Tonopah TACAN station moves in space depending your altitude and possibly speed.

[XCNuse]

nullShould be fairly obvious in the track file; screenshot attached to make it more obvious....

I have steerpoint 5 set directly on top of the tacan station at the airfield.... meanwhile the HSI is showing them 2.7 miles apart in that screenshot alone, and I could absolutely keep going! I got it upwards of 15 miles off at one point.Tonopah TAC moves in space.trktonopah tac bug.miz

[draconus]

Tested in F-14 and found no bug. Just remember TACAN shows slant range and WYPT shows ground range. 15nm difference though does not seem to be possible unless you fly at 91k ft.

[NineLine]

Is this still an issue then? Thanks.

[XCNuse]

On 11/7/2022 at 6:26 PM, draconus said:

Tested in F-14 and found no bug. Just remember TACAN shows slant range and WYPT shows ground range. 15nm difference though does not seem to be possible unless you fly at 91k ft.

I guess I've never noticed this before; I've never noticed a TACAN be in the wrong place on the ground before.

7 hours ago, NineLine said:

Is this still an issue then? Thanks.

I guess it isn't an issue?

I hadn't considered that it was slant range.

 

Doing some quick calculations, I guess it is indeed not an error.

 

Nellis TAC moves in space3.trk Tonopah TAC moves in space2.trk

Edited November 9, 2022 by XCNuse

[draconus]

5 hours ago, XCNuse said:

I hadn't considered that it was slant range.

Doing some quick calculations, I guess it is indeed not an error.

Always was like that (manual, page 168). You can perform NOE flying over the waypoint to confirm both TACAN/WYPT are at the same range and fly vertical over the waypoint to confirm WYPT range stays at 0 while TACAN shows your AGL in nm

Edited November 9, 2022 by draconus

[XCNuse]

Yeah I think this was almost entirely a mental flop more than anything else.

I'm so used to landing on ships and aerial refueling I'm not used to seeing a TACAN on a non-moving object hah!

 

For some reason it never even crossed my mind in terms of functionality, but once you said that, it instantly made sense. I guess I had also just never noticed it before flying the Hornet; so used to just getting an arrow and a range; and made me realize that is exactly how I should continue to think about it; not where it "might be" in dimensional space.

[NineLine]

Thanks guys for looking into it! And thanks for the report even if it wasnt an issue in the end.

[XCNuse]

Just for the sake of clarity if anyone ever randomly comes in here and is also confused like I was, hopefully this should clear the confusion.

(I'm a very visual person, so having two things meant to be in the same place was... not working for me, which is why draconus' simple answer cleared it up instantly).

 

Assume we're looking at a triangle; if the steerpoint is the TACAN station, and we're tuned to said TACAN... what it's showing in terms of range and angle are... essentially the hypotenuse of said triangle.

We can then easily calculate our rough altitude (or at least would be altitude assuming it's flat ground, or.. better yet; the altitude of the airfield), under the assumption that it's a right angle triangle.

 

So using that HSI shot of Nellis, LSV, the waypoint is 2.8nm from me, and the tacan is 6.9nm; calculating for a right triangle, that produces roughly a 6.3nm altitude; which.. is FL380 (close enough to).

Hopefully thinking about it that way helps someone one day; or at least better make sense of why it appears the way it does.

 

Now could have the Hornet figured this calculation out itself? No idea; it's not a difficult calculation, but probably not an important one.

All this proves is how bad I am  at math