Skyhawk 172/Cutlass 172
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 6.1
Confusion; Situational Awareness
Airspace Violation All Types; Conflict Airborne Conflict; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Airport; Human Factors
I was working Ground Control and it was one of the busiest sessions I've had recently. Among other traffic; I had two CL30s taxiing out; and I was trying to ensure I had given Local Control (LC) the strips in the correct sequence; with a C182 taxiing out requesting an intersection departure on 30R. I was concerned with ensuring the 182 taxied to the correct intersection; knew there'd be a delay for wake turbulence; was going to hold him short of the runway; and would not be blocking taxiways that would be needed by aircraft exiting the runway. I was also preparing to give a relief briefing to the incoming controller and was trying to keep an eye on LC's traffic situation; but it was difficult at times due to my own workload. While all of the above was taking place; I heard LC tell the CL30 to line up and wait on 30R; and heard a strange response from the pilot. The pilot said something about 'after the traffic on short final' and I heard another voice on frequency say something about being on short final. I looked up with the rest of the tower cab; heard LC urgently issue instructions to [a C172] to change to 30L; and saw the Cessna on final maneuvering over to RWY 30L. My understanding is that the pilot was supposed to be on final for 30L for his touch and goes. I am not sure if there was a read back issue; confusion from a relief briefing (the previous controller was just relieved); or simply the pilot gave the correct read back; but turned final for the wrong runway. Not to be melodramatic; but it was one of the spookiest events I have seen in a while. After correcting on the first approach; the C172 continued in the pattern and the CL30 departed.This event highlights the importance of a number of critical items. Visual scanning cannot be emphasized enough; and the flight crew on the ground was clearly a hero during this event. They appeared to perform their role flawlessly by scanning the final; detecting an unsafe situation (traffic short final); not accepting the ATC clearance given; and informing the controller politely and calmly that something was wrong or overlooked by the controller. This is a textbook example of the partnership that should exist between controllers and pilots to break the chain of events that can lead to a catastrophic event.
Ground Controller heard an aircraft that was cleared onto the active runway advise the Local Controller of traffic on final. Landing traffic was advised to land on the adjacent parallel runway.