Narrative:

While flying at FL370 we were instructed to hold at an intersection about 50 mi ahead of us approximately half way between dtw and jhw. First officer slowed to charted hold speed of 237 KTS and entered hold. On first 180 degree turn, outbound, the aircraft tried to climb, and first officer corrected at approximately 150 ft high. The airspeed loss was about 5 KTS, and while working on fuel computation went unnoticed. Next turn, inbound, 10 mi leg aircraft again attempted to climb and first officer again corrected back to FL370. The subsequent airspeed loss was not regained as power was already at maximum. At approximately 90 degrees of turn we experienced onset of airframe stall buffet. No stick shaker activated, and no automatic-slat extension. We had to make the inbound track good as there were aircraft on the other side of the holding pattern. While trying to determine the problem we began a 300-400 ft rate of descent to maintain airspeed. Stall buffet occurred 3-4 times and we continued our descent. At approximately FL367 ATC asked if we were at FL370. We replied negative, and that we could not maintain FL370. After some conversation ATC asked if we would be more comfortable at FL350. We said yes, and we were cleared to FL350. First officer accelerated to 250 KTS in the descent, and we experienced no further problems at FL350.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION -- DURING A TURN IN THE HOLDING PATTERN THE AUTOFLT SYS ALLOWED THE ACFT TO CLB, LOSING AIRSPD. THE FLC STARTED A DSCNT TO GAIN AIRSPD, BUT WENT BELOW ASSIGNED ALT.

Narrative: WHILE FLYING AT FL370 WE WERE INSTRUCTED TO HOLD AT AN INTXN ABOUT 50 MI AHEAD OF US APPROX HALF WAY BTWN DTW AND JHW. FO SLOWED TO CHARTED HOLD SPD OF 237 KTS AND ENTERED HOLD. ON FIRST 180 DEG TURN, OUTBOUND, THE ACFT TRIED TO CLB, AND FO CORRECTED AT APPROX 150 FT HIGH. THE AIRSPD LOSS WAS ABOUT 5 KTS, AND WHILE WORKING ON FUEL COMPUTATION WENT UNNOTICED. NEXT TURN, INBOUND, 10 MI LEG ACFT AGAIN ATTEMPTED TO CLB AND FO AGAIN CORRECTED BACK TO FL370. THE SUBSEQUENT AIRSPD LOSS WAS NOT REGAINED AS PWR WAS ALREADY AT MAX. AT APPROX 90 DEGS OF TURN WE EXPERIENCED ONSET OF AIRFRAME STALL BUFFET. NO STICK SHAKER ACTIVATED, AND NO AUTO-SLAT EXTENSION. WE HAD TO MAKE THE INBOUND TRACK GOOD AS THERE WERE ACFT ON THE OTHER SIDE OF THE HOLDING PATTERN. WHILE TRYING TO DETERMINE THE PROB WE BEGAN A 300-400 FT RATE OF DSCNT TO MAINTAIN AIRSPD. STALL BUFFET OCCURRED 3-4 TIMES AND WE CONTINUED OUR DSCNT. AT APPROX FL367 ATC ASKED IF WE WERE AT FL370. WE REPLIED NEGATIVE, AND THAT WE COULD NOT MAINTAIN FL370. AFTER SOME CONVERSATION ATC ASKED IF WE WOULD BE MORE COMFORTABLE AT FL350. WE SAID YES, AND WE WERE CLRED TO FL350. FO ACCELERATED TO 250 KTS IN THE DSCNT, AND WE EXPERIENCED NO FURTHER PROBS AT FL350.

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.