Narrative:

Established at 2500 ft MSL and cleared for the ILS runway 1 at gmu, we received a traffic alert that showed traffic at -100 ft. I immediately initiated a climb away from the traffic. We climbed a maximum of 200-300 ft above assigned altitude. Once cleared of traffic, I descended on the GS and landed uneventfully. In my opinion, the conflicting traffic was in the pattern at a nearby airfield and was 300 ft above the traffic pattern altitude.

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Original NASA ASRS Text

Title: A C550 ON AN ILS APCH AT 2500 FT EXECUTED AN AVOIDANCE MANEUVER FOLLOWING A TCAS ALERT.

Narrative: ESTABLISHED AT 2500 FT MSL AND CLRED FOR THE ILS RWY 1 AT GMU, WE RECEIVED A TFC ALERT THAT SHOWED TFC AT -100 FT. I IMMEDIATELY INITIATED A CLB AWAY FROM THE TFC. WE CLBED A MAX OF 200-300 FT ABOVE ASSIGNED ALT. ONCE CLRED OF TFC, I DSNDED ON THE GS AND LANDED UNEVENTFULLY. IN MY OPINION, THE CONFLICTING TFC WAS IN THE PATTERN AT A NEARBY AIRFIELD AND WAS 300 FT ABOVE THE TFC PATTERN ALT.

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.