GRS 7800 AHRS (011-02278-00) units installed in G1000 equipped King Air C90 aircraft with 3-blade propellers are affected.
Heading and/or attitude information may become unavailable when the propeller RPM is set between 1890 and 2000 RPM. Either or both GRS 7800 AHRS may be affected. The attitude and bank shown on PFD1 and/or PFD2 may briefly show deviations. This condition is identified by a “ROLL” or “PITCH” flag and a “ROL MISCOMP” or “PIT MISCOMP” annunciation on both PFDs, followed by an ATTITUDE FAIL red "X".
Do not dwell at 1890 to 2000 propeller RPM. If the conditions described above are observed, adjust propeller RPM below 1890 RPM or above 2000 RPM.
The GRS 7800 AHRS will reset after approximately 45 seconds.