Air carrier has TCASII RA. Responds.

Attributes
ACN	181722
Time
Date	199106
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : cmh
State Reference	OH
Altitude	msl bound lower : 4000 msl bound upper : 4500
Environment
Flight Conditions	Marginal
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cmh
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 : on vectors
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft, High Wing, 1 Eng, Fixed Gear
Flight Phase	cruise other
Route In Use	enroute : on vectors
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 10000 flight time type : 40
ASRS Report	181722
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 200 flight time total : 10000 flight time type : 4000
ASRS Report	181733
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : clearance other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	horizontal : 0 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

In-flight visibility was less than a mi in haze. Tower visibility was reported at 4 mi. Approach pointed out VFR traffic at 12 O'clock opp direction at 4 mi who was at 3500'. We were at 4000'. Initially his altitude read 500' below us. As he approached 2 mi his altitude read 300' below and climbing. TCASII immediately commanded 'climb, climb now!' we followed the TCASII climb instructions to 4500' and stayed there until TCASII advised 'clear of conflict.' ATC was advised and we returned to assigned altitude and made a non-eventful landing. Never did see the traffic. ATC advised that light aircraft had 'strayed' off his altitude. TCASII worked wonderfully! To avoid further conflicts would recommend that we not mix light aircraft in same patterns as jets. Also we need a better way of determining pattern in-flight visibility, not tower visibility.

Original NASA ASRS Text

Title: ACR HAS TCASII RA. RESPONDS.

Narrative: INFLT VIS WAS LESS THAN A MI IN HAZE. TWR VIS WAS RPTED AT 4 MI. APCH POINTED OUT VFR TFC AT 12 O'CLOCK OPP DIRECTION AT 4 MI WHO WAS AT 3500'. WE WERE AT 4000'. INITIALLY HIS ALT READ 500' BELOW US. AS HE APCHED 2 MI HIS ALT READ 300' BELOW AND CLBING. TCASII IMMEDIATELY COMMANDED 'CLB, CLB NOW!' WE FOLLOWED THE TCASII CLB INSTRUCTIONS TO 4500' AND STAYED THERE UNTIL TCASII ADVISED 'CLR OF CONFLICT.' ATC WAS ADVISED AND WE RETURNED TO ASSIGNED ALT AND MADE A NON-EVENTFUL LNDG. NEVER DID SEE THE TFC. ATC ADVISED THAT LIGHT ACFT HAD 'STRAYED' OFF HIS ALT. TCASII WORKED WONDERFULLY! TO AVOID FURTHER CONFLICTS WOULD RECOMMEND THAT WE NOT MIX LIGHT ACFT IN SAME PATTERNS AS JETS. ALSO WE NEED A BETTER WAY OF DETERMINING PATTERN INFLT VIS, NOT TWR VIS.

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.