A B737-800 IN LIGHT TURB DURING CLBOUT EXPERIENCED A 5 TO 10 DEG DUTCH ROLL WITH PRONOUNCED YAW THAT WAS IMPOSSIBLE TO STOP UNTIL SMOOTH AIR WAS REACHED.

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THIS ACFT HAD A HISTORY OF YAW DAMPER PROBS; AND THE Y/D HAD BEEN PLACARDED ON 5/SUN/02 AND AGAIN ON 5/FRI/02. I THINK IT WAS. DURING THE TIME THE Y/D WAS INOP AFTER 5/SUN/02 THERE WAS A WRITE-UP FROM A CAPT STATING HE THOUGHT THE RIDE WAS UNACCEPTABLE FOR REVENUE PASSENGERS DUE TO THE DUTCH ROLL. THERE WERE FLTS BEFORE AND AFTER THAT WITHOUT COMPLAINTS; SO I DISMISSED IT AS A PROBABLE OVER SENSITIVITY ON THE CAPT'S PART. WE DEPARTED ZZZ IN AN AREA OF STORMS; BUT THE WORST RIDE WE GOT WAS LIGHT TURB AND A LITTLE CHOP. I FIRST FELT SOME VERY MILD YAW ON TKOF; BUT ONCE AIRBORNE IN THE SMOOTH AIR; IT WAS FINE. IN THE TURB DURING CLBOUT; HOWEVER; A 5-10 DEG L AND R DUTCH ROLL WITH YAW BEGAN THAT WAS VERY PRONOUNCED AND IMPOSSIBLE TO STOP UNTIL WE GOT SMOOTH AIR. AT ONE POINT WE GOT A BUMP IN THE EDGE OF A CU; AND THE ROLL RATE AND ANGLE EXCEEDED MY COMFORT ZONE. I WAS HAND FLYING; BUT THE FO REFLEXIVELY REACHED FOR THE YOKE ALSO. THE PLANE DID NOT FEEL STABLE AT ALL; AND A CONSIDERABLE AMOUNT OF OUR COCKPIT ENERGY WAS SPENT SIMPLY ON ACFT CTL. I WAS COMFORTABLE THAT THE AIRPLANE WAS RELATIVELY CONTROLLABLE WHILE IN THE LIGHT TURB CONDITIONS; BUT I HAVE NO INTEREST IN SEEING WHAT WOULD HAPPEN WITH MORE TURB; ESPECIALLY AFTER THE BUMP WE GOT. AFTER A WHILE; I GOT THE FEEL OF IT; BUT I SEE A STRONG POSSIBILITY FOR SOMEONE TO GET IN A PILOT INDUCED OSCILLATIONS OR OVER CONTROL THE PLANE. I REMEMBER THE SIMULATOR TRAINING IN THE B727 WITH THAT DUTCH ROLL AND EMPLOYED THE SAME TECHNIQUES. THE RUDDER WAS VERY SENSITIVE; SO I ONLY USED VERY LIGHT AILERON IN CRUISE; AND WHEN IT WAS WORSE; I JUST HELD THE YOKE STEADY. I HAND FLEW IT FOR ALMOST AN HOUR; NOT TRUSTING THE AUTOPLT AFTER ITS POOR HANDLING AND ABRUPT AILERON INPUTS. THE FA'S WERE AWARE THAT SOMETHING WAS WRONG EVEN WITHOUT PROMPTING; AND I DIDN'T EVEN BRIEF THIS ISSUE PRIOR TO TKOF. THE PASSENGERS PROBABLY WEREN'T AWARE OF ANYTHING BEING WRONG; SINCE THE GENERAL TURB IN THE CLOUDS MASKED THE PROB. LATER IN SMOOTH AIR CRUISE; I REVIEWED THE LOGBOOK MORE THOROUGHLY; AND FOUND A SECOND CAPT'S COMMENTS ABOUT THE DUTCH ROLL BECOMING BAD IN LIGHT CHOP. I LEFT ALONG AND DETAILED INFO TO CREW MX MSG AND NOTIFIED DISPATCH ENRTE TO ZZZ1 FOR COORDINATION OF MX ACTION OR REPLACEMENT OF THE ACFT ON ITS NEXT FLTS. THE MEL SAYS IT'S LEGAL TO GO; WITH ONLY A RECOMMENDATION TO AVOID 40 FLAPS IF NOT NECESSARY FOR ACFT PERFORMANCE. ON APCH IN SMOOTH AIR WITH 30 FLAPS; I DESCRIBE IT BEST AS FEELING LIKE WE WERE ON ICE WITH THE SLIDING YAW MOTION. NORMALLY; I FIND THE MEL TO BE VERY CONSERVATIVE; BUT IN THIS CASE; I THINK MORE RESEARCH NEEDS TO BE DONE TO DETERMINE IF THE HANDLING CHARACTERISTIC ARE ACCEPTABLE IN CHOP OR TURB. I'VE NEVER COME CLOSE TO REFUSING AN AIRPLANE THAT WAS IN COMPLIANCE WITH THE MEL; BUT IF I WERE SCHEDULED TO RETURN TO ZZZ WITH THE LINE OF WX STILL THERE; I WOULDN'T BE CONVINCED THAT I COULD KEEP THE AIRPLANE UNDER CTL. I'M NOT SAYING THAT I WOULDN'T BE ABLE TO; BUT THERE EXISTS A SIGNIFICANT ELEMENT OF DOUBT IN MY MIND AND MY FO'S; PLUS THE TWO PRECEDING CAPT'S WHO WROTE THIS UP. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE HAD A PREVIOUS HISTORY OF YAW DAMPER PROBS AND COMMENTS BY CAPTS THAT THE AIRPLANE WITH THE YAW DAMPER DEFERRED WAS UNACCEPTABLE FOR PAX OP DUE TO THE DUTCH ROLL. THE RPTR SAID THE AIRPLANE HAD THE YAW DAMPER DEFERRED ITEM WORKED AND CLRED IN ZZZ WHERE THE FLIGHT ORIGINATED. THE RPTR STATED ON CLBOUT FROM ZZZ AND ON ENTERING LIGHT TURB A DUTCH ROLL 5 TO 10 DEGS WITH PRONOUNCED YAW WAS STARTED AND ONLY CTLED WHEN ENTERING SMOOTH AIR. THE RPTR SAID NO FEELING OF STABILITY EXISTED AND CONSIDERABLE TIME WAS SPENT HAND FLYING THE AIRPLANE. THE RPTR STATED THE AIRPLANE WAS TAKEN OUT OF SVC AND THE YAW DAMPER WAS CORRECTED BUT THE MAINT ACTION IS UNKNOWN. THE RPTR SAID THE B737-800 SHOULD NOT BE FLOWN WITH THE YAW DAMPER INOPERATIVE AND DEFERRED AND THE MEL CHANGED TO A NO GO ITEM.