Air carrier X overtook air carrier Y on departure climb. Less than standard separation. System error...

Attributes
ACN	193100
Time
Date	199110
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord
State Reference	IL
Altitude	msl bound lower : 3000 msl bound upper : 3000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : ord
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	climbout : intermediate altitude cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : non radar
ASRS Report	193100
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	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 12000 vertical : 0
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	Operational Error

Narrative:

Departed air carrier X off runway 22L left turn heading 120 degree. Observed 22R arrival landing instructed aircraft to turn off and hold short of runway 9L for departing aircraft. Clear an light transport runway 9L turn right 100 degree. Aircraft departed crossed arrival. Then I observed air carrier X off 22L in a left turn which appeared shallower than normal. Then cleared air carrier Y for takeoff runway 22L turn left 120 degree. Observed air carrier Y lift off and turn. I immediately became concerned about the possibility of not having 3 mi longitudinal separation required. I observed air carrier X airspeed 180 KTS. Normally through my experiences I knew air carrier X airspeed would be building. I considered my other options. Turning air carrier Y left was no good because of the 9L departure. Turning right would put air carrier Y in midways airspace violating a tower order. I observed spacing to be a 'tight' 3 mi. Air carrier Y was leaving my airspace. I decided air carrier X would be building his speed and separation would increase. I shipped air carrier Y. I continued to monitor the situation. Air carrier Y speed increased dramatically. Air carrier X speed remained the same. Loss of separation occurred. I reported it to the supervisor.

Original NASA ASRS Text

Title: ACR X OVERTOOK ACR Y ON DEP CLB. LTSS. SYS ERROR.

Narrative: DEPARTED ACR X OFF RWY 22L L TURN HDG 120 DEG. OBSERVED 22R ARR LNDG INSTRUCTED ACFT TO TURN OFF AND HOLD SHORT OF RWY 9L FOR DEPARTING ACFT. CLR AN LTT RWY 9L TURN R 100 DEG. ACFT DEPARTED CROSSED ARR. THEN I OBSERVED ACR X OFF 22L IN A L TURN WHICH APPEARED SHALLOWER THAN NORMAL. THEN CLRED ACR Y FOR TKOF RWY 22L TURN L 120 DEG. OBSERVED ACR Y LIFT OFF AND TURN. I IMMEDIATELY BECAME CONCERNED ABOUT THE POSSIBILITY OF NOT HAVING 3 MI LONGITUDINAL SEPARATION REQUIRED. I OBSERVED ACR X AIRSPD 180 KTS. NORMALLY THROUGH MY EXPERIENCES I KNEW ACR X AIRSPD WOULD BE BUILDING. I CONSIDERED MY OTHER OPTIONS. TURNING ACR Y L WAS NO GOOD BECAUSE OF THE 9L DEP. TURNING R WOULD PUT ACR Y IN MIDWAYS AIRSPACE VIOLATING A TWR ORDER. I OBSERVED SPACING TO BE A 'TIGHT' 3 MI. ACR Y WAS LEAVING MY AIRSPACE. I DECIDED ACR X WOULD BE BUILDING HIS SPD AND SEPARATION WOULD INCREASE. I SHIPPED ACR Y. I CONTINUED TO MONITOR THE SITUATION. ACR Y SPD INCREASED DRAMATICALLY. ACR X SPD REMAINED THE SAME. LOSS OF SEPARATION OCCURRED. I RPTED IT TO THE SUPVR.

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.