This air carrier B737-200 flight crew experienced an uncommanded rudder displacement that caused the...

Attributes
ACN	429547
Time
Date	199902
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : sby
State Reference	MD
Altitude	msl bound lower : 33000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	B737-200
Flight Phase	cruise other
Route In Use	enroute airway : j79
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer oversight : pic
Experience	flight time last 90 days : 200 flight time total : 15000 flight time type : 2000
ASRS Report	429547
Person 2
Affiliation	company : air carrier
Function	flight crew : captain
Qualification	pilot : flight engineer
Experience	flight time last 90 days : 25 flight time total : 10000 flight time type : 2000
ASRS Report	429548
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : declared emergency other
Consequence	Other

Narrative:

Flight from mco to bdl. 33000 ft .67+ mach normal cruise. Experienced uncommanded roll to right. First noted by displacement of control wheel to left with no pilot input. Took control of aircraft, noted that rudder pedals displaced to right, right rudder forward and unable to center. Maintained close to level flight with considerable left aileron input. Declared emergency, complied with procedures in QRH, both pilots could not correct rudder. When 'B' system hydraulic switch placed to standby rudder, rudders centered and controllable. During approach noted vibration in rudder pedals and some rudder 'kicks.' uneventful landing bwi, runway 33L. Made appropriate logbook entry. Supplemental information from acn 429548: I declared an emergency with ATC. Immediate action items consisting of autoplt, autothrottles and yaw damper were turned off. Both pilots attempted to move jammed rudder pedals. No desired movement observed. QRH procedures complied with. Rudders were freed up when 'B' system hydraulic system flight control switch was placed to standby rudder position. Callback conversation with reporter on acn 429547 revealed the following information: the reporter said that the captain was flying the aircraft on autoplt at the time of the rudder displacement and the reporter attempted to assist when the right rudder pedal went, full travel, forward. Then as the flight crew started through their uncommanded rudder input checklist this reporter assumed control of the aircraft. This reporter has spoken to maintenance personnel and they have been unable to discover the cause for the rudder displacement. The aircraft had one of the new rudder control valves installed and it was in proper working order according to maintenance. Callback conversation with reporter on acn 429548 revealed the following information: this reporter said that with both flight crew pushing on the opposite rudder pedal they were unable to correct the right rudder displacement. However, he was able to maintain level flight by using almost full left aileron input. He said that as soon as he placed the 'B' system hydraulic switch to the 'standby rudder' position the rudder became controllable again.

Original NASA ASRS Text

Title: THIS ACR B737-200 FLC EXPERIENCED AN UNCOMMANDED RUDDER DISPLACEMENT THAT CAUSED THE ACFT TO ROLL TO THE R. INITIALLY, THE FLC WAS UNABLE TO OVERPOWER THE UNCOMMANDED INPUT, BUT WERE ABLE TO MAINTAIN APPROX LEVEL FLT BY XCTLING THE ACFT.

Narrative: FLT FROM MCO TO BDL. 33000 FT .67+ MACH NORMAL CRUISE. EXPERIENCED UNCOMMANDED ROLL TO R. FIRST NOTED BY DISPLACEMENT OF CTL WHEEL TO L WITH NO PLT INPUT. TOOK CTL OF ACFT, NOTED THAT RUDDER PEDALS DISPLACED TO R, R RUDDER FORWARD AND UNABLE TO CTR. MAINTAINED CLOSE TO LEVEL FLT WITH CONSIDERABLE L AILERON INPUT. DECLARED EMER, COMPLIED WITH PROCS IN QRH, BOTH PLTS COULD NOT CORRECT RUDDER. WHEN 'B' SYS HYD SWITCH PLACED TO STANDBY RUDDER, RUDDERS CTRED AND CONTROLLABLE. DURING APCH NOTED VIBRATION IN RUDDER PEDALS AND SOME RUDDER 'KICKS.' UNEVENTFUL LNDG BWI, RWY 33L. MADE APPROPRIATE LOGBOOK ENTRY. SUPPLEMENTAL INFO FROM ACN 429548: I DECLARED AN EMER WITH ATC. IMMEDIATE ACTION ITEMS CONSISTING OF AUTOPLT, AUTOTHROTTLES AND YAW DAMPER WERE TURNED OFF. BOTH PLTS ATTEMPTED TO MOVE JAMMED RUDDER PEDALS. NO DESIRED MOVEMENT OBSERVED. QRH PROCS COMPLIED WITH. RUDDERS WERE FREED UP WHEN 'B' SYS HYD SYS FLT CTL SWITCH WAS PLACED TO STANDBY RUDDER POS. CALLBACK CONVERSATION WITH RPTR ON ACN 429547 REVEALED THE FOLLOWING INFO: THE RPTR SAID THAT THE CAPT WAS FLYING THE ACFT ON AUTOPLT AT THE TIME OF THE RUDDER DISPLACEMENT AND THE RPTR ATTEMPTED TO ASSIST WHEN THE R RUDDER PEDAL WENT, FULL TRAVEL, FORWARD. THEN AS THE FLC STARTED THROUGH THEIR UNCOMMANDED RUDDER INPUT CHKLIST THIS RPTR ASSUMED CTL OF THE ACFT. THIS RPTR HAS SPOKEN TO MAINT PERSONNEL AND THEY HAVE BEEN UNABLE TO DISCOVER THE CAUSE FOR THE RUDDER DISPLACEMENT. THE ACFT HAD ONE OF THE NEW RUDDER CTL VALVES INSTALLED AND IT WAS IN PROPER WORKING ORDER ACCORDING TO MAINT. CALLBACK CONVERSATION WITH RPTR ON ACN 429548 REVEALED THE FOLLOWING INFO: THIS RPTR SAID THAT WITH BOTH FLC PUSHING ON THE OPPOSITE RUDDER PEDAL THEY WERE UNABLE TO CORRECT THE R RUDDER DISPLACEMENT. HOWEVER, HE WAS ABLE TO MAINTAIN LEVEL FLT BY USING ALMOST FULL L AILERON INPUT. HE SAID THAT AS SOON AS HE PLACED THE 'B' SYS HYD SWITCH TO THE 'STANDBY RUDDER' POS THE RUDDER BECAME CONTROLLABLE AGAIN.

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.

This air carrier B737-200 flight crew experienced an uncommanded rudder displacement that caused the aircraft to roll to the right. Initially, the flight crew was unable to overpower the uncommanded input, but were able to maintain approximately level flight by xctling the aircraft.