Course line moves by itself?

[HoneyViper]

I'm just learning how to do TACAN navigation, thought I had it all sorted and was ready to approach a runway but it turned out the course line angle was off by about 20 or 30 degrees. I figured I must have input it incorrectly. Tried again a second time, made absolutely sure I put the course line in right - 130 degrees - but when I approached the airfield again I saw the bloody thing shifting. Anyone know what causes this?

 

Another TACAN question, each runway has two angles painted at the end which are opposites. I know it doesn't really matter which one you use, but it's nice have the arrow end the direction you're flying rather than the opposite end. But how do we know which angle to input if we don't really know where we are relative to the runway when we input the TACAN/courseline data?

[squid509]

what is the scale on the HSI and distance to the Tacan station?

if the tacan or the wapoint is a grater distance than the scale on the HSI the line will not be drawn to scale on where the path should be and will appear to shift as the station come with in the size of the HSI is set to

[Bunny Clark]

Nothing should cause the CSEL to change unless you tell it to. You can verify this by looking at the bottom corner of the HSI where it will tell you your currently selected course.

 

You are probably seeing a combination of two things: the TACAN beacon for most airports is not directly adjacent to and centered on the runway, sometimes they're placed as far away as the edge of the airport grounds, so while a radial off that beacon may be parallel with the runway, it won't line up. I've also found several runways in DCS that are off by as much as 30 degrees from their labeled headings. I'm not sure if this is a magnetic vs true heading difference or if something else is going on.

 

It absolutely does matter which direction you land on, or at least it does in real life. In addition to the major collision hazard created when multiple aircraft are landing from reverse directions on the same runway, the "active" runway is chosen by controllers with the intention of minimizing crosswind on landing and takeoff. When you call inbound to an airport in DCS, the controller will give you a runway number for landing.

[Flamin_Squirrel]

It sounds to me like you've misunderstood how to use TACAN.

 

The arrow points in the direction of the course you've set. If the arrow is pointing up the HUD, your heading matches the course; if you turn, the arrow will turn accordingly. Its displacement away from the VV indicates whether you're to the left or right of the course you've set.

 

In the image below, the course set is approximately 280, and the aircraft is to the right of course.

 

 

Here's a VOR trainer that you can play with. It works in a very similar way to TACAN: https://e6bx.com/ifr-simulator/

[HoneyViper]

Thanks for your replies. I don't think I explained myself properly but I think I see what is going on now. I originally thought the course line was supposed to point to the runway heading on the HSI compass points, so when I input a course line angle at 130 I expected it to point at 130. It didn't occur to me that it's relative to the TACAN beacon and nothing to do with the HSI compass points, at least until the two align. Example here: https://youtu.be/N8UC55gJUfc&t=9m22s Overkill inputs a course line of 073, but the arrow itself points to around the 110 degree mark on the HSI compass ring. This is what was confusing me, but I see now that relative to the north point on the HSI the arrow is indeed at 073, and the course line "moves" relative to the alignment of the aircraft and the beacon.

[Bunny Clark]

Ahhh, I see how you're getting confused then. The Hornet's HSI actually works like a map, with the waypoint or TACAN location drawn on the page in its actual location relative to your jet - with your aircraft represented by the little airplane symbol drawn in the middle. To intercept a radial course line, simply fly the little plane in the middle to intercept the course line drawn on the HSI.

 

This is different than an analog HSI, or a hybrid digital one like in the Viper, which draw navigation information only as radial information around your aircraft.

[HoneyViper]

The Hornet's HSI actually works like a map, with the waypoint or TACAN location drawn on the page in its actual location relative to your jet - with your aircraft represented by the little airplane symbol drawn in the middle. To intercept a radial course line, simply fly the little plane in the middle to intercept the course line drawn on the HSI.

 

This is different than an analog HSI, or a hybrid digital one like in the Viper, which draw navigation information only as radial information around your aircraft.

 

Riiiight...the first plane I few in DCS was the F-5 which uses an analogue HSI. All coming together now, thanks!:thumbup:

[HoneyViper]

When you call inbound to an airport in DCS, the controller will give you a runway number for landing.

 

I didn't realise you could call inbound and get the runway number, I was just choosing one arbitrarily from the F10 map. Thanks mate!

[Flamin_Squirrel]

Riiiight...the first plane I few in DCS was the F-5 which uses an analogue HSI.

 

That's how the TACAN display on the HUD works, just to confuse you!