Absolutey, EDDNR. Only posted as I have heard people talk of 'taking out alignment errors' at TOGA and meaning platform errors. Incidentally, I may have misread your earlier post, but I don't think GPS takes a part in the actual alignment process in the 737, but I'm well out of date (used to lecture on IRS/INS fitted with toothed rubber bands, cogs and gyros:eek:) and would welcome input from a 'fundi' on this.

Maybe on the next extended slot delay I could try an alignment at the wrong longitude - I'm sure as you say it is only pos that would be wrong, and corrected at TOGA, but I'm not sure, for example, about heading? I'm sure that if the system allowed, one could align with no input position (as long as FDP allowed:)). It is a clever bit of kit.

If the initial numbers are off by more that a few degrees, particularly latitude, many INS/IRS can detect that on alignment, as the platform does not tilt with earth's rotation as the system expects it to with the wrong numbers entered.

I don't know how far the numbers have to be off for this to work though.

regards,
OORW