MD80 crew misinterped clearance and started descent prior to crossing restr on STAR.

Attributes
ACN	504270
Time
Date	200103
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mmmy.airport
State Reference	FO
Altitude	msl bound lower : 6600 msl bound upper : 7000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	approach : instrument non precision arrival star : irbur ia enroute airway : j11.airway
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 20000 flight time type : 6000
ASRS Report	504270
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : multi engine
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance non adherence : published procedure other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude flight crew : became reoriented
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were on UJ11 inbound to monterey, mexico at 30 DME and 7000 ft. We were cleared via the arbur 1 alpha arrival with a VOR DME-1 to runway 11 at mty. The arrival has you descending to 6000 ft at 20 DME. The controller came on and said, 'I show you 20 DME, descend to 6000 ft now.' I started descending, my first officer asked him to repeat the clearance. He then said 'descend to 6000 ft at the 20 DME.' I thought this was an unnecessary clearance since the arrival depicted the descent at 20 DME. We actually descended 400 ft before correcting back to 7000 ft. Miscom is easy when there is a language difference. In the future, while flying into mexico, I will question strange clrncs.

Original NASA ASRS Text

Title: MD80 CREW MISINTERPED CLRNC AND STARTED DSCNT PRIOR TO XING RESTR ON STAR.

Narrative: WE WERE ON UJ11 INBOUND TO MONTEREY, MEXICO AT 30 DME AND 7000 FT. WE WERE CLRED VIA THE ARBUR 1 ALPHA ARR WITH A VOR DME-1 TO RWY 11 AT MTY. THE ARR HAS YOU DSNDING TO 6000 FT AT 20 DME. THE CTLR CAME ON AND SAID, 'I SHOW YOU 20 DME, DSND TO 6000 FT NOW.' I STARTED DSNDING, MY FO ASKED HIM TO REPEAT THE CLRNC. HE THEN SAID 'DSND TO 6000 FT AT THE 20 DME.' I THOUGHT THIS WAS AN UNNECESSARY CLRNC SINCE THE ARR DEPICTED THE DSCNT AT 20 DME. WE ACTUALLY DSNDED 400 FT BEFORE CORRECTING BACK TO 7000 FT. MISCOM IS EASY WHEN THERE IS A LANGUAGE DIFFERENCE. IN THE FUTURE, WHILE FLYING INTO MEXICO, I WILL QUESTION STRANGE CLRNCS.

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.