The Non-Directional Beacon (NDB) is a radio transmitter in a fixed location on the ground.
The Automatic Direction Finding (ADF) equipment in the aircraft will point a needle towards the NDB.
There are three types of ADF cockpit displays:
Once the correct NDB frequency has been entered into the ADF equipment, the morse code identifier should be confirmed. Each NDB transmits its unique identifier in morse code on its radio frequency so the pilot can confirm the correct frequency is entered and the radio signals are being received. The pilot can then either home or track to the beacon.
The closer you get to the beacon, the more sensitive the ADF needle will be.
As you pass overhead the beacon, the needle will ‘drop’. It will move from roughly the 12 o’clock position to the 6 o’clock position. If you fly directly overhead the NDB, the needle will drop quickly. If you fly to one side of the NDB, the needle will be slower to drop.
You are tracking away from an NDB on a track of 040° while experiencing 10° of port drift. What relative bearing will the RBI show?
1 Always draw a diagram! Start by drawing an NDB with the track you are flying (040°)
2 Draw the aircraft on this line but with the nose pointed into the wind. In this case, the nose will be pointing 10° to starboard to counteract the 10° of port drift.
When the aircraft is drifting left (port), you point the nose to the right (starboard)
When the aircraft is drifting right (starboard), you point the nose to the left (port)
3 Draw in the RBI. The RBI will be indicating 000° in the direction the aircraft’s nose is pointing. The RBI needle will be pointing parallel to the track, towards the NDB. The relative bearing is the degrees from the nose (000°) clockwise around to the head of the needle.
The relative bearing is 170°