Narrative:

I was flying the fisk approach to osh. I was the last aircraft in line; subsequent aircraft had been asked to hold at green lake; while I had left the line of aircraft after ripon but prior to fiske. I have flown in four times previously and was familiar with the NOTAM and had reviewed the NOTAM and had it with me in cockpit; on page 12 ('fisk VFR arrival to osh runway 36L/right'). At 0.75nm from fiske; I was contacted by controllers on the ground by position and type 'low-wing aircraft'. I rocked my wings to acknowledge; and was directed toward runway 36. I made the turn over fisk avenue and was proceeding to 36 and switched to the tower frequency. I could see the sequence of aircraft in front of me and heard them receiving their landing instructions from the tower controller for 36L and 36R. I was contacted by the tower controller as 'low wing aircraft'; was directed to rock my wings; and was told 'good wing rock.' I was cleared to land 36R; began my descent and configured the aircraft for landing. As I was making my base turn to final; I caught sight of another aircraft slightly below me and slightly to my right; already on final approach for 36R. Since I was the higher aircraft; I applied full power and began a climb to the northeast to remove myself from the space surrounding the runway. I waited for space to open on frequency so that I could inform the controllers of my go around per the NOTAM. The tower controllers saw me climbing away from the airport; addressed me as 'low wing aircraft executing a go-around' and gave me instructions to land on either 36R or 36L. I landed on 36L without further incident. The controllers thanked me on frequency for handling the situation. I have replayed the sequence of events in my mind many times in the ensuing days since the incident. I am convinced that the other aircraft followed me to fiske; thought the instructions directed at me were actually for them; and took my clearance. There's no other way I can account for an aircraft being in that position at that time. Had I seen the aircraft prior to the incident I could have prevented the near-midair earlier. I know that the osh special traffic management procedures (stmp) makes for a very busy and challenging environment; and I was continuously scanning for traffic as I made the approach. The controllers could have resolved some ambiguity using a color description of the aircraft (e.g.; 'red and white low wing aircraft'); as the other aircraft was a grey low wing. The other aircraft should have known his distance from fiske and not responded with a wing rock. The other pilot should have been watching me on the ripon to fiske segment and observed my wing rock. It occurs to me that aircraft equipped with ads-B out could help controllers by giving them the registration number of the aircraft so they could identify aircraft that way rather than visually. I'm not certain that the ads-B system is designed to handle traffic density of the osh stmp; however. I am fortunate that I saw the aircraft; as had I not the results would certainly have been disastrous.

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Original NASA ASRS Text

Title: P32 pilot reported an NMAC with another light aircraft on approach to OSH with STMP procedures in effect.

Narrative: I was flying the Fisk Approach to OSH. I was the last aircraft in line; subsequent aircraft had been asked to hold at Green Lake; while I had left the line of aircraft after RIPON but prior to FISKE. I have flown in four times previously and was familiar with the NOTAM and had reviewed the NOTAM and had it with me in cockpit; on page 12 ('FISK VFR Arrival to OSH RWY 36L/R'). At 0.75nm from FISKE; I was contacted by controllers on the ground by position and type 'low-wing aircraft'. I rocked my wings to acknowledge; and was directed toward runway 36. I made the turn over Fisk Avenue and was proceeding to 36 and switched to the tower frequency. I could see the sequence of aircraft in front of me and heard them receiving their landing instructions from the tower controller for 36L and 36R. I was contacted by the tower controller as 'low wing aircraft'; was directed to rock my wings; and was told 'good wing rock.' I was cleared to land 36R; began my descent and configured the aircraft for landing. As I was making my base turn to final; I caught sight of another aircraft slightly below me and slightly to my right; already on final approach for 36R. Since I was the higher aircraft; I applied full power and began a climb to the northeast to remove myself from the space surrounding the runway. I waited for space to open on frequency so that I could inform the controllers of my go around per the NOTAM. The tower controllers saw me climbing away from the airport; addressed me as 'low wing aircraft executing a go-around' and gave me instructions to land on either 36R or 36L. I landed on 36L without further incident. The controllers thanked me on frequency for handling the situation. I have replayed the sequence of events in my mind many times in the ensuing days since the incident. I am convinced that the other aircraft followed me to FISKE; thought the instructions directed at me were actually for them; and took my clearance. There's no other way I can account for an aircraft being in that position at that time. Had I seen the aircraft prior to the incident I could have prevented the near-midair earlier. I know that the OSH Special Traffic Management Procedures (STMP) makes for a very busy and challenging environment; and I was continuously scanning for traffic as I made the approach. The controllers could have resolved some ambiguity using a color description of the aircraft (e.g.; 'red and white low wing aircraft'); as the other aircraft was a grey low wing. The other aircraft should have known his distance from FISKE and not responded with a wing rock. The other pilot should have been watching me on the RIPON to FISKE segment and observed my wing rock. It occurs to me that aircraft equipped with ADS-B Out could help controllers by giving them the registration number of the aircraft so they could identify aircraft that way rather than visually. I'm not certain that the ADS-B system is designed to handle traffic density of the OSH STMP; however. I am fortunate that I saw the aircraft; as had I not the results would certainly have been disastrous.

Data retrieved from NASA's ASRS site 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.