Narrative:

A flight operated between den and kbna. Due to continuous chop/turbulence at our planned cruising altitude of FL330 I elected to request a higher altitude where we anticipated a better (smoother) ride. We were initially assigned FL350 but found conditions to be much the same. After consulting the optimal/safe altitude charts for our current weight and checking the isa deviation and forecast winds aloft, we requested FL370. (The chart indicated FL380 as the maximum altitude for our weight.) while climbing to FL370 at mach 0.70 (our climb profile) the climb rate decreased to zero. I changed to vertical speed mode and selected 500 FPM. As we climbed, the airspeed decreased until we were level at FL370, however, the airspeed did not increase as expected, but continued to decrease. I instructed the first officer to request a lower altitude with ATC, as the airspeed was decreasing towards stall the autoplt disconnected and a descent initiated. We had descended approximately 800 ft when ATC finally cleared us to maintain FL330. In hindsight, I feel that while there was no lack of attention in the situation (ie, no distrs), I was caught by surprise when the aircraft would not accelerate once it had leveled off. In the future, I will never allow the airspeed to decay below the climb profile 0.70 mach, assuming that once we level it will increase. Also, I will be even more skeptical of the safe altitude charts especially in a heavy aircraft.

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Original NASA ASRS Text

Title: CL65 CREW CLBED ACFT TOO HIGH FOR THE ACFT GROSS WEIGHT, GOT ON THE BACK SIDE OF THE PWR CURVE, AND WITH SLOWING AIRSPD, HAD TO DSND TO PREVENT A STALL IN ZKC CLASS A.

Narrative: A FLT OPERATED BTWN DEN AND KBNA. DUE TO CONTINUOUS CHOP/TURB AT OUR PLANNED CRUISING ALT OF FL330 I ELECTED TO REQUEST A HIGHER ALT WHERE WE ANTICIPATED A BETTER (SMOOTHER) RIDE. WE WERE INITIALLY ASSIGNED FL350 BUT FOUND CONDITIONS TO BE MUCH THE SAME. AFTER CONSULTING THE OPTIMAL/SAFE ALT CHARTS FOR OUR CURRENT WT AND CHKING THE ISA DEV AND FORECAST WINDS ALOFT, WE REQUESTED FL370. (THE CHART INDICATED FL380 AS THE MAX ALT FOR OUR WT.) WHILE CLBING TO FL370 AT MACH 0.70 (OUR CLB PROFILE) THE CLB RATE DECREASED TO ZERO. I CHANGED TO VERT SPD MODE AND SELECTED 500 FPM. AS WE CLBED, THE AIRSPD DECREASED UNTIL WE WERE LEVEL AT FL370, HOWEVER, THE AIRSPD DID NOT INCREASE AS EXPECTED, BUT CONTINUED TO DECREASE. I INSTRUCTED THE FO TO REQUEST A LOWER ALT WITH ATC, AS THE AIRSPD WAS DECREASING TOWARDS STALL THE AUTOPLT DISCONNECTED AND A DSCNT INITIATED. WE HAD DSNDED APPROX 800 FT WHEN ATC FINALLY CLRED US TO MAINTAIN FL330. IN HINDSIGHT, I FEEL THAT WHILE THERE WAS NO LACK OF ATTN IN THE SIT (IE, NO DISTRS), I WAS CAUGHT BY SURPRISE WHEN THE ACFT WOULD NOT ACCELERATE ONCE IT HAD LEVELED OFF. IN THE FUTURE, I WILL NEVER ALLOW THE AIRSPD TO DECAY BELOW THE CLB PROFILE 0.70 MACH, ASSUMING THAT ONCE WE LEVEL IT WILL INCREASE. ALSO, I WILL BE EVEN MORE SKEPTICAL OF THE SAFE ALT CHARTS ESPECIALLY IN A HVY ACFT.

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.