(2015) Service Alert 1504: GRS 7800 AHRS in G1000-equipped Beechcraft (B)200 King Air Aircraft

PRODUCTS AFFECTED:
 GRS 7800 AHRS units installed in G1000 equipped Beechcraft 200 and B200 King Air aircraft with 3-blade propellers are affected.

ISSUE:
 Heading and/or attitude information may become unavailable when the propeller RPM is set between 1920 and 1960 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.

PILOT ACTION:
 Do not dwell at 1920 to 1960 propeller RPM.  If the conditions described above are observed, adjust propeller RPM below 1920 RPM or above 1960 RPM.