Medium Large Transport; Low Wing; 2 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe
General None Reported / Taken
Aircraft; Environment - Non Weather Related
to 5r the GPS has had a RNP fail. This occurs before SMO to just after. The FMS for some reason does not keep a satisfactory RNP. Just seems like a safety concern since it is not getting better.
I was pilot flying during the final arc turn to the approach course to runway 05R the GPS lost navigation signals and went into DR mode causing the autopilot to disconnect at a very high workload phase of the flight. We had already had issues with last minute ATC clearance changes and we had been deviating around numerous thunderstorms during the approach so having GPS signal issues made an already difficult arrival even worse.All pilots [of this fleet] were notified several months ago that they could expect anomalies with the GPS going into to Mexico City so I was aware of the problem but as an infrequent flyer to that destination I had not experienced it firsthand until this flight. If a GPS problem like that were to occur in the US or Canada it would be much less of an issue due to superior air traffic control communications; monitoring and procedures. When it occurs in Mexico City with high terrain in close proximity and the frequent severe thunderstorms that we encountered [that] night coupled with vague guidance and instructions from Mexican air traffic control it becomes an extremely hazardous situation.
Another Air Carrier crew reports loss of GPS capability in the vicinity of SMO during approach to MMMX.