B777 ON DSCNT; L ENG DELAY IN ACCELERATION DURING INTERMEDIATE LEVELOFF.

Narrative

ON ARR; I WROTE THE FOLLOWING WRITE-UP IN THE MAINT LOGBOOK. ON APCH; APPROX 2000 FT; AUTOTHROTTLES ON ENGS COMMANDED TO ACCELERATE; L ENG HUNG AT APCH IDLE; R ENG ACCELERATED NORMALLY. APPEARS L ENG WOULD NOT RESPOND TO PWR INPUT THEN FINALLY ACCELERATED 10-15 SECONDS AFTER R ENG. ON ARR; IDLE THRUST AT 280 KTS FROM FL300; CLRED VIA INTXN AT 17000 FT. AT IDLE THRUST 280 KTS; SLOWED TO 250 KTS USING SPD BRAKES ON PATH APCHING 10000 FT; ATC ASKED TO MAINTAIN 250 KTS UNTIL ADVISED THEN CLRED US TO SLOW TO 220 KTS UNTIL ADVISED; SPD BRAKES USED TO SLOW. BELOW 3000 FT CLRED TO MAINTAIN 170 KTS TO OM; STILL AT IDLE ON PROFILE DSCNT; SPD BRAKES USED TO SLOW. APCHING 170 KTS; FO STOWING SPD BRAKES AS AUTOTHROTTLES MOVED TOGETHER TO MAINTAIN COMMANDED SPD. ENGS DID NOT ACCELERATE IMMEDIATELY; SAW COMMAND THRUST ARCS ON EICAS. R ENG BEGAN TO RESPOND AND ACCELERATED NORMALLY; BUT L ENG HUNG AT IDLE THRUST ALTHOUGH AUTOTHROTTLES HAD MOVED; WERE MATCHED AND COMMAND THRUST ARCS EQUAL SHOWING REQUIRED THRUST. AFTER APPROX 10-15 SECONDS; L ENG FINALLY RESPONDED AND ACCELERATED TO MATCH THE R ENG. DURING EVENT; ACFT WAS ON AUTOPLT WITH AUTOTHROTTLES ENGAGED. AUTOPLT HANDLED YAW ASSOCIATED WITH UNEVEN THRUST ACCELERATION UNTIL THRUST FINALLY WAS SYMMETRICAL. NORMAL APCH AND LNDG AFTER EVENT; EXCEPT FOR LOW ALT POSSIBLE BIRD STRIKE; WHICH WAS ALSO ENTERED IN MAINT LOG. AFTER LNDG; CONTACTED MAINT TO ADVISE; DEBRIEFED AMT IN COCKPIT; THEN CALLED DISPATCH. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT ADVISED THAT THE ACR'S MAINT AND FLT OPS DEPTS EXPENDED A GREAT DEAL OF EFFORT ANALYZING FDR DATA AND TESTING SCENARIOS IN THE SIMULATOR AND AGAIN IN THE ACTUAL ACFT. THEIR FINDINGS WERE THAT THE DELAY IN RESPONSE WAS DUE TO THE PF'S (THE FO) ARM RESTRICTING THE THROTTLE FROM PHYSICALLY ADVANCING. THIS HAPPENED BECAUSE HE WAS SIMULTANEOUSLY SLOWLY RETRACTING THE SPOILERS AS THE LEVELOFF PROGRESSED. BECAUSE THE SPOILER CTL LEVER IS ON THE CAPT'S SIDE OF THE THROTTLE QUADRANT; THE FO MUST REACH BEHIND OR OVER THE THROTTLES AT IDLE (THE MOST PROBABLE THRUST SETTING WHEN ACTIVATING THE SPOILERS/SPD BRAKES). IN THIS CASE HIS ARM RESTR THE THROTTLE FROM ADVANCING. IT WAS DETERMINED THAT ONLY A MODEST AMOUNT OF PRESSURE (1 LB OR 1 1/2 LBS) IS REQUIRED TO RESTRICT THROTTLE MOVEMENT ON THE ENGS EMPLOYED BY THIS CARRIER. THE REQUIRED PRESSURE WAS NOT ENOUGH TO ALERT THE FO TO THE AUTOTHROTTLE'S ATTEMPT TO ADVANCE THE LEVER. THE ACR INTENDS TO ISSUE A BULLETIN TO THE B777 PLTS ALERTING THEM TO THIS POTENTIAL.