Aligning the IRS (Inertial Reference System)

I was watching some vids and I saw that they had to align the irs I was wandering what this means and what it does.


Check this.



I know how to fly an ils approach I just don’t know why they have to align them

🙄 why do people comment when they have no grasp of what people are asking?


Okay. You take it from here cap. Since you’ve got it!

Are you talking about the pilot aligning to an ILS, or the actual ILS equipment being aligned?

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I’m talking about the pilot aligning them for example
I’m a 737 there are these knobs that they turn always befor pushback

I was just asking a question, doesn’t really seem like he’s asking how to fly it.

Very helpful inded. :)


Then are you sure you’re talking about an ILS? ILS is for landing, not anything for pushback…if I’m not mistaken.

Ah those are the heading dials so you input the heading you will be flying to track either the VOR/LOC.

Vor/loc? What is that

The button VOR LOC? That is a button so the airplane follows the FPL via the FMC/S, etc.


Ohh ok and why does it take sooo long for them to align?

I’d have to see the video to know exactly what your talking about. It shouldn’t take too long usually you tune into it, check that it’s functioning by listening to the Morse code, then set your heading. @Heavydriver probably has a better idea of what your talking about.

Aligning the ILS can be for a few reasons. For example if a new ILS is installed on the field, it needs to be aligned to the proper headings for the runway that it is intended for. Any maintenance performed on the ILS equipment. There are also test aircraft from the FAA that fly ILS approaches to determine if they are within certain specifications. If it is not, that is another reason to align the ILS. Would you want to fly an approach with zero visibility and want to be guided onto a taxiway parallel to the runway? I wouldn’t.


He said he was talking about the pilots aligning it I honestly have no clue what he’s talking about. Unless he’s talking about a VOR check.

Can someone put a picture of them so people know what the look like

Well, the knobs that pilots turn before pushback are Altitude, Heading, Vertical Speed, Speed just to name a few. If you are in a smaller aircraft and do plan on flying approaches in a 172, a VOR check needs to be done.

INSTRUMENT PRE-FLIGHT *VOR equipment checks for IFR flight:

  • VOT: +/- 4 °. Published in A/FD, tune 108.0MHZ, 180 TO/360 FROM
  • Ground checkpoint: +/- 4 °, specific point on airport listed in A/FD
  • Airborne checkpoint: +/- 6 °, located over easily identifiable terrain or features on the ground, listed in A/FD - VOR/VOR: +/- 4 °, dual check in the air
  • VOR radial on airway centerline over identifiable ground point: +/- 6°


Are you sure you don’t mean IRS (Inertial Reference System)?