The pilot can use this simple method to determine the distance they are from a NDB station in nautical miles (nm):
- Tune the ADF to the desired NDB.
- Turn the aircraft so that the station is directly off one of the wingtips.
- Fly that heading, timing how long it takes to cross a specific number of NDB bearings.
- Use the formula: Time to station = 60 x number of minutes flown / degrees of bearing change
- Calculate the distance the aircraft is from the station using time * speed = distance