Narrative:

Approximately 10 NM north of grw VOR, controled. Assigned initial descent from 12000 ft to 10000 ft. As PNF, I responded with 'air carrier xyz cleared to 1-0 thousand.' at approximately 10400 ft, controller asked present altitude and I responded with '10 point 4 descending to 1-0 thousand.' controller said clearance was for 11000 but to continue descent to 9000. Continued descent to 9000. No further incident. Controller workload was high and readback was not challenged or corrected. Reading back altitude assignments twice such as '1-0, 10 thousand' is a good way to help eliminate the problem. Although we are not trained to use this method, and 'teaching old dogs new tricks' is sometimes difficult, I would recommend that this method be the approved FAA method of clearance readbacks. Supplemental information from acn 210688: flight was en route to mem at 12000, received what was perceived as clearance to 10000. I was PF and heard PNF (captain) readback 10000. Passing 10400 in descent, center said we were cleared to 11000, then issued a continued descent to 9000. I remembered hearing captain read back 10000.

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Original NASA ASRS Text

Title: ALT BUST.

Narrative: APPROX 10 NM N OF GRW VOR, CTLED. ASSIGNED INITIAL DSCNT FROM 12000 FT TO 10000 FT. AS PNF, I RESPONDED WITH 'ACR XYZ CLRED TO 1-0 THOUSAND.' AT APPROX 10400 FT, CTLR ASKED PRESENT ALT AND I RESPONDED WITH '10 POINT 4 DSNDING TO 1-0 THOUSAND.' CTLR SAID CLRNC WAS FOR 11000 BUT TO CONTINUE DSCNT TO 9000. CONTINUED DSCNT TO 9000. NO FURTHER INCIDENT. CTLR WORKLOAD WAS HIGH AND READBACK WAS NOT CHALLENGED OR CORRECTED. READING BACK ALT ASSIGNMENTS TWICE SUCH AS '1-0, 10 THOUSAND' IS A GOOD WAY TO HELP ELIMINATE THE PROBLEM. ALTHOUGH WE ARE NOT TRAINED TO USE THIS METHOD, AND 'TEACHING OLD DOGS NEW TRICKS' IS SOMETIMES DIFFICULT, I WOULD RECOMMEND THAT THIS METHOD BE THE APPROVED FAA METHOD OF CLRNC READBACKS. SUPPLEMENTAL INFO FROM ACN 210688: FLT WAS ENRTE TO MEM AT 12000, RECEIVED WHAT WAS PERCEIVED AS CLRNC TO 10000. I WAS PF AND HEARD PNF (CAPT) READBACK 10000. PASSING 10400 IN DSCNT, CTR SAID WE WERE CLRED TO 11000, THEN ISSUED A CONTINUED DSCNT TO 9000. I REMEMBERED HEARING CAPT READ BACK 10000.

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.