As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
#1 ENGINE FIRE T-HANDLE ILLUMINATED MOMENTARILY AND EXTINGUISHED IN CRUISE FLIGHT NEAR ZAMBOANGA, PHP DURING TRAINING FLIGHT. PILOTS CHECKED FOR SECONDARY INDICATIONS, AND NONE WERE FOUND. THE LIGHT FLICKERED WHILE PILOTS CONTINUED BACK TO BASE. AIRCRAFT LANDED SAFELY IN ZAMBOANGA. REPLACED #1 ENGINE AFT UPPER INBOARD FIRE DETECTOR. AIRCRAFT WAS RETURNED TO SERVICE.