AN ACR FK10 FLC SLOWS THEIR ACFT WHEN THEY ENCOUNTER STEADY MODERATE TURB. THEY DID NOT INFORM THE ARTCC RADAR CTLR BECAUSE OF FREQ CONGESTION AND A FOLLOWING ACFT WAS CLOSING ON THEM WHEN THE CTLR INQUIRED ABOUT THEIR SPD. THE CTLR ORDERED THEM TO PICK UP THEIR SPD AND THEY REFUSED BECAUSE OF THE TURB.

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WE WERE ENRTE FROM MHT TO PHL FLYING THE MAZIE ARR. WE HAD DSNDED TO 11000 FT AND WERE IN THE VICINITY OF THE WILKES BARRE VOR WHEN WE ENCOUNTERED MODERATE TURB. I IMMEDIATELY SLOWED TO TURB PENETRATION SPD (250 KTS). DUE TO THE FREQ CONGESTION ON ZNY; WE WERE UNABLE TO IMMEDIATELY NOTIFY ATC OF OUR SPD REDUCTION. THE CTR ISSUED HOLDING INSTRUCTIONS TO AN AIRPLANE IN FRONT OF US AND GAVE THEM AN EXPECTED FURTHER CLRNC ABOUT 1 HR AWAY. THE FLT ATTENDANT CALLED TO ASK HOW LONG WE WOULD BE IN THIS TURB. THEN CTR CLRED US TO HOLD AT SPUDS INTXN AND GAVE US A 1 HR EXPECTED FURTHER CLRNC. WE BEGAN TO PROGRAM THE FMC AND THEN NOTIFY OUR COMPANY OF THE HOLD. WORKLOAD WAS VERY HIGH. THE MODERATE TURB COUPLED WITH LOTS OF TALK ON THE ATC RADIO MADE US FORGET TO NOTIFY ATC OF OUR SPD REDUCTION. ATC CALLED AND ASKED IF WE HAD SLOWED TO WHICH WE ANSWERED YES; DUE TO THE TURB; WE HAD. HE THEN ASKED US TO SPD UP WHICH WE TOLD HIM WE WERE UNABLE TO DO; AGAIN EXPLAINING THE TURB. HE THEN WANTED TO KNOW WHO HAD APPROVED THE SPD REDUCTION TO WHICH I REPLIED I WAS THE OPERATOR OF THIS FLT AND I DID NOT NEED HIS APPROVAL TO OPERATE THE AIRPLANE IN ACCORDANCE WITH HANDBOOK LIMITATIONS. I ALSO TOLD HIM WE WERE UNABLE TO INFORM HIM BECAUSE OF THE FREQ CONGESTION. HE SAID WE HAD A FLT 3 MI BEHIND US AT OUR ALT WITH A 70 KT OVERTAKE. HE THEN CLBED AND TURNED THE FLT BEHIND US. CONTRIBUTING TO THE PROB WAS THE FACT THIS WAS THE LAST LEG OF A 4 DAY TRIP. THE PREVIOUS DAY WE HAD FLOWN 6 LEGS AND BEEN ON DUTY 14 PLUS HRS. THE NIGHT BEFORE WE GOT TO THE HOTEL AT XA30 AND LEFT AT XJ30. I BELIEVE THE CUMULATIVE EFFECTS OF FATIGUE LED TO SOME TASK SHEDDING DURING THIS INCIDENT.