Date: 202107
Local time of day: 0601-1200
Location: MSN.TRACON, WI
Aircraft: Small Aircraft; Low Wing; 1 Eng; Fixed Gear
Operating under: Part 91
Flight plan: IFR
Flight phase: Cruise
Airspace: Class E ZMP
ATC / advisory: Center ZMP
Second aircraft: Small Aircraft; Low Wing; 1 Eng; Retractable Gear
Reporter organization: Government
Reporter function: Enroute; Handoff / Assist
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert
Contributing factors: Airspace Structure; Human Factors; Procedure
Primary problem: Procedure

Narrative: I was working as TRACON Data for West in position of R1.  I did not notice my Controller drop the tag for Aircraft X.  About 5 minutes later; I coordinated a point out with Lone Rock sector control on Aircraft Y at 8;000 who would just clip our NW airspace.  My Controller; being busy and trying to clean up his scope for a position transfer to me; was dropping tags on several aircraft above our airspace.  He mistakenly dropped Aircraft X.A few minutes later; I was relieved of position and busy taking the position brief for R2 control position.  The new R1 TRACON Data Controller took a call from Lone Rock and was asked if he talking to Aircraft X.  He; of course did not know who they were talking about since the aircraft was a splat with no information.  The R1 Controller asked me if I knew who that was; and I not hearing with the noise in the TRACON; said something like; 'Of course not; that was a point out; I was thinking they were talking about the point out I took on Aircraft Y. Shortly after; the R2 controller figured out the splat was one of our aircraft and took corrective action to avoid the two aircraft getting any closer.The NOTAM that was produced for departing aircraft from OSH during EAA Experimental Aircraft Association contributed to this. Expecting dozens of aircraft to pick up IFR flight over DLL VOR at the same point at the same time is inviting loss of separation.  Many aircraft filed incorrectly; leading to much frequency congestion.  One pilot in particular; during my following 30 minutes on the R2 scope wanted to argue with me that he filed correctly; when he didn't.  Several aircraft were in Lone Rock and Dubuque sectors looking to pick up their IFR; requiring further point outs and coordination. Several aircraft required 6/10 [Flight Plan]  amendments in order to gain their flight plans.  Most aircraft were at same altitudes and required valuable frequency time for separation; to ensure they were at correct altitudes and separated from other IFR aircraft.  In short; the EAA Air Adventure is a set up for controllers at my facility.  The loss of IFR separation is almost inevitable given the volume; complexity and inherent confusion at certain heavy periods.  There is probably no recommendation I can give other than tell a certain number of aircraft to pick up IFR at different points; or just have them fly VFR."




Synopsis: MSN Controller reported issued relating to the Oshkosh fly in and departure.