WP navigation - Ground track vs FPV with wind

Hi,

I am just confused with the relation between the ground track pointer on the HSI and the FPV on the HUD.

I am not flying the F/A-18C in reality, but the 737NG (equipped with also the FPV on the EADI).

So, on the image1.png, the command steering is not aligned with the FPV, while image1a.png, the ground track pointer is aligned with the waypoint bearing pointer.

In my opinion, the command steering should be aligned with the FPV, see image1b.png.

Is it correct or do I missed something ?

Thanks,

Vincent

The VV and heading tapes aren't on a 1:1 relationship I think is what you're going after here. If you fly the carrot on the command steering marker that is a wind corrected direct to course to whatever you're flying to. This obviously includes calculations for crosswinds so your crab is factored in. With said crosswind, your VV will be displaced in the hud as seen. Just think of the heading tape as a macro view of the headings, and the VV as a micro view with little relationship; The VV shows you exactly where the jet is going in front of you 1:1 however you actually have to move the jet 10* to get the tape to move the full 10*, whereas if you just look it seems like its only 1* of angular distance between the two.

Hopefully that wasn't too confusing

If I understand "If you fly the carrot on the command steering marker that is a wind corrected direct to course to whatever you're flying to", this is not correct.

Fly a quite long straight line toward a WP with crosswing, having the command steering aligned with the ^, and the aircraft will not fly direct to this WP.

I think also that WW and the heading tape are 1:1. The NATOPS manual I-2-102 (174/902) does not specify a difference of scale and says "The VV represents the point toward which the aircraft is flying".

So, the informations displayed on the HUD is not correct.

How I described it is how it actually works irl, and should work. The steering marker is corrected for great circle routing and wind drift. Looks like this is improperly modeled. In this scenario you gave, you should be able to fly directly to the point if you’re on the marker (which should be the heading you are flying), and with an uncaged hud you should see the VV 7-8* right of center (in the scenario you have your crab angle would be 7-8*), your HSI should show the waypoint arrow below the ground track marker like you have done. If you look at the waypoint marker in your image, you see that it’s the same heading as the steering marker in game, which means the steering marker in the hud is not correcting for wind drift which is incorrect.

The velocity vectors job is to give you information in direct pilots-eye relation to the outside world and isn’t in relation to the heading tape. The VV is limited to an 8* radius from the center of the hud, the heading tape obviously has quite a few degrees difference.

Think of it this way, I use my heading tape to navigate, my VV to see where I’m going/pointed at.

So yes, the model is wrong, however the VV doesn’t have a 1:1 relationship with the heading tape, and the steering marker should give you wind corrected great circle routing to your point of choosing.

ok, I understand.

So, this post should be moved to the bug section.

Thanks for the explanations.

vctpil,

I have a similar background to yours. I also came to DCS after using HGS from the 737NG for a number of years. So in my mind naturally by aligning flying to the steering line in the heading tape the vv should be immediately underneath it. According to a rw hornet and rhino pilot, the steering line in the heading tape is wind corrected. If you fly towards it you'll arrive at the selected wp, no matter the winds aloft. I can't remember what he said in regards to the vv not being under the steering line, but what Kio said makes a lot of sense in my opinion.

I haven't tested this hypothesis but if you're telling me that placing the wp marker on the heading tape doesn't get you exactly over it no matter the winds than the system is bugged as I suspected and you discovered.

A-10C has had the same bug for years. Steering cue should be wind-corrected but isn't.

It was correct at one point, but like many things--the flashing Maverick pointing cross, for instance--it got messed up one day and was never fixed.

So this issue should be in the bug section!