Air carrier captain experiences a loss of GPS signal approaching smo during arrival to MMMX. This ha...

Narrative:

Approaching mateo (smo) on the avasar 2A approach to rw 5R; 'dr' (dead reckoning) appeared in the pfd. We had discussed and briefed that this could happen based on conversations with other pilots that had recently flown to MMMX. At this point; the terrain display disappeared. Aircraft speed was 160 knots and on profile. We used RMI and raw data to verify situational awareness. Fully configured aircraft for landing prior to mex 253 lead-in radial. Picked up course prior to plaza and double checked position of aircraft. (On glideslope and course). At about 600 feet AGL; we received a 'terrain terrain pull up' warning. Immediate visual reference to surrounding terrain was available in the form of: PAPI; localizer; glideslope; visual cues and approach plate orientation. The aircraft appeared to re-orient itself shortly after the warning; as the 'dr' light extinguished; terrain re-appeared and I chose to continue the approach. No further anomalies were noted and we landed without incident. We suspect there is something causing a navigation anomaly on certain approaches into MMMX.

Original NASA ASRS Text

Title: Air carrier Captain experiences a loss of GPS signal approaching SMO during arrival to MMMX. This had been expected due to other crews having experienced the same anomaly. A terrain warning is issued and ignored on short final as the GPS returns to normal.

Narrative: Approaching Mateo (SMO) on the AVASAR 2A approach to RW 5R; 'DR' (dead reckoning) appeared in the PFD. We had discussed and briefed that this could happen based on conversations with other pilots that had recently flown to MMMX. At this point; the Terrain Display disappeared. Aircraft speed was 160 knots and on profile. We used RMI and Raw Data to verify situational awareness. Fully configured aircraft for landing prior to MEX 253 lead-in radial. Picked up course prior to PLAZA and double checked position of aircraft. (On glideslope and course). At about 600 feet AGL; we received a 'Terrain Terrain Pull Up' warning. Immediate visual reference to surrounding terrain was available in the form of: PAPI; localizer; glideslope; visual cues and Approach Plate Orientation. The aircraft appeared to re-orient itself shortly after the warning; as the 'DR' light extinguished; Terrain re-appeared and I chose to continue the approach. No further anomalies were noted and we landed without incident. We suspect there is something causing a navigation anomaly on certain approaches into MMMX.

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	1181191
Time
Date	201406
Local Time Of Day	0001-0600
Place
Locale Reference	MMMX.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	Medium Large Transport
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Route In Use	STAR AVASAR 2A
Flight Plan	IFR
Component
Aircraft Component	GPS & Other Satellite Navigation
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Events
Anomaly	Aircraft Equipment Problem Less Severe

Air carrier captain experiences a loss of GPS signal approaching smo during arrival to MMMX. This had been expected due to other crews having experienced the same anomaly. A terrain warning is issued and ignored on short final as the GPS returns to normal.