Narrative:

Location: 60 NM south of bna approximately 180 degree radial direct lagra. At cruise altitude of FL290, company flight plan showed that any rough air was to terminate in the vicinity of pocket city. Radar returns showed nothing on wsi during preflight and nothing was seen on the ship radar prior to or during the encounter. The sudden onset of immediate moderate to severe chop and wing rock is the reason for this report. Despite frequent inquiries with ATC during each handoff prior to the position, there were no reports of anything like what we experienced, only light chop. A full moon indicated that we were in the clear on top of all cloud at FL290. Winds were generally 250 degrees and 50 KTS as per the flight plan. During the encounter, winds instantly became 270 degrees 100 KTS per our GPS readout. Lower altitude was requested and a descent to FL270 was made. A PA was made form the cockpit to have the flight attendants be seated immediately when the encounter occurred. Several PA's were made later to calm passenger. Upon landing I could not be certain of the number of G forces that we had experienced and entered in the E-6 log that the G meter be read to determine if an additional aircraft inspection was necessary. No passenger or flight attendant injuries were reported.

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Original NASA ASRS Text

Title: FLC OF A SUPER MD80 EXPERIENCE UNRPTED HIGH ALT WINDSHEAR TURB RESULTING IN NO KNOWN PAX OR FLT ATTENDANT INJURIES.

Narrative: LOCATION: 60 NM S OF BNA APPROX 180 DEG RADIAL DIRECT LAGRA. AT CRUISE ALT OF FL290, COMPANY FLT PLAN SHOWED THAT ANY ROUGH AIR WAS TO TERMINATE IN THE VICINITY OF POCKET CITY. RADAR RETURNS SHOWED NOTHING ON WSI DURING PREFLT AND NOTHING WAS SEEN ON THE SHIP RADAR PRIOR TO OR DURING THE ENCOUNTER. THE SUDDEN ONSET OF IMMEDIATE MODERATE TO SEVERE CHOP AND WING ROCK IS THE REASON FOR THIS RPT. DESPITE FREQUENT INQUIRIES WITH ATC DURING EACH HDOF PRIOR TO THE POS, THERE WERE NO RPTS OF ANYTHING LIKE WHAT WE EXPERIENCED, ONLY LIGHT CHOP. A FULL MOON INDICATED THAT WE WERE IN THE CLR ON TOP OF ALL CLOUD AT FL290. WINDS WERE GENERALLY 250 DEGS AND 50 KTS AS PER THE FLT PLAN. DURING THE ENCOUNTER, WINDS INSTANTLY BECAME 270 DEGS 100 KTS PER OUR GPS READOUT. LOWER ALT WAS REQUESTED AND A DSCNT TO FL270 WAS MADE. A PA WAS MADE FORM THE COCKPIT TO HAVE THE FLT ATTENDANTS BE SEATED IMMEDIATELY WHEN THE ENCOUNTER OCCURRED. SEVERAL PA'S WERE MADE LATER TO CALM PAX. UPON LNDG I COULD NOT BE CERTAIN OF THE NUMBER OF G FORCES THAT WE HAD EXPERIENCED AND ENTERED IN THE E-6 LOG THAT THE G METER BE READ TO DETERMINE IF AN ADDITIONAL ACFT INSPECTION WAS NECESSARY. NO PAX OR FLT ATTENDANT INJURIES WERE RPTED.

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.