Loss of required 2000 ft separation between descending B737 and B747 at FL310.

Attributes
ACN	396267
Time
Date	199803
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : eni
State Reference	CA
Altitude	msl bound lower : 31000 msl bound upper : 32000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zoa
Operator	common carrier : air carrier
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B747 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 2 controller non radar : 8 controller radar : 5
ASRS Report	396267
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : required legal separation non adherence : published procedure
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 1200
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

B737 was descended from FL370 to FL240. Conflict not caught with B747 until conflict alert flashed. B737 reclred to FL330 but was already down to FL320.

Original NASA ASRS Text

Title: LOSS OF REQUIRED 2000 FT SEPARATION BTWN DSNDING B737 AND B747 AT FL310.

Narrative: B737 WAS DSNDED FROM FL370 TO FL240. CONFLICT NOT CAUGHT WITH B747 UNTIL CONFLICT ALERT FLASHED. B737 RECLRED TO FL330 BUT WAS ALREADY DOWN TO FL320.

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.