Could somebody please explain me the differences between using the OBS and the Heading Indicator? As much as I could understand, once you tune into the VOR, the OBS starts to show how much deflection/ deviation is there. You then turn the OBS to align the needle which shows the direction (in terms of angles) that you need to fly to reach that VOR.

Does this mean that the OBS is the instrument to derive the direction, and serves no direct purpose in terms of heading? I.e. the Heading Indicator is the one that then should align be flying in that new direction, right?


1 Answer 1


Could somebody please explain me the differences between using the OBS and the Heading Indicator

They are two very different instruments. The OBS is used to track inbound/outbound from a VOR station, whereas the HI (or, DI - Direction Indicator) shows the current direction of travel (assuming it has been aligned correctly with a compass).

"Turning the OBS to align the needle" is not really the usual way to use that instrument * - you set the OBS to the radial you intend to fly, and use the needle to align yourself with that radial.

If OBS and DI agree with the needle centred, you're on the radial selected by the OBS.

* There is of course a use-case where you just want to go direct to a VOR, and then you may just turn the OBS until it shows "TO" with a centred needle. But if you're doing this regularly you might be using it wrong.

  • $\begingroup$ Hello! Thanks! But apologies, I am still confused. I was watching some YouTube videos, and when tuning into a VOR, the CDI shows To with the needle all the way to the right/ or left. The presenter then turns the OBS knob to align the CDI needle to the centre. That's what I am confused. With that needle pointing straight up (north) it makes it seem that the CDI/ OBS and the heading indicators are all aligned. So, how/ when does one decide to turn? $\endgroup$
    – Ben
    Jun 26, 2019 at 8:37
  • $\begingroup$ Another use case is determining where you are with respect to that VOR. Especially when the VOR is equipped with a DME, this will immediately give you your current location. $\endgroup$
    – Bianfable
    Jun 26, 2019 at 8:38
  • $\begingroup$ @Ben You decide to set the OBS when you know you intend to fly along a radial - from your flight plan probably. $\endgroup$
    – Jamiec
    Jun 26, 2019 at 8:40

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