[Viikate]

MikkOwl is on right track here, but I think that normal triangulation procedure with single NDB would be following:

1. turn so that your plane is perpendicular to NDB. (NDB is at 270 or 90).
2. start watch and fly at constant speed maintaining the current heading.
3. stop watch when NDB bearing has changed 5 dec.
3. calculate distance flown during this time.
4. calculate distance to beacon. (distance flown/sin 5)

For example if we fly at 300km/h TAS for 135 seconds.

((300/3.6)x135)/sin5) = 129km. So the beacon is 129 km away.

I'm not 100% sure about the formula. I just did a quick scribbling on pen & paper. And this is without any wing correction.