Air carrier PIC reports non detection of VFR mode C aircraft on TCASII while in proximity of TCA.

Attributes
ACN	246938
Time
Date	199307
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : lga
State Reference	NY
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90 tower : psm
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other cruise other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 150 flight time total : 20000 flight time type : 4000
ASRS Report	246938
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

With a fully operational TCASII, many VFR targets that we knew to be mode C equipped did not show up on TCASII, and we thought we would point this out, as confidence in TCASII is an important element.

Original NASA ASRS Text

Title: ACR PIC RPTS NON DETECTION OF VFR MODE C ACFT ON TCASII WHILE IN PROX OF TCA.

Narrative: WITH A FULLY OPERATIONAL TCASII, MANY VFR TARGETS THAT WE KNEW TO BE MODE C EQUIPPED DID NOT SHOW UP ON TCASII, AND WE THOUGHT WE WOULD POINT THIS OUT, AS CONFIDENCE IN TCASII IS AN IMPORTANT ELEMENT.

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.