Narrative:

We were climbing through FL290 in a large transport en route to our assigned altitude of FL330 when we encountered moderate to severe turbulence. The turbulence was so bad, we could not maintain altitude with either climb or takeoff power. We requested descent to a lower altitude and were told to maintain FL290 and switch to another frequency. We informed the controller we could not maintain altitude due to severe turbulence and were descending. We were again told to maintain altitude and switch frequencys. We did so and told the next controller we were descending through FL280 requesting lower. We were told to maintain FL270. We informed the controller we were unable due to severe turbulence and were descending. We were told to switch frequencys again. We did so and informed the next controller we were passing FL260 unable to maintain zlt due to severe turbulence. We were then cleared to FL190. The turbulence abated as we passed through FL240. The rest of the flight was uneventful with occasional sessions of light to moderate chop as we passed through clouds in the new york area. During the period we experienced the severe turbulence our slow climb changed to a steady descent at about 280 KIAS (best turbulence airspeed). As I mentioned earlier we could not sustain a climb or cruise at climb or takeoff power. The aircraft was bounced around so violently we could barely read the instruments and the captain could barely maintain control. We simply could not sustain level flight under those conditions. On arrival at our destination (lga) we made an entry in the aircraft maintenance log (eg) encountered severe turbulence of a period of 4-6 mins.

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Original NASA ASRS Text

Title: ACR LGT UNABLE TO MAINTAIN CLB OR LEVEL FLT DUE TO TURB HAS TROUBLE GETTING A LOWER ALT FROM ARTCC.

Narrative: WE WERE CLBING THROUGH FL290 IN A LGT ENRTE TO OUR ASSIGNED ALT OF FL330 WHEN WE ENCOUNTERED MODERATE TO SEVERE TURB. THE TURB WAS SO BAD, WE COULD NOT MAINTAIN ALT WITH EITHER CLB OR TKOF PWR. WE REQUESTED DSCNT TO A LOWER ALT AND WERE TOLD TO MAINTAIN FL290 AND SWITCH TO ANOTHER FREQ. WE INFORMED THE CTLR WE COULD NOT MAINTAIN ALT DUE TO SEVERE TURB AND WERE DSNDING. WE WERE AGAIN TOLD TO MAINTAIN ALT AND SWITCH FREQS. WE DID SO AND TOLD THE NEXT CTLR WE WERE DSNDING THROUGH FL280 REQUESTING LOWER. WE WERE TOLD TO MAINTAIN FL270. WE INFORMED THE CTLR WE WERE UNABLE DUE TO SEVERE TURB AND WERE DSNDING. WE WERE TOLD TO SWITCH FREQS AGAIN. WE DID SO AND INFORMED THE NEXT CTLR WE WERE PASSING FL260 UNABLE TO MAINTAIN ZLT DUE TO SEVERE TURB. WE WERE THEN CLRED TO FL190. THE TURB ABATED AS WE PASSED THROUGH FL240. THE REST OF THE FLT WAS UNEVENTFUL WITH OCCASIONAL SESSIONS OF LIGHT TO MODERATE CHOP AS WE PASSED THROUGH CLOUDS IN THE NEW YORK AREA. DURING THE PERIOD WE EXPERIENCED THE SEVERE TURB OUR SLOW CLB CHANGED TO A STEADY DSCNT AT ABOUT 280 KIAS (BEST TURB AIRSPD). AS I MENTIONED EARLIER WE COULD NOT SUSTAIN A CLB OR CRUISE AT CLB OR TKOF PWR. THE ACFT WAS BOUNCED AROUND SO VIOLENTLY WE COULD BARELY READ THE INSTS AND THE CAPT COULD BARELY MAINTAIN CTL. WE SIMPLY COULD NOT SUSTAIN LEVEL FLT UNDER THOSE CONDITIONS. ON ARR AT OUR DEST (LGA) WE MADE AN ENTRY IN THE ACFT MAINT LOG (EG) ENCOUNTERED SEVERE TURB OF A PERIOD OF 4-6 MINS.

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.