Controller descended an air carrier through an occupied altitude resulting in less than standard sep...

Attributes
ACN	201318
Time
Date	199202
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : sav
State Reference	GA
Altitude	msl bound lower : 29000 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 1
ASRS Report	201318
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller military : 4 controller non radar : 3 controller radar : 33
ASRS Report	200625
Events
Anomaly	non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	Other
Miss Distance	horizontal : 18000 vertical : 1400
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X checked in level at FL310. Traffic was light. Air carrier X landing jax international was issued clearance to cross 50 north of ssi at FL240. He stayed at FL310 for about 2 mins, then started his descent into the face of an small transport Y at FL290. A relief briefing had started and the relieving controller questioned the 2 aircraft and issued clrncs to insure separation but if had already been lost. Complacency is why this error occurred. Supplemental information from acn 200625: as I was relieving the radar controller, I question him on the restriction and realized that he had overlooked the small transport. I then told the air carrier to maintain FL310. The next radar hit show him descending, so I gave the acfts turns to increase separation, but was too late to avoid an incident.

Original NASA ASRS Text

Title: CTLR DSNDED AN ACR THROUGH AN OCCUPIED ALT RESULTING IN LTSS.

Narrative: ACR X CHKED IN LEVEL AT FL310. TFC WAS LIGHT. ACR X LNDG JAX INTL WAS ISSUED CLRNC TO CROSS 50 N OF SSI AT FL240. HE STAYED AT FL310 FOR ABOUT 2 MINS, THEN STARTED HIS DSCNT INTO THE FACE OF AN SMT Y AT FL290. A RELIEF BRIEFING HAD STARTED AND THE RELIEVING CTLR QUESTIONED THE 2 ACFT AND ISSUED CLRNCS TO INSURE SEPARATION BUT IF HAD ALREADY BEEN LOST. COMPLACENCY IS WHY THIS ERROR OCCURRED. SUPPLEMENTAL INFO FROM ACN 200625: AS I WAS RELIEVING THE RADAR CTLR, I QUESTION HIM ON THE RESTRICTION AND REALIZED THAT HE HAD OVERLOOKED THE SMT. I THEN TOLD THE AIR CARRIER TO MAINTAIN FL310. THE NEXT RADAR HIT SHOW HIM DSNDING, SO I GAVE THE ACFTS TURNS TO INCREASE SEPARATION, BUT WAS TOO LATE TO AVOID AN INCIDENT.

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.

Controller descended an air carrier through an occupied altitude resulting in less than standard separation.