An air carrier DC9 flight crew responded to another's clearance and were corrected, but in the confusion descended too low at a VOR crossing on the profile descent. Apparently, no conflict.

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Attributes
ACN	397015
Time
Date	199803
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ywt
State Reference	ON
Altitude	msl bound lower : 11000 msl bound upper : 13000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : czyz
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	arrival : profile descent arrival other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 9000 flight time type : 1600
ASRS Report	397015
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi pilot : flight engineer
Experience	flight time last 90 days : 185 flight time total : 9000 flight time type : 2000
ASRS Report	396690
Events
Anomaly	altitude deviation : crossing restriction not met non adherence : clearance non adherence : far non adherence : published procedure other anomaly other
Independent Detector	other controllera other other : unspecified
Resolutory Action	controller : issued new clearance none taken : detected after the fact other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Toronto center cleared us for the runway 24 profile descent with an altitude of 13000 ft MSL approximately 60 mi west of ywt. We called out of our cruise altitude to descend to 13000 ft MSL on the profile descent, then we responded to a descent to a different altitude, 21000 ft. Another aircraft questioned our clearance because it was for them. Toronto didn't correct our response until the other aircraft (similar call signs) corrected them. After the confusion was cleared up, toronto descended us to 11000 ft approximately 25 mi west of ywt. I set 11000 ft in the altitude alerter and the captain acknowledged the clearance (altitude). We proceeded to cross ywt at 11000 ft. The captain (PF) then realized we were to cross ywt at 13000 ft then descend to 11000 ft after crossing ywt as per the profile descent. Toronto mentioned nothing about the altitude. Because of the confusion of call signs by center and not correcting the clearance, our attention was diverted to the altitude 21000 ft then 13000 ft, then cleared to 11000 ft. I am not sure in canada, if an amended clearance like 11000 ft overrides the profile descent of 13000 ft clearance. It can be very confusing. Supplemental information from acn 396690: we got confused with an ensuing clearance and crossed the VOR at 11000 ft, rather than intersection guelf at 11000 ft.

Original NASA ASRS Text

Title: AN ACR DC9 FLC RESPONDED TO ANOTHER'S CLRNC AND WERE CORRECTED, BUT IN THE CONFUSION DSNDED TOO LOW AT A VOR XING ON THE PROFILE DSCNT. APPARENTLY, NO CONFLICT.

Narrative: TORONTO CTR CLRED US FOR THE RWY 24 PROFILE DSCNT WITH AN ALT OF 13000 FT MSL APPROX 60 MI W OF YWT. WE CALLED OUT OF OUR CRUISE ALT TO DSND TO 13000 FT MSL ON THE PROFILE DSCNT, THEN WE RESPONDED TO A DSCNT TO A DIFFERENT ALT, 21000 FT. ANOTHER ACFT QUESTIONED OUR CLRNC BECAUSE IT WAS FOR THEM. TORONTO DIDN'T CORRECT OUR RESPONSE UNTIL THE OTHER ACFT (SIMILAR CALL SIGNS) CORRECTED THEM. AFTER THE CONFUSION WAS CLRED UP, TORONTO DSNDED US TO 11000 FT APPROX 25 MI W OF YWT. I SET 11000 FT IN THE ALT ALERTER AND THE CAPT ACKNOWLEDGED THE CLRNC (ALT). WE PROCEEDED TO CROSS YWT AT 11000 FT. THE CAPT (PF) THEN REALIZED WE WERE TO CROSS YWT AT 13000 FT THEN DSND TO 11000 FT AFTER XING YWT AS PER THE PROFILE DSCNT. TORONTO MENTIONED NOTHING ABOUT THE ALT. BECAUSE OF THE CONFUSION OF CALL SIGNS BY CTR AND NOT CORRECTING THE CLRNC, OUR ATTN WAS DIVERTED TO THE ALT 21000 FT THEN 13000 FT, THEN CLRED TO 11000 FT. I AM NOT SURE IN CANADA, IF AN AMENDED CLRNC LIKE 11000 FT OVERRIDES THE PROFILE DSCNT OF 13000 FT CLRNC. IT CAN BE VERY CONFUSING. SUPPLEMENTAL INFO FROM ACN 396690: WE GOT CONFUSED WITH AN ENSUING CLRNC AND CROSSED THE VOR AT 11000 FT, RATHER THAN INTXN GUELF AT 11000 FT.

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.