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

Attributes
ACN	203563
Time
Date	199203
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : buf
State Reference	NY
Altitude	msl bound lower : 11000 msl bound upper : 11000
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	climbout : intermediate altitude
Route In Use	enroute : direct enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent other
Route In Use	enroute : direct
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 8
ASRS Report	203563
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	atc equipment other atc equipment : unspecified
Resolutory Action	controller : issued new clearance other
Consequence	faa : investigated
Miss Distance	horizontal : 15000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X departed buffalo climbing (southwest). Air carrier Y was descending over buffalo (eastbound). The descending air carrier Y was issued 4 descent clrncs (stepping down). Conflict alert and mode C altitude reply from the descending air carrier Y alerted the controller that less than standard separation was possible (5 NM is required). The departing air carrier X was turned behind the descending air carrier Y. To prevent such occurrences in the future, fewer clrncs, i.e., aircraft leveling off in lieu of climbing/descending may be prudent. The chances of an error occurring increases with complexity and frequency congestion.

Original NASA ASRS Text

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

Narrative: ACR X DEPARTED BUFFALO CLBING (SW). ACR Y WAS DSNDING OVER BUFFALO (EBOUND). THE DSNDING ACR Y WAS ISSUED 4 DSCNT CLRNCS (STEPPING DOWN). CONFLICT ALERT AND MODE C ALT REPLY FROM THE DSNDING ACR Y ALERTED THE CTLR THAT LTSS WAS POSSIBLE (5 NM IS REQUIRED). THE DEPARTING ACR X WAS TURNED BEHIND THE DSNDING ACR Y. TO PREVENT SUCH OCCURRENCES IN THE FUTURE, FEWER CLRNCS, I.E., ACFT LEVELING OFF IN LIEU OF CLBING/DSNDING MAY BE PRUDENT. THE CHANCES OF AN ERROR OCCURRING INCREASES WITH COMPLEXITY AND FREQ CONGESTION.

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.