Air carrier flight crew descends without ATC clearance, similar call signs.

Attributes
ACN	601871
Time
Date	200312
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : alb.vortac
State Reference	NY
Altitude	msl bound lower : 14000 msl bound upper : 15000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	Medium Transport, Low Wing, 2 Turboprop Eng
Operating Under FAR Part	Part 121
Flight Phase	cruise : level cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : multi engine pilot : atp
Experience	flight time last 90 days : 250 flight time total : 17000 flight time type : 7000
ASRS Report	601871
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	controller : issued advisory controller : issued new clearance
Miss Distance	horizontal : 30000 vertical : 500
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Our crew was flying air carrier X flight from lga to btv. We were 40 NM southeast of alb VOR direct to btv in an area where numerous air carrier's are crossing. We thought we heard the ZBW ATC controller tell us to descend to 14000 ft MSL from 15000 ft MSL. As we were leveling at 14000 ft MSL the controller called out traffic to us at our 1 and 2 O'clock position, at 14000 ft MSL. We saw and reported the traffic to him. ATC then asked us what altitude we were at. We responded '14000 ft.' ATC told us we shouldn't be at 14000 ft, that we took air carrier Y's altitude clearance instead. ATC then told us to climb back to 15000 ft MSL and remain clear of traffic. Our TCASII sounded and we climbed immediately. No conflict of a serious nature occurred and traffic was avoided. We did not listen clearly to the altitude clearance to a similar sounding call sign. ATC was busy with numerous calls and didn't realize we took some other aircraft's clearance until a potential conflict occurred. I apologized to the controller when we leveled off at 15000 ft MSL. No feelings were hurt, no metal was bent, and I learned a valuable lesson: 'listen up!'

Original NASA ASRS Text

Title: ACR FLT CREW DSNDS WITHOUT ATC CLRNC, SIMILAR CALL SIGNS.

Narrative: OUR CREW WAS FLYING ACR X FLT FROM LGA TO BTV. WE WERE 40 NM SE OF ALB VOR DIRECT TO BTV IN AN AREA WHERE NUMEROUS ACR'S ARE XING. WE THOUGHT WE HEARD THE ZBW ATC CTLR TELL US TO DSND TO 14000 FT MSL FROM 15000 FT MSL. AS WE WERE LEVELING AT 14000 FT MSL THE CTLR CALLED OUT TFC TO US AT OUR 1 AND 2 O'CLOCK POS, AT 14000 FT MSL. WE SAW AND RPTED THE TFC TO HIM. ATC THEN ASKED US WHAT ALT WE WERE AT. WE RESPONDED '14000 FT.' ATC TOLD US WE SHOULDN'T BE AT 14000 FT, THAT WE TOOK ACR Y'S ALT CLRNC INSTEAD. ATC THEN TOLD US TO CLB BACK TO 15000 FT MSL AND REMAIN CLR OF TFC. OUR TCASII SOUNDED AND WE CLBED IMMEDIATELY. NO CONFLICT OF A SERIOUS NATURE OCCURRED AND TFC WAS AVOIDED. WE DID NOT LISTEN CLRLY TO THE ALT CLRNC TO A SIMILAR SOUNDING CALL SIGN. ATC WAS BUSY WITH NUMEROUS CALLS AND DIDN'T REALIZE WE TOOK SOME OTHER ACFT'S CLRNC UNTIL A POTENTIAL CONFLICT OCCURRED. I APOLOGIZED TO THE CTLR WHEN WE LEVELED OFF AT 15000 FT MSL. NO FEELINGS WERE HURT, NO METAL WAS BENT, AND I LEARNED A VALUABLE LESSON: 'LISTEN UP!'

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.