What was found
DURING FLIGHT NR 2996, CAPT AND F/O'S HEADING OFF 10 DEGREES. YELLOW HEADING ON EHSI ON ABOUT EVERY 2 MINUTES. HDG SLAVE RESETS TO ABOUT 5 DEGREE DIFFERENCE. F/O'S HDG MATCHES MAG COMPASS, CAPTS HDG DRIFTS TO ABOUT +9 DEGREES. AIR RETURN TO DTW. MAINTENANCE REPLACED NR 1 AHRS COMPUTER P/N 622-6190-113, SN/OFF 3045, SN/ON 279. NR 1 AHRS OPS CHECKS GOOD IAW SF340, MM CHAP 34.