Narrative:

We were descending into the phoenix area west of san simon VOR on J-50 in between itemm and totec intxns to land at scottsdale airport. The ZAB had cleared us to descend to FL240. While north the descent to FL240 we heard the center reclear us to 15,000. We responded by saying 'reclred to 15,000'. While continuing our descent and above FL240 we were given a call for traffic at 11 O'clock 8 mi at FL230. We both looked and saw the small fighter at 11:30 crossing our nose from left to right. We replied traffic in sight and watched the traffic go by. I noticed we were just passing through FL240 and thought it was strange we were cleared to 15,000' with crossing traffic ahead. I immediately stopped my descent at FL237 and asked my copilot to clarify our assigned altitude. While he was doing that I started my climb back to FL240. I was level when the controller replied you were assigned FL240. We replied we had heard our reclrnc to 15,000'. The controller said, no FL240. Before we landed we were given a phone number of quality assurance to call. After landing I immediately called them and have subsequently talked to them 3 times. Callback conversation with reporter revealed the following: reporter finally learned from ATC that when he checked in with ZAB, the controller mentioned something about 15,000' and reporter 'picked up on that' and read back that they were descending to 15,000'. He said that in his conversations, he was surprised to learn that ATC was listening to UHF at the same time and missed his readback. He said that knowing this, he will conduct himself on the air differently in the future. He said the separation was 3 miles.

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Original NASA ASRS Text

Title: CPR MLG DESCENDED BELOW HIS ASSIGNED ALT CAUSING LESS THAN STANDARD SEPARATION WITH FGT AT LOWER ALT.

Narrative: WE WERE DESCENDING INTO THE PHOENIX AREA W OF SAN SIMON VOR ON J-50 IN BETWEEN ITEMM AND TOTEC INTXNS TO LAND AT SCOTTSDALE ARPT. THE ZAB HAD CLRED US TO DSND TO FL240. WHILE N THE DSCNT TO FL240 WE HEARD THE CENTER RECLEAR US TO 15,000. WE RESPONDED BY SAYING 'RECLRED TO 15,000'. WHILE CONTINUING OUR DSCNT AND ABOVE FL240 WE WERE GIVEN A CALL FOR TFC AT 11 O'CLOCK 8 MI AT FL230. WE BOTH LOOKED AND SAW THE SMALL FIGHTER AT 11:30 XING OUR NOSE FROM LEFT TO RIGHT. WE REPLIED TFC IN SIGHT AND WATCHED THE TFC GO BY. I NOTICED WE WERE JUST PASSING THROUGH FL240 AND THOUGHT IT WAS STRANGE WE WERE CLRED TO 15,000' WITH XING TFC AHEAD. I IMMEDIATELY STOPPED MY DSCNT AT FL237 AND ASKED MY COPLT TO CLARIFY OUR ASSIGNED ALT. WHILE HE WAS DOING THAT I STARTED MY CLIMB BACK TO FL240. I WAS LEVEL WHEN THE CTLR REPLIED YOU WERE ASSIGNED FL240. WE REPLIED WE HAD HEARD OUR RECLRNC TO 15,000'. THE CTLR SAID, NO FL240. BEFORE WE LANDED WE WERE GIVEN A PHONE NUMBER OF QUALITY ASSURANCE TO CALL. AFTER LNDG I IMMEDIATELY CALLED THEM AND HAVE SUBSEQUENTLY TALKED TO THEM 3 TIMES. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: REPORTER FINALLY LEARNED FROM ATC THAT WHEN HE CHECKED IN WITH ZAB, THE CTLR MENTIONED SOMETHING ABOUT 15,000' AND REPORTER 'PICKED UP ON THAT' AND READ BACK THAT THEY WERE DESCENDING TO 15,000'. HE SAID THAT IN HIS CONVERSATIONS, HE WAS SURPRISED TO LEARN THAT ATC WAS LISTENING TO UHF AT THE SAME TIME AND MISSED HIS READBACK. HE SAID THAT KNOWING THIS, HE WILL CONDUCT HIMSELF ON THE AIR DIFFERENTLY IN THE FUTURE. HE SAID THE SEPARATION WAS 3 MILES.

Data retrieved from NASA's ASRS site as of July 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.