APP mode dashed line - correct behaviour or bug?

[Althar93]

Hello all,

 

I've been practicing ILS landings with the synthetic runway and while I understand and am fine with getting the chevrons in the brackets for speed & chasing the localizer symbol, the behaviour of the dashed line is just driving me mad to the point where I have to completely ignore it for fear of it throwing me off my approach.

 

Is it the correct/real behaviour for the dashed line to indicate deviation, or is this a bug/oversight & should it really be a projection of the localizer onto the ground (which would make much more sense & be far more intuitive to fly).

 

It just seems strange that a system capable of projecting & rendering a virtual runway wouldn't be able to project & render a dashed line along the axis of the localizer. At the minute I mostly ignore the dashed line and rely on the TACAN needle on the HSI to place myself because the way the dashed line works makes it incredibly difficult to gauge how much deviation needs to be corrected for as the line swings about like crazy with respect to the aircraft's roll even with minor corrections.

 

What do you think? Is this a bug or is this genuinely how the APP hud symbology works in the real aircraft (and if so, do you have any tips so that I may better understand how it works and maybe it'll click for me)?

 

Cheers,

Edited February 23, 2021 by Althar93

[PeneCruz]

I think the issue is the wind, If you take the wind out it will display correctly giving you a CDI dashed line over the Runway and aligned with the QDM. Once you add wind I suspect it places the anchor point for the CDI downwind the difference between the Track and Heading (drift) In reality it would anchor the CDI to the QDM and once you are on centerline it would line up with the runway. I.E it would display desired track. It just needs to be anchored to the runway QDM for the ILS localiser course and it would function correctly. There is also an issue with the Heading scale and flight path maker. This shot below is for a QDM of 119 the ILS Box and flight path maker should be sitting below 119. and with a crosswind like is shown from Left to right the flown heading should be to the left into wind. 

[jojo]

The dashed line has never been reliable in DCS.  Waiting for re-work, it's better to ignore it currently.

 

And overall there is an upgrade in progress on INS system, but that introduced some bugs.

It's better to disable INS drift in Special Options to minimize inconveniences...

 

 

[PeneCruz]

@jojoIn the screenshot above INS drift is disabled. The errors are caused by the wind calculations in the module. I have now invested dome time flying approaches in different wind conditions. Some observations:

• The Course Deviation Indicator behaviors reliably it is just anchored to the wrong place. As you can see above it is anchored to the Aircraft Heading 115. This is incorrect it should be anchored to the aircraft track this would make it sit over the Synthetic Runway Symbol when you are on track. It would also provide steering commands based on the track of the aircraft. This is why it sort of works in Nil wind (tack and Heading are the same).
• There is a massive miscalculation of aircraft drift angle. In the above example I believe Heading is accurate based on 10kts of wind from the North. What is inaccurate is the location of the Flight Path Marker, Steering Cue and Synthetic runway relative to the Heading Scale. They should all be centered under 119. That is my track I'm flying.
• The runway is physically where the symbol is and I calculate the Heading Tick to be roughly accurate Should be 116 (3 degrees of drift). So I conclude that the Drift the aircraft model is displaying Tracking ~140 (24 Degrees of Drift) at 155 kts TAS would require a wind speed of 73 kts from 360.
• All that needs to happen is to have the Aircraft model fly the same drift angle as the Heading scale. I think the two are decoupled at the moment. And Achor the CDI to the track not the aircraft heading as is currently done. Check with your SME, but the HUD I use all ground based guidance is anchored to either the Track or Runway track in the case of the synthetic runway.

[jojo]

Yes, but there is an overhaul of the INS system in progress.

So IMHO, until we have a notification about the release of the new system behavior, it doesn't worth spending too much time on it.

[PeneCruz]

If they are using INS drift calculations I agree. The Anchoring of the CDI though should be investigated. I find it hard to believe it would be referenced to Heading not Track.

[PeneCruz]

Upon some reading of the M2000 Flight Manual it appears the anchor point is the "Repere de cap vrai de piste". Or the Runway True Heading Mark. (QDM) the CDI or Track Axis extends from this point.

[Ramsay]

On 2/23/2021 at 1:08 AM, Althar93 said:

What do you think? Is this a bug or is this genuinely how the APP hud symbology works in the real aircraft (and if so, do you have any tips so that I may better understand how it works and maybe it'll click for me)?

I think the HUD's current ILS guidance is bugged/inaccurate and should behave more like this 

 

 

https://forums.eagle.ru/topic/144961-hud-bugs-since-launch-all-related-to-fpm-amp-pitch-ladder/?do=findComment&comment=3214446

 

[Althar93]

9 hours ago, Ramsay said:

I think the HUD's current ILS guidance is bugged/inaccurate and should behave more like this 

 

 

https://forums.eagle.ru/topic/144961-hud-bugs-since-launch-all-related-to-fpm-amp-pitch-ladder/?do=findComment&comment=3214446

 

 

Yes, that's also what I was expecting. Obviously I have never flown in a real Mirage so I don't know how it really works but your second example is what feels to be the most intuitive & likely behaviour of the dashed line in the real plane.

[PeneCruz]

Yes your bottom example is how it should be. The CDI should be anchored to the runway QDM.