Narrative:

On 8/xx/92, we were taxiing out for departure from O'hare for ft wayne, in, on a scheduled flight. While still moving into the #1 position for takeoff the engine fire warning system for our right engine activated. My first officer and I completed our memory items and associated checklists for this event uneventfully without a catastrophic outcome. As it turns out it was a false fire warning. This was not a first time occurrence for me with the mdt. Some months back (with a different crew and aircraft) I experienced the same situation only that time I was 8 mi out on final to runway 27L at O'hare. At that time we also completed our memory items and associated checklists germane to the event without a catastrophic outcome. It was a false fire warning then also. The first time it happened to me we deplaned our passenger down the airstairs on a taxiway well clear of the 'busy' active runway rather than to blow the chutes as we could see no signs of fire. The second time it happened we did not deplane our passenger as suggested by the checklist for this event. Our reasoning for handling the situation as we did the second time causes me some consternation. The mdt is known to have these false fire warnings from time to time in our experience. As far as I'm able to determine, there has never been an actual engine fire. I am not sure just how many we've had since putting the mdt into service a couple of yrs back but there have been several. When we (as an airline) were first confronted with these false warnings, our company and the manufacture went to obvious great lengths to determine the cause and come up with a modification to alleviate the problem. It seemed to work. Now all of the sudden I find that in the past couple of days these problems have started raising their ugly head again. I have full confidence that a cause and solution for this serious problem will be quickly forthcoming from our company and the manufacture. My biggest concern in this matter is how we handled the situation today. The fire warning system (as with any aircraft I've flown with such a system) leaves no doubt in your mind what the warning is. It's loud and clear. When it happened today my crew and I reacted calmly and in a timely manner to the situation which personally pleased me immensely. However in the back of my and my first officer's mind (as I found out later) this was just another false warning. We stopped short of deplaning our passenger because of this. We monitored the aircraft closely for any visual signs of a fire until it was definitely determined to our satisfaction there was no actual fire. We did this consciously and intentionally because of our experience with this situation before. Our company has gone to great lengths in suggesting we do this because of the past false warnings. We did not want to get someone hurt deplaning/semi-evacuating the aircraft and we certainly did not want passenger possibly panicking and running around on an active runway at the busiest airport in the world because of a possible false fire warning. Because of the fact that we were correct and it was a false warning, our decision would lead one to believe we reacted appropriately under the circumstances. Or did we? We were placed in a situation which in my opinion dictated that we 'take a chance.' making that statement 'take a chance' makes me cringe. It's totally against the grain of all my training and experience in this profession. If you will excuse the pun 'this subject is a hot one among the crews' and I am not personally sure if an appropriate, definitive answer to my consternation may ever be found. Callback conversation with reporter revealed the following information. Both the company and the manufacturer responded promptly to the false fire warning problem, and there have been no recurrences. The reporter noted that the company, manufacturer, and the FAA moved quickly and effectively to handle the situation. The false engine fire warning was traced to moisture contamination of the engine electrical indicating systems wiring harness cannon plug located at the top of the engine nacelle.

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Original NASA ASRS Text

Title: AN ACR COMMUTER ACFT ABORTS TKOF AT ORD FOR A FALSE ENG FIRE WARNING.

Narrative: ON 8/XX/92, WE WERE TAXIING OUT FOR DEP FROM O'HARE FOR FT WAYNE, IN, ON A SCHEDULED FLT. WHILE STILL MOVING INTO THE #1 POS FOR TKOF THE ENG FIRE WARNING SYS FOR OUR R ENG ACTIVATED. MY FO AND I COMPLETED OUR MEMORY ITEMS AND ASSOCIATED CHKLISTS FOR THIS EVENT UNEVENTFULLY WITHOUT A CATASTROPHIC OUTCOME. AS IT TURNS OUT IT WAS A FALSE FIRE WARNING. THIS WAS NOT A FIRST TIME OCCURRENCE FOR ME WITH THE MDT. SOME MONTHS BACK (WITH A DIFFERENT CREW AND ACFT) I EXPERIENCED THE SAME SITUATION ONLY THAT TIME I WAS 8 MI OUT ON FINAL TO RWY 27L AT O'HARE. AT THAT TIME WE ALSO COMPLETED OUR MEMORY ITEMS AND ASSOCIATED CHKLISTS GERMANE TO THE EVENT WITHOUT A CATASTROPHIC OUTCOME. IT WAS A FALSE FIRE WARNING THEN ALSO. THE FIRST TIME IT HAPPENED TO ME WE DEPLANED OUR PAX DOWN THE AIRSTAIRS ON A TAXIWAY WELL CLR OF THE 'BUSY' ACTIVE RWY RATHER THAN TO BLOW THE CHUTES AS WE COULD SEE NO SIGNS OF FIRE. THE SECOND TIME IT HAPPENED WE DID NOT DEPLANE OUR PAX AS SUGGESTED BY THE CHKLIST FOR THIS EVENT. OUR REASONING FOR HANDLING THE SITUATION AS WE DID THE SECOND TIME CAUSES ME SOME CONSTERNATION. THE MDT IS KNOWN TO HAVE THESE FALSE FIRE WARNINGS FROM TIME TO TIME IN OUR EXPERIENCE. AS FAR AS I'M ABLE TO DETERMINE, THERE HAS NEVER BEEN AN ACTUAL ENG FIRE. I AM NOT SURE JUST HOW MANY WE'VE HAD SINCE PUTTING THE MDT INTO SVC A COUPLE OF YRS BACK BUT THERE HAVE BEEN SEVERAL. WHEN WE (AS AN AIRLINE) WERE FIRST CONFRONTED WITH THESE FALSE WARNINGS, OUR COMPANY AND THE MANUFACTURE WENT TO OBVIOUS GREAT LENGTHS TO DETERMINE THE CAUSE AND COME UP WITH A MODIFICATION TO ALLEVIATE THE PROBLEM. IT SEEMED TO WORK. NOW ALL OF THE SUDDEN I FIND THAT IN THE PAST COUPLE OF DAYS THESE PROBLEMS HAVE STARTED RAISING THEIR UGLY HEAD AGAIN. I HAVE FULL CONFIDENCE THAT A CAUSE AND SOLUTION FOR THIS SERIOUS PROBLEM WILL BE QUICKLY FORTHCOMING FROM OUR COMPANY AND THE MANUFACTURE. MY BIGGEST CONCERN IN THIS MATTER IS HOW WE HANDLED THE SITUATION TODAY. THE FIRE WARNING SYS (AS WITH ANY ACFT I'VE FLOWN WITH SUCH A SYS) LEAVES NO DOUBT IN YOUR MIND WHAT THE WARNING IS. IT'S LOUD AND CLR. WHEN IT HAPPENED TODAY MY CREW AND I REACTED CALMLY AND IN A TIMELY MANNER TO THE SITUATION WHICH PERSONALLY PLEASED ME IMMENSELY. HOWEVER IN THE BACK OF MY AND MY FO'S MIND (AS I FOUND OUT LATER) THIS WAS JUST ANOTHER FALSE WARNING. WE STOPPED SHORT OF DEPLANING OUR PAX BECAUSE OF THIS. WE MONITORED THE ACFT CLOSELY FOR ANY VISUAL SIGNS OF A FIRE UNTIL IT WAS DEFINITELY DETERMINED TO OUR SATISFACTION THERE WAS NO ACTUAL FIRE. WE DID THIS CONSCIOUSLY AND INTENTIONALLY BECAUSE OF OUR EXPERIENCE WITH THIS SITUATION BEFORE. OUR COMPANY HAS GONE TO GREAT LENGTHS IN SUGGESTING WE DO THIS BECAUSE OF THE PAST FALSE WARNINGS. WE DID NOT WANT TO GET SOMEONE HURT DEPLANING/SEMI-EVACUATING THE ACFT AND WE CERTAINLY DID NOT WANT PAX POSSIBLY PANICKING AND RUNNING AROUND ON AN ACTIVE RWY AT THE BUSIEST ARPT IN THE WORLD BECAUSE OF A POSSIBLE FALSE FIRE WARNING. BECAUSE OF THE FACT THAT WE WERE CORRECT AND IT WAS A FALSE WARNING, OUR DECISION WOULD LEAD ONE TO BELIEVE WE REACTED APPROPRIATELY UNDER THE CIRCUMSTANCES. OR DID WE? WE WERE PLACED IN A SITUATION WHICH IN MY OPINION DICTATED THAT WE 'TAKE A CHANCE.' MAKING THAT STATEMENT 'TAKE A CHANCE' MAKES ME CRINGE. IT'S TOTALLY AGAINST THE GRAIN OF ALL MY TRAINING AND EXPERIENCE IN THIS PROFESSION. IF YOU WILL EXCUSE THE PUN 'THIS SUBJECT IS A HOT ONE AMONG THE CREWS' AND I AM NOT PERSONALLY SURE IF AN APPROPRIATE, DEFINITIVE ANSWER TO MY CONSTERNATION MAY EVER BE FOUND. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO. BOTH THE COMPANY AND THE MANUFACTURER RESPONDED PROMPTLY TO THE FALSE FIRE WARNING PROBLEM, AND THERE HAVE BEEN NO RECURRENCES. THE RPTR NOTED THAT THE COMPANY, MANUFACTURER, AND THE FAA MOVED QUICKLY AND EFFECTIVELY TO HANDLE THE SITUATION. THE FALSE ENG FIRE WARNING WAS TRACED TO MOISTURE CONTAMINATION OF THE ENG ELECTRICAL INDICATING SYSTEMS WIRING HARNESS CANNON PLUG LOCATED AT THE TOP OF THE ENG NACELLE.

Data retrieved from NASA's ASRS site as of July 2007 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.