RUNAWAY RUDDER TRIM -- ENG-OUT ASSIST SYS DESIGN PROB.

Narrative

AFTER DEPARTING MEM OFF OF RWY 27 WE WERE GIVEN A VECTOR OF 350 DEGS AND A CLRNC TO 16000 FT. PASSING 4000 FT; AIRSPD 250 KTS AND AUTOPLT #1 ENGAGED; A SUDDEN HARD YAW AND CORRESPONDING ROLL TO THE R OCCURRED. THE ACFT MADE AN IMMEDIATE HDG DEV OF 15-20 DEGS TO THE R AS IF LOSING THE R ENG. THE AUTOPLT WAS IMMEDIATELY DISCONNECTED MANUALLY AND RECOVERY TO NORMAL FLT PATH WAS ACCOMPLISHED. THE ENGS WERE RUNNING NORMALLY AND IT WAS DISCOVERED THAT THE YAW PROB WAS A RUNAWAY RUDDER TRIM. RUDDER TRIM IS ELECTRICALLY ACTUATED AND HAD GONE INSTANTANEOUSLY ON ITS OWN FROM 0-21 DEGS R. THE AUTOTHROTTLES WERE DISCONNECTED AND THE FLT MODE ANNUNCIATORS SHOWED A STEADY 'THR L' (THRUST LATCH). NO ECAM OR ANY OTHER WARNINGS OCCURRED THROUGHOUT THE ENTIRE MANEUVER NOR DID ANY OTHER LEVERS OR SWITCHES TRIP OFF LINE. THE ACFT WAS HAND FLOWN AND RUDDER TRIM MANUALLY RESET TO 0 DEGS WHILE OUR MAINT DEPT WAS CONSULTED ABOUT THE SIT. THEIR RESPONSE WAS THAT DEACTIVATION OF THE #1 AUTOPLT SYS WAS APPROPRIATE AND WOULD ISOLATE ANY FURTHER ELECTRICAL INPUTS INTO THE RUDDER TRIM SYS FROM THE #1 AUTOPLT COMMANDS. THEY FURTHER INSISTED THE ACFT WAS SAFE TO BE FLOWN EITHER MANUALLY OR ON AUTOPLT SYS #2; AND TO CONTINUE TO THE ORIGINAL DEST WHERE THE #1 SYS WOULD BE INVESTIGATED. THE #2 AUTOPLT SYS WAS THEN ENGAGED AND THE FLT PROCEEDED WITHOUT FURTHER INCIDENT TO THE ORIGINAL DEST. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: UPON LNDG THE ACFT WAS GNDED AND THE #1 AUTOPLT WAS REMOVED AND REPLACED. ACFT WAS TEST FLOWN BACK TO ORIGINATING STATION WHERE ACFT HAS SINCE BEEN RETURNED TO SVC. THERE HAVE BEEN NO OTHER KNOWN INSTANCES OF THIS HAPPENING ACCORDING TO THE RPTR. THE RUDDER TRIM WAS FOUND TO BE CTLED BY THE AUTOPLT IN THIS CASE. HOWEVER; THEY MADE AN IMPORTANT DISCOVERY REGARDING THE RUDDER TRIM CTL. WHICH IS; IF THE KNOB TO THE RUDDER TRIM IS MOVED MANUALLY; THE TRIM WILL MOVE AS THE KNOB MOVES A SWITCH UNDER THE KNOB. WHEN THE MANUAL KNOB IS RELEASED THE SWITCH SHOULD RELEASE ALSO. IN MANY CASES IT WAS FOUND TO HANG UP; RESULTING IN TRIM BEING APPLIED EVEN THOUGH MANUALLY; IT APPEARED TO BE NEUTRAL. TO DETECT TRIM MOVEMENT A FLC MEMBER HAS TO BE LOOKING DOWN AT THE CTRL CTL PEDESTAL OR HE WILL NOT OBSERVE ANY TRIM CHANGE. THE FEELING IS THAT THIS SIT IS RELATED TO THE AUTOPLT GIVING THE TRIM AN UNCOMMANDED CHANGE. PLT FELT FORTUNATE THAT THIS INCIDENT DID NOT OCCUR CLOSE TO THE GND. SUPPLEMENTAL INFO FROM ACN 303573: A SUDDEN HARD YAW AND CORRESPONDING ROLL TO THE R OCCURRED. THE AUTOPLT WAS DISCONNECTED MANUALLY AND RECOVERY TO NORMAL FLT PATH WAS ACCOMPLISHED. RUDDER TRIM HAD GONE INSTANTANEOUSLY ON ITS OWN FROM 0-21 DEGS R (FULL DEFLECTION). THE AUTOTHROTTLES WERE ALSO DISCONNECTED AND THE FLT MODE ANNUNCIATOR SHOWED A GREEN STEADY 'THRUST LATCH.' NO ELECTRONIC CENTRALIZED AIRPLANE MONITOR WARNING OCCURRED. AT THE TIME OF THE EVENT THE ACFT WAS 26000 LBS OVERWT FOR LNDG WITH NO CAPABILITY TO DUMP FUEL. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO ON 303573: THE RPTR STATES THAT SINCE HE SUBMITTED HIS ASRS RPT THE COMPANY INVESTIGATORS HAVE DISCOVERED THAT THE A-300-600 HAS AN ENG-OUT ASSIST SYS THAT IS ACTIVE ANY TIME THE SLATS ARE EXTENDED. IN THIS CASE; THE COMPANY PROCS ARE TO MANUALLY FLY THE ACFT TO 1000 FT AGL THEN ENGAGE THE AUTOPLT AND THEN START THE FLAP RETRACTION PROC. THE SLATS CAME UP AT 4000 FT AND THE ACFT ROLLED AND YAWED TO THE R. BOTH ENGS WERE AT BALANCED PWR SETTING THROUGHOUT THE EVENT AND OTHER THAN THE TRIM BEING DRIVEN FULL R NO SYS ABNORMALITIES WERE NOTED. THE RPTR FEELS THAT THE ACFT IS NOT USER FRIENDLY; BUT INSTEAD 'IS AN ILLOGICAL; DANGEROUS ACFT.' HE FURTHER STATES THAT THE AVAILABLE DOCUMENTATION ON THE ACFT AND ITS SUB-SYS IS INADEQUATE AND THAT THE MANUFACTURER WAS INITIALLY LESS THAN FORTHCOMING CONCERNING THIS INCIDENT AND SIMILAR ENG-OUT ASSIST RPTS IN THE MANUFACTURER'S FILES. THE RPTR ALSO SAID THAT THE AIRLINE'S PROJECT MGR FOR THE A-300-600 HAD NOT BEEN AWARE OF THE FULL-TIME-WITH-SLATS-EXTENDED FEATURE OF THE ENG-OUT ASSIST SYS EVEN THOUGH HE HAD BEEN THROUGH THE RATHER EXTENSIVE TRAINING PROGRAM AT THE MANUFACTURER AND WAS SUPPOSED TO BE RECEIVING ALL OF THE USER INCIDENT RPTS. THE RPTR SAYS THAT HE IS GOING TO BID OFF THE ACFT.