Narrative:

I was captain flying from oma to sfo. In cruise the aircraft was flown on the autoplt and in trim. The first officer flew the takeoff and cruise segment. I became PF for the 10 mins before descent onward. At 24000 ft cruise, the aircraft was being flown in lateral navigation and vertical navigation modes. Responding to a clearance to descend to 16000 ft the aircraft was switched to vertical speed descent, speed brakes were extended, then stowed in the down position. The autoplt was then disengaged. A roll was felt to the right. I applied correction but the control force was great. The flight continued towards sfo. We were being vectored while we investigated the problem and contacted the company. The rudder trim and aileron trim was moved in an attempt to relieve the control force. After calling the company and discussing the problem I decided on a plan which required a landing with flaps 15 degrees. Then as the airspeed was reduced, the control force seemed to increase. The next consideration was to land the aircraft with the flaps and slats retracted at a higher airspeed. The landing was conducted successfully and maximum braking was applied momentarily then normal brakes. The aircraft touched down at about 210 KTS. The brakes were hot but there was no damage to either aircraft or personnel. Callback conversation with reporter revealed the following information: the reporter stated he was flying a boeing 737-300. He said it is unusual for the captain to change from PNF to PF en route. In this case the #2 VOR could not be manually tuned to the ILS because the VOR remained in agility tuning. The reporter has flown as captain just a little over 100 hours. He has flown the B737 as copilot for over a yr so estimated he had about 1000 hours total time in the B737. There are several configns of the B737 in his company which would perhaps dilute his understanding of this B737 with the glass cockpit. He also has time in the B757 and B767 as copilot and B727 as flight engineer. He was not sure whether the aileron yoke would move if the airplane was on autoplt and the aileron electric trim were applied. When the control problem occurred after having disconnected the autoplt he could not get any responses when he toggled the aileron trim. The aileron trim circuit breakers were checked in but not cycled. He contacted his company maintenance and followed their instructions to the point where they wanted him to slow the plane. It started to get more uncontrollable. For example, he tried turning off the yaw damper and checked the throttles were even and the fuel was even in the wings. The wings were checked to assure the spoilers, flaps and ailerons were as they were supposed to be. At the gate with the engines shut down the yoke was observed displaced to the right about 7 units. The rudder was to the left about 2 units. The reporter did not know how many units left aileron motion in flight would be necessary to counteract the 7 unit right aileron feel centering that existed on the ground. The no flap landing was just as he was trained it would be in the simulator.

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Original NASA ASRS Text

Title: RPTR EXPERIENCES UNCOMMANDED ROLL TENDENCY WHEN THE AUTOPLT IS DISCONNECTED.

Narrative: I WAS CAPT FLYING FROM OMA TO SFO. IN CRUISE THE ACFT WAS FLOWN ON THE AUTOPLT AND IN TRIM. THE FO FLEW THE TKOF AND CRUISE SEGMENT. I BECAME PF FOR THE 10 MINS BEFORE DSCNT ONWARD. AT 24000 FT CRUISE, THE ACFT WAS BEING FLOWN IN LATERAL NAV AND VERT NAV MODES. RESPONDING TO A CLRNC TO DSND TO 16000 FT THE ACFT WAS SWITCHED TO VERT SPD DSCNT, SPD BRAKES WERE EXTENDED, THEN STOWED IN THE DOWN POS. THE AUTOPLT WAS THEN DISENGAGED. A ROLL WAS FELT TO THE R. I APPLIED CORRECTION BUT THE CTL FORCE WAS GREAT. THE FLT CONTINUED TOWARDS SFO. WE WERE BEING VECTORED WHILE WE INVESTIGATED THE PROB AND CONTACTED THE COMPANY. THE RUDDER TRIM AND AILERON TRIM WAS MOVED IN AN ATTEMPT TO RELIEVE THE CTL FORCE. AFTER CALLING THE COMPANY AND DISCUSSING THE PROB I DECIDED ON A PLAN WHICH REQUIRED A LNDG WITH FLAPS 15 DEGS. THEN AS THE AIRSPD WAS REDUCED, THE CTL FORCE SEEMED TO INCREASE. THE NEXT CONSIDERATION WAS TO LAND THE ACFT WITH THE FLAPS AND SLATS RETRACTED AT A HIGHER AIRSPD. THE LNDG WAS CONDUCTED SUCCESSFULLY AND MAX BRAKING WAS APPLIED MOMENTARILY THEN NORMAL BRAKES. THE ACFT TOUCHED DOWN AT ABOUT 210 KTS. THE BRAKES WERE HOT BUT THERE WAS NO DAMAGE TO EITHER ACFT OR PERSONNEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED HE WAS FLYING A BOEING 737-300. HE SAID IT IS UNUSUAL FOR THE CAPT TO CHANGE FROM PNF TO PF ENRTE. IN THIS CASE THE #2 VOR COULD NOT BE MANUALLY TUNED TO THE ILS BECAUSE THE VOR REMAINED IN AGILITY TUNING. THE RPTR HAS FLOWN AS CAPT JUST A LITTLE OVER 100 HRS. HE HAS FLOWN THE B737 AS COPLT FOR OVER A YR SO ESTIMATED HE HAD ABOUT 1000 HRS TOTAL TIME IN THE B737. THERE ARE SEVERAL CONFIGNS OF THE B737 IN HIS COMPANY WHICH WOULD PERHAPS DILUTE HIS UNDERSTANDING OF THIS B737 WITH THE GLASS COCKPIT. HE ALSO HAS TIME IN THE B757 AND B767 AS COPLT AND B727 AS FE. HE WAS NOT SURE WHETHER THE AILERON YOKE WOULD MOVE IF THE AIRPLANE WAS ON AUTOPLT AND THE AILERON ELECTRIC TRIM WERE APPLIED. WHEN THE CTL PROB OCCURRED AFTER HAVING DISCONNECTED THE AUTOPLT HE COULD NOT GET ANY RESPONSES WHEN HE TOGGLED THE AILERON TRIM. THE AILERON TRIM CIRCUIT BREAKERS WERE CHKED IN BUT NOT CYCLED. HE CONTACTED HIS COMPANY MAINT AND FOLLOWED THEIR INSTRUCTIONS TO THE POINT WHERE THEY WANTED HIM TO SLOW THE PLANE. IT STARTED TO GET MORE UNCONTROLLABLE. FOR EXAMPLE, HE TRIED TURNING OFF THE YAW DAMPER AND CHKED THE THROTTLES WERE EVEN AND THE FUEL WAS EVEN IN THE WINGS. THE WINGS WERE CHKED TO ASSURE THE SPOILERS, FLAPS AND AILERONS WERE AS THEY WERE SUPPOSED TO BE. AT THE GATE WITH THE ENGS SHUT DOWN THE YOKE WAS OBSERVED DISPLACED TO THE R ABOUT 7 UNITS. THE RUDDER WAS TO THE L ABOUT 2 UNITS. THE RPTR DID NOT KNOW HOW MANY UNITS L AILERON MOTION IN FLT WOULD BE NECESSARY TO COUNTERACT THE 7 UNIT R AILERON FEEL CENTERING THAT EXISTED ON THE GND. THE NO FLAP LNDG WAS JUST AS HE WAS TRAINED IT WOULD BE IN THE SIMULATOR.

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.