Medium large transport has conflict with light twin, TCASII alert saves the day.

Attributes
ACN	212377
Time
Date	199206
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : obk
State Reference	IL
Altitude	msl bound lower : 10200 msl bound upper : 10600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	enroute airway : zau
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Transport, Low Wing, 2 Recip Eng
Flight Phase	cruise other
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 18000 flight time type : 8000
ASRS Report	212377
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 100 flight time total : 14000 flight time type : 15
ASRS Report	212376
Events
Anomaly	non adherence : far other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 500 vertical : 700
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Descending into ord at 10200 MSL TCASII gave 'traffic' warning (aural and yellow target on map) within 1 second target turned red and TCASII commanded 'climb.' at this same time ATC called visual traffic 12 O'clock, 10000 ft. Climbed as directed by TCASII at 10600 ft (?) TCASII commanded 'monitor climb' and ATC called traffic 11 O'clock (?), and captain and first officer saw light twin private plane approximately 500 ft horizontal, and 1700 ft vertical eastbound. It is the captain's opinion that TCASII saved about 100 lives today. I am a believer in TCASII forever. Supplemental information from acn 212376. This incident was caused by VFR traffic following a heavily traveled route into O'hare. Perhaps a restriction could be placed on the VFR traffic using these approach and departure corridors surrounding major airport. For example, restr use between 18000 ft at pullman and 7000 ft at pappi. Another idea would be to highlight these areas in red on VFR charts and maps and classify them as high risk warning areas.

Original NASA ASRS Text

Title: MLG HAS CONFLICT WITH LIGHT TWIN, TCASII ALERT SAVES THE DAY.

Narrative: DSNDING INTO ORD AT 10200 MSL TCASII GAVE 'TFC' WARNING (AURAL AND YELLOW TARGET ON MAP) WITHIN 1 SECOND TARGET TURNED RED AND TCASII COMMANDED 'CLB.' AT THIS SAME TIME ATC CALLED VISUAL TFC 12 O'CLOCK, 10000 FT. CLBED AS DIRECTED BY TCASII AT 10600 FT (?) TCASII COMMANDED 'MONITOR CLB' AND ATC CALLED TFC 11 O'CLOCK (?), AND CAPT AND FO SAW LIGHT TWIN PRIVATE PLANE APPROX 500 FT HORIZ, AND 1700 FT VERT EBOUND. IT IS THE CAPT'S OPINION THAT TCASII SAVED ABOUT 100 LIVES TODAY. I AM A BELIEVER IN TCASII FOREVER. SUPPLEMENTAL INFO FROM ACN 212376. THIS INCIDENT WAS CAUSED BY VFR TFC FOLLOWING A HEAVILY TRAVELED RTE INTO O'HARE. PERHAPS A RESTRICTION COULD BE PLACED ON THE VFR TFC USING THESE APCH AND DEP CORRIDORS SURROUNDING MAJOR ARPT. FOR EXAMPLE, RESTR USE BTWN 18000 FT AT PULLMAN AND 7000 FT AT PAPPI. ANOTHER IDEA WOULD BE TO HIGHLIGHT THESE AREAS IN RED ON VFR CHARTS AND MAPS AND CLASSIFY THEM AS HIGH RISK WARNING AREAS.

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.