An E120 crew misinterped clearance and descended out of assigned altitude.

Attributes
ACN	501779
Time
Date	200102
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	intersection : unity
State Reference	FL
Altitude	msl bound lower : 8500 msl bound upper : 9000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Brasilia EMB-120 All Series
Operating Under FAR Part	Part 119
Navigation In Use	Other
Flight Phase	descent : vacating altitude
Route In Use	arrival star : minee
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : commercial pilot : instrument pilot : multi engine
Experience	flight time last 90 days : 40 flight time total : 1400 flight time type : 190
ASRS Report	501779
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 240 flight time total : 12000 flight time type : 8000
ASRS Report	501777
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	faa : reviewed incident with flight crew
Supplementary
Problem Areas	ATC Human Performance Company Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

From 9000 ft MSL, ATC instructed us to 5000 ft MSL. While on descent, at approximately 8500 ft, controller asked if we were descending. I responded 'affirmative, to 5000 ft.' the controller told us to stop descent at 8000 ft, 'the 5000 ft instructions were for another aircraft,' she said. There was no conflict with another aircraft. Contributing factors were similar call signs, many aircraft -- all inbound to orl at the same time, same frequency. Also, if the instructions were not for us, no other aircraft, or the controller, caught the mistake after I read back the instructions for at least a min. Supplemental information from acn 501777: this was and has been the problem for many yrs. On the frequency were at least 5 other aircraft from company that had call signs ending in the same number. Our pilot safety group has been working with this problem for yrs, but nothing ever seems to change. The company marketing department is the source of the problem with the flight numbers.

Original NASA ASRS Text

Title: AN E120 CREW MISINTERPED CLRNC AND DSNDED OUT OF ASSIGNED ALT.

Narrative: FROM 9000 FT MSL, ATC INSTRUCTED US TO 5000 FT MSL. WHILE ON DSCNT, AT APPROX 8500 FT, CTLR ASKED IF WE WERE DSNDING. I RESPONDED 'AFFIRMATIVE, TO 5000 FT.' THE CTLR TOLD US TO STOP DSCNT AT 8000 FT, 'THE 5000 FT INSTRUCTIONS WERE FOR ANOTHER ACFT,' SHE SAID. THERE WAS NO CONFLICT WITH ANOTHER ACFT. CONTRIBUTING FACTORS WERE SIMILAR CALL SIGNS, MANY ACFT -- ALL INBOUND TO ORL AT THE SAME TIME, SAME FREQ. ALSO, IF THE INSTRUCTIONS WERE NOT FOR US, NO OTHER ACFT, OR THE CTLR, CAUGHT THE MISTAKE AFTER I READ BACK THE INSTRUCTIONS FOR AT LEAST A MIN. SUPPLEMENTAL INFO FROM ACN 501777: THIS WAS AND HAS BEEN THE PROB FOR MANY YRS. ON THE FREQ WERE AT LEAST 5 OTHER ACFT FROM COMPANY THAT HAD CALL SIGNS ENDING IN THE SAME NUMBER. OUR PLT SAFETY GROUP HAS BEEN WORKING WITH THIS PROB FOR YRS, BUT NOTHING EVER SEEMS TO CHANGE. THE COMPANY MARKETING DEPT IS THE SOURCE OF THE PROB WITH THE FLT NUMBERS.

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.