Commercial Fixed Wing
Air Traffic Control Fully Certified
Air Traffic Control Time Certified In Pos 1 (yrs) 10
Time Pressure; Situational Awareness
ATC Issue All Types; Conflict Airborne Conflict; Inflight Event / Encounter CFTT / CFIT
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Separated Traffic; Flight Crew Took Evasive Action
Airspace Structure; Human Factors; Procedure
Aircraft Y departed ZZZ VFR and wanted to overfly the downtown before picking up his IFR [clearance] and proceeding on course. I told him to proceed on course and advise when he was ready to be on his way. When Aircraft X departed; Aircraft Y was circling over Downtown about 8 miles north of the airport below 4;000 feet. This is a typical spot and generally not a factor for departing jets as they climb above that area. I issued traffic to Aircraft Y since he had no restrictions and he reported Aircraft X in sight. Unfortunately; at this time Aircraft Y had also just exited his circling and had started to fly southwest and begin a climb. This was not apparent to me yet and I was unsure what direction he was headed due to his maneuvering and equipment refresh rate. I was also unable to turn Aircraft X more than 15 degrees due to our departure/terrain limitations and neither 15 degrees left or right seemed prudent for the uncertain course of the traffic. Since Aircraft Y had Aircraft X in sight; I did not believe he would continue a climb directly towards him; but he did; and I issued an immediate right turn to Aircraft Y. Altitude restrictions wouldn't have worked here since the MVA (Minimum Vectoring Altitude) is 5;000 feet in that area. Unfortunately this turn was not timely enough and Aircraft X had to respond to an RA by descending.Although an altitude restriction would not have helped; asking the pilot to advise prior to climbing could have been the heads up I needed to give him a heading to avoid the traffic; or to ask him to delay his climb for traffic. Another option could have been to have Aircraft X remain clean of the class charlie; as this would have also potentially prevented the climb into traffic. It's clear I did not take action soon enough. Aircraft X should have been given a traffic call; on initial call-up ideally. A traffic alert should have been issued at a minimum to Aircraft X since I was able to turn him. Aircraft X had just reached the minimum altitude for a turn at that moment.
Aircraft X departed and conflicted with Aircraft Y orbiting VFR. I observed the event in the departure corridor while on the Tower Controller In Charge Only position. Aircraft Y finished a left turn toward the runway centerline and flew straight towards the departing Aircraft X. As the aircraft converged I noticed the altitudes decreasing in separation. Then subsequently noticed a turning descent of Aircraft X under the Minimum Vectoring Altitude descending to 4;300 feet (estimated). After no factor Aircraft X climbed and departed to the NE. Aircraft Y departed to SW. Recommend larger Class C; due to great increase in ZZZ traffic. Class C 10 mile ring down to surface.
TRACON Controller and Tower Controller in Charge reported a VFR experimental home built aircraft climbed into the path an Air Carrier departure. The Air Carrier responded to a TCAS/RA and according to the Tower Controller's estimate descended below the Minimum Vectoring Altitude.