B757 crew had altitude deviation on modesto 2 STAR into sfo.

Attributes
ACN	466500
Time
Date	200003
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	intersection : cedes
State Reference	CA
Altitude	msl bound lower : 10400 msl bound upper : 11000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zoa.artcc
Operator	common carrier : air carrier
Make Model Name	B757-200
Operating Under FAR Part	Part 121
Navigation In Use	other other vortac
Flight Phase	descent : vacating altitude
Route In Use	arrival star : modesto 2
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 20000 flight time type : 350
ASRS Report	466500
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 180 flight time total : 12000 flight time type : 500
ASRS Report	466245
Events
Anomaly	altitude deviation : overshoot altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : company policies non adherence : clearance non adherence : far
Independent Detector	other controllera
Resolutory Action	controller : issued alert controller : issued new clearance
Supplementary
Problem Areas	ATC Human Performance FAA Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were cleared to 11000 ft on modesto 2 arrival to sfo. As we approached cedes, we heard and read back that we were cleared to descend and maintain 8000 ft. We were passing about 12000 ft at the time. A couple of mins later (after passing cedes), as we approached 10000 ft, the controller told us to maintain 10000 ft. He said he never cleared us to 8000 ft. We leveled at 10000 ft and proceeded without incident. We heard and read back 'cleared to 8000 ft.' supplemental information from acn 466245: it occurred at a very busy time when the frequency was saturated and this doesn't allow pilot or controller to question or query an incorrect clearance or readback.

Original NASA ASRS Text

Title: B757 CREW HAD ALTDEV ON MODESTO 2 STAR INTO SFO.

Narrative: WE WERE CLRED TO 11000 FT ON MODESTO 2 ARR TO SFO. AS WE APCHED CEDES, WE HEARD AND READ BACK THAT WE WERE CLRED TO DSND AND MAINTAIN 8000 FT. WE WERE PASSING ABOUT 12000 FT AT THE TIME. A COUPLE OF MINS LATER (AFTER PASSING CEDES), AS WE APCHED 10000 FT, THE CTLR TOLD US TO MAINTAIN 10000 FT. HE SAID HE NEVER CLRED US TO 8000 FT. WE LEVELED AT 10000 FT AND PROCEEDED WITHOUT INCIDENT. WE HEARD AND READ BACK 'CLRED TO 8000 FT.' SUPPLEMENTAL INFO FROM ACN 466245: IT OCCURRED AT A VERY BUSY TIME WHEN THE FREQ WAS SATURATED AND THIS DOESN'T ALLOW PLT OR CTLR TO QUESTION OR QUERY AN INCORRECT CLRNC OR READBACK.

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.