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Clearly, the VOR signals follow a great circle track. Since, they follow great circle tracks, the track to the station, measured at the aircraft (either, true or magnetic), would be different due to convergency. But the QDM display doesn't take account the earth convergency, it is simply reciprocal of the QDR. So isn't the information displayed slightly incorrect?

Or, is QDM supposed to be a rhumb line track to the vor? in that case we need to apply conversion angle .

SO QDM = QDR +/- 180 would turn out to be wrong right?

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    $\begingroup$ Does this answer your question? Is QDR = QDM ± 180 always true in the case of an NDB? $\endgroup$ Nov 7, 2022 at 15:12
  • $\begingroup$ no, that is in a different context $\endgroup$ Nov 7, 2022 at 16:51
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    $\begingroup$ How so? (besides NDB vs VOR, the answer is the same, no?) $\endgroup$ Nov 7, 2022 at 17:31
  • $\begingroup$ @MichaelHall closing questions based on the answer being the same is a bit problematic. They are similar questions though, I agree. $\endgroup$
    – Jamiec
    Nov 8, 2022 at 10:14
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    $\begingroup$ @MichaelHall I take your point entirely. I'll reserve VtC but if someone else does i'll not object at all. $\endgroup$
    – Jamiec
    Nov 8, 2022 at 16:15

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While you're technically right, that VOR radials are great circles, the effective range of a VOR makes the difference from magnetic whilst tracking a radial irrelevant.

So, for all practical purposes, QDM does indeed equal QDR +/- 180 degrees.

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  • $\begingroup$ Thank you. Also, Is QDM "supposed" to be the magnetic "rhumb" line track to the station, or is it supposed to be the magnetic "great circle" track to the station? $\endgroup$ Nov 7, 2022 at 16:52
  • $\begingroup$ @SachinChaudhary Great circle $\endgroup$
    – Jamiec
    Nov 7, 2022 at 17:12

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