The Channel Map Magnetic Declination info

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The Channel Map Magnetic Declination info

Postby RAF_DaddyO » Mon Feb 15, 2021 11:40 pm

S! Shutter....

Thanks for the help with my nav experience. It was fun and i'm still learning a lot.

After recalculating my nav exercise and reflying legs of it a couple times. First off, my speed calcs were way off, so tuning them up helped a lot. Climb out, cruise, etc. Even after this, I still came up off course an amount that seems strange.. But I was still off, therefore I set about trying to find out the magvar values for the Normandy map to see if that assumption was right. You were using +12west. I looked up and used the UK isolines from the UK ordnance survey, 1944 which say +10west... and neither seems to hit dead on.

I searched and searched the DCS forums and finally found a possible answer, see attached. and this link: ... s/3312200/.

These kneeboards can be very useful! if they are to be believed.
Seems that both were probably wrong! This reference says for Channel 1940-1970 - its +6! .. ahh....
So in my nav calc exercise I had tons of errors introduced due to this:
- first i set my gyro on the RW wrong,
- next my TAS estimates were way off, too fast,
- next my magvar value was too much (+12 instead of +6)

I'll replug, recalc and try the legs again sometime, should get me closer once my e6b comes in! ;-). I gotta believe I'm not that terrible at holding course. I was trying very very hard, and coming way off my mag course.

pps - Normandy is +7west.

RAF662 CFSG C-in-C

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Re: The Channel Map Magnetic Declination info

Postby Shutter » Tue Feb 16, 2021 7:29 pm

I recently came across this: ... clination/... worldwide historical data for magnetic variation and it seems you were right a couple of days ago. The isogonic line running right through the middle of the channel map is at 9W in '43 , '44 and '45. However thesting in DCS resulted in 10W variation on the channel map in 1944. BTW DCS has a different variation from year to year.

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