Narrative:

This report is concerning compliance with FAA emergency depressurization descent oxygen requirements in flight planning through the emergency diversion critical terrain areas in south. America. After airborne; and further review of our routing along the west coast of south. America and transitioning across terrain from santiago to saez; the crew determined the routing (toy UB560 jua) through the critical terrain depressurization route does not meet FAA requirements to achieve 10;000' in 12 min on [this widebody aircraft]. The [larger version of this aircraft] does meet the requirements with 22 min of oxygen. Reference diversion guide 'critical terrain orientation' chart 12 min profile. If we are to assume the UB560 corridor is transitioning a tight no fly zone corridor between points mibas & ilsur; no turn can be made to return to 'titki' for the descent. This forces a 105 mile (approx) commitment from mibas to jua with a 13 min travel time at the depressurization altitude of 18000' before a descent to 10;000' can be accomplished. Also; the 80 mile 'titki ' ring has a FL210 restriction until crossing ilsur. If charts consider the diversion rings safe in the no fly zones; this needs to be annotated. We were originally dispatched on [the larger version of the aircraft] that changed to a [smaller version]. Upon airborne; and analyzing the route again we contacted dispatch to process a reroute south of this critical terrain area with a more conservative routing that we believed met the FAA mandated oxygen requirements for rapid depressurization while operating in critical terrain areas.

Google
 

Original NASA ASRS Text

Title: Air carrier First Officer did not believe that his aircraft met FAA Emergency Depressurization Descent Oxygen requirements in flight through the Emergency Diversion Critical Terrain Areas in S. America. Specifically along UB560 between MIBAS and ILSUR. The flight plan is revised Enroute.

Narrative: This report is concerning compliance with FAA Emergency Depressurization Descent Oxygen requirements in flight planning through the Emergency Diversion Critical Terrain Areas in S. America. After airborne; and further review of our routing along the west coast of S. America and transitioning across terrain from Santiago to SAEZ; the crew determined the routing (TOY UB560 JUA) through the Critical Terrain Depressurization Route does not meet FAA requirements to achieve 10;000' in 12 min on [this widebody aircraft]. The [larger version of this aircraft] does meet the requirements with 22 min of oxygen. Reference Diversion Guide 'Critical Terrain Orientation' chart 12 min profile. If we are to assume the UB560 corridor is transitioning a tight NO FLY ZONE corridor between points MIBAS & ILSUR; no turn can be made to return to 'TITKI' for the descent. This forces a 105 mile (approx) commitment from MIBAS to JUA with a 13 min travel time at the Depressurization Altitude of 18000' before a descent to 10;000' can be accomplished. Also; the 80 mile 'TITKI ' ring has a FL210 restriction until crossing ILSUR. If charts consider the Diversion Rings safe in the NO FLY ZONES; this needs to be annotated. We were originally dispatched on [the larger version of the aircraft] that changed to a [smaller version]. Upon airborne; and analyzing the route again we contacted dispatch to process a reroute south of this critical terrain area with a more conservative routing that we believed met the FAA mandated oxygen requirements for Rapid Depressurization while operating in Critical Terrain Areas.

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.