SF340 PIC DSNDS TOWARDS 4000 FT ON A VECTOR FROM NY APCH. AT 5000 FT APCH CTLR QUESTIONS CLRNC ALT; SAYS HE GAVE 6000 FT. CREW HAD BOTH COPIED AND GIVEN 4000 FT ON THEIR READBACK. CTLR MUST HAVE MISSED THAT.

Narrative

ENRTE FROM MHT TO LGA. AFTER PASSING THE MAD VOR AT 8000 FT; WE WERE GIVEN A 240 DEG HDG AND TO DSND TO 4000 FT BY NEW YORK APCH. THE FO SET 4000 FT IN THE ALT PRESELECT (PER OUR COMPANY OPERATING PROC). I THEN POINTED TO THE ALT PRESELECT AND CONFIRMED 4000 FT; AND THUS STARTED DOWN. APCHING 5000 FT; NEW YORK APCH ASKED WHAT ALT WE WERE GOING TO; AND SAID WE WERE ONLY CLRED TO 6000 FT. THE FO REPLIED 4000 FT AND INFORMED THE CTLR THAT HE HAD READ BACK THAT WE WERE CLRED TO 4000 FT. HE THEN ASKED IF HE NEEDED US AT 6000 FT. THE CTLR THEN SAID NO; AND TOLD US TO MAINTAIN 5000 FT. A FEW MINS LATER; PRIOR TO OUR NEXT FREQ CHANGE; I APOLOGIZED FOR ANY CONFUSION. THE CTLR'S RESPONSE WAS SOMETHING LIKE 'NO PROB.' WE WERE ON AN IFR FLT PLAN; THE WX WAS VMC WITH GOOD VISIBILITY. WE WERE ON TIME; AND WELL RESTED. WE ARE POSITIVE WE WERE GIVEN 4000 FT. IN ADDITION; NO OTHER ACFT WERE GIVEN EVASIVE ACTION BECAUSE OF OUR ALT. I GUESS A GOOD LESSON TO BE LEARNED FROM ALL OF THIS WOULD BE THAT ATC AND FLCS SHOULD BOTH BE MORE ALERT -- ESPECIALLY WITH THE FREQS OF RTES BEING FLOWN.