03 Non-Directional Beacons (NDB)

Question 1

What frequency range does an NDB function in?

Answer 1

190 kHz to 1750 kHz

Question 2

What is the ground and air parts of an NDB called?

Answer 2

• Ground: NDB (non-directional beacon)

- Air: ADF (automatic direction finder)

Question 3

What are to two types of NDB and what are the ranges (nm) of each?

Answer 3

• Locator Beacon: 10 to 25 nm

- NDB: 50+ nm

Question 4

Name the parts on the AC associated with a NDB

Answer 4

• Loop Antenna
• Sense Antenna
• ADF receiver
• Indicator

Question 5

What is the function of the Sense Antenna on an AC for a NDB?

Answer 5

• The sense antenna removes the ambiguity from the system by giving a specific direction
• Sense antenna modifies the shape of the receiving area to allow a direction to be determined

Question 6

What shape is the receiving area created by the Loop antenna and the Sense antenna on a NDF system on an AC?

Answer 6

Cardioid Shape

Question 7

What is the purpose of the BFO option on a NDB?

Answer 7

• N0N A1A type NDB’s become unreliable whilst the system is coding
• BOF option corrects for this unreliability

Question 8

What is the formula for the radius of the cone of silence?

Answer 8

Radius of the cone (nm) = Altitude (nm) x tan (theta)

Theta is the angle from the edge of the cone to vertical centre line

Question 9

What is the average value of Theta for an NDB?

Theta being the angle between the edged of the cone and the vertical centre line of the cone

Answer 9

Theta = 40 degrees

Question 10

Describe the three types of NDB Indicators

Answer 10

• RBI Fixed: Fixed compass
• RBI Moving Card: Compass can be adjusted using a dial
• RMI: Compass moves automatically

Question 11

Describe the main errors associated with NDB’s

Answer 11

• Static: Biggest impact, only one which can make an NDB useless, caused by lightning
• Night / Twilight: Interference from the ionosphere which collapses to 2 layers during night / twilight, causes fluctuating indications of the needle
• Coastal Refraction: Difference in the friction between the sea and the land causes signals to be refracted
• Multi-Path Propagation: Signals are bounced off terrain and so follow several paths between the NDB and the AC
• Quadrantal: Signal is distorted by the shape of the AC, Worst at 45 degrees between nose and wing and tail and wing, no effect at nose wing or tail direction

Question 12

What level of tacking accuracy is required when flying an NDB approach?

Answer 12

+ - 5 degrees

Question 13

What is the relationship of Range and Power for a NBD?

Answer 13

Range = sqrt(Power)

Question 14

When applying Variation to an NDB related heading, where should the variation be applied from, the NDB or the AC?

Answer 14

The variation at the AC is always used

Question 15

What is the difference between Tracking to an NDB and Homing to an NDB?

Answer 15

• Tracking means that wind is corrected for in order to fly a stright line to the NDB
• Homing means to fly straight towards the NDB (relative bearing 000 degrees), resulting in a curved path if there is wind

Question 16

What is the most common type of long range NDB?

Answer 16

LF N0N/A1A

Question 17

What is the formula for the range of an NDB given the power?

Answer 17

Range(nm) = 2 x srt(power)