Small Aircraft
Air Traffic Control Time Certified In Pos 1 (yrs) 10
Human-Machine Interface; Distraction; Confusion; Communication Breakdown; Situational Awareness
Conflict NMAC
Human Factors; Procedure
Aircraft Y operating under a previously coordinated beacon code for agricultural spraying operations appeared to have departed TIP SW bound approximately 16NM north of CMI. At the same time an unidentified VFR target was observed maneuvering 11-13 NM north of CMI. The ceiling in the area had been reported at OVC029 with a field elevation at CMI of 755 feet. Aircraft Y continued to track SW bound before calling East Radar requesting VFR transition through the Class C airspace for agricultural spraying 7NM SW of CMI. East Radar told Aircraft Y to Ident for radar identification. After radar contacting Aircraft Y the Radar controller observed the unidentified VFR target maneuvering in very close proximity and issued a traffic advisory. 'Aircraft Y radar contact 13 mile north of CMI airport; altitude indicates 015. Traffic in your immediate vicinity type unknown; altitude indicates 015 and appears to be turning back eastbound within 1 mile west of your position'. Aircraft Y did not report the aircraft in-sight. Shortly after Aircraft X; called on frequency and said that it was him operating to the north and that the [other aircraft] was 'Really Close'. Aircraft Y then reported Aircraft X in-sight and said 'It appeared to be close'. Neither aircraft advised of any evasive maneuvers and no other aircraft were affected.Advise aircraft that will be maneuvering low level VFR when lowering ceilings are prevalent; to remain with radar for traffic advisories.
CMI Tower Controller reported a Near Mid Air Collision between an aircraft under their control and another VFR aircraft.