Narrative:

The flight approached a scattered line of lower altitude cells with us near the tops. ATC needed us to deviate south, which we did. The aircraft was slowed to turbulent penetration speed with all flight attendants and passenger seated. We were at a safe distance between cells with practically nothing painting on radar between. We entered the clouds and the turbulence began. It increased from light to moderate. The B737-800 has a tendency to speed up in turbulence, but this time it decreased. The autothrottles were at maximum cruise power but the IAS, though bouncing around, steadily decreased. Maximum continuous power was selected to no avail. Soon on the FMS scratch pad 'buffet warning' was indicated. The captain extended the flaps to 1 degree hoping to lower the stall speed. The speed continued to decrease and the captain commanded I begin a descent, which I did. He immediately told ATC we were descending. ATC had us turn right for traffic, we did. After descending 3000 ft, the airspeed finally began increasing enough to raise the flaps and climb back up to altitude. We reported the turbulence and conditions to ATC. The aircraft has a limitation, maximum flap extension altitude of 20000 ft. Normally, the maximum extend airspeed is 250 KTS. I think the captain thought that we were so far below that speed, around 200 KTS, it would be ok to extend the flaps to head off a potential stall. Looking back, we should have descended earlier. We also should have contacted our dispatcher, maintenance and operations duty officer. The captain did write this event up and sent it through inter-company correspondence where many departments would see it.

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Original NASA ASRS Text

Title: A B737-800 FLT CREW EXCEEDED THE OPERATIONAL LIMITS OF THE FLAP SYS WHEN EXTENDING FLAPS TO 1 DEG AT FL370 DURING A LOSS OF AIRSPD NEAR TSTM ACTIVITY ON FREQ WITH ZDV, CO.

Narrative: THE FLT APCHED A SCATTERED LINE OF LOWER ALT CELLS WITH US NEAR THE TOPS. ATC NEEDED US TO DEVIATE S, WHICH WE DID. THE ACFT WAS SLOWED TO TURBULENT PENETRATION SPD WITH ALL FLT ATTENDANTS AND PAX SEATED. WE WERE AT A SAFE DISTANCE BTWN CELLS WITH PRACTICALLY NOTHING PAINTING ON RADAR BTWN. WE ENTERED THE CLOUDS AND THE TURB BEGAN. IT INCREASED FROM LIGHT TO MODERATE. THE B737-800 HAS A TENDENCY TO SPD UP IN TURB, BUT THIS TIME IT DECREASED. THE AUTOTHROTTLES WERE AT MAX CRUISE PWR BUT THE IAS, THOUGH BOUNCING AROUND, STEADILY DECREASED. MAX CONTINUOUS PWR WAS SELECTED TO NO AVAIL. SOON ON THE FMS SCRATCH PAD 'BUFFET WARNING' WAS INDICATED. THE CAPT EXTENDED THE FLAPS TO 1 DEG HOPING TO LOWER THE STALL SPD. THE SPD CONTINUED TO DECREASE AND THE CAPT COMMANDED I BEGIN A DSCNT, WHICH I DID. HE IMMEDIATELY TOLD ATC WE WERE DSNDING. ATC HAD US TURN R FOR TFC, WE DID. AFTER DSNDING 3000 FT, THE AIRSPD FINALLY BEGAN INCREASING ENOUGH TO RAISE THE FLAPS AND CLB BACK UP TO ALT. WE RPTED THE TURB AND CONDITIONS TO ATC. THE ACFT HAS A LIMITATION, MAX FLAP EXTENSION ALT OF 20000 FT. NORMALLY, THE MAX EXTEND AIRSPD IS 250 KTS. I THINK THE CAPT THOUGHT THAT WE WERE SO FAR BELOW THAT SPD, AROUND 200 KTS, IT WOULD BE OK TO EXTEND THE FLAPS TO HEAD OFF A POTENTIAL STALL. LOOKING BACK, WE SHOULD HAVE DSNDED EARLIER. WE ALSO SHOULD HAVE CONTACTED OUR DISPATCHER, MAINT AND OPS DUTY OFFICER. THE CAPT DID WRITE THIS EVENT UP AND SENT IT THROUGH INTER-COMPANY CORRESPONDENCE WHERE MANY DEPTS WOULD SEE IT.

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.