E145 FLT CREW ENCOUNTERS MOMENTARY LAV SMOKE EICAS MSG UNSUPPORTED BY VISUAL INSPECTION. INDICATION IS DISREGARDED. SUBSEQUENT FLT ON SAME ACFT RESULTS IN REPEAT MSG AND AN EMERGENCY IS DECLARED AND RETURN TO TKOF ARPT ACCOMPLISHED.

Narrative

I WAS THE CAPT OF THIS FLT. DURING INITIAL CLBOUT FROM ZZZ ON THE 185 DEG RADIAL FROM ZZZ VOR; WE RECEIVED 'LAVATORY SMOKE' EICAS. THE MESSAGE APPEARED ALONG WITH THE FIRE BELL IN THE CABIN RIGHT AFTER WE APPLIED 'CLB THRUST' PWR SETTING. THE WARNING CAME ON AND THEN WENT OFF BTWN 10-15 SECONDS. BEFORE I COULD EVEN GET TO THE TABLE OF CONTENTS ON THE QRH THE INDICATION HAD DISAPPEARED. I CALLED THE FLT ATTENDANT AND SHE SAID THAT THERE WAS ABSOLUTELY NO SMOKE OR FIRE IN THE LAVATORY OR ANY OF ITS COMPARTMENTS WHATSOEVER AND THAT THE ALARM HAD CEASED A FEW SECONDS AFTER IT BEGAN. SHE ASKED PAX IF ANYBODY SMELLED ANYTHING LIKE SMOKE OR ANYTHING BURNING. NOBODY SMELLED ANYTHING. WE RAN THE LAVATORY SMOKE CHKLIST WHICH INVOLVES PULLING 2 CIRCUIT BREAKERS FOR THE LAVATORY FLUSHER AND THE LIGHTS AND THEN REFERS YOU TO 'CABIN FIRE OR SMOKE' CHKLISTS. THE CONDITIONS DID NOT APPLY FOR THIS ONE; SO WE CONTINUED THE LAVATORY SMOKE CHKLIST WHICH ENDS WITH 'EVAC-CONSIDER.' I DIDN'T BELIEVE AN EVAC WAS NECESSARY. WE INFORMED ATC OF WHAT HAD HAPPENED RIGHT AWAY AND TOLD THEM THAT WE NEEDED A HDG STRAIGHT AHEAD AND TO PLEASE STAND BY IN CASE WE DECIDED A DIVERSION WAS NECESSARY. I ASKED THE FLT ATTENDANT AGAIN ABOUT SMOKE; FIRE; SMOKE ODOR OR ANY INDICATION WHATSOEVER. SHE SAID 'NO; NOTHING.' I TOOK A SECOND SCAN AT THE CHKLIST AND THEN PUT IT AWAY. WE BOTH AGREED THAT THIS WAS A FALSE INDICATION AND THAT IT HAD STOPPED. I DECIDED TO CONTINUE TO ZZZ2 AND NOT DECLARE AN EMER. WHEN WE ARRIVED IN ZZZ2 AND WROTE UP THE PROB; MAINT SAID THAT THE SMOKE DETECTOR LOOKED VERY DIRTY AND THAT WE PROBABLY GOT A FALSE INDICATION WHEN WE PRESSURIZED. ON THIS AIRPLANE; MESSAGES WILL SOMETIMES APPEAR AND THEN GO AWAY. I FELT THAT THIS WAS A FALSE INDICATION AND CONTINUED TO MY DEST. THE MESSAGE CAME ON AND THEN WENT AWAY BEFORE I COULD EVEN GET TO THE CHKLIST. THERE WERE SIMPLY NO FIRE CONDITIONS PRESENT. I CONSULTED THE OPS MANUAL AFTER THE FLT WHICH STATES THAT ANY FIRE OR INDICATION OF FIRE CONSTITUTES AN EMER; AND THAT ATC SHOULD BE ADVISED OF THE EMER. BEFORE I EVER HAD A CHANCE TO TALK WITH ATC ABOUT IT AND WHILE WE WERE STILL ASSESSING THE PROB; ALL INDICATIONS WERE GONE. IN FACT; THE ONLY INDICATION WAS THE FIRE ALARM. NO SMOKE; FIRE OR ODOR. I TOLD MYSELF THAT I WOULD DECLARE AN EMER THE NEXT TIME THAT THIS HAPPENED TO ME AND RETURN TO THE ARPT OR DIVERT. IRONICALLY; IT HAPPENED 2 DAYS LATER IN THE SAME AIRPLANE. THIS FLT BROUGHT ME THE SAME MESSAGE AT NEARLY THE SAME TIME DURING FLT. THIS TIME; WE HAD A GEAR PROB AS WELL. THE LNDG GEAR DIDN'T WANT TO RETRACT WHEN WE TOOK OFF. WHILE I WAS XMITTING TO ATC THAT WE'D BE RETURNING TO LAND IN ZZZ2; THE MASTER WARNING WENT OFF WITH A LAVATORY SMOKE EICAS. THE FLT ATTENDANT KNEW THIS DRILL WELL AFTER THE FIRST INCIDENT AS WELL AS I. THIS TIME WAS DIFFERENT. THE FIRE BELL IN THE CABIN STAYED ON TO 3-4 MINS AND THE FLT ATTENDANT SAID THAT SHE AND A DEADHEADING CREW MEMBER IN THE BACK SMELLED SOMETHING FUNNY; LIKE A DIRTY FURNACE OR SOMETHING HOT AND DUSTY. WE DONNED MASKS AND GOGGLES AND COMPLETED MEMORY ITEMS FOR CABIN FIRE OR SMOKE. I THEN DECLARED AN EMER WITH ATC. WE ACCOMPLISHED ALL CHKLISTS AND THE FLT ATTENDANT SAID THAT THE INDICATION WAS GONE AND SO WAS THE ODOR IN THE BACK. I DOUBLECHKED FOR CONDITIONS JUST BEFORE STARTING THE APCH AND THEN RIGHT AFTER WE CLRED THE RWY. SHE SAID EVERYTHING WAS OK. I FELT THAT THERE WAS NO NEED TO EVAC AT THAT TIME SO WE RETURNED TO THE GATE AND LET THE PAX OFF THERE. FIRST THE GEAR WOULDN'T GO UP AND THEN THE FIRE ALARM -- ONE RIGHT AFTER THE OTHER. WE WERE BUSY UNDER THE MASKS AND GOGGLES THAT'S FOR SURE. THIS TIME AN EMER WAS DECLARED LIKE THE OPS MANUAL SAID TO DO; AND THIS TIME IT SEEMED LIKE THE RIGHT THING TO DO. I HAD SHARED MY FIRST STORY WITH A COUPLE OTHER CHK AIRMEN AND THEY THOUGHT I'D MADE A CLEAN DECISION DURING THE FIRST FLT. I THINK I MAY TELL THEM THAT PERHAPS IT WASN'T IF I'D TAKEN THE OPS MANUAL LITERALLY. EVEN IF I HAD DECLARED AN EMER ON THE FIRST FLT; SHOULD I HAVE CANCELED IT 20 SECONDS LATER WHEN THE ALARM CEASED? I RECOMMEND TRAINING TO NEW HIRES REGARDING THESE EICAS MESSAGES THAT COME ON AND THEN GO AWAY IMMEDIATELY. IT TENDS TO LEAVE AN IMPRESSION THAT IT'S A FALSE INDICATION OR THAT THE PROB HAS GONE AWAY.