Thanks guys. i appreciate the input.
Just one comment. If you need IRS input, or irs drift, how come that GPS primary does appear without aligning the IRS.
ADIRUs have been activated. this activates the MMR what includes the GPS, but i never aligned the IRSs, so no position was known. Only the position calculated by the GPS. The moment GPS primary appeared, the position was updated, the IRSs new their position and from that moment the GPIRS position was calculated.
With other words, IRS did not need to be aligned to for the "GPS primary" to appear.
Did some research on the web, and I believe that GPS primary does appear when there are enough satellites signals received and RAIM is positive. Even with NAV/10 but no positive RAIM, GPS primary is lost.
Thanks again to all,
D1