Skyhawk 172/Cutlass 172
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 4
Communication Breakdown; Confusion; Human-Machine Interface
ATC Issue All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Provided Assistance; Flight Crew Executed Go Around / Missed Approach
Human Factors; Procedure
While working GC; FD; CD; and CIC combined; Aircraft Z had landed Rwy36L which we were on a North flow. Upon our communication Aircraft Z was taxied to park but seconds later the aircraft keyed up and asked if the tower knew that those two airplanes were lined up for the same runway. I keyed up and said 'Affirmative'. I then asked the LC what happened and he replied; 'I sent him around'. Not sure what led up to the event because it was a pretty routine day and nothing difficult at all with the traffic.Better scanning and planning.
I had Aircraft Y in right closed traffic on runway 36R. He was flying a normal pattern with 1 mile bases. Aircraft X called inbound about 5 miles east. Aircraft Y was at the runway so I instructed Aircraft X to enter right base. Aircraft X entered at a 1 mile right base as Aircraft Y began to turn downwind 1 mile north. I was also monitoring a Cessna that had landed 36L to ensure he remained clear of 36R. When Aircraft X turned and began down final; I looked back behind me and saw Aircraft Y midfield right downwind. I had not yet made any transmission to Aircraft Y on this time around. I planned to clear him for his next option number 2 behind the Cessna when his downwind was adjacent to Aircraft X. I observed Aircraft X coming down final and scanned the runway for any problems. As I went to look back to see Aircraft Y's progress on downwind; I saw he had turned a short approach and was turning just in front and beneath Aircraft X on short final. Aircraft X saw him at the same time a keyed up telling me he was going to go around. I told him yes to go around. I then instructed Aircraft Y to stay on the ground so he would not execute a touch and go underneath Aircraft X. Aircraft Y made an unexpected short approach; cut off an aircraft short final; and landed on the runway. All without clearance nor any communication. Had I told Aircraft Y he was going to be number 2; the event probably would not have occurred; however that was not required nor in my opinion at the time needed; as they were well more than adequately spaced in the pattern and would not have been close to a factor had Aircraft Y not decided to approach and land without a clearance. The event occurred do to pilot error. A standalone CIC may have provided an extra pair of eyes that would have seen Aircraft Y turn in sooner however the CIC may also have been checking the Cessna at a critical phase of flight and checking the runway to ensure it was safe to land. The aircraft went from safely on downwind to a factor in seconds. My best recommendation to prevent a re-occurrence would be refresher training for the pilot.
Two Lake Front Tower Controllers reported that an aircraft cut off the sequenced first arrival; causing the first aircraft to go around.