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2 Answers

Navigation Acronyms: TVMDC

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Student Pilot

! TVMDC question

Dear CFIs.

Apologies, a confusing question below. And despite the GS courses I am a bit confused when the terms don't align with the sample questions.

Question: Given the

  • WCA -012°
  • TH 125°
  • MC: 139°
  • DEV: 002°E

What is the TC, MH, and the CH.

So, the formula being either of these

  • TC ± WCA = TH ± V = MH ± DEV = CH where do I fit the MC in the formula?

Could I request somebody's help on this please? Much appreciated.

Thanks,

Ben

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2 Answers

  1. Best Answer


    Bryan on Jan 16, 2023

    There are a couple of ways to figure out your Compass Heading (CH) from True Course (TC). You have to correct for magnetic variation (just V in your formula) and wind (WCA) but it doesn’t matter which you do first.

    If you correct TC for magnetic variation first, you get a Magnetic Course (MC). You then correct the MC for WCA and get Magnetic Heading (MH). Finally, you apply the plane-specific Magnetic Deviation to get your CH. Notice that this method never lands you with a True Heading (TH).

    The other way does wind first so your TC corrected for WCA gets you TH, TH corrected for magnetic variation gets you MH. Then you apply magnetic deviation for CH. In this sequence, you never get a MC.

    The course becomes a heading as soon as you correct for wind or magnetic deviation. That’s whey you don’t see a MC in your formula.

    Does that make sense?

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  2. Benni2000 on Jan 17, 2023

    Absolutely @Bryan, thanks! So, these are two almost parallel calculations.

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