Date: 201707
Local time of day: 0601-1200
Location: BOI.Tower, ID
Light: Daylight
Aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Operator: Personal
Operating under: Part 91
Flight plan: VFR
Mission: Personal
Flight phase: Final Approach
Airspace: Class C BOI
ATC / advisory: Tower BOI
Second aircraft: Small Transport; Low Wing; 2 Recip Eng
Reporter organization: Government
Reporter function: Local; Trainee
Reporter qualification: Air Traffic Control Developmental
Human factors: Communication Breakdown; Distraction; Workload; Training / Qualification
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification
Contributing factors: Procedure; Human Factors
Primary problem: Procedure

Narrative: Very busy training session on local control; runways 28R/28L in use. My trainer and I took the local position with traffic already building from being moderate to heavy traffic. When I took the position there were 4 IFR departures ready to depart Runway 28R; Aircraft Y; first in line followed by 3 commercial airliners. An RJ was departing Runway 28R as well with a jet on a 15-20 mile final for 28R; also with a Cessna 172; approaching base cleared for the option on Runway 28R behind the departing RJ with visual separation. A Cessna 180 was told by the previous controller to make 360's north of the airport for spacing and he was also requesting touch n goes; another Cessna 182 inbound from the south as well for Runway 28L. Aircraft X checked in 15 miles to the north for a full stop Runway 28R. When he checked in; I told Aircraft X Runway 28R continue and he came back with a request for a long landing and short approach in which I responded with I have your request. The Cessna 180 who was holding north of the airport; I told him to enter the downwind and change to runway 28L and I'd call his base turn. The C172 was still on departure roll down field for 28R. I then switched the C172 to change runways and enter left closed traffic for runway 28L and also told him to extend downwind for 28L. The C180 who was on the left downwind for 28L was then told to turn base and told about the jet he was inside of for Runway 28R. A helicopter called and requested to depart the SW corner of the airport SE bound. I gave him his instructions to depart while calling the traffic for the C172 who was crosswind to downwind for 28L now and calling traffic to the helicopter as well. Aircraft X was now told to extend downwind for 28R still inbound from the north. The C180 who was supposed to be on base for 28L did not comply with his instructions to turn base and became a conflict with the jet on 10 mile final now. This became a major distraction because the C180 was not responding and I was also calling traffic to the jet now and trying to keep the C180 off the final in front of the jet. After finally getting a response from the C180; I elected to turn him northbound and then after the jet was no factor and put the C180 on a vector heading 180 to get him south of the final now. Once the jet landed on 28R; I put Aircraft Y into LUAW status on Runway 28R and told him about Aircraft X who was now entering the downwind with an extend downwind instruction. I also had the helicopter now a factor with the C180 who was now on course westbound after he elected to depart the area and this caused a traffic call to both aircraft along with a helicopter who had called up inbound from the south for BOI airport. I then went immediately back to Aircraft X and told him to start a right hand turn; a right base for Runway 28L now; Runway 28L cleared to land because of the stack up of departures on 28R and the C172 was out of his way. I also had a C182 inbound now from the south and another C206 from the north who had checked in and I told him to make 360's over downtown Boise because of the amount of aircraft now that I was dealing with. I cleared Aircraft Y for takeoff; scanning my runways and everything was clear. I then made another couple transmissions for other aircraft and looked up at 28R and 28L finals and back to the runways and as soon as I did that I saw Aircraft X overflying Runway 28R with Aircraft Y still sitting on the runway and Aircraft Y then keyed up and said that he just had an aircraft fly over the top of them. I immediately went back to Aircraft X and told him he was supposed to be on Runway 28L and told him to turn right and enter right closed traffic runway 28R. He turned northbound and entered the downwind for Runway 28R while apologizing. I went back to Aircraft Y and I think he asked if he was still cleared for takeoff and I recleared him for takeoff on Runway 28R without any incident. I then went back to controlling my traffic and gaveAircraft X a landing clearance for runway 28R and let him land before departing anyone else. He landed and taxied in without incident and once again apologized. I then continued on with training. The level complexity; heavy traffic and the amount of things that were going on; made this session very; very difficult. I felt like I was keeping up with the traffic and my trainer and I were on the same page. I think the biggest thing that I could've done differently was making sure that I focused better on read back/hear backs and also using the term 'change to runway' when I changed Aircraft X to the other runway. I also should of emphasized the change to runway with a 'for multiple departures off of 28R' and that would've clued him in on not landing on 28R. With multiple things taking my focus away from the runways and having to give multiple traffic calls to pilots; especially the C180 who was not responding and causing extra work for me; I just got overly task saturated.




Synopsis: BOI Tower Developmental Controller reported an extremely busy and complicated session led to an aircraft overflying another aircraft holding for departure on the runway.