How to Use the ADF

Once an exciting innovation in aircraft navigation, the Automatic Direction Finder, or ADF, is still important and often employed as an emergency backup system. The ADF relies on a Non-Directional Beacon, usually referred to as an NDB. The premise is simple: you home in on the Morse code Identifier for your destination and adjust for wind drift so that you approach at a 90-degree angle. En route, check your time and distance by identifying a beacon to your right or left and calculating your location relative to it. Web sites like Florida International University and Flight Simulator Navigation have in-depth information on the mathematics and procedures involved in these calculations.

Instructions

  1. ADF Components

    • 1

      Familiarize yourself with the ADF components: Fixed Compass Card, Single-needle Radio Magnetic Indicator and Duel-needle Radio Magnetic Indicator. In all of these the needle points to the NDB navigation beam.

    • 2

      Track from a beacon by bracketing a magnetic bearing. This is used to compensate for crosswinds. This is used when you are outbound from a location. It cannot be used accurately when you are en route because you do not know how far you are from the signal.

    • 3

      Set your bearings by locating your destination beacon and home in on it. Every beacon has its own unique Morse code signal. These signals can be carried great distances. You must verify that you have the correct signal. Once you have identified the correct Morse code signal, set your ADF indicator for that signal. The method of setting the signal will vary depending on which type of ADF indicator your aircraft is equipped with.

    • 4

      Track to your destination by making crosswind corrections so that you approach your final destination at a 90-degree angle. This is called bracketing an NDB magnetic bearing. Do this by subtracting the amount of wind drift from the intercept angle so that the aircraft stays on a 100-degree magnetic bearing.

    • 5

      Make time and distance checks while en route. Tune in to a station and turn so that the needle points at a 90-degree angle, directly to the right or left. Then note the time and the bearing, then fly until the bearing changes by 10 degrees. Compute the distance to the station by dividing the elapsed time by ten to find the time to the station in minutes.

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