Date: 201901
Local time of day: 1801-2400
Location: SJC.Airport, CA
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
ATC / advisory: TRACON NCT
Second aircraft: Cessna Citation Undifferentiated or Other Model
Reporter organization: Government
Reporter function: Departure; Approach
Reporter qualification: Air Traffic Control Developmental
Human factors: Situational Awareness
Anomaly: Conflict Airborne Conflict
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Separated Traffic; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure; Airspace Structure
Primary problem: Human Factors

Narrative: I was working Licke/Hooks combined on my last radar session. Aircraft X checked in descending via the Silicon arrival into SJC; and I cleared the aircraft for the approach after an initial scan of the arrival corridor indicating no conflicting VFR targets. It had been an extremely busy day for me on these sectors with numerous unidentified targets in the South Bay Area; so I had been very vigilant in missing numerous targets throughout the day. When I cleared Aircraft X; there was no traffic I saw to be a factor. At the same time; I was vectoring a B737 to final for a visual approach to avoid a C172 that I was vectoring across the SJC finals for a GPS approach at PAO; and I was vectoring a Gulfstream from OSI area north of his normal arrival route at 5000 ft. to miss an unidentified target at 4600 ft; which I missed with vectors by 2 miles. As I was watching this situation; Aircraft X keyed up and said 'Approach Aircraft X'; to which I replied 'Go ahead'; and as the collision alert on my scope was going off he indicated a TCAS RA (Resolution Advisory) (which blocked the frequency from me calling the traffic); and this was the first time I observed the unidentified target at somewhere around 9500 ft. beneath him as Aircraft X climbed out of 9800 to 10300 ft; and the aircraft crossed. I said roger and informed Aircraft X of the alert as well. I failed to give a traffic alert as Aircraft X was already in the climb and I observed they were passing. I felt completely helpless and in shock at the event because I never saw the target coming at Aircraft X. I advised Aircraft X to advise when finished and descended the aircraft to 6000 ft; and he was cleared for an ILS approach to SJC; landing without incident. I queried the pilot about the aircraft and he said he saw what he believed to be Aircraft Y. Aircraft Y later called the arrival sector that Aircraft X was in when the conflict happened and said he had departed Watsonville (WVI); an airport about 5-10 miles west of Aircraft X's STAR; and an uncontrolled field. I have not had an opportunity to review the Falcon replay of the event but plan to do so the first day I am back next week. My assumption at this point is he climbed rapidly and I simply missed it as I was working to miss other aircraft with vectors about 25 miles north of where this incident occurred. I pride myself on catching things out of the ordinary and my scan has protected numerous aircraft from unidentified targets and controlled aircraft regularly; especially today with an exorbitant number of aircraft just outside the Class Charlie not talking to controllers; and I am in utter shock that I did not see this one until the last minute. There is a slight possibility that because I have only been working one sector combination continuously and it was a very busy day; I could have been fatigued from the continuous scan for unidentified targets which I had been missing all day. Breaks were less frequent as a result of staffing being below numbers for the day; due to reduced staffing during the shutdown. I could have been affected by the stress of training being delayed or just complacency in working the same sectors continuously as well. I honestly don't know if these were subconscious factors or not; however; and I can say that I don't feel them on conscious level. I strive to do my best every single day and am still massively shocked and disappointed in what occurred today. My reflections are ongoing from this event and it will only increase my vigilance in the future. I plan to watch the replay on my next working day and will amend this report with any information I find.At the time of this event; I can say that the biggest factor that led to me not observing the other target was the need to miss unidentified targets close to the SFO BRAVO with an arrival at 5000 ft. This arrival route is standard from the Woodside Sector for arrivals to SJC. This arrival route has numerous issues that I have seen be at factor before today. First of all; if an aircraft comes in a 5000 ft. and requires the ILS; the aircraft must be climbed to 5100 ft. to meet MVA (Minimum Vectoring Altitudes) requirements near KLIDE intersection; but Hooks does not have the ability to climb the aircraft for 10-15 miles and only about 10 miles from the MVA because of the conflict with Boulder's airspace at 6000 ft. without a point out. There are also PAO arrivals; SQL arrivals; and NUQ arrivals that can be pushed to descend from the south to 4700 ft. at a bare minimum until they are just east of OSI; putting them in opposite direction conflict with arrivals at 5000 ft. from Woodside. In this case; I did not need to climb the Gulfstream because the aircraft could get a visual approach; and was restricted from doing so by airspace; so I chose to vector the aircraft around an unidentified target because I could not guarantee altitude. The aircraft was close to the Bravo but could have gone up to 4900 ft. which would not have provided separation. This vector required concentration that distracted me from monitoring Aircraft X's descent from the south; as I was also missing other aircraft. Again; I pride myself on my scan and am disappointed and shocked that the target causing the RA was not observed climbing from sea level to 9500 ft. within 8-10 NM. My only suggestion for arrivals from the northwest is the possibility of 6000 ft. and 7000 ft. instead of 5000 ft. and 7000 ft. to help protect the corridor and leave aircraft in the Bravo longer. An extension of the Bravo or Charlie to help protect aircraft in the Bay Area could help as well as numerous targets stay just on the fringes at bad altitudes; causing more harm than good. This is a hotspot almost daily and Optimized Descent Profiles need to be better protected with aircraft at such high speeds. From my understanding; when the ODP's were implemented they now put jets in areas they weren't before; and VFR pilots still have limited knowledge of the new routes. They stay in places that avoided the old routes; which now tend to put them in more conflict areas. Extension of Charlie or Bravo airspace to protect Bay Area arrivals would be ideal; but it seems that this is not a priority due to pushback from GA users. Again; it is my responsibility to separate from unidentified targets and I am disappointed that I was so focused on one that I missed the other. I personally will be even more aware of aircraft departing the WVI area in the future; as they have proven to be an immediate threat to the arrival corridor. The short distance with a high performance aircraft leaves minimal time to react. I pride myself on my scan and will be even more vigilant in the future to detect abnormalities.




Synopsis: NorCal TRACON Controller reported an airborne conflict with an arrival aircraft and a jet that departed an uncontrolled airport.