An air carrier MD80 flight crew experiences a yawing moment in the aircraft during their initial climb out. They shut off the yaw damper, retrim the aircraft and return to stl.

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Attributes
ACN	365240
Time
Date	199704
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : stl
State Reference	MO
Altitude	msl bound lower : 605 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : stl tower : stl tower : ewr
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	climbout : initial landing other other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 2500 flight time type : 250
ASRS Report	365240
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : critical
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

After takeoff on climb out of stl, aircraft started to roll left and right. Turning off yaw damper stopped rolling. Returned to stl and landed. Callback conversation with reporter revealed the following information: the first officer said that the initial yaw was 5 or 6 degrees either side of the aircraft's centerline and after shutting the yaw damper off the aircraft stayed in a slip for a while. He said that the slip was 5 to 10 degrees to the left and the captain was able to trim it out so that the final approach was normal. This analyst questioned the reporter as to whether the rudder's PCU may have been displaced and he said that the slip felt like that, but he never got a confirmation from the mechanics who met the aircraft. The mechanics, according to the reporter, said that the wiring to the yaw damper appeared to be chafed and had evidence of shorting. He has asked since this experience, but nobody that he has talked to at maintenance seems to know what repairs were done.

Original NASA ASRS Text

Title: AN ACR MD80 FLC EXPERIENCES A YAWING MOMENT IN THE ACFT DURING THEIR INITIAL CLB OUT. THEY SHUT OFF THE YAW DAMPER, RETRIM THE ACFT AND RETURN TO STL.

Narrative: AFTER TKOF ON CLBOUT OF STL, ACFT STARTED TO ROLL L AND R. TURNING OFF YAW DAMPER STOPPED ROLLING. RETURNED TO STL AND LANDED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE FO SAID THAT THE INITIAL YAW WAS 5 OR 6 DEGS EITHER SIDE OF THE ACFT'S CTRLINE AND AFTER SHUTTING THE YAW DAMPER OFF THE ACFT STAYED IN A SLIP FOR A WHILE. HE SAID THAT THE SLIP WAS 5 TO 10 DEGS TO THE L AND THE CAPT WAS ABLE TO TRIM IT OUT SO THAT THE FINAL APCH WAS NORMAL. THIS ANALYST QUESTIONED THE RPTR AS TO WHETHER THE RUDDER'S PCU MAY HAVE BEEN DISPLACED AND HE SAID THAT THE SLIP FELT LIKE THAT, BUT HE NEVER GOT A CONFIRMATION FROM THE MECHS WHO MET THE ACFT. THE MECHS, ACCORDING TO THE RPTR, SAID THAT THE WIRING TO THE YAW DAMPER APPEARED TO BE CHAFED AND HAD EVIDENCE OF SHORTING. HE HAS ASKED SINCE THIS EXPERIENCE, BUT NOBODY THAT HE HAS TALKED TO AT MAINT SEEMS TO KNOW WHAT REPAIRS WERE DONE.

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.