B777 CAPT IS RESTRICTED TO 250 KNOTS IN CLIMB FOR TRAFFIC AND IS UNABLE TO CONVINCE ATC OF THE NEED TO ACCELERATE TO 260 KNOTS FOR OPERATIONAL REASONS.

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WE WERE GIVEN A RESTR CLB SPD OF 250 KTS DUE TO TFC. AS WE WERE CLBING ABOVE FL270 I NOTICED THAT WE WERE SLOWLY GETTING CLOSER AND CLOSER TO OUR MINIMUM SPD. WE HAD FORECASTS CALLING FOR POSSIBLE TURB ON THE CLB AND I WAS CONCERNED THAT WE WOULD NEED TO TRANSITION TO A HIGHER INDICATED OR MACH AIRSPD SHORTLY TO KEEP THE SAFETY MARGIN I DESIRED. WE WERE TALKING WITH ZDC. WE ASKED THE CTLR IF WE COULD RESUME NORMAL SPD AND HE REPLIED HE NEEDED US TO MAINTAIN 250 KTS UNTIL FL310. WE TOLD HIM WE WOULD BE UNABLE TO MAINTAIN 250 KTS THROUGH THAT ALT. HE CAME BACK AND TOLD US DUE TO TFC; I NEED YOU TO MAINTAIN 250 KTS. WE ADVISED HIM THAT IT WAS NOT POSSIBLE TO MAINTAIN 250 KTS AND WE WOULD NEED AT LEAST 260 KTS. DURING THIS CONVERSATION THERE WAS A PERIOD WHERE THE CTLR DID NOT ACKNOWLEDGE OUR REQUEST FOR THE HIGHER SPD. WE REPEATED OUR CALL SIGN SEVERAL TIMES BEFORE WE GOT AN ACKNOWLEDGEMENT FROM THE CTLR. MY FO WHO HAD BEEN WORKING THE RADIO; COMMUNICATED THAT 250 KTS WAS TOO SLOW AND WE DIDN'T WANT TO STALL THE ACFT. IT FELT LIKE WE WERE IN A CONTEST AS TO WHO HAD MORE AUTH OVER THE SITUATION. I BEGAN TO ACCELERATE TO 260 KTS INDICATED AND ADVISED (OR ATTEMPTED TO ADVISE) THE CTLR THAT WE REQUIRED A MINIMUM OF 260 KTS AND IF NEEDED THAT HE COULD TURN US FOR TFC SEPARATION. I BELIEVE ALL 3 OF US MAY HAVE BEEN COMMUNICATING ON THE RADIO AT THIS TIME; BOTH MY FO; THE CTLR AND ME. WE RECEIVED A CLRNC WHILE WE WERE AT FL300 THAT CLRED US TO FL350 NORMAL SPD OUT OF FL310. THE CTLR THEN ASKED US TO EXPEDITE OUR CLB FOR TFC; BUT DUE TO OUR SLOW ENERGY STATE COULD ONLY MANAGE ABOUT A 400 FT CLB RATE. I COULD SENSE THAT THE CTLR DIDN'T UNDERSTAND THAT THIS LIMITED AIRSPD HAD GOTTEN US BEHIND THE PWR CURVE AND THAT THE ONLY WAY WE COULD INCREASE OUR RATE OF CLB WAS TO FIRST ACCELERATE OUR AIRSPD. IT HAS BEEN A LONG TIME SINCE I HAVE ENCOUNTERED A SITUATION LIKE THIS. I DON'T BELIEVE WE HAVE DONE ANYTHING TO RECEIVE A VIOLATION FOR THIS EVENT; BUT FELT IT WAS IMPORTANT TO FILE THE RPT TO DOCUMENT THE EVENT; AND POSSIBLY GIVE THE ERC SOME CONSIDERATION AS TO WHETHER THERE WAS ANY MERIT TO HAVE THE TAPES PULLED AND REVIEWED WITH THE ZDC QUALITY ASSURANCE PEOPLE TO MAKE SURE THAT THE CTLRS UNDERSTAND THAT WHEN A PLT INDICATES HE CANNOT MAINTAIN A REQUESTED SPD THAT IT IS THE CTLRS' JOB TO COME UP WITH AN ALTERNATE PLAN. OUR ACFT WAS A B777 WEIGHING 463000 LBS; WITH 73000 LBS OF FUEL AT THE TIME OF THE EVENT.