Narrative:

The morning of nov/wed/95, flight XXX, a B727-100, pushed out of the oakland air carrier ramp for a planned route of oak-pdx- geg. After clearing the ramp and taxing out to runway 29 for departure, we proceeded with our routine checks. After doing the flight control checks, the captain asked me to feel the rudder pedals. Doing this check, he asked me if the pedals felt abnormal to me. I said they felt like they had a little less pressure than normal, but every indication in the cockpit, verified that they were functioning normally. We proceeded with the rest of the checks, the captain asked me to call ground control to see if it would be ok to hold on the taxiway, so we could call the company and talk to maintenance to assure us that the rudder pedals were functioning normally. After a thorough run down of all indicators in the cockpit, maintenance assured us everything was normal and stated on the radio 'there's no problem, see you later.' knowing in the back of my mind that the feel of the rudder pedals was still in question, I did not use them to start this turn, but rested both feet on them gently. This intercept turn was to the left. During this turn the rudder pedals went full deflection to the right. The nose of the airplane went to the right in a skid. As this was happening, I corrected with the opposite rudder, and the airplane nose went to the left very quickly. I let up on the left rudder and the nose went to the right in a skid. The rudder pedal wanted to continue to go full right. But every time I corrected it, it was like having 'power steering that was out of control.' although I was fighting this situation, having the crosswind and turbulence, the landing was accomplished safely and without incident. The rudder pedal steering was still the same as in flight, being very over-sensitive to touch. It was way over sensitive until the speed was slow enough to use the tiller. After taxiing off the runway, we tested the rudder pedals and it became apparent that all the back pressure was gone from the rudder pedals when doing this check and all indications in the cockpit were still normal. Taxiing into the gate we had maintenance come into the cockpit and test the pedals. At this time upon the write-up in the logbook, maintenance grounded the airplane. After a crew rest we returned to the airport and were informed that the rudder centering and feel mechanism had broken and both the broken piece and one side of the spring mechanism was missing. As the rudder had went full right exposing a hole in the bottom of the rudder section, I think the piece and spring had exited at that time because these pieces were nowhere to be found in the bottom of the rudder section. My question is, does the yaw damper have anything to do with the centering mechanism, and was the yaw damper looking for center which was not there, causing the rudder to go full right? Callback conversation with reporter revealed the following information: the reporter stated he has learned from the NTSB the yaw damper does get feedback from the centering mechanism of the rudder feel. Boeing stated to the reporter that this huge assembly arm had never broken before. However, there were indications this arm had been cracking for some time. There was dirt and oil in portions of the break and portions of the break were clean. The reporter stated he had checked the rudder feel pitot heat prior to departing oakland and the flight engineer had done so also. The reporter stated he did not understand why the airplane rudder went full right when he disconnected the autoplt. He said there is no established procedure for this event, but, suspects turning off the yaw damper would help and suggests that a procedure be established. There is a union action versus a company grievance which discourages a pilot from taking an airplane back to the gate unless there is a clear indication of a problem. The reporter stated when the rudder anomaly occurred the flaps were 15 degrees and the speed was about 180 KTS and slowing. The reporter did not know if the feel mechanism pitot heat or spring breaking could have caused the arm to break but did know the pitot heat was on and working out of oakland. The reporter said he could not find out if this centering problem could occur on the B737 but was told the related part on the B737's that mysteriously crashed were intact. Curiously, the airplane had no tendency to roll with the rudder movements but only yaw, according to the reporter. Supplemental information from acn 322299: on taxi out, we did our normal control check. The rudder seemed more free (B727 aircraft) than normal. Rudder moved in its full range, no load limiter light. I contacted maintenance and they assured me there was no problem. I was not convinced, but did not feel the problem was significant if there was indeed a problem. So we launched. After takeoff we applied pressure to the rudder and it was extremely sensitive. I felt that there was a problem with the artificial feel system and relayed that to maintenance. I felt that it was as safe to proceed to pdx as to return to oak as long as we were careful of any rudder input. Yaw dampers both ok. We proceeded to pdx without major incident and wrote-up aircraft. Turns out there was a broken part in the feel system of the rudder. Boeing is very interested as well as NTSB.

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Original NASA ASRS Text

Title: RPTR EXPERIENCES UNGOVERNABLE RUDDER CTL.

Narrative: THE MORNING OF NOV/WED/95, FLT XXX, A B727-100, PUSHED OUT OF THE OAKLAND ACR RAMP FOR A PLANNED RTE OF OAK-PDX- GEG. AFTER CLRING THE RAMP AND TAXING OUT TO RWY 29 FOR DEP, WE PROCEEDED WITH OUR ROUTINE CHKS. AFTER DOING THE FLT CTL CHKS, THE CAPT ASKED ME TO FEEL THE RUDDER PEDALS. DOING THIS CHK, HE ASKED ME IF THE PEDALS FELT ABNORMAL TO ME. I SAID THEY FELT LIKE THEY HAD A LITTLE LESS PRESSURE THAN NORMAL, BUT EVERY INDICATION IN THE COCKPIT, VERIFIED THAT THEY WERE FUNCTIONING NORMALLY. WE PROCEEDED WITH THE REST OF THE CHKS, THE CAPT ASKED ME TO CALL GND CTL TO SEE IF IT WOULD BE OK TO HOLD ON THE TXWY, SO WE COULD CALL THE COMPANY AND TALK TO MAINT TO ASSURE US THAT THE RUDDER PEDALS WERE FUNCTIONING NORMALLY. AFTER A THOROUGH RUN DOWN OF ALL INDICATORS IN THE COCKPIT, MAINT ASSURED US EVERYTHING WAS NORMAL AND STATED ON THE RADIO 'THERE'S NO PROB, SEE YOU LATER.' KNOWING IN THE BACK OF MY MIND THAT THE FEEL OF THE RUDDER PEDALS WAS STILL IN QUESTION, I DID NOT USE THEM TO START THIS TURN, BUT RESTED BOTH FEET ON THEM GENTLY. THIS INTERCEPT TURN WAS TO THE L. DURING THIS TURN THE RUDDER PEDALS WENT FULL DEFLECTION TO THE R. THE NOSE OF THE AIRPLANE WENT TO THE R IN A SKID. AS THIS WAS HAPPENING, I CORRECTED WITH THE OPPOSITE RUDDER, AND THE AIRPLANE NOSE WENT TO THE L VERY QUICKLY. I LET UP ON THE L RUDDER AND THE NOSE WENT TO THE R IN A SKID. THE RUDDER PEDAL WANTED TO CONTINUE TO GO FULL R. BUT EVERY TIME I CORRECTED IT, IT WAS LIKE HAVING 'PWR STEERING THAT WAS OUT OF CTL.' ALTHOUGH I WAS FIGHTING THIS SIT, HAVING THE XWIND AND TURB, THE LNDG WAS ACCOMPLISHED SAFELY AND WITHOUT INCIDENT. THE RUDDER PEDAL STEERING WAS STILL THE SAME AS IN FLT, BEING VERY OVER-SENSITIVE TO TOUCH. IT WAS WAY OVER SENSITIVE UNTIL THE SPD WAS SLOW ENOUGH TO USE THE TILLER. AFTER TAXIING OFF THE RWY, WE TESTED THE RUDDER PEDALS AND IT BECAME APPARENT THAT ALL THE BACK PRESSURE WAS GONE FROM THE RUDDER PEDALS WHEN DOING THIS CHK AND ALL INDICATIONS IN THE COCKPIT WERE STILL NORMAL. TAXIING INTO THE GATE WE HAD MAINT COME INTO THE COCKPIT AND TEST THE PEDALS. AT THIS TIME UPON THE WRITE-UP IN THE LOGBOOK, MAINT GNDED THE AIRPLANE. AFTER A CREW REST WE RETURNED TO THE ARPT AND WERE INFORMED THAT THE RUDDER CENTERING AND FEEL MECHANISM HAD BROKEN AND BOTH THE BROKEN PIECE AND ONE SIDE OF THE SPRING MECHANISM WAS MISSING. AS THE RUDDER HAD WENT FULL R EXPOSING A HOLE IN THE BOTTOM OF THE RUDDER SECTION, I THINK THE PIECE AND SPRING HAD EXITED AT THAT TIME BECAUSE THESE PIECES WERE NOWHERE TO BE FOUND IN THE BOTTOM OF THE RUDDER SECTION. MY QUESTION IS, DOES THE YAW DAMPER HAVE ANYTHING TO DO WITH THE CENTERING MECHANISM, AND WAS THE YAW DAMPER LOOKING FOR CTR WHICH WAS NOT THERE, CAUSING THE RUDDER TO GO FULL R? CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE HAS LEARNED FROM THE NTSB THE YAW DAMPER DOES GET FEEDBACK FROM THE CENTERING MECHANISM OF THE RUDDER FEEL. BOEING STATED TO THE RPTR THAT THIS HUGE ASSEMBLY ARM HAD NEVER BROKEN BEFORE. HOWEVER, THERE WERE INDICATIONS THIS ARM HAD BEEN CRACKING FOR SOME TIME. THERE WAS DIRT AND OIL IN PORTIONS OF THE BREAK AND PORTIONS OF THE BREAK WERE CLEAN. THE RPTR STATED HE HAD CHKED THE RUDDER FEEL PITOT HEAT PRIOR TO DEPARTING OAKLAND AND THE FE HAD DONE SO ALSO. THE RPTR STATED HE DID NOT UNDERSTAND WHY THE AIRPLANE RUDDER WENT FULL R WHEN HE DISCONNECTED THE AUTOPLT. HE SAID THERE IS NO ESTABLISHED PROC FOR THIS EVENT, BUT, SUSPECTS TURNING OFF THE YAW DAMPER WOULD HELP AND SUGGESTS THAT A PROC BE ESTABLISHED. THERE IS A UNION ACTION VERSUS A COMPANY GRIEVANCE WHICH DISCOURAGES A PLT FROM TAKING AN AIRPLANE BACK TO THE GATE UNLESS THERE IS A CLR INDICATION OF A PROB. THE RPTR STATED WHEN THE RUDDER ANOMALY OCCURRED THE FLAPS WERE 15 DEGS AND THE SPD WAS ABOUT 180 KTS AND SLOWING. THE RPTR DID NOT KNOW IF THE FEEL MECHANISM PITOT HEAT OR SPRING BREAKING COULD HAVE CAUSED THE ARM TO BREAK BUT DID KNOW THE PITOT HEAT WAS ON AND WORKING OUT OF OAKLAND. THE RPTR SAID HE COULD NOT FIND OUT IF THIS CENTERING PROB COULD OCCUR ON THE B737 BUT WAS TOLD THE RELATED PART ON THE B737'S THAT MYSTERIOUSLY CRASHED WERE INTACT. CURIOUSLY, THE AIRPLANE HAD NO TENDENCY TO ROLL WITH THE RUDDER MOVEMENTS BUT ONLY YAW, ACCORDING TO THE RPTR. SUPPLEMENTAL INFO FROM ACN 322299: ON TAXI OUT, WE DID OUR NORMAL CTL CHK. THE RUDDER SEEMED MORE FREE (B727 ACFT) THAN NORMAL. RUDDER MOVED IN ITS FULL RANGE, NO LOAD LIMITER LIGHT. I CONTACTED MAINT AND THEY ASSURED ME THERE WAS NO PROB. I WAS NOT CONVINCED, BUT DID NOT FEEL THE PROB WAS SIGNIFICANT IF THERE WAS INDEED A PROB. SO WE LAUNCHED. AFTER TKOF WE APPLIED PRESSURE TO THE RUDDER AND IT WAS EXTREMELY SENSITIVE. I FELT THAT THERE WAS A PROB WITH THE ARTIFICIAL FEEL SYS AND RELAYED THAT TO MAINT. I FELT THAT IT WAS AS SAFE TO PROCEED TO PDX AS TO RETURN TO OAK AS LONG AS WE WERE CAREFUL OF ANY RUDDER INPUT. YAW DAMPERS BOTH OK. WE PROCEEDED TO PDX WITHOUT MAJOR INCIDENT AND WROTE-UP ACFT. TURNS OUT THERE WAS A BROKEN PART IN THE FEEL SYS OF THE RUDDER. BOEING IS VERY INTERESTED AS WELL AS NTSB.

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.