Less than standard separation between air carrier X and Y while on approach. System error.

Attributes
ACN	121127
Time
Date	198908
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 4000 msl bound upper : 4500
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent : approach descent other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	descent : approach
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 11000 flight time type : 450
ASRS Report	121127
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
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 : 1500 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Air carrier X on approach to 22R at ord. We were asked to slow down. While passing 4500' MSL, we were advised to hold our altitude and turn right immediately. As we turned right and held altitude, I saw an air carrier Y large transport turn left below us. Apparently ATC tried to vector the large transport on a left base to final in front of us. We were still slowing down and he was much slower than us, so ATC vectored us apart, then back to final. Upon landing, I called the approach supervisor and he said the tapes would be pulled and he would investigate. I was told the air carrier Y large transport was slower to turn than ATC had anticipated.

Original NASA ASRS Text

Title: LESS THAN STANDARD SEPARATION BETWEEN ACR X AND Y WHILE ON APCH. SYSTEM ERROR.

Narrative: ACR X ON APCH TO 22R AT ORD. WE WERE ASKED TO SLOW DOWN. WHILE PASSING 4500' MSL, WE WERE ADVISED TO HOLD OUR ALT AND TURN RIGHT IMMEDIATELY. AS WE TURNED RIGHT AND HELD ALT, I SAW AN ACR Y LGT TURN LEFT BELOW US. APPARENTLY ATC TRIED TO VECTOR THE LGT ON A LEFT BASE TO FINAL IN FRONT OF US. WE WERE STILL SLOWING DOWN AND HE WAS MUCH SLOWER THAN US, SO ATC VECTORED US APART, THEN BACK TO FINAL. UPON LNDG, I CALLED THE APCH SUPVR AND HE SAID THE TAPES WOULD BE PULLED AND HE WOULD INVESTIGATE. I WAS TOLD THE ACR Y LGT WAS SLOWER TO TURN THAN ATC HAD ANTICIPATED.

Data retrieved from NASA's ASRS site as of August 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.