Opposite direction A320 at FL310 descends 200 ft when passing a B73Q level at FL330.

Attributes
ACN	456850
Time
Date	199912
Day	Wed
Local Time Of Day	1201 To 1800
Place
State Reference	NE
Altitude	msl bound lower : 30800 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zmp.artcc
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Aircraft 2
Controlling Facilities	artcc : zmp.artcc
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 6
ASRS Report	456850
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	atc equipment other atc equipment : radar aircraft equipment : tcas other controllera other flight crewa
Resolutory Action	flight crew : took precautionary avoidance action flight crew : returned to assigned airspace
Miss Distance	horizontal : 0 vertical : 2000
Supplementary
Problem Areas	Aircraft Airspace Structure
Primary Problem	Aircraft

Narrative:

The A320 X was wbound at FL310 and the B73Q Y was eastbound at FL330. The wbound got an RA from the TCASII and descended 200 ft. There was no traffic below the A320. No evasive action was taken. The A320 returned to assigned altitude and proceeded on course.

Original NASA ASRS Text

Title: OPPOSITE DIRECTION A320 AT FL310 DSNDS 200 FT WHEN PASSING A B73Q LEVEL AT FL330.

Narrative: THE A320 X WAS WBOUND AT FL310 AND THE B73Q Y WAS EBOUND AT FL330. THE WBOUND GOT AN RA FROM THE TCASII AND DSNDED 200 FT. THERE WAS NO TFC BELOW THE A320. NO EVASIVE ACTION WAS TAKEN. THE A320 RETURNED TO ASSIGNED ALT AND PROCEEDED ON COURSE.

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.