As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GNDED. AIR INTERRUPT, EMER DECLARED, LANDING UNEVENTFUL & ACFT NOT OVERWEIGHT. DURING CRUISE ALTERNATE HORIZON LIGHT ILLUMINATED IN BOTH FMAS & THE FIRST OFFICER`S DIRECTIONAL GYRO BECAME INOPERATIVE. R & R NR 2 VERTICAL GYRO IAW AMM 34-23-01 & NR 2 DIGITAL FLIGHT GUIDANCE COMPUTER IAW AMM 22-01-01. PERFORMED RTS IAW AMM 22-01-05. OK FOR SERVICE. SEE ALSO AALA20160111002.