A cpr gulfstream iv crew descended through its assigned altitude. Error admitted.

Attributes
ACN	340790
Time
Date	199607
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : yyz
State Reference	ON
Altitude	msl bound lower : 23000 msl bound upper : 28000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	general aviation : corporate
Make Model Name	Gulfstream IV
Operating Under FAR Part	Part 91
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 91
Person 1
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 90 flight time total : 5500 flight time type : 30
ASRS Report	340790
Person 2
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 12000 flight time type : 3000
ASRS Report	340791
Events
Anomaly	altitude deviation : excursion from assigned altitude altitude deviation : overshoot non adherence : clearance
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During descent into toronto, our gulfstream iv, was directed to descend and maintain FL230 (or so we thought). We read back the clearance, began our dsnct, and set 23000 ft in our altitude select window. Our altimeters remained set at 29.92. As we descended through FL280, the center controller asked us our altitude. We reported through FL255 for FL230. The controller advised that we had been assigned FL280, but to continue descent to 12000 ft. He indicated that he may have missed our original readback, but seemed unconcerned about possible conflicts. The remainder of our flight was uneventful.

Original NASA ASRS Text

Title: A CPR GULFSTREAM IV CREW DSNDED THROUGH ITS ASSIGNED ALT. ERROR ADMITTED.

Narrative: DURING DSCNT INTO TORONTO, OUR GULFSTREAM IV, WAS DIRECTED TO DSND AND MAINTAIN FL230 (OR SO WE THOUGHT). WE READ BACK THE CLRNC, BEGAN OUR DSNCT, AND SET 23000 FT IN OUR ALT SELECT WINDOW. OUR ALTIMETERS REMAINED SET AT 29.92. AS WE DSNDED THROUGH FL280, THE CTR CTLR ASKED US OUR ALT. WE RPTED THROUGH FL255 FOR FL230. THE CTLR ADVISED THAT WE HAD BEEN ASSIGNED FL280, BUT TO CONTINUE DSCNT TO 12000 FT. HE INDICATED THAT HE MAY HAVE MISSED OUR ORIGINAL READBACK, BUT SEEMED UNCONCERNED ABOUT POSSIBLE CONFLICTS. THE REMAINDER OF OUR FLT WAS UNEVENTFUL.

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.