Narrative:

In cruise at FL330, .78 mach. Aircraft was IMC and experiencing light chop. WX radar was operating and painting no returns along our route of flight. Without warning, aircraft entered intense convective phenomenon. Aircraft experienced severe turbulence as it first lost altitude, followed by an altitude gain, followed by another loss. Aircraft deviated between 32500 ft and 33500 ft MSL. Aircraft was being flown by autoplt when incident began, but lost both the pitch and roll modes during altitude excursions. Incident lasted 20-30 seconds. Pilots assumed control from autoplt and returned to stable conditions at FL330 as turbulence ended. When the incident occurred, the seat belt sign was on and the flight attendants were conducting their service. The flight attendants reported no injuries to themselves and at the time reported no injuries to passenger. During the deplaning at dca, 1 passenger stated she had a sore neck. None of the pilots had experienced anything like that before. We advised ATC or our altitude deviation but we were not explicit. We did not say we had experienced 30 seconds of severe turbulence as we should have stated. We should also have explicit informed ATC we were unable to maintain assigned altitude, rather than saying we had deviated from our assigned altitude due to WX. The incident itself was unavoidable. In hindsight, I would have been much more explicit and informative in communicating our experience to ATC. I should have given a PIREP rather than merely advising of our altitude deviation.

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Original NASA ASRS Text

Title: TURB ENCOUNTER NEAR SPARTANBURG, SC.

Narrative: IN CRUISE AT FL330, .78 MACH. ACFT WAS IMC AND EXPERIENCING LIGHT CHOP. WX RADAR WAS OPERATING AND PAINTING NO RETURNS ALONG OUR RTE OF FLT. WITHOUT WARNING, ACFT ENTERED INTENSE CONVECTIVE PHENOMENON. ACFT EXPERIENCED SEVERE TURB AS IT FIRST LOST ALT, FOLLOWED BY AN ALT GAIN, FOLLOWED BY ANOTHER LOSS. ACFT DEVIATED BTWN 32500 FT AND 33500 FT MSL. ACFT WAS BEING FLOWN BY AUTOPLT WHEN INCIDENT BEGAN, BUT LOST BOTH THE PITCH AND ROLL MODES DURING ALT EXCURSIONS. INCIDENT LASTED 20-30 SECONDS. PLTS ASSUMED CTL FROM AUTOPLT AND RETURNED TO STABLE CONDITIONS AT FL330 AS TURB ENDED. WHEN THE INCIDENT OCCURRED, THE SEAT BELT SIGN WAS ON AND THE FLT ATTENDANTS WERE CONDUCTING THEIR SVC. THE FLT ATTENDANTS RPTED NO INJURIES TO THEMSELVES AND AT THE TIME RPTED NO INJURIES TO PAX. DURING THE DEPLANING AT DCA, 1 PAX STATED SHE HAD A SORE NECK. NONE OF THE PLTS HAD EXPERIENCED ANYTHING LIKE THAT BEFORE. WE ADVISED ATC OR OUR ALTDEV BUT WE WERE NOT EXPLICIT. WE DID NOT SAY WE HAD EXPERIENCED 30 SECONDS OF SEVERE TURB AS WE SHOULD HAVE STATED. WE SHOULD ALSO HAVE EXPLICIT INFORMED ATC WE WERE UNABLE TO MAINTAIN ASSIGNED ALT, RATHER THAN SAYING WE HAD DEVIATED FROM OUR ASSIGNED ALT DUE TO WX. THE INCIDENT ITSELF WAS UNAVOIDABLE. IN HINDSIGHT, I WOULD HAVE BEEN MUCH MORE EXPLICIT AND INFORMATIVE IN COMMUNICATING OUR EXPERIENCE TO ATC. I SHOULD HAVE GIVEN A PIREP RATHER THAN MERELY ADVISING OF OUR ALTDEV.

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.