Magnetic deviation chart

[ATAG_Walstein]

Good day everybody!

I have flown test routes to find out more detailed numbers concerning the Magnetic Deviation than just the average 10° on the Channel map – this does not concern the African map. I found and downloaded one chart for Bleinheim and Wellington, but I have not found any for the German bombers. That´s why I made it by myself.

Magnetic deviation
Test: Heinkel 111 H-2, Heinkel 111 P-2 and Junkers Ju 88-1

0° 12°
45° 11°
90° 10°
135° 9°
180° 17°
225° 16°
270° 18°
315° 13°

*Results are not exact nor are they precisely the same with the above mentioned aeroplanes. They variate a couple of degrees as -1° - +1°

Sobering explanation: First cipher is the true direction. Second is the number which you have to add to the direction. Sum is the direction you need in your compass = indicated direction.

Example: you want to fly to north. True direction is 0°. Magnetic deviation is 12°. You have to add: 0° + 12° = 12°. This is what your compass has to show.

I have faced difficulties in navigating long flights back and forth. With these figures I have succeeded in finding my way much better. However, If there is a proper chart somewhere I would appreciate to download it. There is one for Blenheim and Wellington and that I already have.

Have a nice Sunday!
Walstein

[ATAG_Colander]

Interestingly enough, there is a site with historical declinations:
https://www.ncei.noaa.gov/maps/historical_declination/

And interestingly enough (for me anyway), the lines are not vertical which in theory would explain the differences depending on the angles (I think).

1940 channel (10 degrees line selected):
Untitled.jpg

[ATAG_Noofy]

Yes and no...

There are two things to consider:

Declination: this is the magnetic variation that changes over time (+10 deg in the Channel in the 1940s)
Deviation: this is the error induced in a compass by local magnetic fields (metallic masses, bombs, guns, etc.). It is different for each aircraft, and also depends on the heading.

If your geographical heading is HDG, then you have to add the declination, and add/substract the deviation (which will vary depending on the aircraft and the direction). Plus/minus wind drift of course…

This was discussed here for the Wellington: https://theairtacticalassaultgroup.c...ad.php?t=34828

Below you will find the correction chart I had prepared some time ago for the German bombers.

You will notice two entries: REP and MAG. German planes have one magnetic compass and one repeater.
The deviation values can be different on one or the other (because they are placed differently and therefore are affected differently by the metallic masses of the plane?).
So depending on which instrument you are using, you should correct according to the REP or the MAG line.

Compass Correction Charts - German Bombers.pdf

Enjoy

[ATAG_Noofy]

Interestingly enough, there is a site with historical declinations:
https://www.ncei.noaa.gov/maps/historical_declination/

And interestingly enough (for me anyway), the lines are not vertical which in theory would explain the differences depending on the angles (I think).

1940 channel (10 degrees line selected):
Untitled.jpg

The lines do not appear vertical because they are pointing to the magnetic North Pole, which is one point on a sphere, so all line cannot be parallel otherwise they would never meet.
Same goes for the geographical North Pole. The chart below also shows that the lines are not parallel. They point about 10 degrees to the left of the lines in your noaa historical declination chart (which is normal).

2022-07-17_143436.jpg

[Rostic]

This was discussed here for the Wellington: https://theairtacticalassaultgroup.c...ad.php?t=34828

1) This link is not available for me. Probably post in private forum...


2) Here is a link to some my post that may be useful for topic starter:
a) Picture with correction for He111 for England/France map
https://theairtacticalassaultgroup.c...l=1#post348341

b) Blenheim IV precise navigation (and more in discussuion)
https://theairtacticalassaultgroup.c...ight=deviation
do no miss this post:
https://theairtacticalassaultgroup.c...l=1#post340428

3) He111 navigation and bombing tool (Excel sheet)
https://theairtacticalassaultgroup.c...ad.php?t=30256

[ATAG_Noofy]

1) This link is not available for me. Probably post in private forum...

Ah yes, perhaps because it is in the Wimpy Squad private forum. You can request access from ATAG_Snapper.
Anyway it basically says the same that I summarized in my post above.
Plus this Wellington correction chart:

Attachment 53390

[ATAG_Snapper]

Ah yes, perhaps because it is in the Wimpy Squad private forum. You can request access from ATAG_Snapper.
Anyway it basically says the same that I summarized in my post above.
Plus this Wellington correction chart:

Attachment 53390

Good call, Noofy. Rostic, you are now an honoured member of The Wimpey Squad with full access to its private forum.

Even if Wellingtons are not everyone’s cup of tea, fighter cover is always appreciated!

[ATAG_Noofy]

Even if Wellingtons are not everyone’s cup of tea…

If only the forward sighting lever of the Mark XVI bombsight could be fixed…

[ATAG_Walstein]

Yes and no...

There are two things to consider:

Declination: this is the magnetic variation that changes over time (+10 deg in the Channel in the 1940s)
Deviation: this is the error induced in a compass by local magnetic fields (metallic masses, bombs, guns, etc.). It is different for each aircraft, and also depends on the heading.

If your geographical heading is HDG, then you have to add the declination, and add/substract the deviation (which will vary depending on the aircraft and the direction). Plus/minus wind drift of course…

This was discussed here for the Wellington: https://theairtacticalassaultgroup.c...ad.php?t=34828

Below you will find the correction chart I had prepared some time ago for the German bombers.

You will notice two entries: REP and MAG. German planes have one magnetic compass and one repeater.
The deviation values can be different on one or the other (because they are placed differently and therefore are affected differently by the metallic masses of the plane?).
So depending on which instrument you are using, you should correct according to the REP or the MAG line.

Compass Correction Charts - German Bombers.pdf

Enjoy

Thank you very much! I am aware of these things but in Finnish language only. I was too lazy to check the dictionary for vocabulary as I should have done. In addition to all magnetic "stuff" there is also the error or "thing" what is based on the wind - of course. I am ever so grateful in learning detailed information in English, since it is sometimes time consuming to find the proper ways of saying. I have to do some "googeling" to find out how do you call the wind effect on navigation... as well as the effect of the waves and streams if you are navigating a boat.

Decades ago when I took part in sailing contests as a navigator we always studied the magnetic errors - deviation - caused by the sailingboat it self in the springtime. I am sure you know what I say. There were also available certain bits of magnetic metal to correct the deviation. Those were attached to the compass stand, rack or holder or how do you say that in english. Then we moved the boat to different true directions while attached to a buoy. That is how we found out the exact figures of the compass on every true direction. I write this more or less in the meaning of to practise my english. It is surprisingly difficult to express oneself in subjects foreign to one´s everyday life. I take a delight in reading your explanation and from now on I might remember how to say these things. So, thank you one more time.

[ATAG_Snapper]

If only the forward sighting lever of the Mark XVI bombsight could be fixed…

Agree, that's a must. I'll get a Feature Request into the Bugtracker, plus bring it up in discussion with the Team Fusion boffins. I know right now they are working feverishly to get the VR Visual Update finalized, but hopefully this can be addressed, too.

Additionally, I'm hoping the Lorenz Beacon can be made operational so we can try some night time navigation when TrueSky's beautiful night sky -- accurate to 1940 - is implemented!

Update: new Feature Request in the Bugtracker:

Guys: get yourselves registered into the Bugtracker and upvote this Feature Request!

Feature Request #1452: Wellington lc Late Mark XIV bombsight collimeter - IL*2 Sturmovik Cliffs Of Dover 5.0 - Team Fusion Bugtracker (nuvturais.de)

Description
The Mark XIV bombsight in Clod only looks vertically downward, unlike the real Mark XIV bombsight that could look far ahead to its target by rotating the collimator handle. At present in Clod, the only work-around is to jump into the forward gunner's seat, click on "Lean to Gun Sight", and check through the gun sight reticle to spot the target and make adjustments in the plane's heading to stay on target. Once the target is near, the bombardier must then get back to the Mark XIV bombsight, click on Lean to Gun Sight once again, and hope the aircraft hasn't drifted too far off course in the interim. Not good.
The collimator needs a working handle to pivot the bombsight to look far ahead to acquire the target in a timely fashion.
https://en.wikipedia.org/wiki/Mark_X...External_links
"The vertical line on the sight was relatively short, and could not be used directly to measure drift – unlike the long drift wires of the CSBS it replaced. To address this, the collimator handle could be used to manually rotate the sighting assembly forward, allowing the bomb aimer to point the sight further in front of the aircraft's location. This allowed the bomb aimer to select any convenient object on the ground for drift measurements, including the target itself, long before the aircraft reached it."

[ATAG_Noofy]

Guys: get yourselves registered into the Bugtracker and upvote this Feature Request!

Feature Request #1452: Wellington lc Late Mark XIV bombsight collimeter - IL*2 Sturmovik Cliffs Of Dover 5.0 - Team Fusion Bugtracker (nuvturais.de)

Done

[ATAG_Noofy]

Thank you very much! I am aware of these things but in Finnish language only. I was too lazy to check the dictionary for vocabulary as I should have done. In addition to all magnetic "stuff" there is also the error or "thing" what is based on the wind - of course. I am ever so grateful in learning detailed information in English, since it is sometimes time consuming to find the proper ways of saying. I have to do some "googeling" to find out how do you call the wind effect on navigation... as well as the effect of the waves and streams if you are navigating a boat.

Decades ago when I took part in sailing contests as a navigator we always studied the magnetic errors - deviation - caused by the sailingboat it self in the springtime. I am sure you know what I say. There were also available certain bits of magnetic metal to correct the deviation. Those were attached to the compass stand, rack or holder or how do you say that in english. Then we moved the boat to different true directions while attached to a buoy. That is how we found out the exact figures of the compass on every true direction. I write this more or less in the meaning of to practise my english. It is surprisingly difficult to express oneself in subjects foreign to one´s everyday life. I take a delight in reading your explanation and from now on I might remember how to say these things. So, thank you one more time.

The "thing what is based on the wind" is called "wind drift" and you need to also add it or subtract it (as mentioned in my post’s second paragraph). However in missions winds are not often significantly implemented, unfortunately…

I know what you mean with establishing the correction charts for sailing boats. Did that myself when I was sailing regattas, also decades ago…

And don’t worry, your english is very good

[Dawson]

Interesting discussion. Is magnetic deviation modelled in every plane or just the seven in Noofy's slides?

[ATAG_Noofy]

Interesting discussion. Is magnetic deviation modelled in every plane or just the seven in Noofy's slides?

It should be in every plane.
The Bf-109 (not sure if all models) have the correction chart in the cockpits. It is a little piece of paper next to the pressure (ata) dial with the deviation numbers on it…

This discussion has been long going. Check here for example: https://theairtacticalassaultgroup.c...ad.php?t=31531

[ATAG_Slot]

Done

Ditto

[GANIX]

If only the forward sighting lever of the Mark XVI bombsight could be fixed…

Still better than the Heinkel 111 fantasy bombsight (reticle).