Narrative:

The event started when we encountered light turbulence at FL310. I was the PF. Our weight, 123000 pounds, allowed a climb to FL350 so we asked for and received clearance to climb to FL350. We were in clouds and the anti-ice system were on. Climb performance seemed poor and I allowed the airspeed to slow to .64 mach which was above the minimum indicated on the pms. As we approached FL350 I felt a pronounced buffeting which felt like a low speed wing buffet and the wing dipped several times as if it were near stall. There were no other indications of a near stall condition, ie, speed low, etc. I immediately asked the first officer to request lower and started descending. We received clearance to FL310 as we approached FL340. The controller did not comment on our altitude. Given the circumstances I would have declared an emergency if we had not received clearance for lower at first contact with center. All indications I had said the aircraft was capable of FL350 at that weight and airspeed. I did not do any abrupt maneuvering during the event but some passenger commented on the buffeting. Supplemental information from acn 418259: there was no indication of icing or any other clue why the plane would not hold FL350.

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Original NASA ASRS Text

Title: A CLBING S80 IS UNABLE TO MAINTAIN ITS ASSIGNED ALT WITH ANTI-ICE SYS ON. AN ALT EXCURSION OCCURS WHEN THE ACFT IS FELT TO BE IN AN INITIAL BUFFET.

Narrative: THE EVENT STARTED WHEN WE ENCOUNTERED LIGHT TURB AT FL310. I WAS THE PF. OUR WT, 123000 LBS, ALLOWED A CLB TO FL350 SO WE ASKED FOR AND RECEIVED CLRNC TO CLB TO FL350. WE WERE IN CLOUDS AND THE ANTI-ICE SYS WERE ON. CLB PERFORMANCE SEEMED POOR AND I ALLOWED THE AIRSPD TO SLOW TO .64 MACH WHICH WAS ABOVE THE MINIMUM INDICATED ON THE PMS. AS WE APCHED FL350 I FELT A PRONOUNCED BUFFETING WHICH FELT LIKE A LOW SPD WING BUFFET AND THE WING DIPPED SEVERAL TIMES AS IF IT WERE NEAR STALL. THERE WERE NO OTHER INDICATIONS OF A NEAR STALL CONDITION, IE, SPD LOW, ETC. I IMMEDIATELY ASKED THE FO TO REQUEST LOWER AND STARTED DSNDING. WE RECEIVED CLRNC TO FL310 AS WE APCHED FL340. THE CTLR DID NOT COMMENT ON OUR ALT. GIVEN THE CIRCUMSTANCES I WOULD HAVE DECLARED AN EMER IF WE HAD NOT RECEIVED CLRNC FOR LOWER AT FIRST CONTACT WITH CTR. ALL INDICATIONS I HAD SAID THE ACFT WAS CAPABLE OF FL350 AT THAT WT AND AIRSPD. I DID NOT DO ANY ABRUPT MANEUVERING DURING THE EVENT BUT SOME PAX COMMENTED ON THE BUFFETING. SUPPLEMENTAL INFO FROM ACN 418259: THERE WAS NO INDICATION OF ICING OR ANY OTHER CLUE WHY THE PLANE WOULD NOT HOLD FL350.

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.