Narrative:

Prior to departure of flight X, maintenance was investigating right pack operation and subsequently placarded the right pack inoperative. I notified dispatch per MEL advanced notification procedure of single pack operation. When maintenance complete, I personally inspected the pack access door was closed and visually that all latches were latched prior to departure. In climb to FL310 (intermediate altitude) just past la belle (lbv) prior to sarasota on J-86 at FL280 and 305 KTS, aircraft experienced a thud followed by a vibration. Flight attendants informed me of abnormal vibration most pronounced in business class floor section of the aircraft. I directed air carrier X airlines pilot jump seat rider to investigate flight attendant's report. Pilot confirmed flight attendant's report stating the vibration was more pronounced in business class. Declared emergency to ZJX and requested return to ZZZ. Notified dispatch via ACARS of return to ZZZ due to aircraft vibration. Descended to FL240 and slowed to 240 KTS on return to ZZZ. Vibration was reduced at the lower altitude and decreased airspeed. Requested arff as precaution and visual inspection upon landing. Requested and landed on runway 9R (13000 ft) at 278500 pounds (500 pounds overweight). Landing and touchdown was smooth. Postflt maintenance inspection found right pack access door missing from aircraft.

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Original NASA ASRS Text

Title: A B767 IN CLB AT FL280 HAD THE R AIR CONDITIONING PACK ACCESS DOOR DEPART THE ACFT. MAINT WORK DONE PRIOR TO DEP ON R PACK.

Narrative: PRIOR TO DEP OF FLT X, MAINT WAS INVESTIGATING R PACK OP AND SUBSEQUENTLY PLACARDED THE R PACK INOP. I NOTIFIED DISPATCH PER MEL ADVANCED NOTIFICATION PROC OF SINGLE PACK OP. WHEN MAINT COMPLETE, I PERSONALLY INSPECTED THE PACK ACCESS DOOR WAS CLOSED AND VISUALLY THAT ALL LATCHES WERE LATCHED PRIOR TO DEP. IN CLB TO FL310 (INTERMEDIATE ALT) JUST PAST LA BELLE (LBV) PRIOR TO SARASOTA ON J-86 AT FL280 AND 305 KTS, ACFT EXPERIENCED A THUD FOLLOWED BY A VIBRATION. FLT ATTENDANTS INFORMED ME OF ABNORMAL VIBRATION MOST PRONOUNCED IN BUSINESS CLASS FLOOR SECTION OF THE ACFT. I DIRECTED ACR X AIRLINES PLT JUMP SEAT RIDER TO INVESTIGATE FLT ATTENDANT'S RPT. PLT CONFIRMED FLT ATTENDANT'S RPT STATING THE VIBRATION WAS MORE PRONOUNCED IN BUSINESS CLASS. DECLARED EMER TO ZJX AND REQUESTED RETURN TO ZZZ. NOTIFIED DISPATCH VIA ACARS OF RETURN TO ZZZ DUE TO ACFT VIBRATION. DSNDED TO FL240 AND SLOWED TO 240 KTS ON RETURN TO ZZZ. VIBRATION WAS REDUCED AT THE LOWER ALT AND DECREASED AIRSPD. REQUESTED ARFF AS PRECAUTION AND VISUAL INSPECTION UPON LNDG. REQUESTED AND LANDED ON RWY 9R (13000 FT) AT 278500 LBS (500 LBS OVERWEIGHT). LNDG AND TOUCHDOWN WAS SMOOTH. POSTFLT MAINT INSPECTION FOUND R PACK ACCESS DOOR MISSING FROM ACFT.

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.