Narrative:

While taking off and climbing out of mty we did not comply with the instrument departure procedures as specified on airport chart. All of our conversations with the ATC facility at mty were quite arduous due to difficulty in understanding the english spoken by the mty ground/tower controller. The clearance we received was 'as filed' to our final altitude of FL370. It also included a restriction to cross the 10 DME fix on the arwy at or above 7000'. Since there was no SID at mty I assumed that we were cleared to turn on course. Later I could not recall any specific left or right turn clearance. The captain and I did not properly brief the departure. If we had I feel that our lack of a true departure plan would have come out in the discussion. It was only after climbing above 18000' did I begin to wonder if we had properly executed the departure. At that time I looked at the departure procedures on page 11-1 and realized there were very detailed instructions for takeoffs from mty. I pointed this out to the captain and he agreed we had made an error. At no time did ATC ever question our actions. Since 99% of our operations are from airports with SID's, the fact that a specific departure procedure even exists slips easily out of mind. A thorough pre-departure briefing would have certainly cleared up this particular situation. Had our communications with ATC been less laborious I believe this problem may not have occurred. However, this is an ongoing problem with operations in mexico.

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Original NASA ASRS Text

Title: ACR LGT NON ADHERENCE TO PUBLISHED INSTRUMENT DEP PROC FROM FO ARPT.

Narrative: WHILE TAKING OFF AND CLBING OUT OF MTY WE DID NOT COMPLY WITH THE INSTRUMENT DEP PROCS AS SPECIFIED ON ARPT CHART. ALL OF OUR CONVERSATIONS WITH THE ATC FAC AT MTY WERE QUITE ARDUOUS DUE TO DIFFICULTY IN UNDERSTANDING THE ENGLISH SPOKEN BY THE MTY GND/TWR CTLR. THE CLRNC WE RECEIVED WAS 'AS FILED' TO OUR FINAL ALT OF FL370. IT ALSO INCLUDED A RESTRICTION TO CROSS THE 10 DME FIX ON THE ARWY AT OR ABOVE 7000'. SINCE THERE WAS NO SID AT MTY I ASSUMED THAT WE WERE CLRED TO TURN ON COURSE. LATER I COULD NOT RECALL ANY SPECIFIC LEFT OR RIGHT TURN CLRNC. THE CAPT AND I DID NOT PROPERLY BRIEF THE DEP. IF WE HAD I FEEL THAT OUR LACK OF A TRUE DEP PLAN WOULD HAVE COME OUT IN THE DISCUSSION. IT WAS ONLY AFTER CLBING ABOVE 18000' DID I BEGIN TO WONDER IF WE HAD PROPERLY EXECUTED THE DEP. AT THAT TIME I LOOKED AT THE DEP PROCS ON PAGE 11-1 AND REALIZED THERE WERE VERY DETAILED INSTRUCTIONS FOR TKOFS FROM MTY. I POINTED THIS OUT TO THE CAPT AND HE AGREED WE HAD MADE AN ERROR. AT NO TIME DID ATC EVER QUESTION OUR ACTIONS. SINCE 99% OF OUR OPS ARE FROM ARPTS WITH SID'S, THE FACT THAT A SPECIFIC DEP PROC EVEN EXISTS SLIPS EASILY OUT OF MIND. A THOROUGH PRE-DEP BRIEFING WOULD HAVE CERTAINLY CLRED UP THIS PARTICULAR SITUATION. HAD OUR COMS WITH ATC BEEN LESS LABORIOUS I BELIEVE THIS PROB MAY NOT HAVE OCCURRED. HOWEVER, THIS IS AN ONGOING PROB WITH OPS IN MEXICO.

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.