Narrative:

Approaching initial cruise altitude FL340 encountered light to moderate chop conditions in clear air; as the ride smoothed out detected a vibration in the hull. Noted with center autopilot on; as hull vibration would increase with speed; autopilot would apply right aileron. All other indications were normal. [We] notified dispatch of our status; engaged three-way call with maintenance control. Maintenance control reviewed the aircraft history advised many reports of AC pack rumble/vibration. [We] discussed further game plan with dispatch regarding flight alternates and weather. Soon after signing off with dispatch; flight encountered more light chop followed by much heavier hull vibration; noted much larger autopilot input of right aileron. All other indications appeared normal. At this time a flight attendant reported from the cabin; hearing a loud bang and unusual heavy vibration in the floor from over the wing back to aft galley. The relief officer walked through the aft cabin and reported feeling the vibration; otherwise everything looked normal. I declared an emergency/mayday with ATC received clearance to descend and return along outbound route back to departure airport; briefed first officers; briefed flight attendants; made a PA to passengers. [We] notified dispatch of our deteriorating situation and decision to return to departure airport. Aircraft hull vibration lessened with slower airspeed. Landed overweight; inspected by airport rescue and fire fighting; terminated emergency; and taxied to park without any additional complications. Notes: maintenance found 2 support links for right wing inbd T/east panel sheared. Flight attendants working aft cabin from inbound flight noted 'not normal occasional vibration' which they reported to the purser. However due to unusual circumstances the purser did not pass this information along to the other pilots. Important to stress to all flight attendants they are our eyes and ears in the back; trust their time and experience to tell us when something is/seems wrong. This potentially dangerous event could possibly have been avoided if purser had passed on information to captain on previous flight aboard this aircraft. On our flight; a flight attendant dropped everything to immediately notify us that something was wrong in a most professional manner; outstanding job.

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Original NASA ASRS Text

Title: A B757 flight crew declared an emergency and returned to the departure airport after a hull vibration was detected. Maintenance reported that a right wing inboard trailing edge panel had sheared.

Narrative: Approaching initial cruise altitude FL340 encountered light to moderate chop conditions in clear air; as the ride smoothed out detected a vibration in the hull. Noted with center autopilot on; as hull vibration would increase with speed; autopilot would apply right aileron. All other indications were normal. [We] notified Dispatch of our status; engaged three-way call with Maintenance Control. Maintenance Control reviewed the aircraft history advised many reports of AC Pack rumble/vibration. [We] discussed further game plan with Dispatch regarding flight alternates and weather. Soon after signing off with Dispatch; flight encountered more light chop followed by much heavier hull vibration; noted much larger autopilot input of right aileron. All other indications appeared normal. At this time a Flight Attendant reported from the cabin; hearing a loud bang and unusual heavy vibration in the floor from over the wing back to aft galley. The Relief Officer walked through the aft cabin and reported feeling the vibration; otherwise everything looked normal. I declared an emergency/mayday with ATC received clearance to descend and return along outbound route back to departure airport; briefed First Officers; briefed Flight Attendants; made a PA to passengers. [We] notified Dispatch of our deteriorating situation and decision to return to departure airport. Aircraft hull vibration lessened with slower airspeed. Landed overweight; inspected by Airport Rescue and Fire Fighting; terminated emergency; and taxied to park without any additional complications. Notes: Maintenance found 2 support links for right wing INBD T/E PANEL sheared. Flight Attendants working aft cabin from inbound flight noted 'not normal occasional vibration' which they reported to the Purser. However due to unusual circumstances the Purser did not pass this information along to the other pilots. Important to stress to all Flight Attendants they are our eyes and ears in the back; trust their time and experience to tell us when something is/seems wrong. This potentially dangerous event could possibly have been avoided if Purser had passed on information to Captain on previous flight aboard this aircraft. On our flight; a Flight Attendant dropped everything to immediately notify us that something was wrong in a most professional manner; outstanding job.

Data retrieved from NASA's ASRS site as of April 2012 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.