B737-300 crew had the yaw damper fail at FL350 in moderate turbulence.

Attributes
ACN	632146
Time
Date	200409
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : den.airport
State Reference	CO
Altitude	msl single value : 35000
Environment
Weather Elements	Turbulence Thunderstorm
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 120 flight time total : 7200 flight time type : 1800
ASRS Report	632146
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 240 flight time total : 9700 flight time type : 1400
ASRS Report	632316
Events
Anomaly	aircraft equipment problem : critical inflight encounter : weather
Independent Detector	aircraft equipment other aircraft equipment : yaw damp light other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance controller : provided flight assist flight crew : landed in emergency condition flight crew : declared emergency other
Consequence	other other
Supplementary
Problem Areas	Aircraft Weather
Primary Problem	Aircraft

Narrative:

Flying along at FL350 about 150 NM east of den, yaw damper light came on and switch flipped to 'off.' while first officer pulled out flight manual that min, light chop became moderate. Dutch roll ensued left to right continuously (seemed like 10 degrees either side, but probably was 5 degrees). First officer asked for lower immediately while I turned on seatbelt sign and used PA to seat flight attendant. ATC assumed emergency and moved an air carrier Y flight while turning us and giving us lower (we also slowed down). Accomplished flight manual procedure while descending (no help, yaw damper inoperative but no more dutch roll). Because of lower and other unrelated factors, we were now landing with about 5.0 with traffic backing up into den with storms. We declared minimum fuel. ATC declared emergency, but flight crew and dispatch did not declare emergency. After subsequent rerte into den, we asked for and received priority handling and landed with 4.6 fuel.

Original NASA ASRS Text

Title: B737-300 CREW HAD THE YAW DAMPER FAIL AT FL350 IN MODERATE TURB.

Narrative: FLYING ALONG AT FL350 ABOUT 150 NM E OF DEN, YAW DAMPER LIGHT CAME ON AND SWITCH FLIPPED TO 'OFF.' WHILE FO PULLED OUT FLT MANUAL THAT MIN, LIGHT CHOP BECAME MODERATE. DUTCH ROLL ENSUED L TO R CONTINUOUSLY (SEEMED LIKE 10 DEGS EITHER SIDE, BUT PROBABLY WAS 5 DEGS). FO ASKED FOR LOWER IMMEDIATELY WHILE I TURNED ON SEATBELT SIGN AND USED PA TO SEAT FLT ATTENDANT. ATC ASSUMED EMER AND MOVED AN ACR Y FLT WHILE TURNING US AND GIVING US LOWER (WE ALSO SLOWED DOWN). ACCOMPLISHED FLT MANUAL PROC WHILE DSNDING (NO HELP, YAW DAMPER INOP BUT NO MORE DUTCH ROLL). BECAUSE OF LOWER AND OTHER UNRELATED FACTORS, WE WERE NOW LNDG WITH ABOUT 5.0 WITH TFC BACKING UP INTO DEN WITH STORMS. WE DECLARED MINIMUM FUEL. ATC DECLARED EMER, BUT FLT CREW AND DISPATCH DID NOT DECLARE EMER. AFTER SUBSEQUENT RERTE INTO DEN, WE ASKED FOR AND RECEIVED PRIORITY HANDLING AND LANDED WITH 4.6 FUEL.

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.