B767 is unsure of ATC descent clearance in ZOA, class a airspace.

Attributes
ACN	578600
Time
Date	200304
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : sfo.airport
State Reference	CA
Altitude	msl single value : 30000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa.artcc
Operator	common carrier : air carrier
Make Model Name	B767-300 and 300 ER
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 60 flight time total : 3000 flight time type : 1300
ASRS Report	578600
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : overshoot non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While descending through FL300, ATC said, 'aircraft X, say altitude.' we responded, 'FL300 for FL280.' after a long silence, the controller said 'ok, aircraft X, descend to FL280.' as the captain and I discussed the situation, we wondered if we had been given FL300 with a speed of 280 KTS. Nothing further was said by the controller and we were unsure if there was a problem. Contributing factors were speeds being given in the same clearance with similar altitudes. The crew was also fatigued due to an early trip start time.

Original NASA ASRS Text

Title: B767 IS UNSURE OF ATC DSCNT CLRNC IN ZOA, CLASS A AIRSPACE.

Narrative: WHILE DSNDING THROUGH FL300, ATC SAID, 'ACFT X, SAY ALT.' WE RESPONDED, 'FL300 FOR FL280.' AFTER A LONG SILENCE, THE CTLR SAID 'OK, ACFT X, DSND TO FL280.' AS THE CAPT AND I DISCUSSED THE SIT, WE WONDERED IF WE HAD BEEN GIVEN FL300 WITH A SPD OF 280 KTS. NOTHING FURTHER WAS SAID BY THE CTLR AND WE WERE UNSURE IF THERE WAS A PROB. CONTRIBUTING FACTORS WERE SPDS BEING GIVEN IN THE SAME CLRNC WITH SIMILAR ALTS. THE CREW WAS ALSO FATIGUED DUE TO AN EARLY TRIP START TIME.

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.