Narrative:

This was the second ETOPS flight for the first officer and myself, having made the first flight the day before. The check airman sitting in the jump seat was fairly new at it too. This was a new airplane for all of us. It was the first officer's leg. I had flown over to the destination the day before. We were doing a slow rate of climb to FL400 as instructed by the check airman. I was glancing down working on the flight log for a couple of mins. As we climbed to about FL394, the autoplt disengaged. It surprised all of us. The first officer said, 'I have it,' and applied back pressure on the control yoke which resulted in 2 very slight 'G' buffets. I said 'easy' and put my hands as though I were blocking any more aft movement of the control column. I then called center to descend to FL380 and we did. At the time the autoplt disengaged, the pfd airspeed display airspeed was indicating on the top of the minimum maneuvering speed yellow bar. Also during the last 5-10 mins, we had been encountering occasional moderate turbulence. The 'G' buffets were small but we wondered if anybody in the back felt them. I think all 3 of us learned something today about maximum altitude and turbulence combinations can reduce maneuvering speed very fast.

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Original NASA ASRS Text

Title: WHEN CLBING THROUGH FL394 IN A B737-700, THE ACFT AUTOPLT DISCONNECTED AND BUFFETED 2 TIMES BEFORE THE FLYING FO COULD DSND AND REGAIN COMPLETE ACFT CTL.

Narrative: THIS WAS THE SECOND ETOPS FLT FOR THE FO AND MYSELF, HAVING MADE THE FIRST FLT THE DAY BEFORE. THE CHK AIRMAN SITTING IN THE JUMP SEAT WAS FAIRLY NEW AT IT TOO. THIS WAS A NEW AIRPLANE FOR ALL OF US. IT WAS THE FO'S LEG. I HAD FLOWN OVER TO THE DEST THE DAY BEFORE. WE WERE DOING A SLOW RATE OF CLB TO FL400 AS INSTRUCTED BY THE CHK AIRMAN. I WAS GLANCING DOWN WORKING ON THE FLT LOG FOR A COUPLE OF MINS. AS WE CLBED TO ABOUT FL394, THE AUTOPLT DISENGAGED. IT SURPRISED ALL OF US. THE FO SAID, 'I HAVE IT,' AND APPLIED BACK PRESSURE ON THE CTL YOKE WHICH RESULTED IN 2 VERY SLIGHT 'G' BUFFETS. I SAID 'EASY' AND PUT MY HANDS AS THOUGH I WERE BLOCKING ANY MORE AFT MOVEMENT OF THE CTL COLUMN. I THEN CALLED CTR TO DSND TO FL380 AND WE DID. AT THE TIME THE AUTOPLT DISENGAGED, THE PFD AIRSPD DISPLAY AIRSPD WAS INDICATING ON THE TOP OF THE MINIMUM MANEUVERING SPD YELLOW BAR. ALSO DURING THE LAST 5-10 MINS, WE HAD BEEN ENCOUNTERING OCCASIONAL MODERATE TURB. THE 'G' BUFFETS WERE SMALL BUT WE WONDERED IF ANYBODY IN THE BACK FELT THEM. I THINK ALL 3 OF US LEARNED SOMETHING TODAY ABOUT MAX ALT AND TURB COMBINATIONS CAN REDUCE MANEUVERING SPD VERY FAST.

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.