Narrative:

Crew arrived at the aircraft in ZZZ1. With APU supplying electricity/air; the right air conditioning pack had overtemp'ed (pack reset ok after it cooled). Right pack operating but still putting out warm air. Maintenance arrived and decided to MEL the right pack. Dispatch notified for re-release and issued new release; stating right pack inoperative. Takeoff and climb out normal. At approximately XA45Z over abc VORTAC; leveled off at FL330. Within approximately 1 min; heard a distinct thud with corresponding brief puff of smoke with burning smell in the flight deck. (Smell lasted 15-30 seconds. All engine; pressurization; aircraft system normal with no EICAS/status messages.) flight attendants called on interphone with report of the same thud and smell from area around door 2. This cabin smell quickly dissipates. Captain and first officer considered diverting and concurred the prudent and safe action was to declare an emergency and divert to ZZZ2. Captain contacted dispatch via radio to advise of diversion to ZZZ2 and to relay to ZZZ2 operations. In our descent into ZZZ2 (approximately XB05Z); had second thud and brief smoke smell similar to the first occurrence. First officer was PF. Captain was PNF and reviewed the emergency checklist. Due to zero presence of smoke in flight deck and cabin; captain decided (with first officer concurrence) that it was more prudent to keep the oxygen masks at the ready; but wasn't necessary to don the equipment. Everything checked out normal and we taxied to gate. Maintenance replaced right recirculation fan and some filters (no obvious damage).

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Original NASA ASRS Text

Title: A B757-200 EXPERIENCED BRIEF SMOKE AND FUMES AT CRUISE ALT; DECLARED AN EMER; AND DIVERTED TO AN ALTERNATE ARPT.

Narrative: CREW ARRIVED AT THE ACFT IN ZZZ1. WITH APU SUPPLYING ELECTRICITY/AIR; THE R AIR CONDITIONING PACK HAD OVERTEMP'ED (PACK RESET OK AFTER IT COOLED). R PACK OPERATING BUT STILL PUTTING OUT WARM AIR. MAINT ARRIVED AND DECIDED TO MEL THE R PACK. DISPATCH NOTIFIED FOR RE-RELEASE AND ISSUED NEW RELEASE; STATING R PACK INOP. TKOF AND CLBOUT NORMAL. AT APPROX XA45Z OVER ABC VORTAC; LEVELED OFF AT FL330. WITHIN APPROX 1 MIN; HEARD A DISTINCT THUD WITH CORRESPONDING BRIEF PUFF OF SMOKE WITH BURNING SMELL IN THE FLT DECK. (SMELL LASTED 15-30 SECONDS. ALL ENG; PRESSURIZATION; ACFT SYS NORMAL WITH NO EICAS/STATUS MESSAGES.) FLT ATTENDANTS CALLED ON INTERPHONE WITH RPT OF THE SAME THUD AND SMELL FROM AREA AROUND DOOR 2. THIS CABIN SMELL QUICKLY DISSIPATES. CAPT AND FO CONSIDERED DIVERTING AND CONCURRED THE PRUDENT AND SAFE ACTION WAS TO DECLARE AN EMER AND DIVERT TO ZZZ2. CAPT CONTACTED DISPATCH VIA RADIO TO ADVISE OF DIVERSION TO ZZZ2 AND TO RELAY TO ZZZ2 OPS. IN OUR DSCNT INTO ZZZ2 (APPROX XB05Z); HAD SECOND THUD AND BRIEF SMOKE SMELL SIMILAR TO THE FIRST OCCURRENCE. FO WAS PF. CAPT WAS PNF AND REVIEWED THE EMER CHKLIST. DUE TO ZERO PRESENCE OF SMOKE IN FLT DECK AND CABIN; CAPT DECIDED (WITH FO CONCURRENCE) THAT IT WAS MORE PRUDENT TO KEEP THE OXYGEN MASKS AT THE READY; BUT WASN'T NECESSARY TO DON THE EQUIP. EVERYTHING CHKED OUT NORMAL AND WE TAXIED TO GATE. MAINT REPLACED R RECIRCULATION FAN AND SOME FILTERS (NO OBVIOUS DAMAGE).

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.