Small Aircraft; Low Wing; 1 Eng; Fixed Gear
Air Traffic Control Time Certified In Pos 1 (yrs) 2
Distraction; Workload
ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Took Evasive Action
Environment - Non Weather Related; Aircraft; ATC Equipment / Nav Facility / Buildings; Human Factors
Aircraft X was IFR; level 120; and eastbound.Aircraft X reported Aircraft Y; four hundred feet above; opposite direction; crossing directly above. It was not confirmed; but the pilot believes the Aircraft Y climbed to avoid Aircraft X at the last minute; thus passing above by 400 feet. Aircraft Y was VFR and not talking to any HLN controllers. Aircraft Y later checked on with LC after the conflict was over. There was no time for evasive action by Aircraft X or control instructions from Approach in-between the report of Aircraft Y and the two aircraft passing.HLN is entirely non-radar. Approach cannot and does not see any VFR aircraft; and can only pass traffic if VFR pilots identify themselves. In this case; Aircraft Y did not check on with approach so no traffic was given.Both pieces of traffic were at 120; so they would have been on ZLC's radar and both had ADS-B. HLN does not have access to either of these. If HLN did have access to either one; approach could have called traffic in a timely manner and could have climbed or descended Aircraft X accordingly.HLN needs some form of surveillance; whether it is an ADS-B feed; or a display of already existing radar coverage.
HLN Tower Controller reported a NMAC between two opposite direction aircraft.