Narrative:

En route from cle to lga at about XA50 local, we began our descent into lga. Initially we were cleared to FL240. This clearance was superseded by a clearance to cross marrc intersection on the milton 5 arrival at FL180. Prior to reaching FL180 we were issued another clearance to cross 5 west of allentown at 10000' with the local altimeter setting. Each clearance was acknowledged and read back west/O correction. They did ask the captain to repeat the marrc crossing restriction, which he did. The captain's readback of the last clearance was (5 west of allentown at 10000'). It was not challenged or corrected so we assumed it to be correct. I wrote this on my pad and started the descent. I was flying. At that time I took over the radios. Also, as the captain got lga ATIS and talked to lga operations, we completed the in range checklist and I was issued a traffic advisory at 12 O'clock and 12000' (I'm not sure about the distance). I reported that we were IMC at the time, and since we were, the traffic didn't really register with me. As the captain took over the radios the controller broke in abruptly and asked our altitude. The captain said we just passed through 12000'. ATC then told us we were only cleared to 13000'. The captain said we read back 10000' and were not corrected. He then asked about the traffic we were issued. The captain said that I had reported we were IMC. We were then told to call center when we landed. We did talk to the shift supervisor who said that I had reported we were IMC. We were then told to call center when we landed. We did talk to the shift supervisor who said they reviewed the tapes. We were cleared to 13000' but read back 10000' and were not corrected. He then stated that it clearly was their fault and that no further action was appropriate nor would be initiated toward the captain nor myself. In review, we should have caught the altitude error as so far as the published arrival states, 'expect 5 west at 13000'.' the clearance to 10000' should have triggered a question. Even though we were IMC at the time the traffic information issued by ATC should have ben completely thought out and triggered another question to the validity of the 10000' clearance limit.

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Original NASA ASRS Text

Title: MLG READ BACK WRONG ALT AND DESCENDED THROUGH ALT OF ANOTHER ACFT WITH LESS THAN STANDARD SEPARATION.

Narrative: ENRTE FROM CLE TO LGA AT ABOUT XA50 LCL, WE BEGAN OUR DSCNT INTO LGA. INITIALLY WE WERE CLRED TO FL240. THIS CLRNC WAS SUPERSEDED BY A CLRNC TO CROSS MARRC INTXN ON THE MILTON 5 ARR AT FL180. PRIOR TO REACHING FL180 WE WERE ISSUED ANOTHER CLRNC TO CROSS 5 W OF ALLENTOWN AT 10000' WITH THE LCL ALTIMETER SETTING. EACH CLRNC WAS ACKNOWLEDGED AND READ BACK W/O CORRECTION. THEY DID ASK THE CAPT TO REPEAT THE MARRC XING RESTRICTION, WHICH HE DID. THE CAPT'S READBACK OF THE LAST CLRNC WAS (5 W OF ALLENTOWN AT 10000'). IT WAS NOT CHALLENGED OR CORRECTED SO WE ASSUMED IT TO BE CORRECT. I WROTE THIS ON MY PAD AND STARTED THE DSCNT. I WAS FLYING. AT THAT TIME I TOOK OVER THE RADIOS. ALSO, AS THE CAPT GOT LGA ATIS AND TALKED TO LGA OPS, WE COMPLETED THE IN RANGE CHKLIST AND I WAS ISSUED A TFC ADVISORY AT 12 O'CLOCK AND 12000' (I'M NOT SURE ABOUT THE DISTANCE). I RPTED THAT WE WERE IMC AT THE TIME, AND SINCE WE WERE, THE TFC DIDN'T REALLY REGISTER WITH ME. AS THE CAPT TOOK OVER THE RADIOS THE CTLR BROKE IN ABRUPTLY AND ASKED OUR ALT. THE CAPT SAID WE JUST PASSED THROUGH 12000'. ATC THEN TOLD US WE WERE ONLY CLRED TO 13000'. THE CAPT SAID WE READ BACK 10000' AND WERE NOT CORRECTED. HE THEN ASKED ABOUT THE TFC WE WERE ISSUED. THE CAPT SAID THAT I HAD RPTED WE WERE IMC. WE WERE THEN TOLD TO CALL CENTER WHEN WE LANDED. WE DID TALK TO THE SHIFT SUPVR WHO SAID THAT I HAD RPTED WE WERE IMC. WE WERE THEN TOLD TO CALL CENTER WHEN WE LANDED. WE DID TALK TO THE SHIFT SUPVR WHO SAID THEY REVIEWED THE TAPES. WE WERE CLRED TO 13000' BUT READ BACK 10000' AND WERE NOT CORRECTED. HE THEN STATED THAT IT CLEARLY WAS THEIR FAULT AND THAT NO FURTHER ACTION WAS APPROPRIATE NOR WOULD BE INITIATED TOWARD THE CAPT NOR MYSELF. IN REVIEW, WE SHOULD HAVE CAUGHT THE ALT ERROR AS SO FAR AS THE PUBLISHED ARR STATES, 'EXPECT 5 W AT 13000'.' THE CLRNC TO 10000' SHOULD HAVE TRIGGERED A QUESTION. EVEN THOUGH WE WERE IMC AT THE TIME THE TFC INFO ISSUED BY ATC SHOULD HAVE BEN COMPLETELY THOUGHT OUT AND TRIGGERED ANOTHER QUESTION TO THE VALIDITY OF THE 10000' CLRNC LIMIT.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.