Narrative:

I made a normal approach and landing at mtn. While taxiing, I was advised to contact potomac TRACON. When I contacted them, they told me that they had received several hits on a 'primary' target, then my dedicated squawk appeared. I had confirmed with potomac on the first flight that the transponder was showing correctly on their screens. I had not changed codes on the transponder at any time. The cockpit indication was that the transponder was working. The aircraft involved was taken OTS immediately and both xponders were svced.

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Original NASA ASRS Text

Title: POTOMAC TRACON NOTES AN ACFT WITHOUT A XPONDER ON APCH TO MTN, MD, WAS REQUIRED FOR OP IN THE AREA OF THE DC ADIZ.

Narrative: I MADE A NORMAL APCH AND LNDG AT MTN. WHILE TAXIING, I WAS ADVISED TO CONTACT POTOMAC TRACON. WHEN I CONTACTED THEM, THEY TOLD ME THAT THEY HAD RECEIVED SEVERAL HITS ON A 'PRIMARY' TARGET, THEN MY DEDICATED SQUAWK APPEARED. I HAD CONFIRMED WITH POTOMAC ON THE FIRST FLT THAT THE XPONDER WAS SHOWING CORRECTLY ON THEIR SCREENS. I HAD NOT CHANGED CODES ON THE XPONDER AT ANY TIME. THE COCKPIT INDICATION WAS THAT THE XPONDER WAS WORKING. THE ACFT INVOLVED WAS TAKEN OTS IMMEDIATELY AND BOTH XPONDERS WERE SVCED.

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.