Air carrier large transport altitude deviation excursion from clearance altitude.

Attributes
ACN	176673
Time
Date	199104
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : mmex airport : mex
State Reference	FO
Altitude	msl bound lower : 12000 msl bound upper : 16000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : mmex
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 120 flight time total : 10650 flight time type : 75
ASRS Report	176673
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Deviation Pilot Deviation

Narrative:

During descent into mexico city, a center controller gave us a descent to 16000', followed a few mins later by a descent to 12000'. Upon passing 13500', the controller asked what our altitude was and then told us that we were only cleared to 16000', but to continue to 12000'. Communications while flying in mexico are marginal at best, many times requiring 2 and sometimes 3 verifications. Most other aircraft are spoken to in spanish, so you have no idea what is going on around you. Suggestion: it would be nice if mexico city had a profile descent to include altitude crossing restrictions (similar to lax). The only communication required would be, 'cleared for profile descent,' and there would be less of a chance for missed communications. The pilots would know exactly what is expected of them until being picked up by the final controller.

Original NASA ASRS Text

Title: ACR LGT ALT DEVIATION EXCURSION FROM CLRNC ALT.

Narrative: DURING DSNT INTO MEXICO CITY, A CENTER CTLR GAVE US A DSNT TO 16000', FOLLOWED A FEW MINS LATER BY A DSNT TO 12000'. UPON PASSING 13500', THE CTLR ASKED WHAT OUR ALT WAS AND THEN TOLD US THAT WE WERE ONLY CLRED TO 16000', BUT TO CONTINUE TO 12000'. COMS WHILE FLYING IN MEXICO ARE MARGINAL AT BEST, MANY TIMES REQUIRING 2 AND SOMETIMES 3 VERIFICATIONS. MOST OTHER ACFT ARE SPOKEN TO IN SPANISH, SO YOU HAVE NO IDEA WHAT IS GOING ON AROUND YOU. SUGGESTION: IT WOULD BE NICE IF MEXICO CITY HAD A PROFILE DSNT TO INCLUDE ALT XING RESTRICTIONS (SIMILAR TO LAX). THE ONLY COM REQUIRED WOULD BE, 'CLRED FOR PROFILE DSNT,' AND THERE WOULD BE LESS OF A CHANCE FOR MISSED COMS. THE PLTS WOULD KNOW EXACTLY WHAT IS EXPECTED OF THEM UNTIL BEING PICKED UP BY THE FINAL CTLR.

Data retrieved from NASA's ASRS site as of July 2007 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.