Narrative:

On climb out phase of flight (captain flying) requested a higher than normal altitude to take advantage of the favorable winds. I had mentioned to the captain about flying above optimum altitude on the FMS but we proceeded higher. As we leveled off at our cruise altitude; with some light to medium turbulence; the yellow caution lines above and below our airspeed window were close; if not touching the indicated airspeed box. There was very little or no distance between the upper and lower limits. I was uncomfortable with the situation and expressed my feelings to the captain. In essence saying 'why are we doing this?' after making that statement; the FMS gave a 'buffet warning' yellow alert. Nothing was said or done at this point. We continued on at altitude and eventually the yellow caution lines backed off the airspeed box. The entire evolution was uncomfortable. I stated to the captain my concerns; and offered some CRM to try to rectify the situation. On the return leg the next day; I flew at a lower altitude after he wanted to go higher again. We were in a block altitude situation; blocking FL370-FL390. The optimum altitude was FL380. I was flying level at FL380; approaching etp when we encountered medium to heavy turbulence. The aircraft pitched and rolled significantly. Without warning; the stick shaker engaged. I expressed my concern to the captain and asked what he wanted me to do. The new captain obviously had not seen this situation before. Acting instinctively; I proposed a speed reduction from approximately .78 mach to .76 mach and executed. The turbulence continued (right about 45 min) but the stick shaker did not engage again. The turbulence eventually subsided; and the rest of the flight was normal.

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Original NASA ASRS Text

Title: B737-700 FLT CREW CLBS TO AN ALT ABOVE THE RECOMMENDED ALT FOR THE WT OF THE ACFT. HIGH AND LOW BUFFET WARNINGS TAPES WERE PRESENT WITHIN THE AIRSPD INDICATOR. FMS GAVE A 'BUFFET WARNING' ALERT UPON ENCOUNTERING TURB.

Narrative: ON CLBOUT PHASE OF FLT (CAPT FLYING) REQUESTED A HIGHER THAN NORMAL ALT TO TAKE ADVANTAGE OF THE FAVORABLE WINDS. I HAD MENTIONED TO THE CAPT ABOUT FLYING ABOVE OPTIMUM ALT ON THE FMS BUT WE PROCEEDED HIGHER. AS WE LEVELED OFF AT OUR CRUISE ALT; WITH SOME LIGHT TO MEDIUM TURB; THE YELLOW CAUTION LINES ABOVE AND BELOW OUR AIRSPD WINDOW WERE CLOSE; IF NOT TOUCHING THE INDICATED AIRSPD BOX. THERE WAS VERY LITTLE OR NO DISTANCE BTWN THE UPPER AND LOWER LIMITS. I WAS UNCOMFORTABLE WITH THE SITUATION AND EXPRESSED MY FEELINGS TO THE CAPT. IN ESSENCE SAYING 'WHY ARE WE DOING THIS?' AFTER MAKING THAT STATEMENT; THE FMS GAVE A 'BUFFET WARNING' YELLOW ALERT. NOTHING WAS SAID OR DONE AT THIS POINT. WE CONTINUED ON AT ALT AND EVENTUALLY THE YELLOW CAUTION LINES BACKED OFF THE AIRSPD BOX. THE ENTIRE EVOLUTION WAS UNCOMFORTABLE. I STATED TO THE CAPT MY CONCERNS; AND OFFERED SOME CRM TO TRY TO RECTIFY THE SITUATION. ON THE RETURN LEG THE NEXT DAY; I FLEW AT A LOWER ALT AFTER HE WANTED TO GO HIGHER AGAIN. WE WERE IN A BLOCK ALT SITUATION; BLOCKING FL370-FL390. THE OPTIMUM ALT WAS FL380. I WAS FLYING LEVEL AT FL380; APCHING ETP WHEN WE ENCOUNTERED MEDIUM TO HVY TURB. THE ACFT PITCHED AND ROLLED SIGNIFICANTLY. WITHOUT WARNING; THE STICK SHAKER ENGAGED. I EXPRESSED MY CONCERN TO THE CAPT AND ASKED WHAT HE WANTED ME TO DO. THE NEW CAPT OBVIOUSLY HAD NOT SEEN THIS SITUATION BEFORE. ACTING INSTINCTIVELY; I PROPOSED A SPD REDUCTION FROM APPROX .78 MACH TO .76 MACH AND EXECUTED. THE TURB CONTINUED (R ABOUT 45 MIN) BUT THE STICK SHAKER DID NOT ENGAGE AGAIN. THE TURB EVENTUALLY SUBSIDED; AND THE REST OF THE FLT WAS NORMAL.

Data retrieved from NASA's ASRS site as of January 2009 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.