Skyhawk 172/Cutlass 172
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 5
Situational Awareness
Conflict Airborne Conflict
Flight Crew Took Evasive Action
Procedure; Human Factors
Aircraft X was inbound from the south making left traffic to Runway 31. The aircraft first made a report on frequency about passing a drone; with few details and no call sign. Subsequent back and forth established that Aircraft X passed a drone around the Stanford University at approximately one thousand one hundred feet. They reported to pass about one hundred to two hundred feet from the drone and that they had to descend to avoid hitting it. It was reported to be a black and white quad copter estimated to weigh between ten and fifteen pounds. I immediately made sure the CIC (Controller-in-Charge) heard the report and tried to facilitate information requests the CIC and the pilot.The main CIC computer has been replaced recently and no longer has the quick link for UAS (Unmanned Aircraft System) activity authorizations in the vicinity. So I can't speak to whether or not the UAS was authorized or not. But; at that location (which was around the edge of the PAO class D) and altitude regularly has air traffic and UAS activity should be required to call Palo Alto Tower.The link for checking UAS authorizations needs to be added back to the CIC computer.
PAO Tower Controller reported an airborne conflict between an aircraft under their control and a drone.