AHRS Directional Gyro drift
Hi all,
I am currently operating on a PC-24 on high northern latitudes and we are having problem with heading disagrees between PFD 1 and 2.
The Pilatus company decided to build an aircraft with one IRS (PFD1) and one AHRS (PFD2)
The issue we are having is that on some latitudes around N65 the PFD2 heading is showing around 20-30 degrees off on ground.
There is a supplementary procedure to temporary align the AHRS in DG-mode to IRS heading, but this is not a constant sync, just a momentary sync.
The issue is that immediately after the sync, the AHRS drifts around -1 to -2 degrees per minute rendering the PFD2 useless once again quite rapidly.
My question is:
What is a normal drift rate of a AHRS gyro on N65?
I thought maximum gyro drift (for a perfect gyro) is 15 degrees / hour.
60-70 degrees / hour seems like there is something wrong with the Directional gyro?