Is QDM displayed wrong for the VOR in the aircraft?

Question

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?

Does this answer your question? Is QDR = QDM ± 180 always true in the case of an NDB? — Michael Hall, Nov 07 '22 at 15:12
@MichaelHall closing questions based on the answer being the same is a bit problematic. They are similar questions though, I agree. — Jamiec, Nov 08 '22 at 10:14
@Jamiec, Beyond a vague similarity, the fundamental concept behind the two questions appears identical. If the OP was responsive and could clarify their confusion over possible perceived differences I would be understanding. Otherwise, should we expect another question about the effects of earth curvature on TACAN bearings a year from now? — Michael Hall, Nov 08 '22 at 15:33
@MichaelHall I take your point entirely. I'll reserve VtC but if someone else does i'll not object at all. — Jamiec, Nov 08 '22 at 16:15
Maybe we should edit the first question to be more broad and cover any ground based navaid? — Michael Hall, Nov 08 '22 at 17:43

score 3 · Answer 1 · answered Nov 07 '22 at 14:52

3

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.

answered Nov 07 '22 at 14:52

Jamiec

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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? – Sachin Chaudhary Nov 07 '22 at 16:52
@SachinChaudhary Great circle – Jamiec Nov 07 '22 at 17:12

Is QDM displayed wrong for the VOR in the aircraft?

1 Answers1