ADF is easy if you remember this basic formula:
RB + MH = MB
Rubber Boots +
Muddy Hole =
Muddy Boots
or
Relative Bearing +
Magnetic Heading =
Magnetic Bearing
The problems are solved like this....
Say you are flying along and your instructor asks you to "fly to the XYZ NDB". What course do you need to fly to accomplish that? That course is "Magnetic Bearing" or MB
So you check your chart to find the frequency, tune it into the ADF and properly identify it. The needle on the ADF swings to point at 150-degrees.
This means that from your present position, the NDB is behind you and to your left (remember, the ADF compass rose card is fixed and cannot be moved. The needle always points to the station relative to where your nose is.
150-degrees is the Relative Bearing (Rubber Boots) to the station. Again, relative to which way the aircraft's nose is pointed.
Now when you check your compass and Directional Gyro, they are saying you're on a 30-degree course. This is....... Magnetic Heading. (Muddy Hole)
So, if you are flying on a 30-degree course ( MH ) and a the needle ( RB ) is pointing at 150-degrees, Which way do you turn and what course do you fly to head toward the NDB?
RB + MH = MB
30 + 150 = ??
Answer: 180 Degrees
And you're already at 30-degrees, so what's the simplest way to get to 180-degrees? Turn to the right.
Another way this will get asked is "The magnetic bearing to the station is 270, and your magnetic compass is indicating that you're flying Northeast. Where is the station relative to your location.
RB + MH = MB
?? + 45 = 270
?? = 270 -45
?? = 215
And where is 215 on the ADF compass rose? Behind and to your right.
This video does a good job explaining the concepts:
http://youtu.be/_TZ3EjSYWfY
