First officer of air carrier mdt doubts whether clearance to descend to 10000' was truly for his air...

Attributes
ACN	138105
Time
Date	199002
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : pbi
State Reference	FL
Altitude	msl bound lower : 13710 msl bound upper : 14000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zma tower : syr
Operator	common carrier : air carrier
Make Model Name	Medium Transport, High Wing, 2 Turboprop Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 200 flight time total : 3385 flight time type : 200
ASRS Report	138105
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

Returning to pbi from nassau, after about 15 mins at cruise altitude, heard a center controller instruct us to descend and maintain 10000 (I believe). PNF rogered instruction with our call sign and reset our altitude select to lower altitude. I was uncertain of call sign, so began slow descent while he attempted to confirm. After several other ATC xmissions he got through to center, who stated the descent instruction was for different aircraft (I believe). We had dropped about 290' by the time we got confirmation of the error and immediately reestablished cruise at our previously assigned altitude. In my 3 months of flying with the company this is about the 6TH instance of serious confusion caused by extremely similar call signs being in the same airspace. There are so many flts with call signs almost identical that it's not practical for ATC to specifically identify each and every instance of similar call signs being on one frequency. I'm convinced the companies must be made to change this practice or a catastrophe is statistically inevitable.

Original NASA ASRS Text

Title: FO OF ACR MDT DOUBTS WHETHER CLRNC TO DESCEND TO 10000' WAS TRULY FOR HIS ACFT, BUT STARTS DESCENT WHILE CAPT IS TRYING TO CONFIRM WITH ATC. CLRNC WAS FOR ANOTHER ACFT WITH A SIMILAR SOUNDING CALL SIGN.

Narrative: RETURNING TO PBI FROM NASSAU, AFTER ABOUT 15 MINS AT CRUISE ALT, HEARD A CENTER CTLR INSTRUCT US TO DSND AND MAINTAIN 10000 (I BELIEVE). PNF ROGERED INSTRUCTION WITH OUR CALL SIGN AND RESET OUR ALT SELECT TO LOWER ALT. I WAS UNCERTAIN OF CALL SIGN, SO BEGAN SLOW DSCNT WHILE HE ATTEMPTED TO CONFIRM. AFTER SEVERAL OTHER ATC XMISSIONS HE GOT THROUGH TO CENTER, WHO STATED THE DSCNT INSTRUCTION WAS FOR DIFFERENT ACFT (I BELIEVE). WE HAD DROPPED ABOUT 290' BY THE TIME WE GOT CONFIRMATION OF THE ERROR AND IMMEDIATELY REESTABLISHED CRUISE AT OUR PREVIOUSLY ASSIGNED ALT. IN MY 3 MONTHS OF FLYING WITH THE COMPANY THIS IS ABOUT THE 6TH INSTANCE OF SERIOUS CONFUSION CAUSED BY EXTREMELY SIMILAR CALL SIGNS BEING IN THE SAME AIRSPACE. THERE ARE SO MANY FLTS WITH CALL SIGNS ALMOST IDENTICAL THAT IT'S NOT PRACTICAL FOR ATC TO SPECIFICALLY IDENTIFY EACH AND EVERY INSTANCE OF SIMILAR CALL SIGNS BEING ON ONE FREQ. I'M CONVINCED THE COMPANIES MUST BE MADE TO CHANGE THIS PRACTICE OR A CATASTROPHE IS STATISTICALLY INEVITABLE.

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.

First officer of air carrier mdt doubts whether clearance to descend to 10000' was truly for his aircraft, but starts descent while captain is trying to confirm with ATC. Clearance was for another aircraft with a similar sounding call sign.