Bardufoss localizer offset?

[Nealius]

I tried an ILS approach on Bardufoss RWY28 following the IFR charts that come default with the map. The localizer was showing way right when I was lined up on the runway. The IFR chart doesn't seem to indicate an offset, and if I tried to fly the localizer as indicated I would hit that small hill that's about a kilometer east of the field. Anyone else noticed this?

[Guille H. Mono]

Same here. I started to practice ILS landings on my new F4 and fortunately choosed Bardufoss for no reason 

[drPhibes]

LOC28 at Bardufoss is offset 2.1° to the north, and the LOC is located to the south of the runway (as opposed to the usual location, along the extender centerline, ~300m beyond the threshold of the reciprocal rwy), so you will definitely get some unusual indications on your CDI when on the ground. 

 

https://aim-prod.avinor.no/no/AIP/View/Index/141/2025-06-12-AIRAC/html/eAIP/EN-AD-2.ENDU-en-GB.html#AD-2.ENDU

Edited September 1 by drPhibes

[Nealius]

Appears to be 3 degrees north on the ME. Runway heading 291, loc 288. However in flying the Viper my loc was so far right I would have hit the terrain to the northeast of the threshold. Why would the localizer be offset to put aircraft closer to that hill rather than offset south where there's no terrain? A south offset makes more logical sense due to the terrain here.

[drPhibes]

That sounds strange. I flew an approach for RWY28 in the F16, and even though the GP isn't as steep as it should be (it's 3,7° IRL, but DCS defaults to 3°), there is still plenty of terrain clearence:

[Nealius]

I'll have to try it again because the offset when I was aligned with the runway axis was in excess of the 3 degrees indicated on the mission editor. In the Viper's ILS did you input the course as-is from the included IFR chart (278 degrees)? 

[drPhibes]

The course setting only affects the command steering symbol, not the LOC/GP bars in the HUD/ADI.

[Nealius]

Ah. That's always been a point of confusion for me in the Viper; magnetic or true as well. Sometimes I see it automatically changes to match what I have set in the HSI as well. 

Anyway, I shot another ILS and it doesn't put me into the hill, but it does put me quite close to the hill when there's a perfectly flat space along the river right along the runway axis. So I still don't understand the logic of offsetting the LOC to put an aircraft closer to terrain.

[drPhibes]

The 2,1° offset places the localizer centerline (CL) pretty much down the center of the Målselv valley. Here's a crude illustration made in google earth:

1: The CL, offset 2,1° from the runway centerline.

2/3: the outer limits of the course sector (CS). The course sector is the region defined by the maximum left and right deflection (5 dots in the ADI/cross pointer) of the LOC bar in the ADI, with the deflection decreasing linearly as you approach the CL. Max deflection = ±15,5% (or 150μA) DDM. The CS for Bardufoss LOC 28 is 5°, i.e. 2,5° to each side of the CL.

4/5: The outer limits of the course signal (±10°). Between 2-4 and 3-5, the ADI will show full left/right deflection. 

6/7: The outer limits of the clearence sector (only applicable for dual frequency/capture effect localizers). The clearence signal can be seen as an extension of what I described in the previous paragraph, giving a full deflection ADI. 

Having no offset would place the CL and CS too close to the mountain to the right of the #3 line.

Edited 3 hours ago by drPhibes