I’ll have my PPL exam soon. I asked my instructor at the school about this question and even he doesn’t know the answer. I’ll appreciate your help.

Question 22

Flight from point A to point B. NDB is point B.

  • magnetic track (MKK)=245°
  • magnetic variation (“delta” m)=5° W
  • magnetic compass swing ( “delta” k)=3° E

When 30 km inbound to point B, your QDM-225° What is aircraft deviation from track?

  1. Right of track 10km(5.4 nm) (Nk=+10km)
  2. Left of track 10 km (5.4 nm) (Nk=-10km)
  3. Right of track 6km(3.2 nm) (Nk=+6km)
  4. Right of track 12,55km(6.7nm) (Nk=-12.5km)
  • $\begingroup$ You might like to add what you've already tried and what you don't understand. People generally respond better to questions like this if they see you've already made some effort, and understanding your difficulty helps to get a better answer. $\endgroup$
    – Pondlife
    Jul 20, 2018 at 19:56
  • $\begingroup$ As I understand my actual track is MT =245” and QDM is magnatic track from the station as I’m going to point B what it is QDM =225” and I have to get the track error what it is 5,4 NM . I just don’t know how I know if I’m left of Track or right of track ? $\endgroup$ Jul 20, 2018 at 20:01
  • $\begingroup$ QDM is magnetic bearing from aircraft TO station $\endgroup$ Jul 20, 2018 at 20:25

1 Answer 1


Pretty easy... You are 225° QDM, the track was 245°. Neither QDM nor MKK is nothing about variation or deviation, because both of them are magnetic (i. e. variation already applied) courses (i. e. not heading, therefore deviation is also not an issue).

20° deviation from track at 30 km to the station gives us 30 * sin(20°) = 10.26 km, i. e. approximately 10 km. Our QDM is less than desired track, and we are moving to the South-West, so we are to the North-West of our desired track, i. e. we are on the right side of the desired track. Therefore, the answer is 1, right of track 10km (5.4 nm) (Nk=+10km).

  • $\begingroup$ I want to know now , that which one is my actual track is it the MT or the QDM ? Dose the question means that I was on MT but suddenly my A/C drifted to QDM or what ? That what I don’t know which one is my real track ? $\endgroup$ Jul 21, 2018 at 15:41
  • $\begingroup$ Your actual track is neither MT not QDM in that case, because actual track can be even curved (nobody knows how you deviated from your intended track: flew different course all the time until obtaining bearing, or suddenly turned perpendicular to your intended track, or failed to maintain one direction and wandered all the time, or whatever). And QDM is not track at all, it is a bearing, i. e. magnetic direction to the station. $\endgroup$
    – avtomaton
    Jul 21, 2018 at 17:47
  • $\begingroup$ ok got you thank you so much $\endgroup$ Jul 21, 2018 at 17:49

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