Narrative:

We were vectored to intercept ILS 28 at mmgl and cleared for the approach. At the request of the captain I initially extended off of the NDB. The captain then asked me to set 7200 ft in the altitude window. Shortly thereafter; the captain asked me to extend off of igdl D4.0 and set 6200 ft in the altitude window. If I remember correctly the turn onto the localizer was relatively close to the NDB. At some point the captain announced that we could start down and commenced a descent. I do not recall looking at the DME at this point (I was looking outside) since it was daylight. The visibility was good -- we already had the runway and all the surrounding terrain in sight. I expected that the captain would follow the GS to the runway. When I shortly thereafter looked inside we were descending below the GS; and I announced that we were going below the GS. Momentarily thereafter we received an egpws 'terrain' followed by 'whoop; whoop; pull up.' (flaps were not yet in landing confign.) the first thing I looked at was the RA on my side which indicated just over 1200 ft. The captain immediately leveled off and re-intercepted the GS and was fully configured and stable by 1000 ft AGL. The primary contributing factor for me as pilot monitoring was that I was not vigilant enough about verifying DME from runway and allowable descent altitudes on the approach since it was daylight; good visibility and surrounding terrain and the runway was in sight. I was also communicating with mmgl tower and we were told to expect a late landing clearance. I have flown into mmgl probably 8-10 times; but mostly in relatively poor visibility. Other partially contributing factors may have been that it had been a long day for both the captain and me (third leg of the morning). The captain had not flown in mexico for quite some time (therefore; I offered that he could fly all the legs) and that ATC brought us in high at both mmex; and mmgl making it an effort for us to get down. Additionally; the ILS 28 approach in mmgl can be a little deceiving with the 8300 ft altitude restr between D12.0 and D14.0 which is not depicted on the profile view and only in the plan view. The big lesson for me in this event is to be more vigilant about step-down altitudes when in daylight visual conditions on an approach; even though the runway and all surrounding terrain is clearly visible. Next time I fly this or similar approachs; I will verbalize to the captain (if he does not state so in his approach briefing) that I strongly recommend he intercept the GS from the last ATC assigned altitude. It is my job as an first officer to fully back up the captain during all approachs whether in visual or instrument conditions. Supplemental information from acn 732259: flight was being vectored to the ILS final approach to runway 28L. Flight was cleared to 9000 ft on a heading of 200 degrees to a point just outside the 12 DME fix on final. At about 3 mi north of the ILS course and abeam of a point about 1 mi inside of the 12 DME fix flight was given a heading of 250 degrees and cleared; I believed; visual approach. I could clearly see the runway as the visibility was at least 25 mi. I began a descent to FAF altitude of 6200 ft flying visual to the runway using the localizer and GS as a backup. I and the first officer were being mindful of terrain and saw no imminent conflict. As I looked inside to scan instruments; I saw that I had descended below the GS and started a leveloff and did 1 last visual scan. Just as I was starting a climb to keep safe terrain clearance the egpws advised 'terrain; terrain.' so I increased my rate and kept visual with the ground. At 'terrain pull up' I made a more aggressive climb to silence the warning and level at approximately 8000 ft scanned instruments and visually for terrain and continued the approach without further incident. Contributing factors: I had never flown into mmgl before. However; I have seen this approach in the simulator many times without real terrain visible. Although the language barrier was a problem during the entire trip I had clrncs clarified before this event and should have done so again. Lessons learned: when the WX is clear and visibility is good it is easier to be distraction by outside references which take away from your normal cockpit scan. I will be even more vigilant during VFR conditions to the cockpit area. Don't become a victim of expectation bias. I will make absolutely sure that I hear and understand clrncs correctly.

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Original NASA ASRS Text

Title: B757 CREW DESCENDS BELOW GS ON VISUAL APPROACH TO MMGL AND RECEIVES TERRAIN WARNING.

Narrative: WE WERE VECTORED TO INTERCEPT ILS 28 AT MMGL AND CLRED FOR THE APCH. AT THE REQUEST OF THE CAPT I INITIALLY EXTENDED OFF OF THE NDB. THE CAPT THEN ASKED ME TO SET 7200 FT IN THE ALT WINDOW. SHORTLY THEREAFTER; THE CAPT ASKED ME TO EXTEND OFF OF IGDL D4.0 AND SET 6200 FT IN THE ALT WINDOW. IF I REMEMBER CORRECTLY THE TURN ONTO THE LOC WAS RELATIVELY CLOSE TO THE NDB. AT SOME POINT THE CAPT ANNOUNCED THAT WE COULD START DOWN AND COMMENCED A DSCNT. I DO NOT RECALL LOOKING AT THE DME AT THIS POINT (I WAS LOOKING OUTSIDE) SINCE IT WAS DAYLIGHT. THE VISIBILITY WAS GOOD -- WE ALREADY HAD THE RWY AND ALL THE SURROUNDING TERRAIN IN SIGHT. I EXPECTED THAT THE CAPT WOULD FOLLOW THE GS TO THE RWY. WHEN I SHORTLY THEREAFTER LOOKED INSIDE WE WERE DSNDING BELOW THE GS; AND I ANNOUNCED THAT WE WERE GOING BELOW THE GS. MOMENTARILY THEREAFTER WE RECEIVED AN EGPWS 'TERRAIN' FOLLOWED BY 'WHOOP; WHOOP; PULL UP.' (FLAPS WERE NOT YET IN LNDG CONFIGN.) THE FIRST THING I LOOKED AT WAS THE RA ON MY SIDE WHICH INDICATED JUST OVER 1200 FT. THE CAPT IMMEDIATELY LEVELED OFF AND RE-INTERCEPTED THE GS AND WAS FULLY CONFIGURED AND STABLE BY 1000 FT AGL. THE PRIMARY CONTRIBUTING FACTOR FOR ME AS PLT MONITORING WAS THAT I WAS NOT VIGILANT ENOUGH ABOUT VERIFYING DME FROM RWY AND ALLOWABLE DSCNT ALTS ON THE APCH SINCE IT WAS DAYLIGHT; GOOD VISIBILITY AND SURROUNDING TERRAIN AND THE RWY WAS IN SIGHT. I WAS ALSO COMMUNICATING WITH MMGL TWR AND WE WERE TOLD TO EXPECT A LATE LNDG CLRNC. I HAVE FLOWN INTO MMGL PROBABLY 8-10 TIMES; BUT MOSTLY IN RELATIVELY POOR VISIBILITY. OTHER PARTIALLY CONTRIBUTING FACTORS MAY HAVE BEEN THAT IT HAD BEEN A LONG DAY FOR BOTH THE CAPT AND ME (THIRD LEG OF THE MORNING). THE CAPT HAD NOT FLOWN IN MEXICO FOR QUITE SOME TIME (THEREFORE; I OFFERED THAT HE COULD FLY ALL THE LEGS) AND THAT ATC BROUGHT US IN HIGH AT BOTH MMEX; AND MMGL MAKING IT AN EFFORT FOR US TO GET DOWN. ADDITIONALLY; THE ILS 28 APCH IN MMGL CAN BE A LITTLE DECEIVING WITH THE 8300 FT ALT RESTR BTWN D12.0 AND D14.0 WHICH IS NOT DEPICTED ON THE PROFILE VIEW AND ONLY IN THE PLAN VIEW. THE BIG LESSON FOR ME IN THIS EVENT IS TO BE MORE VIGILANT ABOUT STEP-DOWN ALTS WHEN IN DAYLIGHT VISUAL CONDITIONS ON AN APCH; EVEN THOUGH THE RWY AND ALL SURROUNDING TERRAIN IS CLRLY VISIBLE. NEXT TIME I FLY THIS OR SIMILAR APCHS; I WILL VERBALIZE TO THE CAPT (IF HE DOES NOT STATE SO IN HIS APCH BRIEFING) THAT I STRONGLY RECOMMEND HE INTERCEPT THE GS FROM THE LAST ATC ASSIGNED ALT. IT IS MY JOB AS AN FO TO FULLY BACK UP THE CAPT DURING ALL APCHS WHETHER IN VISUAL OR INST CONDITIONS. SUPPLEMENTAL INFO FROM ACN 732259: FLT WAS BEING VECTORED TO THE ILS FINAL APCH TO RWY 28L. FLT WAS CLRED TO 9000 FT ON A HDG OF 200 DEGS TO A POINT JUST OUTSIDE THE 12 DME FIX ON FINAL. AT ABOUT 3 MI N OF THE ILS COURSE AND ABEAM OF A POINT ABOUT 1 MI INSIDE OF THE 12 DME FIX FLT WAS GIVEN A HDG OF 250 DEGS AND CLRED; I BELIEVED; VISUAL APCH. I COULD CLRLY SEE THE RWY AS THE VISIBILITY WAS AT LEAST 25 MI. I BEGAN A DSCNT TO FAF ALT OF 6200 FT FLYING VISUAL TO THE RWY USING THE LOC AND GS AS A BACKUP. I AND THE FO WERE BEING MINDFUL OF TERRAIN AND SAW NO IMMINENT CONFLICT. AS I LOOKED INSIDE TO SCAN INSTS; I SAW THAT I HAD DSNDED BELOW THE GS AND STARTED A LEVELOFF AND DID 1 LAST VISUAL SCAN. JUST AS I WAS STARTING A CLB TO KEEP SAFE TERRAIN CLRNC THE EGPWS ADVISED 'TERRAIN; TERRAIN.' SO I INCREASED MY RATE AND KEPT VISUAL WITH THE GND. AT 'TERRAIN PULL UP' I MADE A MORE AGGRESSIVE CLB TO SILENCE THE WARNING AND LEVEL AT APPROX 8000 FT SCANNED INSTS AND VISUALLY FOR TERRAIN AND CONTINUED THE APCH WITHOUT FURTHER INCIDENT. CONTRIBUTING FACTORS: I HAD NEVER FLOWN INTO MMGL BEFORE. HOWEVER; I HAVE SEEN THIS APCH IN THE SIMULATOR MANY TIMES WITHOUT REAL TERRAIN VISIBLE. ALTHOUGH THE LANGUAGE BARRIER WAS A PROB DURING THE ENTIRE TRIP I HAD CLRNCS CLARIFIED BEFORE THIS EVENT AND SHOULD HAVE DONE SO AGAIN. LESSONS LEARNED: WHEN THE WX IS CLR AND VISIBILITY IS GOOD IT IS EASIER TO BE DISTR BY OUTSIDE REFS WHICH TAKE AWAY FROM YOUR NORMAL COCKPIT SCAN. I WILL BE EVEN MORE VIGILANT DURING VFR CONDITIONS TO THE COCKPIT AREA. DON'T BECOME A VICTIM OF EXPECTATION BIAS. I WILL MAKE ABSOLUTELY SURE THAT I HEAR AND UNDERSTAND CLRNCS CORRECTLY.

Data retrieved from NASA's ASRS site as of January 2009 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.