A crew cleared to descend via the MMMX avsar two alpha crossed slm at 13;000 ft then began a descent...

Attributes
ACN	1177476
Time
Date	201406
Local Time Of Day	0601-1200
Place
Locale Reference	MMMX.Airport
State Reference	FO
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Large Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 121
Flight Phase	Descent
Route In Use	STAR AVSAR TWO ALPHA
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Pilot Flying First Officer
Person 2
Function	Pilot Flying Captain
Experience	Flight Crew Last 90 Days 70 Flight Crew Total 12800 Flight Crew Type 4800
Events
Anomaly	Conflict Airborne Conflict Deviation - Altitude Overshoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

Avsar 2A arrival into MMMX (same issue applies to all arrivals from the north). Per ATC 'cleared to descend via avsar 2A.' looking at chart; STAR clearly ends at smo; not slm. Altitude at smo is 12;000 per chart. Passing slm we noticed traffic below us at 12;000. We were descending from 13;000 over slm to 12;000. ATC told us to level off at 13;000; so we climbed back up from about 12;700 to 13;000.ATC appears to be under the impression that the minimum altitude is 13;000 when cleared to descend via. From everything I read and my interpretation; the minimum altitude on the descend via is 12;000 after passing slm; to smo. Someone should clarify this with mexican ATC.

Original NASA ASRS Text

Title: A crew cleared to DESCEND VIA the MMMX AVSAR TWO ALPHA crossed SLM at 13;000 FT then began a descent to 12;000 FT; which they believed that to be the SMO crossing altitude; but ATC told them to return to 13;000 FT for traffic. The crew was informed 12;000 FT was the MEA; not segment altitude.

Narrative: AVSAR 2A arrival into MMMX (same issue applies to all arrivals from the north). Per ATC 'Cleared to descend via AVSAR 2A.' Looking at chart; STAR clearly ends at SMO; not SLM. Altitude at SMO is 12;000 per chart. Passing SLM we noticed traffic below us at 12;000. We were descending from 13;000 over SLM to 12;000. ATC told us to level off at 13;000; so we climbed back up from about 12;700 to 13;000.ATC appears to be under the impression that the minimum altitude is 13;000 when cleared to descend via. From everything I read and my interpretation; the minimum altitude on the descend via is 12;000 after passing SLM; to SMO. Someone should clarify this with Mexican ATC.

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.

A crew cleared to descend via the MMMX avsar two alpha crossed slm at 13;000 ft then began a descent to 12;000 ft; which they believed that to be the smo crossing altitude; but ATC told them to return to 13;000 ft for traffic. The crew was informed 12;000 ft was the MEA; not segment altitude.