Narrative:

I was approaching pwk from the wnw. I made contact with the tower, gave my approximately location, my inbound intentions and ATIS. (I had noticed that tower had just switched controllers.) the tower responded to me with just my call sign. I repeated my intentions. The tower then confirmed my intentions. I heard a call from cirrus traffic over arlington heights race course, just south and west of my positioning. The tower told me that I was #2 for runway 16 and requested that I report when I had the landing traffic in sight. A few seconds later I called the tower and told them that I had the landing traffic, on final, in sight. At that moment I caught the aircraft Y just below me (less than 100 ft) off my 8 O'clock position, heading in a northerly direction. I also mentioned to the tower that 'the cirrus had just passed below me.' on my approach to final the controller instructed me to go around due to delayed traffic on the runway. I proceed to go around and aircraft Y was cleared to land and upon landing taxied to FBO. I was cleared to land and I also taxied to FBO (my base). I just missed meeting the PIC of aircraft Y but his identify was given to me by the line and front desk staff at FBO. I contacted the tower to discuss this near miss. They were well aware of the incident. The controller in charge told me that aircraft Y had either failed to squawk the assigned code or had his transponder off, I don't recall. What caused this problem? I think that the new controller may not have been fully aware of the situation. The controller seem a bit 'out of sink' for some reason. I did not know that the pilot of aircraft Y was experiencing some sort of transponder trouble and could not be idented by the tower.

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Original NASA ASRS Text

Title: NMAC OCCURRED WHEN AN SR22 CROSSED WITHIN 100 FT BELOW A TB20 ON A MODIFIED BASE LNDG RWY 16 AT PWK.

Narrative: I WAS APCHING PWK FROM THE WNW. I MADE CONTACT WITH THE TWR, GAVE MY APPROX LOCATION, MY INBOUND INTENTIONS AND ATIS. (I HAD NOTICED THAT TWR HAD JUST SWITCHED CTLRS.) THE TWR RESPONDED TO ME WITH JUST MY CALL SIGN. I REPEATED MY INTENTIONS. THE TWR THEN CONFIRMED MY INTENTIONS. I HEARD A CALL FROM CIRRUS TFC OVER ARLINGTON HEIGHTS RACE COURSE, JUST S AND W OF MY POSITIONING. THE TWR TOLD ME THAT I WAS #2 FOR RWY 16 AND REQUESTED THAT I RPT WHEN I HAD THE LNDG TFC IN SIGHT. A FEW SECONDS LATER I CALLED THE TWR AND TOLD THEM THAT I HAD THE LNDG TFC, ON FINAL, IN SIGHT. AT THAT MOMENT I CAUGHT THE ACFT Y JUST BELOW ME (LESS THAN 100 FT) OFF MY 8 O'CLOCK POS, HEADING IN A NORTHERLY DIRECTION. I ALSO MENTIONED TO THE TWR THAT 'THE CIRRUS HAD JUST PASSED BELOW ME.' ON MY APCH TO FINAL THE CTLR INSTRUCTED ME TO GO AROUND DUE TO DELAYED TFC ON THE RWY. I PROCEED TO GO AROUND AND ACFT Y WAS CLRED TO LAND AND UPON LNDG TAXIED TO FBO. I WAS CLRED TO LAND AND I ALSO TAXIED TO FBO (MY BASE). I JUST MISSED MEETING THE PIC OF ACFT Y BUT HIS IDENT WAS GIVEN TO ME BY THE LINE AND FRONT DESK STAFF AT FBO. I CONTACTED THE TWR TO DISCUSS THIS NEAR MISS. THEY WERE WELL AWARE OF THE INCIDENT. THE CIC TOLD ME THAT ACFT Y HAD EITHER FAILED TO SQUAWK THE ASSIGNED CODE OR HAD HIS XPONDER OFF, I DON'T RECALL. WHAT CAUSED THIS PROB? I THINK THAT THE NEW CTLR MAY NOT HAVE BEEN FULLY AWARE OF THE SIT. THE CTLR SEEM A BIT 'OUT OF SINK' FOR SOME REASON. I DID NOT KNOW THAT THE PLT OF ACFT Y WAS EXPERIENCING SOME SORT OF XPONDER TROUBLE AND COULD NOT BE IDENTED BY THE TWR.

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.