Less than standard separation between 2 air carrier aircraft in toronto airspace.

Attributes
ACN	155394
Time
Date	199008
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : 4qo
State Reference	ON
Altitude	msl bound lower : 31000 msl bound upper : 35000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : czyz
Operator	common carrier : air carrier
Make Model Name	Widebody, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 160 flight time total : 11000
ASRS Report	155394
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : overshoot non adherence : required legal separation other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 30000 vertical : 2000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

We were at cruise en route to dtw from cdg and were level at FL390. We received a clearance to descend to 31000' by 100 NM north of aylmer VOR. This was approximately 180 degrees north of 4QO at the time. Clearance amended to descend to 35000' now, then pilot's discretion to cross 100 north of aylmer at 31000'. At 33000' center said to turn right immediately and descend now to 31000'. There was company traffic Y coming our way I think at 33000'. I saw company flight Y pass 3-5 mi east and above by 2000'. My readback of clearance was down to 35000' cross aylmer VOR 100 north at 310 degrees. There was miscom somewhere. Center thought they only cleared us to FL350. I read back 'down to 350 cross, 100 north of aylmer VOR at 310.' there were buildups in area and I can't remember if either flight was deviating of the time.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN 2 ACR ACFT IN TORONTO AIRSPACE.

Narrative: WE WERE AT CRUISE ENRTE TO DTW FROM CDG AND WERE LEVEL AT FL390. WE RECEIVED A CLRNC TO DSND TO 31000' BY 100 NM N OF AYLMER VOR. THIS WAS APPROX 180 DEGS N OF 4QO AT THE TIME. CLRNC AMENDED TO DSND TO 35000' NOW, THEN PLT'S DISCRETION TO CROSS 100 N OF AYLMER AT 31000'. AT 33000' CENTER SAID TO TURN RIGHT IMMEDIATELY AND DSND NOW TO 31000'. THERE WAS COMPANY TFC Y COMING OUR WAY I THINK AT 33000'. I SAW COMPANY FLT Y PASS 3-5 MI E AND ABOVE BY 2000'. MY READBACK OF CLRNC WAS DOWN TO 35000' CROSS AYLMER VOR 100 N AT 310 DEGS. THERE WAS MISCOM SOMEWHERE. CENTER THOUGHT THEY ONLY CLRED US TO FL350. I READ BACK 'DOWN TO 350 CROSS, 100 N OF AYLMER VOR AT 310.' THERE WERE BUILDUPS IN AREA AND I CAN'T REMEMBER IF EITHER FLT WAS DEVIATING OF THE TIME.

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.