A B737-300 aircraft descending into clt, nc, has an uncommanded roll of 15-20 degrees.

Attributes
ACN	376050
Time
Date	199708
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : clt
State Reference	NC
Altitude	msl bound lower : 2500 msl bound upper : 2500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : clt
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 300 flight time total : 14750 flight time type : 10000
ASRS Report	376050
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
ASRS Report	376160
Events
Anomaly	aircraft equipment problem : critical other anomaly
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : regained aircraft control
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

During descent on back course localizer runway 23 clt, aircraft rolled right, yaw damper indicator shows full left deflection. Aircraft was brought back on localizer and no further problems. Callback conversation with reporter revealed the following information: as the B737-300 descended on the localizer, it made an abrupt roll to the right of 15-20 degrees. Autoplt was off and the yaw damper indicator showed full left deflection. Aircraft was easily rolled back to level with aileron and rudder inputs. Because the captain was unsure of the cause of the roll, he wrote the event up in the logbook which grounded the aircraft. Aircraft was inspected and several interviews followed the event with high level company officials. One union safety official believes it was some leftover wake turbulence that was encountered. The captain doubts that was the case, he is just uncertain, which is why he wrote up the uncommanded roll into the logbook. Aircraft was thoroughly inspected and flight crew interviewed several times to make certain the appropriate action would take place. Aircraft has been returned to service. Supplemental information from acn 376160: aircraft rolled right (uncommanded).

Original NASA ASRS Text

Title: A B737-300 ACFT DSNDING INTO CLT, NC, HAS AN UNCOMMANDED ROLL OF 15-20 DEGS.

Narrative: DURING DSCNT ON BACK COURSE LOC RWY 23 CLT, ACFT ROLLED R, YAW DAMPER INDICATOR SHOWS FULL L DEFLECTION. ACFT WAS BROUGHT BACK ON LOC AND NO FURTHER PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: AS THE B737-300 DSNDED ON THE LOC, IT MADE AN ABRUPT ROLL TO THE R OF 15-20 DEGS. AUTOPLT WAS OFF AND THE YAW DAMPER INDICATOR SHOWED FULL L DEFLECTION. ACFT WAS EASILY ROLLED BACK TO LEVEL WITH AILERON AND RUDDER INPUTS. BECAUSE THE CAPT WAS UNSURE OF THE CAUSE OF THE ROLL, HE WROTE THE EVENT UP IN THE LOGBOOK WHICH GNDED THE ACFT. ACFT WAS INSPECTED AND SEVERAL INTERVIEWS FOLLOWED THE EVENT WITH HIGH LEVEL COMPANY OFFICIALS. ONE UNION SAFETY OFFICIAL BELIEVES IT WAS SOME LEFTOVER WAKE TURB THAT WAS ENCOUNTERED. THE CAPT DOUBTS THAT WAS THE CASE, HE IS JUST UNCERTAIN, WHICH IS WHY HE WROTE UP THE UNCOMMANDED ROLL INTO THE LOGBOOK. ACFT WAS THOROUGHLY INSPECTED AND FLC INTERVIEWED SEVERAL TIMES TO MAKE CERTAIN THE APPROPRIATE ACTION WOULD TAKE PLACE. ACFT HAS BEEN RETURNED TO SVC. SUPPLEMENTAL INFO FROM ACN 376160: ACFT ROLLED R (UNCOMMANDED).

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.