ZAB CHALLENGES A320 FLC'S ENRTE SPD.

Narrative

DEPARTED PHX TO JFK AND WAS TALKING TO ZAB. I WAS THE PF. THE ACFT SPD WAS 280 KTS (HAD IT BACK FOR TURB). CTR CALLED US AND GAVE US INSTRUCTIONS TO TURN TO A HDG OF 160 DEGS. WE COMPLIED AND THEN HE ASKED WHAT OUR SPD WAS. THE FO REPLIED THAT WE WERE AT 280 KTS. HE THEN SAID WE WERE INSTRUCTED TO MAINTAIN 250 KTS. NEITHER ONE OF US REMEMBER HEARING THIS SPD RESTR AT ANY TIME. WE DO NOT KNOW AT THIS TIME WHETHER HE ACTUALLY DID GIVE US THE SPD RESTR AND WE DID NOT HEAR IT OR HE JUST THOUGHT HE GAVE US THE RESTR. THE PROB HERE IS CTLR 'SAY BACK.' IF A CTLR GIVES US A SPD RESTR AND WE DON'T ACKNOWLEDGE IT; HE IS NOT REQUIRED TO QUESTION WHETHER WE ACTUALLY HEARD IT OR NOT. I FEEL THIS PRACTICE IS NOT CONDUCIVE TO SAFETY. THERE COULD HAVE BEEN AN NMAC BECAUSE WE WERE NOT AT THE SPD HE THOUGHT WE WERE AT. I ALWAYS READ BACK THE INSTRUCTIONS AS PROC DICTATES. I KNOW IT TAKES EXTRA TIME FOR A CTLR TO ACKNOWLEDGE MY READBACK AND FREQS ARE BECOMING SO CONGESTED WITH THE INCREASING TFC; THAT THIS NEW PROC IS A WAY OF CUTTING DOWN ON THE AMOUNT OF TIME IT TAKES PER XMISSION; BUT THIS IS A BAND-AID FOR THE REAL PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THE FLC DISCUSSED THIS SIT IN DETAIL AND NEITHER COULD REMEMBER ATC ASSIGNING A SPD RESTR ANY WAY ALONG THE RTE PRIOR TO BEING CHALLENGED BY ZAB. THE RPTR ADVISED HE UNDERSTOOD THE IMPORTANCE FOR CLRNC READBACK; AND WAS ADVISED BY ANALYST ATC'S REQUIREMENT TO CONFIRM AND CORRECT PLT READBACKS AS NECESSARY.