Narrative:

Captain and I had been to mexico city twice before in april and had flown the arcos 1 departure without incident. On this day, there was a revision to the arcos 1. Before the revision, the restr was to not exceed 250 KTS below 18000 ft MSL. With the revision, it changed to not exceed 250 KTS below 10000 ft within 30 NM of mex. What we didn't catch was the 10000 ft was AGL, translating to 17700 ft MSL. We thought it was 10000 ft MSL, so at 10000 ft MSL we accelerated to 300 KTS. Now, there is an altitude restr at lucia (slm) VOR to cross it at or above 15000 ft MSL. Because we accelerated at 10000 ft MSL, and had momentarily forgotten about the altitude restr at lucia, we crossed lucia at 14200 ft MSL at 300 KTS. Control questioned us, but there was no conflict. We were well rested and alert. The change from 18000 ft MSL to 10000 ft AGL, which is really 17700 ft MSL, or a real change of 300 ft, and changing the format contributed to this incident. Complacency and/or recency of experience flying that particular departure, are also possible contributors.

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Original NASA ASRS Text

Title: FLC OF AN AIRBUS A320 EA32 EXCEEDED AIRSPD AND UNDERSHOT AN ALT FIX DURING A SID DEP FROM A FOREIGN AIRSPACE. THE SID HAD RECENTLY CHANGED AND THEY HAD REMEMBERED THE PROC PRIOR TO A SPD RESTR.

Narrative: CAPT AND I HAD BEEN TO MEXICO CITY TWICE BEFORE IN APRIL AND HAD FLOWN THE ARCOS 1 DEP WITHOUT INCIDENT. ON THIS DAY, THERE WAS A REVISION TO THE ARCOS 1. BEFORE THE REVISION, THE RESTR WAS TO NOT EXCEED 250 KTS BELOW 18000 FT MSL. WITH THE REVISION, IT CHANGED TO NOT EXCEED 250 KTS BELOW 10000 FT WITHIN 30 NM OF MEX. WHAT WE DIDN'T CATCH WAS THE 10000 FT WAS AGL, TRANSLATING TO 17700 FT MSL. WE THOUGHT IT WAS 10000 FT MSL, SO AT 10000 FT MSL WE ACCELERATED TO 300 KTS. NOW, THERE IS AN ALT RESTR AT LUCIA (SLM) VOR TO CROSS IT AT OR ABOVE 15000 FT MSL. BECAUSE WE ACCELERATED AT 10000 FT MSL, AND HAD MOMENTARILY FORGOTTEN ABOUT THE ALT RESTR AT LUCIA, WE CROSSED LUCIA AT 14200 FT MSL AT 300 KTS. CTL QUESTIONED US, BUT THERE WAS NO CONFLICT. WE WERE WELL RESTED AND ALERT. THE CHANGE FROM 18000 FT MSL TO 10000 FT AGL, WHICH IS REALLY 17700 FT MSL, OR A REAL CHANGE OF 300 FT, AND CHANGING THE FORMAT CONTRIBUTED TO THIS INCIDENT. COMPLACENCY AND/OR RECENCY OF EXPERIENCE FLYING THAT PARTICULAR DEP, ARE ALSO POSSIBLE CONTRIBUTORS.

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.