Date: 201701
Local time of day: 1801-2400
Location: AFW.Airport, TX
Flight conditions: VMC
Light: Daylight
Aircraft: Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Operating under: Part 91
Flight plan: VFR
Mission: Training
Flight phase: Final Approach
Airspace: Class D AFW
ATC / advisory: Tower AFW
Second aircraft: Small Aircraft; Low Wing; 2 Eng; Retractable Gear
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Confusion; Fatigue; Situational Awareness
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
Result: Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed
Contributing factors: Airport; Human Factors
Primary problem: Human Factors

Narrative: Traffic was heavy and complex. The first incident with Aircraft X; he was in left closed traffic following [company traffic]; and had been in left closed traffic for several minutes doing touch and goes. I had him on the left because there were smaller slower aircraft in the traffic pattern for Runway 16R. The [company traffic] that he was following requested a stop and go; and there was a [General aviation aircraft] on about a 4 mile final for an RNAV approach to Runway 16L as Aircraft X was about midfield downwind. I asked Aircraft X how far he needed to go in the downwind and he responded that he could turn at any time. I instructed him to fly 1/4 mile more in the downwind and then turn base and cleared him for the option.This would have worked well for spacing behind the stop and go and in front of the [General aviation aircraft]. During my scan I saw that radar indicated Aircraft X was still on downwind about 1 1/4 to 1 1/2 miles past when he was supposed to turn base. I could not find him visually in the sky. It was evident then that there would not be adequate spacing for him to go in front of the [General aviation aircraft]. I instructed Aircraft X to continue downwind to follow the [General aviation aircraft] traffic. As I was un-keying from the transmission his target jumped 90 degrees to a hard left base to final. Aircraft X responded that he was turning back to downwind and he would avoid the traffic.  Aircraft X did not turn base as instructed. I believe he realized he flew beyond and then turned hard to base in an attempt to correct. By the time I realized he had turned a hard base; and he was responding to my last instruction to continue downwind with the response that he would avoid the traffic; I could not think of any other instruction that would better resolve that situation since he said he would avoid the traffic.The next turn in the pattern Aircraft X indicated that he was requesting to full stop. There was a Aircraft A and Aircraft B awaiting departure on 16L. The [aircraft on the ground] departed without incident. I received the release for Aircraft Y while clearing Aircraft X to land. I was awaiting wake turbulence separation for the Aircraft A and working traffic on Runway 16R. I believe I also had to cross Runway 16L with a [General aviation aircraft] that landed Runway 16R. I then hesitantly cleared Aircraft Y for takeoff while scanning; feeling I was missing something but I did not see Aircraft X basing for the runway. Aircraft Y started his departure roll just prior to Aircraft X transmitted that he was going around just before he reached the airport boundary on about a 1/2 mile final. I responded with 'Aircraft X go around left side; speed and altitude permitting start your left crosswind to reenter downwind.' Aircraft X continued to the threshold before offsetting to the left. When he crossed the runway threshold Aircraft Y was about 2000 to 3000 feet down the runway.Complex traffic; position fatigue; drift. Possibly clearing the Aircraft X early in the downwind allowed me to forget about him while dealing with other situations.




Synopsis: AFW Tower Controller reported not observing an aircraft that turned base late until it was in conflict with a strain in traffic. After a go around; the Controller forgot he had cleared the same aircraft to land and did not notice it on short final when he cleared an aircraft for takeoff.