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5 Answers

Why is it called a “Compass Locator?”

Asked by: 13080 views ,
Instrument Rating

Why is it called a compass locator? If I can't locate my compass I really shouldn't be flying IFR!

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5 Answers

  1. John D. Collins on Nov 19, 2011

    I really don’t know why it is called a Compass Locator.  One of its functions is to provide ADF navigational guidance to the NDB located at the IAF, typically at the  marker beacon location. When you are within the service volume of the NDB, it can provide a means of navigating directly on a random route to the IAF to commence the approach.  So maybe it gets its name from beign able to locate and navigate to the IAF from anywhere on the Compass? Marker beacons and Compass Locators are going away.

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  2. Best Answer

    Paul Tocknell on Nov 19, 2011

    Actually, the reason it is called a compass locator has little to do with the compass at all.  It actually comes from the old radio compasses installed on airplanes.  

    Radio Compass

    These were visual type radio direction indicators.  The “compass” doesn’t point to magnetic north but to the direction of the selected radio station.  In the first proposals of what would eventually become an ILS, they set up two markers.   

    You would make sure the compass indictor centered and lose altitude as presribed above.  Pretty rough, but back in the late 30s, this is all they had!  

    Thanks for the question, these are the types of questions I love to answer.


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  3. Donnie Beene on Nov 21, 2011

    @Paul — thanks for sharing this. Very interesting to know a little bit of navigational history.

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  4. Ramius Lai on Dec 12, 2014

    Thank you very much Paul. It helps a lot.

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  5. Mark C. on Feb 22, 2015


    I recently taught a class on the ILS in one of my CFI-I classes. Neither I, the instructor, nor the students could explain what the purpose of the compass locator was; only that it was considered supplementary equipment for the ILS.

    All the FAA materials I came across were very vague on the subject.

    Thank you for the information!

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