Narrative:

On descent into mmgl we briefed the planned ILS runway 28 approach; the speed limits; and the terrain. We discussed the need for the pilot monitoring to cross check navigation with meaningful raw data. We specifically reviewed the location of the hill near the 14 DME fix on the runway 28 localizer and a tower on another hill northeast of the 14 DME fix. We were given vectors for the ILS approach runway 28. I was the pilot flying. After several vectors; we were given instructions to descend to 8;200 ft on a 250 degree heading to intercept the localizer and we were cleared for the ILS approach. The minimum altitude on the approach inside 14 DME is 8;300 ft; dropping to 7;200 ft inside 12 DME so the altitude clearance appeared reasonable for a radar vector glide slope intercept at about 13 DME in visual conditions. We leveled at 8;200 ft slightly before anticipated localizer capture. The glide slope was coming down within a dot as were turning well inside the 14 DME fix. Speed was stable at 163 KTS and flaps 5. We could see the runway through some light showers and scattered clouds and the map display appeared to be in agreement with the visual runway centerline which we were approaching. Raw data and the map display were also in agreement with the displayed location of the 14 DME fix and the VOR course leading to the localizer. As I anticipated my call for gear down; flaps 20 upon localizer capture; we received a brief 'caution terrain' aural egpws warning followed by 'terrain; terrain; pull up'. Although we had visual ground contact through light rain showers and I felt that the egpws alerts were most likely a nuisance warning from the rising slope of the hill under the 14 DME fix; which we were turning away from; I elected to commence a cftt recovery maneuver to absolutely assure safe terrain clearance. Configuration of flaps 5 was initially maintained and the egpws warnings ceased immediately as the aircraft pitched up from level flight. We advised the approach controller that we had climbed due to an egpws warning and requested vectors to re-intercept the ILS for another approach. The subsequent approach and landing were uneventful. Since mmgl has a company NOTAM concerning CFIT awareness; we attempted to be slowed and level approaching the localizer course to avoid an egpws alert from excessive descent rate toward the rapidly rising terrain. A delayed descent would have probably prevented the alert; however; intercepting the glide slope from above in a B-757 at a high altitude airport has been cited as a cause for unstable approaches so care must be taken with this method. Although the cleared altitude of 8;200 ft was only 100 ft below the charted minimum altitude of 8;300 inside the 14 DME fix; the minimum vectoring altitude of 8;500 ft in the area would have provided additional terrain clearance margin. We were very aware of the terrain in the vicinity of the approach path and felt that the egwps alert was spurious due to the proximity of the hill which we could see that we had passed and were turning away from. However; the cftt recovery maneuver enabled us to assure safe terrain clearance in response to the egwps alert.

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Original NASA ASRS Text

Title: A B757 flight crew reported receiving a terrain alert on approach to MMGL even though they were very terrain aware and fully briefed.

Narrative: On descent into MMGL we briefed the planned ILS Runway 28 approach; the speed limits; and the terrain. We discussed the need for the pilot monitoring to cross check navigation with meaningful raw data. We specifically reviewed the location of the hill near the 14 DME fix on the Runway 28 localizer and a tower on another hill northeast of the 14 DME fix. We were given vectors for the ILS approach Runway 28. I was the pilot flying. After several vectors; we were given instructions to descend to 8;200 FT on a 250 degree heading to intercept the localizer and we were cleared for the ILS approach. The minimum altitude on the approach inside 14 DME is 8;300 FT; dropping to 7;200 FT inside 12 DME so the altitude clearance appeared reasonable for a radar vector glide slope intercept at about 13 DME in visual conditions. We leveled at 8;200 FT slightly before anticipated localizer capture. The glide slope was coming down within a dot as were turning well inside the 14 DME fix. Speed was stable at 163 KTS and flaps 5. We could see the runway through some light showers and scattered clouds and the map display appeared to be in agreement with the visual runway centerline which we were approaching. Raw data and the map display were also in agreement with the displayed location of the 14 DME fix and the VOR course leading to the localizer. As I anticipated my call for gear down; flaps 20 upon localizer capture; we received a brief 'Caution Terrain' aural EGPWS warning followed by 'Terrain; Terrain; Pull Up'. Although we had visual ground contact through light rain showers and I felt that the EGPWS alerts were most likely a nuisance warning from the rising slope of the hill under the 14 DME fix; which we were turning away from; I elected to commence a CFTT Recovery Maneuver to absolutely assure safe terrain clearance. Configuration of flaps 5 was initially maintained and the EGPWS warnings ceased immediately as the aircraft pitched up from level flight. We advised the Approach Controller that we had climbed due to an EGPWS warning and requested vectors to re-intercept the ILS for another approach. The subsequent approach and landing were uneventful. Since MMGL has a company NOTAM concerning CFIT awareness; we attempted to be slowed and level approaching the localizer course to avoid an EGPWS alert from excessive descent rate toward the rapidly rising terrain. A delayed descent would have probably prevented the alert; however; intercepting the glide slope from above in a B-757 at a high altitude airport has been cited as a cause for unstable approaches so care must be taken with this method. Although the cleared altitude of 8;200 FT was only 100 FT below the charted minimum altitude of 8;300 inside the 14 DME fix; the minimum vectoring altitude of 8;500 FT in the area would have provided additional terrain clearance margin. We were very aware of the terrain in the vicinity of the approach path and felt that the EGWPS alert was spurious due to the proximity of the hill which we could see that we had passed and were turning away from. However; the CFTT Recovery maneuver enabled us to assure safe terrain clearance in response to the EGWPS alert.

Data retrieved from NASA's ASRS site as of April 2012 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.