Narrative:

Cleared direct otu VOR. (No further clearance or expected arrival given.) cleared to descend to 8800 ft while still north of the otu VOR. Approximately overhead otu VOR at approximately 10000 ft MSL, cleared for the otu 1 arrival after switched from mexico center (126.6) to approach control. (I had the arrival out in front of me. Since we had been cleared direct otu VOR previously, I anticipated this arrival, had looked at it, and placed it on the yoke cupboard. I also told the first officer to take it out.) as I was turning outbound on the 195 degree radial of otu VOR, ATC asked if we were familiar with the arrival. The first officer responded 'yes'. ATC asked, 'what is your altitude?' first officer responded 9600 ft climbing up to 11000 ft. The ground proximity warning system terrain warning sounded and I immediately applied maximum power and executed a positive pull-up out of the danger zone to above 10000 ft climbing toward 11000 ft. By this point, we were flying the otu 1 arrival and already established on the otu VOR 195 degree radial outbound and at cruise (7 DME) turning right to intercept the mex VOR 232 degree course inbound backed-up with the imex 232 degree localizer. I now began descending toward 9600 ft and continued the otu 1 arrival on the high side of published altitudes until established on the imex localizer/GS inbound. When I was first cleared direct to otu VOR and anticipated/took out the otu 1 arrival plate (also told first officer to take out same plate), I did not brief 'in-depth' both vertical and lateral navigation procedures as I have been trained to do over and over again, especially since we were flying outside united states airspace. Thus, when ATC (126.6) cleared us to descend to 8800 ft while we were still north of otu VOR, I should have never accepted any altitude clearance lower than 12000 ft. We were behind schedule (started when we began duty day) and I was trying to make up some time, I planned and began descent closer in to maintain a higher airspeed for as long as I could. I focused more on lateral navigation and relied on ATC for vertical navigation since I had heard the 'magic' words 'radar contact.' I allowed myself to become complacent and trust ATC for vertical navigation. One must never, ever do this while flying anywhere, especially outside united states airspace whether in radar contact or not. Supplemental information from acn 188454: the clearance for the otu 1 arrival should have been given before we arrived overhead otu. Supplemental information from acn 188682: the PNF usually checks all altitude and crossing radials. This night it did not take place. We missed the mountain peak on J39-49 from otu to mex by less than 500 ft AGL. I feel there is a language barrier also. It is often hard to tell what an ATC controller wants or is saying. He may have actually cleared us properly to the otu 1 arrival, but the way we interpreted it was completely different. Our readback in english may have been misunderstood also.

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Original NASA ASRS Text

Title: ACR LGT ALTDEV DSNDED BELOW MEA ON AN ARR RTE INTO MEX.

Narrative: CLRED DIRECT OTU VOR. (NO FURTHER CLRNC OR EXPECTED ARR GIVEN.) CLRED TO DSND TO 8800 FT WHILE STILL N OF THE OTU VOR. APPROX OVERHEAD OTU VOR AT APPROX 10000 FT MSL, CLRED FOR THE OTU 1 ARR AFTER SWITCHED FROM MEXICO CENTER (126.6) TO APCH CTL. (I HAD THE ARR OUT IN FRONT OF ME. SINCE WE HAD BEEN CLRED DIRECT OTU VOR PREVIOUSLY, I ANTICIPATED THIS ARR, HAD LOOKED AT IT, AND PLACED IT ON THE YOKE CUPBOARD. I ALSO TOLD THE FO TO TAKE IT OUT.) AS I WAS TURNING OUTBOUND ON THE 195 DEG RADIAL OF OTU VOR, ATC ASKED IF WE WERE FAMILIAR WITH THE ARR. THE FO RESPONDED 'YES'. ATC ASKED, 'WHAT IS YOUR ALT?' FO RESPONDED 9600 FT CLBING UP TO 11000 FT. THE GND PROX WARNING SYS TERRAIN WARNING SOUNDED AND I IMMEDIATELY APPLIED MAX PWR AND EXECUTED A POSITIVE PULL-UP OUT OF THE DANGER ZONE TO ABOVE 10000 FT CLBING TOWARD 11000 FT. BY THIS POINT, WE WERE FLYING THE OTU 1 ARR AND ALREADY ESTABLISHED ON THE OTU VOR 195 DEG RADIAL OUTBOUND AND AT CRUISE (7 DME) TURNING R TO INTERCEPT THE MEX VOR 232 DEG COURSE INBOUND BACKED-UP WITH THE IMEX 232 DEG LOC. I NOW BEGAN DSNDING TOWARD 9600 FT AND CONTINUED THE OTU 1 ARR ON THE HIGH SIDE OF PUBLISHED ALTS UNTIL ESTABLISHED ON THE IMEX LOC/GS INBOUND. WHEN I WAS FIRST CLRED DIRECT TO OTU VOR AND ANTICIPATED/TOOK OUT THE OTU 1 ARR PLATE (ALSO TOLD FO TO TAKE OUT SAME PLATE), I DID NOT BRIEF 'IN-DEPTH' BOTH VERT AND LATERAL NAV PROCS AS I HAVE BEEN TRAINED TO DO OVER AND OVER AGAIN, ESPECIALLY SINCE WE WERE FLYING OUTSIDE UNITED STATES AIRSPACE. THUS, WHEN ATC (126.6) CLRED US TO DSND TO 8800 FT WHILE WE WERE STILL N OF OTU VOR, I SHOULD HAVE NEVER ACCEPTED ANY ALT CLRNC LOWER THAN 12000 FT. WE WERE BEHIND SCHEDULE (STARTED WHEN WE BEGAN DUTY DAY) AND I WAS TRYING TO MAKE UP SOME TIME, I PLANNED AND BEGAN DSCNT CLOSER IN TO MAINTAIN A HIGHER AIRSPD FOR AS LONG AS I COULD. I FOCUSED MORE ON LATERAL NAV AND RELIED ON ATC FOR VERT NAV SINCE I HAD HEARD THE 'MAGIC' WORDS 'RADAR CONTACT.' I ALLOWED MYSELF TO BECOME COMPLACENT AND TRUST ATC FOR VERT NAV. ONE MUST NEVER, EVER DO THIS WHILE FLYING ANYWHERE, ESPECIALLY OUTSIDE UNITED STATES AIRSPACE WHETHER IN RADAR CONTACT OR NOT. SUPPLEMENTAL INFO FROM ACN 188454: THE CLRNC FOR THE OTU 1 ARR SHOULD HAVE BEEN GIVEN BEFORE WE ARRIVED OVERHEAD OTU. SUPPLEMENTAL INFO FROM ACN 188682: THE PNF USUALLY CHKS ALL ALT AND XING RADIALS. THIS NIGHT IT DID NOT TAKE PLACE. WE MISSED THE MOUNTAIN PEAK ON J39-49 FROM OTU TO MEX BY LESS THAN 500 FT AGL. I FEEL THERE IS A LANGUAGE BARRIER ALSO. IT IS OFTEN HARD TO TELL WHAT AN ATC CTLR WANTS OR IS SAYING. HE MAY HAVE ACTUALLY CLRED US PROPERLY TO THE OTU 1 ARR, BUT THE WAY WE INTERPRETED IT WAS COMPLETELY DIFFERENT. OUR READBACK IN ENGLISH MAY HAVE BEEN MISUNDERSTOOD ALSO.

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.