Narrative:

While on descent into ilm, passing through 3000 ft MSL, being vectored for visual approach runway 24, had a near miss with a piper tomahawk converging from the 1 O'clock position. Evasive action was necessary to avoid impact. We were in a descent and missed the other aircraft from above. It was close enough that I was able to see the pilot's face. TCASII was in RA/TA mode, he did not appear on the screen nor was an RA triggered. Approach was advised and they did not have the other airplane on radar either. WX was VFR, daytime, with flight visibility of 20+ mi. Our approximately heading was 120 degrees, other aircraft estimated heading was 310 degrees. This is my closest point of possible contact with another aircraft in-flight to date. Preventable in the future? Yes. How? Mandatory use of a mode C or better transponder. While not all aircraft have TCASII, ours did, it only takes 1 aircraft to take corrective action. However, if 1 aircraft has no transponder, TCASII is useless, as is the majority of the air traffic controllers radar. I am an first officer for a fractional cpr ownership company. I have over 4000 hours of flight experience, from small cessnas to boeing 727's. This is a situation I feel will become more and more commonplace with the rise in fractional aircraft ownership. We fly into many uncontrolled fields where this type of situation is most likely to occur.

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Original NASA ASRS Text

Title: NMAC BTWN A PIPER TOMAHAWK AND A C560XL IN THE ARR AREA OF ILM. THE TOMAHAWK WAS NOT DETECTED BY ATC RADAR OR TCASII ON BOARD THE C560XL.

Narrative: WHILE ON DSCNT INTO ILM, PASSING THROUGH 3000 FT MSL, BEING VECTORED FOR VISUAL APCH RWY 24, HAD A NEAR MISS WITH A PIPER TOMAHAWK CONVERGING FROM THE 1 O'CLOCK POS. EVASIVE ACTION WAS NECESSARY TO AVOID IMPACT. WE WERE IN A DSCNT AND MISSED THE OTHER ACFT FROM ABOVE. IT WAS CLOSE ENOUGH THAT I WAS ABLE TO SEE THE PLT'S FACE. TCASII WAS IN RA/TA MODE, HE DID NOT APPEAR ON THE SCREEN NOR WAS AN RA TRIGGERED. APCH WAS ADVISED AND THEY DID NOT HAVE THE OTHER AIRPLANE ON RADAR EITHER. WX WAS VFR, DAYTIME, WITH FLT VISIBILITY OF 20+ MI. OUR APPROX HEADING WAS 120 DEGS, OTHER ACFT ESTIMATED HEADING WAS 310 DEGS. THIS IS MY CLOSEST POINT OF POSSIBLE CONTACT WITH ANOTHER ACFT INFLT TO DATE. PREVENTABLE IN THE FUTURE? YES. HOW? MANDATORY USE OF A MODE C OR BETTER XPONDER. WHILE NOT ALL ACFT HAVE TCASII, OURS DID, IT ONLY TAKES 1 ACFT TO TAKE CORRECTIVE ACTION. HOWEVER, IF 1 ACFT HAS NO XPONDER, TCASII IS USELESS, AS IS THE MAJORITY OF THE AIR TFC CTLRS RADAR. I AM AN FO FOR A FRACTIONAL CPR OWNERSHIP COMPANY. I HAVE OVER 4000 HRS OF FLT EXPERIENCE, FROM SMALL CESSNAS TO BOEING 727'S. THIS IS A SIT I FEEL WILL BECOME MORE AND MORE COMMONPLACE WITH THE RISE IN FRACTIONAL ACFT OWNERSHIP. WE FLY INTO MANY UNCTLED FIELDS WHERE THIS TYPE OF SIT IS MOST LIKELY TO OCCUR.

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.