Date: 201711
Local time of day: 1801-2400
Location: BJC.Tower, CO
Flight conditions: VMC
Aircraft: Skyhawk 172/Cutlass 172
Operator: FBO
Operating under: Part 91
Flight plan: VFR
Mission: Training
Flight phase: Final Approach
Airspace: Class D BJC
ATC / advisory: Tower BJC
Second aircraft: Skyhawk 172/Cutlass 172
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Confusion
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Runway
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Aircraft X was in the traffic pattern for Runway 30L; was extended upwind and told Tower would call crosswind turn to accommodate Aircraft Z [a Vintage warbird] performing the overhead maneuver on same Runway behind them. Aircraft Y was following Aircraft X and was told to extend upwind to follow that traffic. Aircraft X was observed approximate 3NM southwest of the field and questioned whether they were staying in pattern or departing area. Aircraft X responded that they were on the crosswind awaiting for me to instruct downwind turn. I then instructed them to make a right 180 degree turn to rejoin left downwind and issued traffic to follow that would be just south of the VOR. Aircraft X repeated instructions. Aircraft Y was sequenced number one for Runway 30L and issued Touch and Go Clearance.Aircraft X was observed via radar close to downwind; was told to enter downwind and issued number 2 sequence behind the traffic downwind to base and cleared Runway 30L Touch and Go. Aircraft X repeated all instructions; including clearance to Runway30L. Other calls were made when I noticed Aircraft Y stopped midfield on the Runway; I recognized that Aircraft X may have to go around and began a visual scan to locate them; they should have been on final at this time. I could not locate them on final and at that time; Aircraft X reported 'Going Around'. I scanned from the approach end of Runway 30L then towards the departure end and I saw Aircraft X opposite direction approximately 100 FT AGL over the Aircraft Y on the Runway. Aircraft Y was stopped; not because of an issue with their aircraft; but they saw the opposite direction traffic approaching and they pulled off to the side to try to accommodate. Aircraft X was issued further instructions to sequence for the appropriate Runway. No further issues came from this event. When questioned Aircraft X said there was a lot of 'radio chatter' and he got confused; there was no instructor on board at the time.Recommendation: Maintain awareness of all areas; when a pilot is not doing what they were instructed to begin with they should require more attention. Keep a good scan and when you notice something is not looking/feeling right solicit help from other tower team members.




Synopsis: BJC Tower Controller reported that after issuing instructions to an aircraft on pattern traffic and receiving the correct read-back instructions; the pilot aligned on final to the opposite runway.