ACR X DSCNT TO WRONG ALT. PLTDEV.

Narrative

THE CLRNC I REMEMBER; AND THE CLRNC MY FO RESPONDED TO; WAS 'ACR X CLRED DIRECT PROVIDENCE; VICTOR 151 TO BOSTON; MAINTAIN 10000 FT.' THE FO WAS FLYING AND PROGRAMMED THE MODE CTL PANEL FOR ALT (10000 FT) WHILE I WAS INSERTING THE RTE INTO THE FMS. AT 10500 FT OR SO; THE CTR CTLR REQUESTED THAT WE MAINTAIN 11000 FT. I REPLIED THAT I THOUGHT WE WERE CLRED TO 10000; BUT THAT WE WERE RETURNING TO 11000. THE CTLR; WITHOUT FURTHER COMMENT; TURNED US OVER TO APCH CTL; AND WE CHKED ON AT 11000. AFTER LNDG BOSTON; A TELEPHONE CALL TO APCH CTL CONFIRMED THAT THE CTR CTLR WAS AS SURE ABOUT ISSUING 11000 AS WE WERE ABOUT RECEIVING 10000. OUR COM SYS IS PROBABLY OUR WEAKEST LINK. BOSTON WAS IMC; TFC WAS BACKED UP ALL THE WAY TO SEVERAL STACKED HOLDING PATTERNS AROUND THE AREA. UNDER THOSE CONDITIONS THE LOAD ON THE FLC IS HVY WHILE THE TASK OF THE CTLR SOUNDS ALMOST IMPOSSIBLE. EVERYONE DOES THEIR BEST; BUT THE NUMBER OF MISIDENTS; PARTIALLY BLOCKED CLRNCS AND REPLIES; THE TRANSPOSITIONS; REQUIRED REPEATS; AND UNDETECTED ERRORS IN READBACKS CAN AND OFTEN DOES APCH THE LEVEL OF CHAOS.