Air carrier X had less than standard separation from air carrier Y. System error.

Attributes
ACN	251563
Time
Date	199309
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lvt
State Reference	TN
Altitude	msl bound lower : 24000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zme
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	general aviation : corporate
Make Model Name	Light Transport, Low Wing, 2 Turbojet Eng
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 military : 4 controller non radar : 7 controller radar : 4
ASRS Report	251563
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : published procedure non adherence : required legal separation
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 21000 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

I was working the radar controller position at rebel high sector during the nashville arrival phase. Air carrier X was vectored left of course for traffic in the descent and also for spacing. Then I descended air carrier X from FL280 to FL240. After coordinating with the co-altitude sector for a lower altitude for air carrier X, I descended him to FL190. This was to get air carrier X under traffic climbing out of nashville. Cpr Y was turned to go behind air carrier X and descend to FL240. After seeing that the initial vector wasn't going to be sufficient, cpr Y was turned further left. I called traffic to air carrier X at 2 O'clock, 6 mi, sebound at FL240 and instructed him to report leaving FL230. Lateral separation was lost before vertical separation was established. Later, going back through the flight progress strips, I noticed that air carrier X and cpr Y were both assigned 280 KTS IAS by the previous sector. Had I looked at the strips more carefully earlier, I wouldn't have expected a very good rate of descent from air carrier X and would have turned cpr Y more to begin with.

Original NASA ASRS Text

Title: ACR X HAD LTSS FROM ACR Y. SYS ERROR.

Narrative: I WAS WORKING THE RADAR CTLR POS AT REBEL HIGH SECTOR DURING THE NASHVILLE ARR PHASE. ACR X WAS VECTORED L OF COURSE FOR TFC IN THE DSCNT AND ALSO FOR SPACING. THEN I DSNDED ACR X FROM FL280 TO FL240. AFTER COORDINATING WITH THE CO-ALT SECTOR FOR A LOWER ALT FOR ACR X, I DSNDED HIM TO FL190. THIS WAS TO GET ACR X UNDER TFC CLBING OUT OF NASHVILLE. CPR Y WAS TURNED TO GO BEHIND ACR X AND DSND TO FL240. AFTER SEEING THAT THE INITIAL VECTOR WASN'T GOING TO BE SUFFICIENT, CPR Y WAS TURNED FURTHER L. I CALLED TFC TO ACR X AT 2 O'CLOCK, 6 MI, SEBOUND AT FL240 AND INSTRUCTED HIM TO RPT LEAVING FL230. LATERAL SEPARATION WAS LOST BEFORE VERT SEPARATION WAS ESTABLISHED. LATER, GOING BACK THROUGH THE FLT PROGRESS STRIPS, I NOTICED THAT ACR X AND CPR Y WERE BOTH ASSIGNED 280 KTS IAS BY THE PREVIOUS SECTOR. HAD I LOOKED AT THE STRIPS MORE CAREFULLY EARLIER, I WOULDN'T HAVE EXPECTED A VERY GOOD RATE OF DSCNT FROM ACR X AND WOULD HAVE TURNED CPR Y MORE TO BEGIN WITH.

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.