Private: Demo Ground School

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Intercepting a Track to a Station

To intercept a desired ADF track to a station, first determine the aircraft’s position relative to that track by turning to the same heading as the desired track. Next, turn 90° from the parallel heading in the direction of the ADF needle. As you approach the desired track the needle will move towards either a 090° or a 270° relative bearing depending on whether you are left or right of the desired track. As the needle nears the wing-tip position, turn inbound on the desired track.

Example

In the figure below the aircraft is south of track with the ADF needle reading 030°. For an intercept angle of 90°, a heading of 015° would be required. When established on the intercept heading, the ADF will indicate the station is to the left and ahead of the wing tip. When the angle opens to a relative bearing of 270°, the aircraft is on the desired track and a turn should be made to the desired heading of 285°. If after turning to parallel the required track the ADF needle indicates a relative bearing between 090° clockwise to 270°, the beacon is behind the aeroplane. From this position, you will be unable to use the 90° intercept method to establish yourself on an inbound track of 285°.

Intercepting a track of 285° towards an NDB.

Although a 90° intercept angle is the shortest route to a desired radial or track, it isn’t the shortest route to the station. As you become more proficient in the basic intercept technique, your instructor will show you how to use shallower intercept angles that will take you more directly to your destination. In these cases, care must be taken to achieve the intercept before reaching the station. Below are some useful tips when using intercept angles less than 90°.

  • The relative bearing noted after turning parallel to the desired track can be doubled to determine an appropriate intercept angle. In the example above, the relative bearing after turning to a heading of 285° is 030°. Therefore a 60° intercept angle would be appropriate.
  • Maintain the intercept heading until the needle is deflected by the same number of degrees from the zero position as the intercept angle. In the original example above, since the intercept angle was 90°, the turn to intercept the desired course began as the needle was deflected to the left by 90°. If a 60° intercept angle was used, the turn would have begun when the needle was deflected 60° to the left.

The use of a shallower intercept angle is also often used when intercepting near a station where the radials or tracks are close together, or when correcting for wind drift.

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