A B757-200. ON INITIAL CLB AT 1500 FT; THE ACFT WOULD NOT ACCELERATE BEYOND 160 KTS IN VNAV MODE WITH THROTTLES MOVING TO IDLE. AUTOTHROTTLE DISCONNECT SWITCH ERRATIC.

Narrative

THIS INCIDENT OCCURRED ON CLBOUT FROM ZZZ. PREDEP SOP'S WERE FOLLOWED. THE DEP WAS BRIEFED TWICE SINCE I AM RELATIVELY NEW TO THE B757 AND THE FO HAD NOT BEEN TO ZZZ IN SOME TIME. TKOF ROLL WAS NORMAL. WE WERE VERY LIGHT (184000 LBS). ROTATION WAS NORMAL. GEAR WAS RAISED. PITCH WAS APPROX 21-22 DEGS; SOMEWHAT LESS THAN I EXPECTED BASED ON OUR WT. AT 800 FT VNAV WAS SELECTED AND PITCH WAS REDUCED TO 9-10 DEGS. AGAIN; LESS THAN THE 12-13 DEGS I ANTICIPATED TO MAINTAIN V2 +15 KTS. AT 1500 FT; THE INTERNAL SPD BUG INCREASED TO 160 KTS. AIRSPD WAS INCREASED AND FLAPS 1 DEG WERE SELECTED. THE ACFT WOULD NOT ACCELERATE BEYOND 160 KTS AND WE COULD NOT CLB. WE AGREED THIS WAS NOT NORMAL; ABANDONED REDUCED CLB; AND SELECTED NORMAL CLB. THIS DID NOT HELP. THE THROTTLES CAME BACK TO IDLE. I STARTED A DSCNT TO MAINTAIN AIRSPD WHILE PRESSING THE THROTTLE-DISCONNECT BUTTON AND ATTEMPTING TO MANUALLY PUSH UP THE THROTTLES. INITIALLY; THIS DID NOT WORK EITHER. THE THROTTLES STILL TRIED TO COME BACK. A SECOND ATTEMPT TO PRESS THE THROTTLE-DISCONNECT BUTTON; HOLDING IT FOR A COUPLE OF SECONDS WHILE PUSHING THE THROTTLES UP; WAS SUCCESSFUL. HOWEVER; BY THAT TIME WE HAD LOST 500 FT AND HAD GOTTEN A SINK ALERT. THE PROB CORRECTED THE ACFT ACCELERATED NORMALLY. A MAINT RPT WAS FILED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE FMS WAS PROGRAMMED CORRECTLY AND THE AUTOTHROTTLE SYS AND AUTOPLT WERE OPERATIONAL WITH NO OPEN RPTS. THE RPTR SAID NO RPT FROM MAINT WAS RECEIVED BY THE CREW ON THE FAILURE OF THE AUTOTHROTTLE SYS TO INCREASE THE SPD AFTER FLAP RETRACTION AND THE FAILURE OF THE AUTOTHROTTLE DISCONNECT SWITCH. THE RPTR STATED WHEN MAINT WAS CONTACTED HE WAS TOLD THE INCIDENT WAS CLOSED. THE RPTR SAID THE ACFT WAS RETURNED TO SVC AND IT WAS HINTED THE COMPANY BELIEVED THE INCIDENT WAS CAUSED BY CREW ERROR.