A/A TACAN Issues

[Shadow KT]

1) Tankers give bearing. (They should not)

I've spoken with multiple fighter pilots, some of which ED SMEs and they all say the same thing! A/A TACAN on tanker aircraft does not give bearing information (Even on the KC-10).

I did some research of my own and I found a patent paper, regarding TACAN. It does mention the ability to receive bearing information from  air-to-air TACAN, but there is one major limitation/drawback, which makes this feature not feasible. The pulses required, for the bearing portion of TACAN to work, draw a huge amount of electrical power. This creates heat and that is a problem, as this heat has to be somehow dissipated. This, combined with other issues, explain why tankers do not provide TACAN bearing. 

https://web.archive.org/web/20121024231616/http://www.patentstorm.us/patents/5128873/fulltext.html

2) A/A TACAN Y Channel does not provide distance information.

This should not be the case.

3) The "Bearing" checkbox in the Mission Editor action "Activate TACAN" has no effect, when used with Refueling aircraft.

I could not find a definition for this feature and how it is supposed to work. It is not mentioned in the 2020 DCS Manual.

My interpretation is that, if you would like to keep it realistic, as it is not checked by default (meaning: bearing disabled), you leave it like that and your tanker should not provide bearing.

What happens in reality, in the current version of DCS OB (2.7.0.5659), is that either checked or unchecked, you always get bearing information.AA TACAN.trk

I am attaching a track below, which demonstrates this. In the track there will be four tankers. Two, set to 34X and 35Y, have the Bearing box unchecked. The rest of the tankers, channels 36X and 37Y, do have the Bearing box checked.

I cycle, in both an A-10 and an F/A-18, all four tankers TACAN channels. What you will see is exactly as described above. Y channel does not give distance and all tankers provide bearing, no matter the checkbox in the Mission Editor.

NOTE: A/G (or just T/R) and A/A TACAN channels do not correspond to the same frequencies (e.g. 35X in A/G and 35X in A/A do not correspond to the same frequencies). https://www.ntia.doc.gov/legacy/osmhome/redbook/4d.pdf. In addition to that, where in A/G 35X and 35Y point to different frequencies as well, in A/A 35X and 35Y do point to the same frequency. This means that the only difference between X and Y in A/A is the microsecond period between pulses. This is why in the track you can see be cycle through both X and Y on the same number channel and still get bearing. The only problem being that in Y, there is no distance information.

AA TACAN.trk

 

NOTE: Whoever is watching the track, might need to reset his views, as Track IR movement does not translate 100%.

[Krippz]

Good catch.

[Raven (Elysian Angel)]

Also, since you used the F-18 for your testing: I seem to remember from the F-18 NATOPS that A/A TACAN channels below 39 (and above 64 iirc) are not used because that would interfere with MIDS. I don't know how well this is modelled in DCS.

[Tom Kazansky]

confirm that 1) is still an issue in DCS 2.7.3.8494 - 14.07.2021

 

AND:

 

"new 4)":  whith a tanker on Y (in my track's case 10Y) it still shows bearing when I switch my Hornet's TACAN to X (10X)!

 

see short track that shows  1) and 4)

 

 

FA-18C 2.7 AA TACAN Y=B+R X=B 01.trk

Edited July 16, 2021 by Tom Kazansky

[MARLAN_]

Some tankers do give bearing information, the KC-10 included (the KC-135 however, should not)

 

There are documents out there that list the features of the tankers, I found them before in a deep dive, you can probably find them too if you search around.

 

A close friend of mine is a KC-10 Flight Engineer and has confirmed that there absolutely is bearing on the tacan, however, they do not always transmit bearing (they can choose to shut it off) and it depends on the mission. This is likely the root of the discrepancy if the source of the information is from fighter pilots, not tanker crew. 

[Tom Kazansky]

thanks. but they should not give anything (and of course not bearing only) when i switch from "Y" to "X" on the receiver's side anyway.

[Tusky]

I've just run a test and with an "X" channel, even with the BEARING option not selected, the tanker (KC-135MPRS) provides bearing.

 

The BEARING option in the Mission Editor seems to have no effect.

Edited August 5, 2021 by Xamik75