As an A320 approached a known 7;840 foot obstacle on the mmgl ILS 10 approach; the egpws alerted cau...

Narrative:

After gdl approach control changed our approach 3 times we finally flew the VOR to runway 10 to intercept the ILS to runway 10. This was a very confusing clearance seeing as the controller could have just cleared us to the VOR to start the ILS procedure turn. Our original clearance was vectors to the ILS 10. Also; my ipad did not have a single VOR approach in it. Only the first officer's ipad had the VOR approach. We confirmed that the radials and altitudes on the approach were the same; so we continued the approach. After crossing the 12 DME fix outbound on the procedure turn we could descend to 8400 feet until crossing the 12 DME fix inbound on the ILS. During the turn inbound to intercept the ILS at approximately 8500 feet we got a caution terrain on the GPWS. We were both somewhat confused about the warning as we could see the top of the hill and per procedure cleared to 8400 feet on the turn inbound. I turned off the autopilot and stopped the descent rate and climbed a few hundred feet. As soon as I stopped the descent the warning went away. We could only assume that it was the descent rate with open descent selected on the mode control panel that caused the warning. In any case; that certainly was a very confusing warning as per procedure you are cleared to 8400 feet on the turn inbound to the ILS. We continued to land without incident and discussed the warning after the parking checklist was finished. We both concluded that we flew the procedure correctly and that the only issue that could have caused the GPWS warning was our descent rate closure to the hills below us.

Original NASA ASRS Text

Title: As an A320 approached a known 7;840 foot obstacle on the MMGL ILS 10 approach; the EGPWS alerted CAUTION; TERRAIN nearing the 8;400 foot descent constraint.

Narrative: After GDL approach control changed our approach 3 times we finally flew the VOR to runway 10 to intercept the ILS to runway 10. This was a very confusing clearance seeing as the controller could have just cleared us to the VOR to start the ILS procedure turn. Our original clearance was vectors to the ILS 10. Also; my iPad did not have a single VOR approach in it. Only the FO's iPad had the VOR approach. We confirmed that the radials and altitudes on the approach were the same; so we continued the approach. After crossing the 12 DME fix outbound on the procedure turn we could descend to 8400 feet until crossing the 12 DME fix inbound on the ILS. During the turn inbound to intercept the ILS at approximately 8500 feet we got a Caution Terrain on the GPWS. We were both somewhat confused about the warning as we could see the top of the hill and per procedure cleared to 8400 feet on the turn inbound. I turned off the autopilot and stopped the descent rate and climbed a few hundred feet. As soon as I stopped the descent the warning went away. We could only assume that it was the descent rate with open descent selected on the mode control panel that caused the warning. In any case; that certainly was a very confusing warning as per procedure you are cleared to 8400 feet on the turn inbound to the ILS. We continued to land without incident and discussed the warning after the parking checklist was finished. We both concluded that we flew the procedure correctly and that the only issue that could have caused the GPWS warning was our descent rate closure to the hills below us.

Data retrieved from NASA's ASRS site 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.

Attributes
ACN	1239724
Time
Date	201502
Local Time Of Day	1201-1800
Place
Locale Reference	MMGL.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	A320
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 200 Flight Crew Total 18000 Flight Crew Type 500
Person 2
Function	Pilot Not Flying First Officer
Experience	Flight Crew Last 90 Days 65 Flight Crew Total 6000 Flight Crew Type 460
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy

As an A320 approached a known 7;840 foot obstacle on the mmgl ILS 10 approach; the egpws alerted caution; terrain nearing the 8;400 foot descent constraint.