Flight crew of commuter descended 500 ft and made turn to avoid traffic. No radar contact with traff...

Attributes
ACN	198702
Time
Date	199201
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lax airport : sna
State Reference	CA
Altitude	msl bound lower : 4500 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : sna
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : instrument pilot : atp
Experience	flight time last 90 days : 250 flight time total : 3000
ASRS Report	198702
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe
Independent Detector	other flight crewa
Resolutory Action	flight crew : took evasive action
Consequence	Other
Miss Distance	horizontal : 1500 vertical : 500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While on a vector by coast approach to sna from lax 5000 ft MSL heading 110 degree in cruise flight, both flight crew members idented an approaching aircraft at 11 O'clock position 1/4 mi on converging course at same altitude (5000) and climbing slowly. We took evasive action, right turn 30 degree and descent of 500 ft to avoid collision. Inquired approach of radar contact with said other aircraft. A response of 'nothing on screen' was told. Advised ATC of situation and continued with the rest of flight.

Original NASA ASRS Text

Title: FLC OF COMMUTER DSNDED 500 FT AND MADE TURN TO AVOID TFC. NO RADAR CONTACT WITH TFC BY TRACON.

Narrative: WHILE ON A VECTOR BY COAST APCH TO SNA FROM LAX 5000 FT MSL HDG 110 DEG IN CRUISE FLT, BOTH FLC MEMBERS IDENTED AN APCHING ACFT AT 11 O'CLOCK POS 1/4 MI ON CONVERGING COURSE AT SAME ALT (5000) AND CLBING SLOWLY. WE TOOK EVASIVE ACTION, R TURN 30 DEG AND DSNT OF 500 FT TO AVOID COLLISION. INQUIRED APCH OF RADAR CONTACT WITH SAID OTHER ACFT. A RESPONSE OF 'NOTHING ON SCREEN' WAS TOLD. ADVISED ATC OF SITUATION AND CONTINUED WITH THE REST OF FLT.

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.

Flight crew of commuter descended 500 ft and made turn to avoid traffic. No radar contact with traffic by TRACON.