Narrative:

Altitude deviation occurred as a result of recovery action prompted by the aircraft stall shaker. Unable to notify ATC until 500 ft of altitude lost. Conditions contributing to the onset of the aircraft stall shaker were the weight of the aircraft, approximately 1000 pounds below maximum takeoff weight, light mixed icing conditions, operating altitude, and moderate turbulence. These factors coupled with the modest performance capabilities of the aircraft at the given weight, temperature, and altitude resulted in the stall. It is my belief that the saab 340A model aircraft is inadequately pwred resulting in a significant hazard to flight safety. Supplemental information from acn 403298: we were in cruise flight at 14000 ft going to lga from yow. There were thunderstorms in the vicinity. We were 20 mi or so west (upwind) of a severe line of thunderstorms but there were only a few isolated and very scattered cells of light to moderate intensity within 10 mi of us. The airplane was only indicating 140 KIAS at 14000 ft MSL. We encountered some moderate turbulence and the autoplt pitched up to 10 degrees in an attempt to maintain altitude which introduced an immediate stick shaker response. It was a simultaneous occurrence of an unacceptable altitude at too low of an airspeed, stick shaker, and autoplt disengagement with a descent to maintain a safe airspeed. We were descending through 13500 ft before the first officer could get a word in to ZBW informing him that we could not maintain altitude and were in a descent. ZBW responded and cleared us to 10000 ft MSL. The airplane simply was not capable of holding altitude in the turbulence which is due entirely to the less than acceptable performance of the saab 340A model. We were fairly heavy, 27000 pounds with a gross weight of 28000 pounds. I never saw the airspeed go below 140 KIAS. The outside air temperature was -2 degrees C. The engine anti-ice system was operating which further reduced the performance of the airplane.

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Original NASA ASRS Text

Title: AN SF340A STALLS OUT AT 14000 FT AFTER ENCOUNTERING SOME MODERATE TURB. THERE WAS SOME DISTANT TSTM ACTIVITY AND THE ACFT WAS HVY, WITH ENG ANTI-ICE SYS TURNED ON.

Narrative: ALTDEV OCCURRED AS A RESULT OF RECOVERY ACTION PROMPTED BY THE ACFT STALL SHAKER. UNABLE TO NOTIFY ATC UNTIL 500 FT OF ALT LOST. CONDITIONS CONTRIBUTING TO THE ONSET OF THE ACFT STALL SHAKER WERE THE WT OF THE ACFT, APPROX 1000 LBS BELOW MAX TKOF WT, LIGHT MIXED ICING CONDITIONS, OPERATING ALT, AND MODERATE TURB. THESE FACTORS COUPLED WITH THE MODEST PERFORMANCE CAPABILITIES OF THE ACFT AT THE GIVEN WT, TEMP, AND ALT RESULTED IN THE STALL. IT IS MY BELIEF THAT THE SAAB 340A MODEL ACFT IS INADEQUATELY PWRED RESULTING IN A SIGNIFICANT HAZARD TO FLT SAFETY. SUPPLEMENTAL INFO FROM ACN 403298: WE WERE IN CRUISE FLT AT 14000 FT GOING TO LGA FROM YOW. THERE WERE TSTMS IN THE VICINITY. WE WERE 20 MI OR SO W (UPWIND) OF A SEVERE LINE OF TSTMS BUT THERE WERE ONLY A FEW ISOLATED AND VERY SCATTERED CELLS OF LIGHT TO MODERATE INTENSITY WITHIN 10 MI OF US. THE AIRPLANE WAS ONLY INDICATING 140 KIAS AT 14000 FT MSL. WE ENCOUNTERED SOME MODERATE TURB AND THE AUTOPLT PITCHED UP TO 10 DEGS IN AN ATTEMPT TO MAINTAIN ALT WHICH INTRODUCED AN IMMEDIATE STICK SHAKER RESPONSE. IT WAS A SIMULTANEOUS OCCURRENCE OF AN UNACCEPTABLE ALT AT TOO LOW OF AN AIRSPD, STICK SHAKER, AND AUTOPLT DISENGAGEMENT WITH A DSCNT TO MAINTAIN A SAFE AIRSPD. WE WERE DSNDING THROUGH 13500 FT BEFORE THE FO COULD GET A WORD IN TO ZBW INFORMING HIM THAT WE COULD NOT MAINTAIN ALT AND WERE IN A DSCNT. ZBW RESPONDED AND CLRED US TO 10000 FT MSL. THE AIRPLANE SIMPLY WAS NOT CAPABLE OF HOLDING ALT IN THE TURB WHICH IS DUE ENTIRELY TO THE LESS THAN ACCEPTABLE PERFORMANCE OF THE SAAB 340A MODEL. WE WERE FAIRLY HVY, 27000 LBS WITH A GROSS WT OF 28000 LBS. I NEVER SAW THE AIRSPD GO BELOW 140 KIAS. THE OUTSIDE AIR TEMP WAS -2 DEGS C. THE ENG ANTI-ICE SYS WAS OPERATING WHICH FURTHER REDUCED THE PERFORMANCE OF THE AIRPLANE.

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.