Narrative:

Md-80 flight from iah to dca, while climbing to 37000 ft, autoplt, autothrottles, and flight directors kept tripping off, in various combinations at intermittent intervals. At the time of the event, I was hand flying the aircraft, as a result. Upon leaving 36500 ft for 3700 ft, the aircraft began a rapid roll to the left, which I was able to stop at 35 degree of bank and return to level flight. I also felt a severe yaw motion and immediately suspected the yaw damper, which was confirmed by an intermittent illumination of the 'yaw damper off' annunciator. We immediately switched the yaw damper off, moved the rudder power lever to manual, descended to (yaw damper off) maximum altitude, and continued to destination uneventfully. The next morning I found out that technical services discovered a bad yaw rate sensor (gyroscope) and replaced it. Callback conversation with reporter revealed the following information: the reporter said the md-80 weighed, he thought, about 117000 pounds he calculated the maximum gross weight at FL370 to be 118000 that day. He said he thought it was lucky the autoplt had tripped off and he was hand flying the airplane when the yaw rate sensor acted up and the airplane started to roll because he could better control the airplane and counteract the roll and dutch roll tendencies.

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Original NASA ASRS Text

Title: FLC LOSE ROLL CTL AT FL365 IN CLB TO FL370 AND HAVE TO DSND.

Narrative: MD-80 FLT FROM IAH TO DCA, WHILE CLBING TO 37000 FT, AUTOPLT, AUTOTHROTTLES, AND FLT DIRECTORS KEPT TRIPPING OFF, IN VARIOUS COMBINATIONS AT INTERMITTENT INTERVALS. AT THE TIME OF THE EVENT, I WAS HAND FLYING THE ACFT, AS A RESULT. UPON LEAVING 36500 FT FOR 3700 FT, THE ACFT BEGAN A RAPID ROLL TO THE L, WHICH I WAS ABLE TO STOP AT 35 DEG OF BANK AND RETURN TO LEVEL FLT. I ALSO FELT A SEVERE YAW MOTION AND IMMEDIATELY SUSPECTED THE YAW DAMPER, WHICH WAS CONFIRMED BY AN INTERMITTENT ILLUMINATION OF THE 'YAW DAMPER OFF' ANNUNCIATOR. WE IMMEDIATELY SWITCHED THE YAW DAMPER OFF, MOVED THE RUDDER PWR LEVER TO MANUAL, DSNDED TO (YAW DAMPER OFF) MAX ALT, AND CONTINUED TO DEST UNEVENTFULLY. THE NEXT MORNING I FOUND OUT THAT TECHNICAL SVCS DISCOVERED A BAD YAW RATE SENSOR (GYROSCOPE) AND REPLACED IT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR SAID THE MD-80 WEIGHED, HE THOUGHT, ABOUT 117000 LBS HE CALCULATED THE MAX GROSS WT AT FL370 TO BE 118000 THAT DAY. HE SAID HE THOUGHT IT WAS LUCKY THE AUTOPLT HAD TRIPPED OFF AND HE WAS HAND FLYING THE AIRPLANE WHEN THE YAW RATE SENSOR ACTED UP AND THE AIRPLANE STARTED TO ROLL BECAUSE HE COULD BETTER CTL THE AIRPLANE AND COUNTERACT THE ROLL AND DUTCH ROLL TENDENCIES.

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.