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

Attributes
ACN	148911
Time
Date	199006
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : lan
State Reference	MI
Altitude	msl bound lower : 30300 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 31
ASRS Report	148911
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 : 27600 vertical : 700
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X and Y on vectors to ord adhering to 15 mit restrictions as per LOA with ZAU. Heavy amount of traffic in sector. Extremely complex vectors and altitudes to get spacing requirements for traffic to ord. Vectors and altitudes were used to separate air carrier X and Y involved. Contributing factors were turbulence and not talking to other aircraft when needed on frequency. Callback conversation with reporter revealed the following: reporter states types of aircraft were air carrier X (medium large transport) and air carrier Y (large transport). Sep was horizontal: 4.6 mi, vertical: 700'. The reporter stated he was distraction by traffic in the other end of the sector. Traffic from another center was not establishing communication in a timely manner. Air carrier X had to be put in trail with air carrier Y. Air carrier X was descended to the same altitude as air carrier Y. The reporter did not notice that air carrier X was faster than air carrier Y. C/a activated but not in time for the reporter to keep standard radar separation. Reporter has 31 yrs of experience and is now retired.

Original NASA ASRS Text

Title: ACR X HAD LESS THAN STANDARD SEPARATION FROM ACR Y. SYSTEM ERROR.

Narrative: ACR X AND Y ON VECTORS TO ORD ADHERING TO 15 MIT RESTRICTIONS AS PER LOA WITH ZAU. HEAVY AMOUNT OF TFC IN SECTOR. EXTREMELY COMPLEX VECTORS AND ALTS TO GET SPACING REQUIREMENTS FOR TFC TO ORD. VECTORS AND ALTS WERE USED TO SEPARATE ACR X AND Y INVOLVED. CONTRIBUTING FACTORS WERE TURB AND NOT TALKING TO OTHER ACFT WHEN NEEDED ON FREQ. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR STATES TYPES OF ACFT WERE ACR X (MLG) AND ACR Y (LGT). SEP WAS HORIZ: 4.6 MI, VERT: 700'. THE RPTR STATED HE WAS DISTR BY TFC IN THE OTHER END OF THE SECTOR. TFC FROM ANOTHER CENTER WAS NOT ESTABLISHING COM IN A TIMELY MANNER. ACR X HAD TO BE PUT IN TRAIL WITH ACR Y. ACR X WAS DSNDED TO THE SAME ALT AS ACR Y. THE RPTR DID NOT NOTICE THAT ACR X WAS FASTER THAN ACR Y. C/A ACTIVATED BUT NOT IN TIME FOR THE RPTR TO KEEP STANDARD RADAR SEPARATION. RPTR HAS 31 YRS OF EXPERIENCE AND IS NOW RETIRED.

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.