B727 FLC DSNDED THROUGH CLRED ALT APCHING EWR.

Narrative

WHILE ON WILLIAMSPORT 1 ARR INBOUND TO EWR AND BEING CTLED BY ZNY; RECEIVED CLRNC TO FL190 BY THE HAYED INTXN. APCHING FL190 (APPROX 10 MI FROM HAYED) RECEIVED CLRNC TO FIRST SLOW TO 250 KTS THEN CONTINUE DSCNT. CAPT AND FO (FLYING) HEARD DSCNT LIMIT TO BE 10000 FT (FREQ VERY BUSY) AND CAPT READ BACK CLRNC OF 10000 FT TO ATC. FO SET 10000 FT IN ALT ALERT WINDOW; AND VERBALIZED NEW ALT. AFTER CAPT'S READBACK; NO FURTHER ACKNOWLEDGEMENT/CORRECTION WAS RECEIVED FROM ATC. THE SO WAS NOT MONITORING RADIO XMISSIONS AT THIS TIME DUE TO DIFFICULTY RECEIVING ATIS INFO AT EWR. CREW DEEMED TIMING OF ATIS INFO IMPORTANT; SO APPROPRIATE BRIEF AT UNFAMILIAR ARPT COULD COMMENCE. AT APPROX 13000 FT; ATC CALLED OUT TFC AT OUR 12 O'CLOCK POS. ALMOST SIMULTANEOUSLY CREW VERIFIED TFC ON TCASII (ADVISORY) AND VISUALLY SIGHTED SMALL ACFT. DSCNT WAS SHALLOWED; AND LEVELOFF COMMENCED AT 12500 FT. OUR ACFT LEVELED OFF AT 12200 FT. PASSING 12500 FT; ATC ASKED 'WHAT ALT ARE YOU AT?' WE DID NOT IMMEDIATELY RESPOND BECAUSE OF REACTING TO SIGHTED ACFT. OUR CLOSEST PROX TO SIGHTED ACFT WAS NEVER LESS THAN 2.5 MI. ATC STATED WE SHOULD BE AT 13000 FT. WHILE CLBING BACK (800 FT) TO 13000 FT; CAPT XMITTED THAT 10000 FT HAD BEEN READ BACK DURING EARLIER XMISSION AND THAT 10000 FT WAS WHAT WAS SET IN THE ALT ALERT WINDOW. ATC STATED THAT THE ALARM HAD TRIGGERED; AND THAT THE TAPES WOULD BE PULLED. AFTER ARRIVING AT EWR; CAPT PHONED ZNY SUPVR. THE SUPVR VERIFIED THAT THE TAPES REVEALED THAT THE CTLR CLRED US TO 13000 FT; BUT OUR READBACK HAD BEEN 10000 FT. THE CTLR HAD FAILED TO ACKNOWLEDGE/CORRECT OUR READBACK XMISSION. THE SUPVR STATED; 'IT WAS OUR (ATC) FAULT.' CONTRIBUTING FACTORS: EXTREMELY BUSY FREQ WITH LIKE-SOUNDING CALL SIGN TO OUR OWN. SUSPECT 10000 FT CALL MAY HAVE BEEN XMITTED TO OTHER ACFT. COULD NOT RECEIVE ATIS INSIDE OF 50 MI AT EWR; CAUSING SO TO BE OUT OF THE ATC LOOP. NO CTLR ACKNOWLEDGEMENT/CORRECTION OF OUR ALT READBACK. ARR CHART EXPECT ALT OF 7000 FT AT SWEET INTXN (IN FRONT OF US) CONTRIBUTED TO ACCEPTANCE OF 10000 FT AS APPROPRIATE ALT. CORRECTION OF 250 KT SLOW DOWN AND 10000 FT TENDED TO VALIDATE CREW'S READBACK. HOW TO PREVENT RECURRENCE: ATC ACKNOWLEDGEMENT/CORRECTIONS TO ALL ACFT ALT READBACKS; ESPECIALLY IN BUSY RADIO XMISSION ENVIRONMENT. ACARS ON ALL ACFT TO RECEIVE ATIS INFO IN ORDER TO KEEP SO IN LOOP DURING CRITICAL PHASES OF FLT.