A canadair cl-65 during a maintenance ferry to correct rudder oscillations when on a 6 mi final appr...

Narrative:

We were flying a scheduled flight from ZZZ to ZZZ1 and started to notice a yawing motion with the autoplt. We were at FL310 at 0.74 mach. I brought up the flight control page to see if the rudder was oscillating. It was. I turned off the autoplt to see if the yawing continued. It did. I called maintenance to discuss the problems since there was no approved checklist. It took a while to get the information we needed from them. By the time that we came back into contact with them we were starting our descent in to ZZZ1. When on the ground in ZZZ1 I called maintenance. We discussed the problem. They had me go to the aircraft and power up the hydraulic systems and engage the yaw damper and see if the rudder oscillations continued to occur. They did not duplicate. I told maintenance that I as well as my first officer were comfortable ferrying the aircraft to a maintenance base. We got all of the required paperwork completed and took off to ZZZ2 maintenance base. Once again we experienced the same yawing. We expected this. The flight was normal for the climb, cruise, and descent. On approach to runway at ZZZ2 in VMC conditions the yawing increased. I was hand flying the aircraft. About 2500 MSL on the descent to the runway we experienced some light turbulence. With this turbulence we experienced an uncommanded yaw and roll to the left. When I looked down I saw the bank on the primary flight display at or above 40 degree to the left. I counteracted this with right aileron. We then got a bank to the right. This I counteracted with left aileron. I estimate the bank to the right at about 20-25 degree. This was the only upset we experienced. When looking at the instruments I saw the brick, like a ball go full out to the left 3/4 and out to the right. We landed without further incident. I filled out the required company paperwork and turned it in. Callback conversation with reporter revealed the following information: the reporter stated that during the maintenance ferry he experienced the yaw oscillations as expected. The reporter said on the six mi final approach at 2500 ft on descent he encountered light turbulence and an uncommanded yaw and roll to the left at or above 40 degrees and counter acted with right aileron. The reporter stated he then got a bank to the right 25 degrees and used left aileron to correct and the airplane then flew ok to a normal landing. The reporter said the maintenance action was to adjust the rudder secondary feel unit spring tension due to being found out of limits. The reporter said the airplane was test flown and oscillations were still present. The reporter stated the corrective action was replacement of the lightening/high intensity radiated field protection circuit card in the integrated avionics processor. The reporter said this circuit card was found 'fried' and replaced. The reporter said no further rudder oscillations were reported on the airplane when back in service.

Original NASA ASRS Text

Title: A CANADAIR CL-65 DURING A MAINT FERRY TO CORRECT RUDDER OSCILLATIONS WHEN ON A 6 MI FINAL APCH EXPERIENCED AN UNCOMMANDED YAW AND ROLL 40 DEGS TO THE LEFT THEN A BANK TO THE R 25 DEGS. LANDED WITHOUT FURTHER INCIDENT.

Narrative: WE WERE FLYING A SCHEDULED FLT FROM ZZZ TO ZZZ1 AND STARTED TO NOTICE A YAWING MOTION WITH THE AUTOPLT. WE WERE AT FL310 AT 0.74 MACH. I BROUGHT UP THE FLT CTL PAGE TO SEE IF THE RUDDER WAS OSCILLATING. IT WAS. I TURNED OFF THE AUTOPLT TO SEE IF THE YAWING CONTINUED. IT DID. I CALLED MAINT TO DISCUSS THE PROBLEMS SINCE THERE WAS NO APPROVED CHKLIST. IT TOOK A WHILE TO GET THE INFO WE NEEDED FROM THEM. BY THE TIME THAT WE CAME BACK INTO CONTACT WITH THEM WE WERE STARTING OUR DSCNT IN TO ZZZ1. WHEN ON THE GND IN ZZZ1 I CALLED MAINT. WE DISCUSSED THE PROB. THEY HAD ME GO TO THE ACFT AND POWER UP THE HYDRAULIC SYSTEMS AND ENGAGE THE YAW DAMPER AND SEE IF THE RUDDER OSCILLATIONS CONTINUED TO OCCUR. THEY DID NOT DUPLICATE. I TOLD MAINT THAT I AS WELL AS MY FO WERE COMFORTABLE FERRYING THE ACFT TO A MAINT BASE. WE GOT ALL OF THE REQUIRED PAPERWORK COMPLETED AND TOOK OFF TO ZZZ2 MAINT BASE. ONCE AGAIN WE EXPERIENCED THE SAME YAWING. WE EXPECTED THIS. THE FLT WAS NORMAL FOR THE CLB, CRUISE, AND DSCNT. ON APCH TO RWY AT ZZZ2 IN VMC CONDITIONS THE YAWING INCREASED. I WAS HAND FLYING THE ACFT. ABOUT 2500 MSL ON THE DSCNT TO THE RWY WE EXPERIENCED SOME LIGHT TURBULENCE. WITH THIS TURB WE EXPERIENCED AN UNCOMMANDED YAW AND ROLL TO THE L. WHEN I LOOKED DOWN I SAW THE BANK ON THE PRIMARY FLT DISPLAY AT OR ABOVE 40 DEG TO THE L. I COUNTERACTED THIS WITH RIGHT AILERON. WE THEN GOT A BANK TO THE RIGHT. THIS I COUNTERACTED WITH LEFT AILERON. I ESTIMATE THE BANK TO THE RIGHT AT ABOUT 20-25 DEG. THIS WAS THE ONLY UPSET WE EXPERIENCED. WHEN LOOKING AT THE INSTRUMENTS I SAW THE BRICK, LIKE A BALL GO FULL OUT TO THE LEFT 3/4 AND OUT TO THE R. WE LANDED WITHOUT FURTHER INCIDENT. I FILLED OUT THE REQUIRED COMPANY PAPERWORK AND TURNED IT IN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT DURING THE MAINT FERRY HE EXPERIENCED THE YAW OSCILLATIONS AS EXPECTED. THE RPTR SAID ON THE SIX MI FINAL APCH AT 2500 FT ON DSCNT HE ENCOUNTERED LIGHT TURB AND AN UNCOMMANDED YAW AND ROLL TO THE LEFT AT OR ABOVE 40 DEGS AND COUNTER ACTED WITH R AILERON. THE RPTR STATED HE THEN GOT A BANK TO THE R 25 DEGS AND USED L AILERON TO CORRECT AND THE AIRPLANE THEN FLEW OK TO A NORMAL LNDG. THE RPTR SAID THE MAINT ACTION WAS TO ADJUST THE RUDDER SECONDARY FEEL UNIT SPRING TENSION DUE TO BEING FOUND OUT OF LIMITS. THE RPTR SAID THE AIRPLANE WAS TEST FLOWN AND OSCILLATIONS WERE STILL PRESENT. THE RPTR STATED THE CORRECTIVE ACTION WAS REPLACEMENT OF THE LIGHTENING/HIGH INTENSITY RADIATED FIELD PROTECTION CIRCUIT CARD IN THE INTEGRATED AVIONICS PROCESSOR. THE RPTR SAID THIS CIRCUIT CARD WAS FOUND 'FRIED' AND REPLACED. THE RPTR SAID NO FURTHER RUDDER OSCILLATIONS WERE RPTED ON THE AIRPLANE WHEN BACK IN SVC.

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.

Attributes
ACN	538247
Time
Date	200202
Day	Sun
Local Time Of Day	0001 To 0600
Place
Locale Reference	airport : zzz2.airport
State Reference	US
Altitude	msl single value : 2500
Environment
Flight Conditions	VMC
Weather Elements	Turbulence
Light	Night
Aircraft 1
Controlling Facilities	tower : zzz2.tower
Operator	common carrier : air carrier
Make Model Name	Regional Jet CL65, Undifferentiated or Other Model
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 pilot : commercial
Experience	flight time last 90 days : 270 flight time total : 3600 flight time type : 625
ASRS Report	538247
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : turn and slip indicator other flight crewa other flight crewb
Resolutory Action	flight crew : regained aircraft control
Consequence	other other
Supplementary
Problem Areas	Aircraft Environmental Factor
Primary Problem	Aircraft

A canadair cl-65 during a maintenance ferry to correct rudder oscillations when on a 6 mi final approach experienced an uncommanded yaw and roll 40 degrees to the left then a bank to the right 25 degrees. Landed without further incident.