Narrative:

The chain of events causing the situation are as follows: on the above stated date I was flying XXXX on an IFR flight plan from hks to new. Upon being descended by ZHU to 10000' we were handed off to new approach. WX was IMC and approach control frequency was extremely busy with heavy traffic. Two airline crews were arguing with approach on the frequency about a NOTAM at msy. My aircraft was vectored several times during all the discussion and remained at 10000'. Finally my aircraft was given a descent clearance by approach to what I and the copilot thought to 2000' while we were approximately 16 NM from our destination airport. We could not read back this clearance due to the aforementioned airline crews and other radio traffic on the frequency. While we were descending through 2400' for 2000', the approach controller asked what our altitude was. The copilot in my aircraft stated, 'we're out of 2400 for 2000.' the controller then informed us we were cleared to 3000', not 2000'. He (the controller) then told us to climb back to 3000' and turn to heading 220 degrees, which we did immediately. After a series of vector, headings, and descent we were cleared to the ILS 18R approach at new, which was accomplished at minimums. About 10 mins after arriving at lakefront the new approach control supervisor called me to advise me that he had listened to the tapes for the time period in the above incident and said that the tapes clearly revealed that our clearance was from 10000 to 3000' instead of 2000' like we thought. He also stated that our proximity to another aircraft was less than standard and that he would have to turn the incident over to FAA district for action. It is unfortunate that the crew of my aircraft had difficulty hearing clearly the descent clearance and even more unfortunate that we could not read back the clearance for confirmation.

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Original NASA ASRS Text

Title: ON APCH THE REPORTER ACFT DESCENDED TO 2000' BELIEVING THAT TO BE THEIR CLEARED ALT. ATC STATED THE CLRNC WAS 3000' AND REQUESTED REPORTER ACFT TO IMMEDIATELY CLIMB TO 3000', WHICH IT DID.

Narrative: THE CHAIN OF EVENTS CAUSING THE SITUATION ARE AS FOLLOWS: ON THE ABOVE STATED DATE I WAS FLYING XXXX ON AN IFR FLT PLAN FROM HKS TO NEW. UPON BEING DSNDED BY ZHU TO 10000' WE WERE HANDED OFF TO NEW APCH. WX WAS IMC AND APCH CTL FREQ WAS EXTREMELY BUSY WITH HVY TFC. TWO AIRLINE CREWS WERE ARGUING WITH APCH ON THE FREQ ABOUT A NOTAM AT MSY. MY ACFT WAS VECTORED SEVERAL TIMES DURING ALL THE DISCUSSION AND REMAINED AT 10000'. FINALLY MY ACFT WAS GIVEN A DSCNT CLRNC BY APCH TO WHAT I AND THE COPLT THOUGHT TO 2000' WHILE WE WERE APPROX 16 NM FROM OUR DEST ARPT. WE COULD NOT READ BACK THIS CLRNC DUE TO THE AFOREMENTIONED AIRLINE CREWS AND OTHER RADIO TFC ON THE FREQ. WHILE WE WERE DSNDING THROUGH 2400' FOR 2000', THE APCH CTLR ASKED WHAT OUR ALT WAS. THE COPLT IN MY ACFT STATED, 'WE'RE OUT OF 2400 FOR 2000.' THE CTLR THEN INFORMED US WE WERE CLRED TO 3000', NOT 2000'. HE (THE CTLR) THEN TOLD US TO CLB BACK TO 3000' AND TURN TO HDG 220 DEGS, WHICH WE DID IMMEDIATELY. AFTER A SERIES OF VECTOR, HDGS, AND DSCNT WE WERE CLRED TO THE ILS 18R APCH AT NEW, WHICH WAS ACCOMPLISHED AT MINIMUMS. ABOUT 10 MINS AFTER ARRIVING AT LAKEFRONT THE NEW APCH CTL SUPVR CALLED ME TO ADVISE ME THAT HE HAD LISTENED TO THE TAPES FOR THE TIME PERIOD IN THE ABOVE INCIDENT AND SAID THAT THE TAPES CLEARLY REVEALED THAT OUR CLRNC WAS FROM 10000 TO 3000' INSTEAD OF 2000' LIKE WE THOUGHT. HE ALSO STATED THAT OUR PROX TO ANOTHER ACFT WAS LESS THAN STANDARD AND THAT HE WOULD HAVE TO TURN THE INCIDENT OVER TO FAA DISTRICT FOR ACTION. IT IS UNFORTUNATE THAT THE CREW OF MY ACFT HAD DIFFICULTY HEARING CLEARLY THE DSCNT CLRNC AND EVEN MORE UNFORTUNATE THAT WE COULD NOT READ BACK THE CLRNC FOR CONFIRMATION.

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.