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

Attributes
ACN	183215
Time
Date	199107
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 1500 msl bound upper : 1500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : ord
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent : approach
Route In Use	approach : straight in
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	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 10500 flight time type : 7000
ASRS Report	183215
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	conflict : airborne less severe non adherence : clearance non adherence : published procedure non adherence : required legal separation
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action other
Consequence	faa : investigated
Miss Distance	horizontal : 2000 vertical : 500
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error Inter Facility Coordination Failure

Narrative:

Air carrier X being vectored for the ILS 22R at ord, a near miss almost occurred between our aircraft and air carrier Y. After being cleared for the ILS approach to 22R we were instructed to maintain 170 KTS until ridge OM and contact the ord tower on 126.9 at that point. As I was changing to the tower frequency at ridge for landing clearance, I heard the tower clear air carrier Y flight to land on our same runway. The first officer simultaneously saw the aircraft on a close-in right base for our intended runway. It was obvious that a conflict would occur if we did not take some action. We initiated a go around at that point. After several radio transmissions to the tower, it was apparent they were not aware of the conflict. When they did realize what was happening, they reclred air carrier Y flight to side-step to runway 22L (by the controller's phraseology it was the second change in landing runways for air carrier Y). At that point we were cleared to land but were unable to make a safe landing from our position, so we continued with our missed approach. When we asked the departure controller what had happened he gave us the local tower telephone number to talk to the supervisor. A very dangerous situation. See and be seen saved us from a collision in a controled environment. We had no TCAS.

Original NASA ASRS Text

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

Narrative: ACR X BEING VECTORED FOR THE ILS 22R AT ORD, A NEAR MISS ALMOST OCCURRED BTWN OUR ACFT AND ACR Y. AFTER BEING CLRED FOR THE ILS APCH TO 22R WE WERE INSTRUCTED TO MAINTAIN 170 KTS UNTIL RIDGE OM AND CONTACT THE ORD TWR ON 126.9 AT THAT POINT. AS I WAS CHANGING TO THE TWR FREQ AT RIDGE FOR LNDG CLRNC, I HEARD THE TWR CLR ACR Y FLT TO LAND ON OUR SAME RWY. THE FO SIMULTANEOUSLY SAW THE ACFT ON A CLOSE-IN R BASE FOR OUR INTENDED RWY. IT WAS OBVIOUS THAT A CONFLICT WOULD OCCUR IF WE DID NOT TAKE SOME ACTION. WE INITIATED A GAR AT THAT POINT. AFTER SEVERAL RADIO TRANSMISSIONS TO THE TWR, IT WAS APPARENT THEY WERE NOT AWARE OF THE CONFLICT. WHEN THEY DID REALIZE WHAT WAS HAPPENING, THEY RECLRED ACR Y FLT TO SIDE-STEP TO RWY 22L (BY THE CTLR'S PHRASEOLOGY IT WAS THE SECOND CHANGE IN LNDG RWYS FOR ACR Y). AT THAT POINT WE WERE CLRED TO LAND BUT WERE UNABLE TO MAKE A SAFE LNDG FROM OUR POS, SO WE CONTINUED WITH OUR MISSED APCH. WHEN WE ASKED THE DEP CTLR WHAT HAD HAPPENED HE GAVE US THE LCL TWR TELEPHONE NUMBER TO TALK TO THE SUPVR. A VERY DANGEROUS SITUATION. SEE AND BE SEEN SAVED US FROM A COLLISION IN A CTLED ENVIRONMENT. WE HAD NO TCAS.

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.