Narrative:

At flaps 5 degrees and 180 KTS, we experienced a strong airframe vibration. Shortly thereafter the aircraft began an uncommanded roll to the right with bank angles exceeding 30 degrees. Full opposite control wheel input had no immediate effect on decreasing roll rate. It was my perception that the aircraft was going to continue rolling over onto its back. A short time later I was able to regain control of the aircraft. The autoplt was then engaged but strong vibration continued. Shortly after the autoplt was disengaged, the aircraft went into an abrupt 10 degree dive and full aft control wheel position had no effect. At this point no one on board believed we were going to recover. Eventually the controls took effect and a normal pitch attitude was attained. An emergency was declared and landing was uneventful. Callback conversation with reporter revealed the following information: the reporter stated that during the pitch down the copilot noticed the stabilizer trim was not moving but heard a grinding noise coming from the throttle quadrant. After the flight landed, a test flight was accomplished which was normal except the copilot noticed metal shavings coming from the control quadrant. On taxi in from the test flight, the spoiler handle would not stow and an inspection revealed several bearings in the stabilizer trim follow up system failed. A tie rod and a drive gear. The reporter stated he did not believe the company position that his experience was related to the wake of a previously landed dc-8 and a boeing 757 which landed ahead of the dc-8. The roll was so slow and persistent the flight crew thought they were going to roll over on their back. Then the pitch over was so slow and persistent they thought they were going to hit the ground. Both motions were opposed by full control inputs and seconds went by before the airplane showed any tendency to respond to both roll and pitch.

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Original NASA ASRS Text

Title: FLC EXPERIENCES UNCOMMANDED ROLL AND PITCH DOWN.

Narrative: AT FLAPS 5 DEGS AND 180 KTS, WE EXPERIENCED A STRONG AIRFRAME VIBRATION. SHORTLY THEREAFTER THE ACFT BEGAN AN UNCOMMANDED ROLL TO THE R WITH BANK ANGLES EXCEEDING 30 DEGS. FULL OPPOSITE CTL WHEEL INPUT HAD NO IMMEDIATE EFFECT ON DECREASING ROLL RATE. IT WAS MY PERCEPTION THAT THE ACFT WAS GOING TO CONTINUE ROLLING OVER ONTO ITS BACK. A SHORT TIME LATER I WAS ABLE TO REGAIN CTL OF THE ACFT. THE AUTOPLT WAS THEN ENGAGED BUT STRONG VIBRATION CONTINUED. SHORTLY AFTER THE AUTOPLT WAS DISENGAGED, THE ACFT WENT INTO AN ABRUPT 10 DEG DIVE AND FULL AFT CTL WHEEL POS HAD NO EFFECT. AT THIS POINT NO ONE ON BOARD BELIEVED WE WERE GOING TO RECOVER. EVENTUALLY THE CTLS TOOK EFFECT AND A NORMAL PITCH ATTITUDE WAS ATTAINED. AN EMER WAS DECLARED AND LNDG WAS UNEVENTFUL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT DURING THE PITCH DOWN THE COPLT NOTICED THE STABILIZER TRIM WAS NOT MOVING BUT HEARD A GRINDING NOISE COMING FROM THE THROTTLE QUADRANT. AFTER THE FLT LANDED, A TEST FLT WAS ACCOMPLISHED WHICH WAS NORMAL EXCEPT THE COPLT NOTICED METAL SHAVINGS COMING FROM THE CTL QUADRANT. ON TAXI IN FROM THE TEST FLT, THE SPOILER HANDLE WOULD NOT STOW AND AN INSPECTION REVEALED SEVERAL BEARINGS IN THE STABILIZER TRIM FOLLOW UP SYS FAILED. A TIE ROD AND A DRIVE GEAR. THE RPTR STATED HE DID NOT BELIEVE THE COMPANY POS THAT HIS EXPERIENCE WAS RELATED TO THE WAKE OF A PREVIOUSLY LANDED DC-8 AND A BOEING 757 WHICH LANDED AHEAD OF THE DC-8. THE ROLL WAS SO SLOW AND PERSISTENT THE FLC THOUGHT THEY WERE GOING TO ROLL OVER ON THEIR BACK. THEN THE PITCH OVER WAS SO SLOW AND PERSISTENT THEY THOUGHT THEY WERE GOING TO HIT THE GND. BOTH MOTIONS WERE OPPOSED BY FULL CTL INPUTS AND SECONDS WENT BY BEFORE THE AIRPLANE SHOWED ANY TENDENCY TO RESPOND TO BOTH ROLL AND PITCH.

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.