Narrative:

At cruise of FL330, the captain noticed the cargo halon fire bottle light was illuminated. We discussed that it shouldn't have discharged on its own. Then we received a call from the purser. She told us there was smoke in the cabin and it was hot in the back. We declared an emergency and got a radar vector from ZJX. The captain was flying the airplane and descended to 6000 ft. I fought the fire. I kept the purser on the intercom. I asked where the heat was coming from and she said rows 6-9. I suspected a forward cargo fire. I did the cargo fire checklist. I shot the cargo halon bottle just in case it was a false indication and didn't really discharge previously. 1 min later, we had a fire bell, fire warning and forward cargo red light. I told the captain we had a forward cargo fire. The purser told me the carpet was glowing. I turned off the left air conditioning pack because of a previous write-up about smoke coming from the pack. Maintenance replaced it, but I was still suspicious. We got sea reports because we were going to ditch the plane. I asked the purser how it was in the back and she said the smoke was clearing and it was getting cooler. I asked her if the floor was still glowing. She said no. We canceled the ditching plans and landed at jax. The fire department checked both forward and aft cargo compartments on runway. I worked with maintenance to figure out why things were not in a normal sequence. We checked the left acm -- it was new. There were no traces of fire. I told him the floor was hot forward of the acm. The mechanic took off the back panels of the forward cargo. He found the cargo halon bottle and it had thermally discharged. Then he found a bleed air leak in the mixing chamber of the left acm. It had caused the thermal discharge of the cargo halon bottle. The smoke was coming from the oil heating up in that area. The cargo fire bell and lights were caused by the high pressure bleed leak pushing the halon into the forward cargo compartment and the smoke detectors (density meters) thought it was smoke. Suggestion: have the halon bottles thermally discharge overboard. This system was designed after the autoplt was built.

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Original NASA ASRS Text

Title: A B737-200 IN CRUISE AT FL330 DECLARED AN EMER AND DIVERTED DUE TO SMOKE IN THE CABIN AND FORWARD CARGO FIRE WARNING. CAUSED BY A LEAKING PNEUMATIC DUCT.

Narrative: AT CRUISE OF FL330, THE CAPT NOTICED THE CARGO HALON FIRE BOTTLE LIGHT WAS ILLUMINATED. WE DISCUSSED THAT IT SHOULDN'T HAVE DISCHARGED ON ITS OWN. THEN WE RECEIVED A CALL FROM THE PURSER. SHE TOLD US THERE WAS SMOKE IN THE CABIN AND IT WAS HOT IN THE BACK. WE DECLARED AN EMER AND GOT A RADAR VECTOR FROM ZJX. THE CAPT WAS FLYING THE AIRPLANE AND DSNDED TO 6000 FT. I FOUGHT THE FIRE. I KEPT THE PURSER ON THE INTERCOM. I ASKED WHERE THE HEAT WAS COMING FROM AND SHE SAID ROWS 6-9. I SUSPECTED A FORWARD CARGO FIRE. I DID THE CARGO FIRE CHKLIST. I SHOT THE CARGO HALON BOTTLE JUST IN CASE IT WAS A FALSE INDICATION AND DIDN'T REALLY DISCHARGE PREVIOUSLY. 1 MIN LATER, WE HAD A FIRE BELL, FIRE WARNING AND FORWARD CARGO RED LIGHT. I TOLD THE CAPT WE HAD A FORWARD CARGO FIRE. THE PURSER TOLD ME THE CARPET WAS GLOWING. I TURNED OFF THE L AIR CONDITIONING PACK BECAUSE OF A PREVIOUS WRITE-UP ABOUT SMOKE COMING FROM THE PACK. MAINT REPLACED IT, BUT I WAS STILL SUSPICIOUS. WE GOT SEA RPTS BECAUSE WE WERE GOING TO DITCH THE PLANE. I ASKED THE PURSER HOW IT WAS IN THE BACK AND SHE SAID THE SMOKE WAS CLRING AND IT WAS GETTING COOLER. I ASKED HER IF THE FLOOR WAS STILL GLOWING. SHE SAID NO. WE CANCELED THE DITCHING PLANS AND LANDED AT JAX. THE FIRE DEPT CHKED BOTH FORWARD AND AFT CARGO COMPARTMENTS ON RWY. I WORKED WITH MAINT TO FIGURE OUT WHY THINGS WERE NOT IN A NORMAL SEQUENCE. WE CHKED THE L ACM -- IT WAS NEW. THERE WERE NO TRACES OF FIRE. I TOLD HIM THE FLOOR WAS HOT FORWARD OF THE ACM. THE MECH TOOK OFF THE BACK PANELS OF THE FORWARD CARGO. HE FOUND THE CARGO HALON BOTTLE AND IT HAD THERMALLY DISCHARGED. THEN HE FOUND A BLEED AIR LEAK IN THE MIXING CHAMBER OF THE L ACM. IT HAD CAUSED THE THERMAL DISCHARGE OF THE CARGO HALON BOTTLE. THE SMOKE WAS COMING FROM THE OIL HEATING UP IN THAT AREA. THE CARGO FIRE BELL AND LIGHTS WERE CAUSED BY THE HIGH PRESSURE BLEED LEAK PUSHING THE HALON INTO THE FORWARD CARGO COMPARTMENT AND THE SMOKE DETECTORS (DENSITY METERS) THOUGHT IT WAS SMOKE. SUGGESTION: HAVE THE HALON BOTTLES THERMALLY DISCHARGE OVERBOARD. THIS SYS WAS DESIGNED AFTER THE AUTOPLT WAS BUILT.

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.