Date: 202104
Local time of day: 0601-1200
Location: ZZZ.Tower, US
Flight conditions: VMC
Aircraft: Small Aircraft
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Personal
Flight phase: Final Approach
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Second aircraft: Small Aircraft
Reporter organization: Government
Reporter function: Other / Unknown
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Distraction; Training / Qualification
Anomaly: ATC Issue All Types; Conflict NMAC
Detector: Person Air Traffic Control; Person Observer
When detected: In-flight
Result: Air Traffic Control Issued New Clearance
Contributing factors: Procedure; Environment - Non Weather Related; Human Factors
Primary problem: Human Factors

Narrative: This event happened While training was in progress on the local one position. Aircraft X was sequenced to follow Aircraft Y in the pattern. The trainee did not observe that Aircraft X was much faster and had turned in too close behind Aircraft Y. Aircraft Y was on short final approximately 100 feet AGL. Aircraft X was off the left wing of Aircraft Y at approximately the same altitude. It was apparent that Aircraft X had offset to the left side of Aircraft Y in an effort not to land on top of or create a collision with Aircraft Y ahead. This being said; Aircraft X never attempted to query ATC. It was not until the ground controller said 'what is happening' That the trainee; trainer and the Controller in Charge even looked out the window. The trainee was staring at the radar; the OJTI and the Controller in Charge were not paying any attention and we're engaged in a non ATC related conversation. Neither one of them were looking out the window. At the time of the incident; the Instructor had his back turned away from the runway threshold. Once the incident was brought to everybody's attention; the trainee who looked out the window but did not make any attempt to send the aircraft around until the Instructor instructed the trainee to send the aircraft around.  I saw the incident; however; I chose not to say anything.After this Incident; I brought it to the Supervisors attention. That said; at the time of the incident the Supervisor was not in the tower cab. I later heard that the Controller in Charge stated to a management official that the situation was 'not that bad.' In fact; the situation was incredibly dangerous. The aircraft probably were only separated by maybe 200 to 300 feet laterally and 0 feet in altitude. I do believe this statement was made by the Controller in Charge in an effort to cover up the situation considering that the Controller in Charge was distracted in a non ATC conversation and did not see the situation developing.  I believe the only thing that needs to change from this incident; is the Controller in Charge and Instructor paying attention. There is too much trust put in a trainee that has a history of dangerous happenings.




Synopsis: Tower Controller reported an NMAC on short final was not detected by the Local Control trainee; the Instructor; or the Controller in Charge until the Ground Controller brought it to their attention.