18

How does static from precipitation and TSs affect ADF?

Answer 18

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

Question 19

How does the night effect affect ADF?

Answer 19

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

Question 20

How does station interference affect ADF?

Answer 20

The signal from a different NDB causes erroneous indication, therefore we need to use the NDB in its promulgated range.

Question 21

How does coastal refraction affect ADF?

Answer 21

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.

Question 22

How does mountain effect affect ADF?

Answer 22

Mountains cause reflection and defraction which causes multipath situation leading to destructive interference.

Question 23

How does Quadrantal error affect ADF?

Answer 23

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

Question 24

How does dip error affect ADF?

Answer 24

Caused by banking A/C inducing a current in the horizontal part of the loop antenna, leading to erroneous indications.