A319 flight crew reports two instances of uncommanded yaw inputs; one enroute and one while downwind...

Attributes
ACN	790707
Time
Date	200806
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : zzz.airport
State Reference	US
Environment
Flight Conditions	VMC
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	A319
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
ASRS Report	790707
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	other
Supplementary
Problem Areas	Aircraft
Primary Problem	Aircraft

Narrative:

We received this aircraft on our first flight of the day and were scheduled to keep it all day. The aircraft listed 4 MEL items when we received it. During the final leg of the day; we experienced 2 or 3 slight disturbances that felt like an abrupt but small rudder displacement. On downwind to runway 10L at ZZZ there occurred about 3 or 4 rapid and pronounced lateral displacements of the aircraft. Again it felt like uncommanded rudder inputs. All of these occurred while the autoplt was engaged. The first officer and I discussed what actions we would take if the situation worsened. The landing was uneventful. Upon arrival at the gate; I made a maintenance write-up in the aircraft logbook. I related our experiences to both the local maintenance crew and the oncoming flight crew. I stressed my concerns that this may indicate a very serious condition. I offered to stay and speak with the maintenance control representatives (this was a layover leg); but was told that would not be necessary. I do not know what corrective actions were then taken.

Original NASA ASRS Text

Title: A319 FLT CREW REPORTS TWO INSTANCES OF UNCOMMANDED YAW INPUTS; ONE ENROUTE AND ONE WHILE DOWNWIND AT DESTINATION.

Narrative: WE RECEIVED THIS ACFT ON OUR FIRST FLT OF THE DAY AND WERE SCHEDULED TO KEEP IT ALL DAY. THE ACFT LISTED 4 MEL ITEMS WHEN WE RECEIVED IT. DURING THE FINAL LEG OF THE DAY; WE EXPERIENCED 2 OR 3 SLIGHT DISTURBANCES THAT FELT LIKE AN ABRUPT BUT SMALL RUDDER DISPLACEMENT. ON DOWNWIND TO RWY 10L AT ZZZ THERE OCCURRED ABOUT 3 OR 4 RAPID AND PRONOUNCED LATERAL DISPLACEMENTS OF THE ACFT. AGAIN IT FELT LIKE UNCOMMANDED RUDDER INPUTS. ALL OF THESE OCCURRED WHILE THE AUTOPLT WAS ENGAGED. THE FO AND I DISCUSSED WHAT ACTIONS WE WOULD TAKE IF THE SITUATION WORSENED. THE LNDG WAS UNEVENTFUL. UPON ARR AT THE GATE; I MADE A MAINT WRITE-UP IN THE ACFT LOGBOOK. I RELATED OUR EXPERIENCES TO BOTH THE LCL MAINT CREW AND THE ONCOMING FLT CREW. I STRESSED MY CONCERNS THAT THIS MAY INDICATE A VERY SERIOUS CONDITION. I OFFERED TO STAY AND SPEAK WITH THE MAINT CTL REPRESENTATIVES (THIS WAS A LAYOVER LEG); BUT WAS TOLD THAT WOULD NOT BE NECESSARY. I DO NOT KNOW WHAT CORRECTIVE ACTIONS WERE THEN TAKEN.

Data retrieved from NASA's ASRS site as of May 2009 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.

A319 flight crew reports two instances of uncommanded yaw inputs; one enroute and one while downwind at destination.