CDI Needle Off?

[bonesvf103]

Sometimes when I am headed toward a TACAN station, the HSI CDI needle shows a TO indication, but the HUD TACAN bearing needles are dashed, indicating FROM. Or vice verse. Is this a bug? I would think that the bearing needle in the HUD and VDI should correspond to what the HSI indicates (or vice versa).

 

v6,

boNes

 

Edited October 21, 2020 by bonesvf103

[bonesvf103]

Any thoughts on this? I come from a VOR navigation type and apply it to this TACAN which is basically the same so I'm trying to wrap my head around itr. Maybe I'm not getting the HSI symbology right?

 

v6,

boNes

[draconus]

http://www.heatblur.se/F-14Manual/ge...ering-submodes

As you can read in "Take-Off-TACAN Steering" section the solid line just shows that you fly toward the station disregarding the course.

Edited October 26, 2020 by draconus

[bonesvf103]

Yes, I read that but what about the arrow in the HSD?

 

According to the page you referenced:

 

On the HSD and multiple display indicator, an arrow on the deviation bar pointing in the same direction as the TACAN course indicates a course toward the station, an arrow pointing in the opposite direction indicates a course away from the station.

 

If you look at the picture I posted, the HUD and VDI show solid green (TO indication) but the HSI arrow is pointing in the opposite direction of the selected course (FROM indication). This contradicts the HUD and the VDI.

 

v6,

boNes

 

[draconus]

You're confusing direction to a station and course direction.

If you keep flying 170 for about 20 you'll have Tacan From indications on 320 in line with your course direction.

Oh, and the big arrow is the set course, small arrow on the right side is deviation bar and tells that you fly toward the station.

Edited October 27, 2020 by draconus

[bonesvf103]

Yes, I think you are right about my confusion. I'm finding that the solid/dashed line in the HUD and VDI are independent of the CDI in the HSD.

 

It may very well be that the solid/dashed line in the HUD and VDI only show if you are heading generally toward or away from the TACAN, and have nothing to do with the course you selected in the HSD. In fact, it seems as if the indicators in the HUD and VSI basically act like the TACAN arrow in the HSD (the triangle for the head and the x for the tail).

 

Now in terms of tracking a radial for navigation, then the HSD is the only instrument to be used for this purpose, using the course selection arrow and the CDI arrows/indicator.

 

To test this I put myself in various positions around the TACAN and guessed where I would be on the F10 map based on what the HUD/VDI and HSD were showing me. AFter I made this distinction, I guessed right every time.

 

So in short, the civilian to military equivalents are the HUD and VSI indicators are like the civilian ADF pointers. The HSD with its CDI and to and from arrows are equivalent to a civilian HSI and/or VOR.

 

If that makes sense...it does to me anyway, in my own noggin.

 

Thanks!

 

v6,

boNes

[draconus]

OK, there's also BDHI with its TACAN and ADF arrows but no course lines. I use it a lot as a quick direction orientation relative to bearings I get through radio.

http://www.heatblur.se/F-14Manual/cockpit.html#bearing-distance-heading-indicator-bdhi

[bonesvf103]

OK, there's also BDHI with its TACAN and ADF arrows but no course lines. I use it a lot as a quick direction orientation relative to bearings I get through radio.

http://www.heatblur.se/F-14Manual/cockpit.html#bearing-distance-heading-indicator-bdhi

 

Yup, I use that as a backup sometimes.

 

Thanks!

 

v6,

boNes