757 Magnetic Heading Error
I have noticed that the 757s that I fly all seem to have a 3 degree error in magnetic heading. (Published ILS course is ALWAYS 3 degrees less than magnetic track flown on ILS or the track maintained during takeoff on that runway)
Magnetic variation on the maps/charts/aerads is approx 3W in western Europe. Switching from Magnetic to True changes the heading or track by 6 degrees lower. eg mag hdg 090, true hdg 084.
This means that our aircraft think that the mag variation in is 6W, and not the published 3W.
Speculation time:
Does the mag variation that the 757 uses come from the IRS computers or the FMC database?
If it comes from the IRS computers, could it be that our 10-15 yr old 757s are still using the mag variation from 10-15yrs ago, hence the discrepancy?
Any thoughts/info?