ARTCC radar controller descended an MD80 through the altitude of a DC9 overflt with less than standard separation. Reporter admits that the overflt was forgotten and blended into the backgnd on the scope. Controller turned both aircraft, but separation was lost anyway.

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Attributes
ACN	369959
Time
Date	199705
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : brl
State Reference	IA
Altitude	msl bound lower : 31000 msl bound upper : 31000
Environment
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zau
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 6
ASRS Report	369959
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
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 24000 vertical : 1000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Was working ord inbound rush. Many aircraft on frequency and in airspace. Multiple aircraft on vectors for sequencing. Descended first aircraft through altitude of second. Looked back moments later and saw the confliction. Turned both aircraft away from each other and descended overflt. The overflt had been on frequency for about 5 mins slightly south of the normal route. When he had checked on, it was not busy and no apparent conflictions existed. In the next few mins, 6-8 aircraft on 2 airways appeared, each paired with another aircraft, requiring assigned speeds and vectors for at least 1 of each pair. The overflt had already 'blended' into the backgnd and I forgot he was there. Recommendation: FL310 southeast to northwest overflts are very hazardous at rush times. All inbounds are at FL330 and have 75 mi to descend to FL240 and be put in trail. Rerouting or taking flts to lower altitude would help greatly, but the airlines resist this.

Original NASA ASRS Text

Title: ARTCC RADAR CTLR DSNDED AN MD80 THROUGH THE ALT OF A DC9 OVERFLT WITH LTSS. RPTR ADMITS THAT THE OVERFLT WAS FORGOTTEN AND BLENDED INTO THE BACKGND ON THE SCOPE. CTLR TURNED BOTH ACFT, BUT SEPARATION WAS LOST ANYWAY.

Narrative: WAS WORKING ORD INBOUND RUSH. MANY ACFT ON FREQ AND IN AIRSPACE. MULTIPLE ACFT ON VECTORS FOR SEQUENCING. DSNDED FIRST ACFT THROUGH ALT OF SECOND. LOOKED BACK MOMENTS LATER AND SAW THE CONFLICTION. TURNED BOTH ACFT AWAY FROM EACH OTHER AND DSNDED OVERFLT. THE OVERFLT HAD BEEN ON FREQ FOR ABOUT 5 MINS SLIGHTLY S OF THE NORMAL RTE. WHEN HE HAD CHKED ON, IT WAS NOT BUSY AND NO APPARENT CONFLICTIONS EXISTED. IN THE NEXT FEW MINS, 6-8 ACFT ON 2 AIRWAYS APPEARED, EACH PAIRED WITH ANOTHER ACFT, REQUIRING ASSIGNED SPDS AND VECTORS FOR AT LEAST 1 OF EACH PAIR. THE OVERFLT HAD ALREADY 'BLENDED' INTO THE BACKGND AND I FORGOT HE WAS THERE. RECOMMENDATION: FL310 SE TO NW OVERFLTS ARE VERY HAZARDOUS AT RUSH TIMES. ALL INBOUNDS ARE AT FL330 AND HAVE 75 MI TO DSND TO FL240 AND BE PUT IN TRAIL. REROUTING OR TAKING FLTS TO LOWER ALT WOULD HELP GREATLY, BUT THE AIRLINES RESIST THIS.

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.