A SF340's Fire Warning and Fire Detections systems were both giving intermittent warnings in flight so the Captain returned to the departure airport and at the gate the Fire Warning annunciated. The Captain ordered an evacuation and called for the Airport Crash Fire Crew.
Synopsis
A SF340's Fire Warning and Fire Detections systems were both giving intermittent warnings in flight so the Captain returned to the departure airport and at the gate the Fire Warning annunciated. The Captain ordered an evacuation and called for the Airport Crash Fire Crew.
Narrative
Upon gear retraction [after takeoff]; we received a Master Caution 'L FIRE DET FAIL' (Left Fire Detector Fail). We accomplished the appropriate QRH for that indication and elected to continue the flight while monitoring engine parameters closely. The light eventually went out on its own; but then illuminated again and again. At this point we started discussing a possible return to our departure airport. Shortly after this we received a Master Warning and 'L ENG FIRE' light. This light extinguished on its own; but just as before with the 'L FIRE DET FAIL'; the 'L ENG FIRE' light went on and off. We elected to keep the engine running because we figured the 'L ENG FIRE' Master Warning was associated with the 'L FIRE DET FAIL' light and we saw no abnormal engine indications and no fire was seen from the Captain's side window. Both the Master Warning and Master Caution continued to go on and off as we made our approach into the departure airport. After landing; we taxied into the gate without either the Master Caution or the Master Warning lights. Once we shut down the left engine and we were parked at the gate; we immediately received a Master Warning and 'L ENG FIRE'. This time the Master Warning and 'L ENG FIRE' lights remained illuminated; and the ITT was rising. We decided to back away the Jet Bridge; run the emergency evacuation checklist (pull left fire handle and left fire extinguisher switch) and evacuate the aircraft from the right side. I called the Tower and requested Crash/Fire/Rescue for possible left engine fire.
Second reporter narrative
I made the decision to return to the departure airport. We did not declare an emergency as we were treating it as a precautionary return for a malfunctioning system. We made a normal approach to a normal landing. After landing we cleared the runway and taxied to the gate. Upon parking at the gate as I shut down the left engine; and I got a left engine fire light with a master warning and fire alarm. I immediately told the gate agent to back the jetway off away from the airplane and that we would be evacuating. I pulled the fire handle and selected the fire switch to extinguish; blowing the fire bottle. The First Officer called Tower and requested crash fire rescue for a possible engine fire. We ran the emergency checklist and told the Flight Attendant to evacuate off the right side of the airplane. We evacuated and assisted the Flight Attendant with the passengers. In the end this turned out to be a malfunction of detection equipment.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.