Narrative:

ZHU cleared me from 13000-11000 ft and had me call mob approach. I thought, that approach cleared me on down to 6000 ft. Later, a different approach controller said I had only been cleared to 9000 ft. I was busy and apparently heard 6000 ft and wrote that down. If I reported back 6000 ft, no correction was called. If I wrote 6000 ft and called back 9000 ft, that would certainly be my error. I believe I was very busy and perhaps heard 9000 ft, but didn't write it down immediately. What I should have done is check with approach about the altitude before writing down anything. I believe contributing factors may be that I had been cruising for 3+ hours at 13000 ft (with oxygen) and becoming very busy after 3+ hours of very routine cavu cruising.

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Original NASA ASRS Text

Title: PA28 PLT DSNDED BELOW CLRED ALT. INATTN AND POOR RADIO TECHNIQUE CONTRIBUTED TO THE ERROR.

Narrative: ZHU CLRED ME FROM 13000-11000 FT AND HAD ME CALL MOB APCH. I THOUGHT, THAT APCH CLRED ME ON DOWN TO 6000 FT. LATER, A DIFFERENT APCH CTLR SAID I HAD ONLY BEEN CLRED TO 9000 FT. I WAS BUSY AND APPARENTLY HEARD 6000 FT AND WROTE THAT DOWN. IF I RPTED BACK 6000 FT, NO CORRECTION WAS CALLED. IF I WROTE 6000 FT AND CALLED BACK 9000 FT, THAT WOULD CERTAINLY BE MY ERROR. I BELIEVE I WAS VERY BUSY AND PERHAPS HEARD 9000 FT, BUT DIDN'T WRITE IT DOWN IMMEDIATELY. WHAT I SHOULD HAVE DONE IS CHK WITH APCH ABOUT THE ALT BEFORE WRITING DOWN ANYTHING. I BELIEVE CONTRIBUTING FACTORS MAY BE THAT I HAD BEEN CRUISING FOR 3+ HRS AT 13000 FT (WITH OXYGEN) AND BECOMING VERY BUSY AFTER 3+ HRS OF VERY ROUTINE CAVU CRUISING.

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.