DH8 crew started a descent on clearance meant for a company aircraft.

Attributes
ACN	575822
Time
Date	200303
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zse.artcc
State Reference	WA
Altitude	msl bound lower : 9000 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zse.artcc
Operator	common carrier : air carrier
Make Model Name	Dash 8 Series Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : helens 4
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zse.artcc
Operator	common carrier : air carrier
Make Model Name	Dash 8 Series Undifferentiated or Other Model
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 : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 100 flight time total : 7200 flight time type : 3500
ASRS Report	575822
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : clearance
Independent Detector	other controllera other flight crewa other flight crewb other other : 3
Resolutory Action	controller : issued new clearance none taken : anomaly accepted other
Supplementary
Problem Areas	ATC Human Performance Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

At approximately XA30 local, contact with ZSE was made and they were slowing traffic due to WX in pdx. Another DHC8 was in front of us and their communication with ZSE was difficult. The pilot's english was poor and each communication was repeated at least twice. We were given a 360 degree turn for spacing, then asked to keep it tight. Then cleared to descend to 10000 ft. All calls were very close to each other, all repeated by us with no question or verification. After descending 600-800 ft, the other aircraft called and asked if the descent was for them. That is where it got confusing. We thought the clearance was for us and no one questioned our reply. My best guess is, as usual, communications became stressed, and we made a mistake, due to bad calls the controller was extremely busy, and the other aircraft was not staying with any of their calls, causing frustration for all. Not knowing what was happening in the other aircraft, we requested new altitude clearance and ZSE cleared us to 10000 ft. No conflict existed or any evasive action taken. The only contributing factor other than communications, would be fatigue. On a 5 week schedule all other trips show around XA00 and finish between XK00-XM00. Except this trip, one oddball with an XQ00 report that day and 6 legs. Our internal clocks were definitely not their norm. Our company is trying to have all trips of the same type, am/pm.

Original NASA ASRS Text

Title: DH8 CREW STARTED A DSCNT ON CLRNC MEANT FOR A COMPANY ACFT.

Narrative: AT APPROX XA30 LCL, CONTACT WITH ZSE WAS MADE AND THEY WERE SLOWING TFC DUE TO WX IN PDX. ANOTHER DHC8 WAS IN FRONT OF US AND THEIR COM WITH ZSE WAS DIFFICULT. THE PLT'S ENGLISH WAS POOR AND EACH COM WAS REPEATED AT LEAST TWICE. WE WERE GIVEN A 360 DEG TURN FOR SPACING, THEN ASKED TO KEEP IT TIGHT. THEN CLRED TO DSND TO 10000 FT. ALL CALLS WERE VERY CLOSE TO EACH OTHER, ALL REPEATED BY US WITH NO QUESTION OR VERIFICATION. AFTER DSNDING 600-800 FT, THE OTHER ACFT CALLED AND ASKED IF THE DSCNT WAS FOR THEM. THAT IS WHERE IT GOT CONFUSING. WE THOUGHT THE CLRNC WAS FOR US AND NO ONE QUESTIONED OUR REPLY. MY BEST GUESS IS, AS USUAL, COMS BECAME STRESSED, AND WE MADE A MISTAKE, DUE TO BAD CALLS THE CTLR WAS EXTREMELY BUSY, AND THE OTHER ACFT WAS NOT STAYING WITH ANY OF THEIR CALLS, CAUSING FRUSTRATION FOR ALL. NOT KNOWING WHAT WAS HAPPENING IN THE OTHER ACFT, WE REQUESTED NEW ALT CLRNC AND ZSE CLRED US TO 10000 FT. NO CONFLICT EXISTED OR ANY EVASIVE ACTION TAKEN. THE ONLY CONTRIBUTING FACTOR OTHER THAN COMS, WOULD BE FATIGUE. ON A 5 WK SCHEDULE ALL OTHER TRIPS SHOW AROUND XA00 AND FINISH BTWN XK00-XM00. EXCEPT THIS TRIP, ONE ODDBALL WITH AN XQ00 RPT THAT DAY AND 6 LEGS. OUR INTERNAL CLOCKS WERE DEFINITELY NOT THEIR NORM. OUR COMPANY IS TRYING TO HAVE ALL TRIPS OF THE SAME TYPE, AM/PM.

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.