B777 CREW INADVERTENTLY HAS AUTOTHROTTLE OFF AND AUTOPLT ON DURING THE TKOF ROLL.

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AFTER RECEIVING TKOF CLRNC FOR RWY 13R FROM JFK TWR; I ADVANCED THE THROTTLES TO SPOOL UP THE ENGS. THAT ACCOMPLISHED; I HIT THE TOGA SWITCH FOR TKOF THRUST AND THE AUTOTHROTTLES DID NOT RESPOND; SO I ADVANCED THE THROTTLES MANUALLY AND BEGAN THE TKOF ROLL. THE CAPT DISCOVERED THE AUTOTHROTTLE PADDLE SWITCHES IN THE OFF POS AND TURNED THEM ON. I PUSHED TOGA AGAIN; BUT THE ACFT HAD ALREADY ACCELERATED THROUGH 50 KTS AND THE AUTOTHROTTLES WOULD NOT ENGAGE. THE CAPT CONTINUED PUSHING SWITCHES ON THE MODE CTL PANEL. AT VR; I ATTEMPTED TO ROTATE THE ACFT TO THE TKOF ATTITUDE; BUT THE ELEVATOR WOULD NOT MOVE. WE RAPIDLY ACCELERATED THROUGH V2. RWY 13R WAS CUTBACK AND THERE WERE MEN AND EQUIP WORKING ON THE END OF THE RWY. I NEVER CONSIDERED STOPPING BECAUSE OF OUR SPD AND THE EQUIP; SO I PULLED MUCH HARDER ON THE YOKE. SUDDENLY THE ELEVATOR SNAPPED LOOSE AND THE NOSE ROTATED RAPIDLY. THE MASTER WARNING SOUNDED AND THE EICAS INDICATED AUTOPLT DISCONNECT. MY IMMEDIATE CONCERN WAS TO SLOW THE ROTATION RATE BEFORE WE STRUCK THE TAIL. THAT ACCOMPLISHED; I CANCELED THE MASTER WARNING AND FLEW THE DEP. THIS EVENT SHOULD NOT BE POSSIBLE. THE CAPT WAS RELATIVELY NEW ON THE ACFT AND THAT WAS A CONTRIBUTING FACTOR. HIS SYS KNOWLEDGE WAS SUCH THAT HE CONTINUED TO ATTEMPT AUTOTHROTTLE ENGAGEMENT BEYOND 50 KTS. IN THIS CRITICAL PHASE OF FLT; THE CAPT SELECTED THE AUTOPLT SWITCH INSTEAD OF THE AUTOTHROTTLE SWITCH. I WAS CONCENTRATING ON THE TKOF ROLL AND DID NOT NOTICE THE AUTOPLT WAS ENGAGED. MY REACTION WAS TO ASSUME THE ELEVATOR HAD JAMMED. I PULLED THE REQUIRED 35 LBS OF FORCE TO DISCONNECT THE AUTOPLT SIMPLY BECAUSE THERE WAS NO OTHER OPTION. WE HAD TO TAKEOFF BECAUSE IT WAS TOO LATE TO STOP. ON SUCH A SOPHISTICATED ACFT; THERE SHOULD BE LOGIC THAT PREVENTS THE AUTOPLT FROM ENGAGING ON THE TKOF ROLL. THIS COULD HAVE BEEN AN ACCIDENT IF WE HAD ATTEMPTED TO STOP. IT ALSO COULD HAVE CAUSED A TAIL STRIKE AND DAMAGED THE ACFT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR SAID THAT THERE WAS NO PROB WITH THE ACFT. AUTOTHROTTLES ARE NEVER TURNED OFF OTHER THAN FOR IRREGULAR PROCS. IN THIS CASE MAINT HAD TURNED THEM OFF AND DUE TO A RUSHED DEP THE CREW MISSED THE FACT THAT THEY WERE OFF DURING CHKLIST COMPLETION. EXPERIENCE LEVEL OF THE CAPT ON THE ACFT WAS LESS THAN THAT OF THE RPTR. THERE HAS BEEN VERY RAPID TRAINING OF CREWS AND MANY HAVE SIMILAR LOW FLT TIMES SINCE TRAINING WAS COMPLETED. IN THE CREW DEBRIEFING IT WAS AGREED THAT NOTHING MORE THAN THE MANUAL APPLICATION OF TKOF THRUST WAS NEEDED AND THAT UNCOORDINATED MANIPULATION OF THE MODE CTL PANEL SWITCHES WAS NOT SOP OR ADVISABLE AS WAS DEMONSTRATED BY THE PROBS IT CAUSED. THE COMPANY HAS INCLUDED THIS SCENARIO IN THEIR RECURRENT TRAINING SYLLABUS. THERE IS AN INVESTIGATION BEING MADE TO SEE IF THE AUTOPLT CAN BE BIASED OUT SO IT CANNOT BE ENGAGED ON THE GND.