Narrative:

Why; I don't know other than the overtemp control failed; with no indications to us and the heater mat melted. There is no check list for this or no indication that we saw or heard; only the smell of fertilizer. On our way to ZZZ we passed through a mild low; which made us turn on the engine anti-ice system. We were at 9;000 ft and were given a clearance to 6;000 ft. We came out of the WX and I hit the timer button (as per pom; leave ice on for 5 mins before turning off after exiting icing conditions). Around 8;000 ft we entered VMC conditions and were about 20-25 miles from ZZZ airport. After the 5 mins; I turned off the engine anti-ice switches (no abnormalities noted/why would I think otherwise). We were given a clearance to 4;000 ft and we called the airport in sight. We were given a 'cleared visual approach' by center and we proceeded towards the ridge-line (airport is in the valley). We both smelled a strange smell and I thought it smelled like fertilizer. It's spring time and everyone is using fertilizer; so I just thought that someone was using the stuff in the area. My first officer thought that it smelled like 100LL; but I thought it smelled more like fertilizer. I have flown the saab for 8 years. That's 8+ thousand hours of PIC/IOE check airman time and have never smelled a fertilizer smell coming from this airplane. At the time; I didn't even think that it was coming from the airplane; just someone using fertilizer. We flew over the airport and entered a left downwind for runway 24 and landed without incident. Note: at this time we didn't know that anything was wrong! We landed and taxied into the gate; set the parking brake; waited for the chocks sign; shut down the engines and went through our shutdown checklist. When the engines stopped; I opened the cockpit door and the flight attendant ask me if we knew about the fire coming from the right engine. I thought she was kidding as this was our last round trip of a four day. Well; she wasn't kidding and said that a passenger told her that he saw a fire coming from the right engine for about 1 1/2 mins during our descent. Note: he told her this as they were gathering their bags for deplaning. She had no prior notice of problem of any kind! Why this passenger didn't tell her during the event is beyond my comprehension; but he didn't. During my post flight I noticed that the right engine intake heater mat was burned through. At this time the strange fertilizer smell made sense to me. I wrote up the heater mat; the flight back to ZZZ1 was canceled and we went to the hotel for the night. Maintenance came on the last flight; replaced the heater mat and we flew it back to ZZZ1 the next morning. Flight attendant was told from a passenger at the gate that he saw a fire coming from the right engine. It was not an engine fire; but the engine intake heater mat. They are made of coiled wires with ceramic insulation embedded into the rubber that makes up the intake heater mat. Upon post flight; I notice that the right engine heater mat was melted. There is no checklist or memory item for this event. I have been told that this is the 4TH time in the last few months that this has occurred; but nothing like this. In my many thousands of hours as PIC on this aircraft; I have never smelled a smell like this; but now; I will put it in my memory experience bag. Perhaps the company should put out a memo of some kind that states something about a strange fertilizer smell. Question. What would have happened if the passenger didn't tell the flight attendant about the fire and during my post flight inspection; I missed the heater mat being melted? What would have happened if we then took off for home on our last leg of a four day; went back through the mild low system and I turned on the engine anti-ice system?

Related reports:

Google
 

Original NASA ASRS Text

Title: A SAAB 340B PLT RPTS AN ENG INTAKE HEATER MAT FIRE UNDETECTED BY THE CREW.

Narrative: WHY; I DON'T KNOW OTHER THAN THE OVERTEMP CONTROL FAILED; WITH NO INDICATIONS TO US AND THE HEATER MAT MELTED. THERE IS NO CHECK LIST FOR THIS OR NO INDICATION THAT WE SAW OR HEARD; ONLY THE SMELL OF FERTILIZER. ON OUR WAY TO ZZZ WE PASSED THROUGH A MILD LOW; WHICH MADE US TURN ON THE ENGINE ANTI-ICE SYSTEM. WE WERE AT 9;000 FT AND WERE GIVEN A CLRNC TO 6;000 FT. WE CAME OUT OF THE WX AND I HIT THE TIMER BUTTON (AS PER POM; LEAVE ICE ON FOR 5 MINS BEFORE TURNING OFF AFTER EXITING ICING CONDITIONS). AROUND 8;000 FT WE ENTERED VMC CONDITIONS AND WERE ABOUT 20-25 MILES FROM ZZZ AIRPORT. AFTER THE 5 MINS; I TURNED OFF THE ENGINE ANTI-ICE SWITCHES (NO ABNORMALITIES NOTED/WHY WOULD I THINK OTHERWISE). WE WERE GIVEN A CLRNC TO 4;000 FT AND WE CALLED THE AIRPORT IN SIGHT. WE WERE GIVEN A 'CLRED VISUAL APCH' BY CENTER AND WE PROCEEDED TOWARDS THE RIDGE-LINE (AIRPORT IS IN THE VALLEY). WE BOTH SMELLED A STRANGE SMELL AND I THOUGHT IT SMELLED LIKE FERTILIZER. IT'S SPRING TIME AND EVERYONE IS USING FERTILIZER; SO I JUST THOUGHT THAT SOMEONE WAS USING THE STUFF IN THE AREA. MY FO THOUGHT THAT IT SMELLED LIKE 100LL; BUT I THOUGHT IT SMELLED MORE LIKE FERTILIZER. I HAVE FLOWN THE SAAB FOR 8 YEARS. THAT'S 8+ THOUSAND HOURS OF PIC/IOE CHECK AIRMAN TIME AND HAVE NEVER SMELLED A FERTILIZER SMELL COMING FROM THIS AIRPLANE. AT THE TIME; I DIDN'T EVEN THINK THAT IT WAS COMING FROM THE AIRPLANE; JUST SOMEONE USING FERTILIZER. WE FLEW OVER THE AIRPORT AND ENTERED A LEFT DOWNWIND FOR RWY 24 AND LANDED WITHOUT INCIDENT. NOTE: AT THIS TIME WE DIDN'T KNOW THAT ANYTHING WAS WRONG! WE LANDED AND TAXIED INTO THE GATE; SET THE PARKING BRAKE; WAITED FOR THE CHOCKS SIGN; SHUT DOWN THE ENGINES AND WENT THROUGH OUR SHUTDOWN CHECKLIST. WHEN THE ENGINES STOPPED; I OPENED THE COCKPIT DOOR AND THE FA ASK ME IF WE KNEW ABOUT THE FIRE COMING FROM THE R ENGINE. I THOUGHT SHE WAS KIDDING AS THIS WAS OUR LAST ROUND TRIP OF A FOUR DAY. WELL; SHE WASN'T KIDDING AND SAID THAT A PAX TOLD HER THAT HE SAW A FIRE COMING FROM THE R ENGINE FOR ABOUT 1 1/2 MINS DURING OUR DESCENT. NOTE: HE TOLD HER THIS AS THEY WERE GATHERING THEIR BAGS FOR DEPLANING. SHE HAD NO PRIOR NOTICE OF PROBLEM OF ANY KIND! WHY THIS PAX DIDN'T TELL HER DURING THE EVENT IS BEYOND MY COMPREHENSION; BUT HE DIDN'T. DURING MY POST FLIGHT I NOTICED THAT THE R ENGINE INTAKE HEATER MAT WAS BURNED THROUGH. AT THIS TIME THE STRANGE FERTILIZER SMELL MADE SENSE TO ME. I WROTE UP THE HEATER MAT; THE FLIGHT BACK TO ZZZ1 WAS CANCELED AND WE WENT TO THE HOTEL FOR THE NIGHT. MAINT CAME ON THE LAST FLIGHT; REPLACED THE HEATER MAT AND WE FLEW IT BACK TO ZZZ1 THE NEXT MORNING. FA WAS TOLD FROM A PAX AT THE GATE THAT HE SAW A FIRE COMING FROM THE RIGHT ENGINE. IT WAS NOT AN ENGINE FIRE; BUT THE ENGINE INTAKE HEATER MAT. THEY ARE MADE OF COILED WIRES WITH CERAMIC INSULATION EMBEDDED INTO THE RUBBER THAT MAKES UP THE INTAKE HEATER MAT. UPON POST FLIGHT; I NOTICE THAT THE RIGHT ENGINE HEATER MAT WAS MELTED. THERE IS NO CHECKLIST OR MEMORY ITEM FOR THIS EVENT. I HAVE BEEN TOLD THAT THIS IS THE 4TH TIME IN THE LAST FEW MONTHS THAT THIS HAS OCCURRED; BUT NOTHING LIKE THIS. IN MY MANY THOUSANDS OF HOURS AS PIC ON THIS AIRCRAFT; I HAVE NEVER SMELLED A SMELL LIKE THIS; BUT NOW; I WILL PUT IT IN MY MEMORY EXPERIENCE BAG. PERHAPS THE COMPANY SHOULD PUT OUT A MEMO OF SOME KIND THAT STATES SOMETHING ABOUT A STRANGE FERTILIZER SMELL. QUESTION. WHAT WOULD HAVE HAPPENED IF THE PAX DIDN'T TELL THE FLT ATTENDANT ABOUT THE FIRE AND DURING MY POST FLIGHT INSPECTION; I MISSED THE HEATER MAT BEING MELTED? WHAT WOULD HAVE HAPPENED IF WE THEN TOOK OFF FOR HOME ON OUR LAST LEG OF A FOUR DAY; WENT BACK THROUGH THE MILD LOW SYSTEM AND I TURNED ON THE ENGINE ANTI-ICE SYSTEM?

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.