AN ACR FLYING OVER THE ATLANTIC IS UNABLE TO ACCEPT HIGHER ALT AS ASSIGNED. ACR IS A WDB CARRYING FREIGHT.

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BOTTOM LINE: CAPT VIOLATED BY GANDER RADIO CTR FOR EXERCISING COMMAND AND NOT STEP CLBING. GANDER CTR; GANDER RADIO NEVER CONFIRMED A REQUIRED CLRNC TO STEP CLB. ACARS MESSAGE NOT COMPLETE -- 200 NM SW OF TORBAY; RECEIVED ACARS OCEANIC CLRNC TO 'EXPECT FL350 AND EXPECT CLRNC TO CLB TO REACH FL370 BY XX15Z.' (NO BEGIN CLB TIME WAS EVER ISSUED.) ALL FMS PARAMETERS CHKED. FMS INITIAL ALTS SELECTED FL330; FL350; FL370. FMS COMPUTED STEP CLBS WERE USED TO ACCEPT HIGHER ALTS. AT XX15Z THE WINDS WERE 20-30 KTS HIGHER THAN FORECAST; AND WE STAYED AHEAD OF FLT PLAN. WE WERE ACCURATE ON ALL WAYPOINT POS RPTS BASED ON ACTUAL WINDS WHICH WE UPDATED IN THE FMS. THE TEMP AT FL290 WAS ISA -8 DEGS (COLDER THAN ISA). THE TEMP AT FL330 WAS APPROX ISA. WE WERE LATER CLRED TO FL350; BUT THE EXPECTED CLRNC TO FL370 WAS NOT ISSUED. THE WINDS CONTINUED TO INCREASE TO 120-130 KTS TAILWIND. THE TEMP AT FL350 WAS NOW ISA +12 DEGS. THE FMS NOW DID NOT PROVIDE SAFE BUFFET MARGIN TO CLB TO FL370. THE CRUISE N1 WAS ONLY 4% BELOW THE CRUISE LIMIT. THE LOW SPD FOOT WAS STILL TOO CLOSE TO OUR CRUISE MACH. I CHKED OUR WT AND THE FLT MANUAL AND DECIDED NOT TO CLB DUE TO NOT ENOUGH BUFFET PROTECTION. AT XY07Z I CALLED GANDER RADIO (HF) APPROX 200 MI W OF 30W LONGITUDE AND ADVISED THEM 'UNABLE TO CLB TO FL370 DUE TO BUFFET RESTRS.' THE FMS MAX ALT WAS 37.8. I ADVISED SHANWICK RADIO (GANDER WOULD NOT RESPOND OR ANSWER MY CALLS) THAT I COULD DSND TO A LOWER ALT. GANDER RADIO CAME BACK AND SAID; 'YOU ARE IN VIOLATION OF YOUR CLRNC; I AM ISSUING AN INFRACTION OF A NAT'S CLRNC.' NOTE #1: BECAUSE OF THE INCREASE IN TEMP OUR TRUE AIRSPD (TAS) AT FL370 (WHICH WE REACHED 50 MINS LATER) WAS HIGHER BY 2 KTS THAN OUR TAS AT FL290 AT THE SAME MACH .83. NOTE #2: I SPOKE DIRECTLY WITH GANDER CTR OVER THE TELEPHONE AND THEY WITHDREW THE VIOLATION. THEY ADMITTED THEIR ERROR. NOTE #3: THE ACARS MESSAGE (CLRNC) WAS NOT CORRECT. NOTE #4: GANDER RADIO CTR DID NOT FOLLOW THEIR OWN RADIO READBACK AND CLRNC PROCS FOR ISSUING STEP CLBS. THE NORTH ATLANTIC MNPS REQUIRES BETTER TECHNOLOGY THAN HF RADIOS. ALL ACFT SHOULD BE REQUIRED TO HAVE TCASII AND POS RPTING VIA ACARS/SATCOM LINK.