Compass Question

[zcrazyx]

Hey all, quick question on the p8 compass and DI regarding dcs. 

when aligned to get the mag heading I then use that to align the DI. however the issue seems to be that what is output is different to what dcs shows in terms direction needed to fly, in this example, nill wind, flying from one airfield to the other, none of the headings match up between the sim and tacview, neither magnetic or true. so my question is is there Deviation that i'm missing out or something out?

 

For reference the variation in this case is 12W. 

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[Ramsay]

18 hours ago, zcrazyx said:

in this example, nill wind, flying from one airfield to the other, none of the headings match up between the sim and tacview, neither magnetic or true. so my question is is there Deviation that i'm missing out or something out?

No, you are not missing anything I am aware of.

Using 1944 and similar airfields - I see DCS reporting a heading/track of approx. 110°M (98°T) with a MagVar = -12°W

The default air spawn Mosquito's DI read the WRONG bearing, 86° = 98°-12° was neither the Magnetic or True heading.

[Perhaps the Mosquito's spawn logic is subtracting a +MagVar rather than using Magnetic = True - MagVar = 98°T - ( -12°) = 98° + 12° = 110°M ?]

I therefore adjusted the DI to read 110°M (not sure why the dial compass was reading 138°M in the picture below - likely I was in accelerated flight or climbing/descending prior to taking the screen shot)

Tacview reported the approx. True heading/track of 98°T as given by DCS (F10 map's vertical axis = True North).

Note

• LCtrl + Y will toggle the DCS cockpit info bar
• Setting the DI needs to done flying straight and level as last time I checked, the remote compass was subject to magnet dip (while on the ground) due to the Mosquito being a tail dragger and DCS not modelling the remote compass's gimbal (seems common to all DCS tail draggers with RMIs).

Tested DCS Open Beta 2.8.2.35759 using Normandy with mission date 21st June 1944

Edited February 6, 2023 by Ramsay
Checked the default compass DI setting and found it wrong, being neither True or Magnetic.

[zcrazyx]

12 minutes ago, Ramsay said:

No, you are not missing anything I am aware of.

Using 1944 and similar airfields - I see DCS reporting a heading/track of approx. 110°M (98°T)

By default the Mosquito's DI was set to read True bearings i.e 98°, so I needed to adjust it to read 110°M

With Tacview reporting the approx. True heading/track of 98°T as given by DCS (F10 map's vertical axis = True North).

Note

• LCtrl + Y will toggle's the cockpit DCS info bar
• Setting the DI needs to done flying straight and level as last time I checked, the remote compass was subject to magnet dip (while on the ground) due to the Mosquito being a tail dragger and DCS not modelling the remote compass's gimbal (seems common to all DCS tail draggers with RMIs).

 

I set it using active pause in the air while straight and level, so I'm rather confused as to my compass would be so far off, I shall attempt another test. Thanks for helping.

Edited February 5, 2023 by zcrazyx

[Terry Dactil]

T-V-M-D-C  (True Virgins Make Dull Company) Is one of the first things you learn in flight school Navigation 101.

• Ger the True bearing from the map and apply the Variation to get the Magnetic Bearing.
• Use the wind correction triangle of velocities to calculate the magnetic heading to fly. (no wind correction in this case).
• To the Magnetic heading apply the Deviation correction to get the Compass heading to fly.

Unfortunately, we have no idea of what the Deviation is.  

(Has anyone found a deviation card hidden anywhere in the cockpit?)

[zcrazyx]

16 hours ago, Ramsay said:

No, you are not missing anything I am aware of.

Using 1944 and similar airfields - I see DCS reporting a heading/track of approx. 110°M (98°T) with a MagVar = -12°W

The default air spawn Mosquito's DI read the WRONG bearing, 86° = 98°-12° was neither the Magnetic or True heading.

[Perhaps the Mosquito's spawn logic is subtracting a +MagVar rather than using Magnetic = True - MagVar = 98°T - ( -12°) = 98° + 12° = 110°M ?]

I therefore adjusted the DI to read 110°M (not sure why the dial compass was reading 138°M in the picture below - likely I was in accelerated flight or climbing/descending prior to taking the screen shot)

Tacview reported the approx. True heading/track of 98°T as given by DCS (F10 map's vertical axis = True North).

Note

• LCtrl + Y will toggle's the cockpit DCS info bar
• Setting the DI needs to done flying straight and level as last time I checked, the remote compass was subject to magnet dip (while on the ground) due to the Mosquito being a tail dragger and DCS not modelling the remote compass's gimbal (seems common to all DCS tail draggers with RMIs).

Tested DCS Open Beta 2.8.2.35759 using Normandy with mission date 21st June 1944

 

Done another test and it seems as if its just very hard to get it lined up properly, thanks for the assist!

[Terry Dactil]

I have just flown that route with no problems.

• Forget about using the P8 compass as we have no deviation card for it.
• The RI compass is far more accurate and does not need corrections.
• Synchronize the DI to the RI and fly a heading of 110°

This is what it looks like There appears to be about a 10° error on the P8 on this heading. (The AI never erected properly , but the DI worked OK)

And here is our position marked on the map.

I know it was only a short distance from overhead the departure airfield, but I'm sure we are on the right track (pun!) using the remote compass and not the P8.

 

 

Edited February 6, 2023 by Terry Dactil

[zcrazyx]

On 2/5/2023 at 8:55 PM, Terry Dactil said:

T-V-M-D-C  (True Virgins Make Dull Company) Is one of the first things you learn in flight school Navigation 101.

• Ger the True bearing from the map and apply the Variation to get the Magnetic Bearing.
• Use the wind correction triangle of velocities to calculate the magnetic heading to fly. (no wind correction in this case).
• To the Magnetic heading apply the Deviation correction to get the Compass heading to fly.

Unfortunately, we have no idea of what the Deviation is.  

(Has anyone found a deviation card hidden anywhere in the cockpit?)

yeah I know, I did my atpl exams and finished them last year, that's why i was scratching my head, think I just had a  hard time adjusting the p8 compass, all is fine in dcs  except strangely for how they report wind but oh well lmao.

Also seems in you're example the p8 isn't correctly alligned either, they had to stick it in the weirdest positions. As for deviation I would be neato to have it modelled bit it is nowhere mentioned in the manuals. A shame.

I do need to learn how to use the RI compass though

Edited February 6, 2023 by zcrazyx

[Terry Dactil]

3 hours ago, zcrazyx said:

Also seems in you're example the p8 isn't correctly alligned either,

Yes. The P8 ring is set to the desired 110°M. The RI and DI has us on the correct heading, but the P8 wants us to turn about 10° to the right and stuff thing up!.

3 hours ago, zcrazyx said:

I do need to learn how to use the RI compass t

Easy. Just turn it on with the 2 switches on the left and synchronize the DI to what is now showing on the RI cockpit instrument.

Edited February 7, 2023 by Terry Dactil

[Nealius]

The 10-degree error sounds a lot like the compass issues I've reported before, not limited to the Mossie. 

 

[Terry Dactil]

Bugger!

The RI compass is not as good as I thought it was. It has a large parallax error (about 10° on E-W headings) depending on how high your eye position is in the cockpit.

Here is what the actual heading of 270° looks like - it's not the  260° the needle points to.

 

I initially thought the needle pivot point was not concentric with the scale, and shot myself in the foot putting in a bug report about that.

You can laugh at me here ...

https://forum.dcs.world/topic/319007-remote-indicating-compass-needle-pivot-off-center/#comment-5149039

So it looks like we need to apply a parallax correction from zero if the needle is vertical, to about 10° if it is horizontal.

Actually, I think I know why the RI has such an unusually long pointer - it is so you can also read the tail of the needle. It should be 180° off from the head of the needle. If it is not, take half the difference and that is the parallax correction needed. Apply this correction in the upwards direction from the indicated heeding. (or just think of a number between 0 and 10 and use that   )

[Bozon]

15 hours ago, Terry Dactil said:

Bugger!

The RI compass is not as good as I thought it was. It has a large parallax error (about 10° on E-W headings) depending on how high your eye position is in the cockpit.

Here is what the actual heading of 270° looks like - it's not the  260° the needle points to.

 

I initially thought the needle pivot point was not concentric with the scale, and shot myself in the foot putting in a bug report about that.

You can laugh at me here ...

https://forum.dcs.world/topic/319007-remote-indicating-compass-needle-pivot-off-center/#comment-5149039

So it looks like we need to apply a parallax correction from zero if the needle is vertical, to about 10° if it is horizontal.

Actually, I think I know why the RI has such an unusually long pointer - it is so you can also read the tail of the needle. It should be 180° off from the head of the needle. If it is not, take half the difference and that is the parallax correction needed. Apply this correction in the upwards direction from the indicated heeding. (or just think of a number between 0 and 10 and use that   )

I believe that the correct way to use the RI is by setting the broad, manually rotating arrow to the direction you wish to keep. Then, the heading-indicating needle needs to be parallel to it - it stays parallel at all perspectives and is easy to monitor  by a quick glance towards the dial. No need to read the numbers during cruise.

[Terry Dactil]

4 hours ago, Bozon said:

I believe that the correct way to use the RI is by setting the broad, manually rotating arrow to the direction you wish to keep. Then, the heading-indicating needle needs to be parallel to it - it stays parallel at all perspectives and is easy to monitor  by a quick glance towards the dial. No need to read the numbers during cruise.

You have nailed it!

It is designed for use on a heading that you select. It doesn't really care about the accuracy when the aircraft is pointing in other directions.

Seems obvious when you put it this way.