Air carrier X TCASII RA with VFR Y. Evasive action taken climb. See and avoid concept.

Attributes
ACN	272633
Time
Date	199405
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : rfd
State Reference	IL
Altitude	msl bound lower : 9600 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise other
Route In Use	enroute : direct enroute airway : zau
Flight Plan	IFR
Aircraft 2
Operator	general aviation : personal
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Route In Use	enroute : direct
Flight Plan	VFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller non radar : 10 controller radar : 8
ASRS Report	272633
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	vertical : 400
Supplementary
Air Traffic Incident	other

Narrative:

Air carrier X inbound to ord at 1000 ft. I issued VFR traffic Y to X, 12 O'clock 15 mi slow moving at 9600 ft and asked to advise in sight or on TCASII. I then issued X a descent to 9000 ft. X asked to delay that descent until clear of traffic because we're about to get an RA. X then got an RA to climb. The TCASII worked well and is a good backup to the ATC system. If I had been busy, I might have missed the slow VFR and it could have prevented a near midair collision.

Original NASA ASRS Text

Title: ACR X TCASII RA WITH VFR Y. EVASIVE ACTION TAKEN CLB. SEE AND AVOID CONCEPT.

Narrative: ACR X INBOUND TO ORD AT 1000 FT. I ISSUED VFR TFC Y TO X, 12 O'CLOCK 15 MI SLOW MOVING AT 9600 FT AND ASKED TO ADVISE IN SIGHT OR ON TCASII. I THEN ISSUED X A DSCNT TO 9000 FT. X ASKED TO DELAY THAT DSCNT UNTIL CLR OF TFC BECAUSE WE'RE ABOUT TO GET AN RA. X THEN GOT AN RA TO CLB. THE TCASII WORKED WELL AND IS A GOOD BACKUP TO THE ATC SYS. IF I HAD BEEN BUSY, I MIGHT HAVE MISSED THE SLOW VFR AND IT COULD HAVE PREVENTED A NMAC.

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.