Originally Posted by
FlyingStone
The exact latitude limitations will depend on the aircraft type. Most manufacturers offer "polar" option, which removes the latitude limitations and I believe the limitation is more related to the FMC and autoflight rather than the IRS, as the FMC has to transit into the "polar" mode and use true headings/tracks/courses for navigation rather than magnetic ones. Same goes for the autoflight system.
This Boeing
article on navigation in polar regions might be useful.
I agree. Correct me if I'm wrong but doesn't the IRS always give true track/GS/ True heading?