What was found
PIT - FLT 0669 - AFTER TAKEOFF FROM PIT, RA FLAG ON PFD ILLUMINATED ALONG WITH THE FOLLOWING FAULT MESSAGES: GPWS, ALAND, STAB TRIM 1. THE NR 1 AUTOPILOT DISENGAGED. FLIGHT RETURNED TO PIT WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED THE NR 1 RADIO ALTIMETER RECEIVER/TRANSMITTER. (X)