Flight Crew Private
Flight Crew Last 90 Days 21; Flight Crew Total 153; Flight Crew Type 153
Communication Breakdown; Situational Awareness
ATC Issue All Types; Conflict NMAC; Deviation / Discrepancy - Procedural Clearance
Flight Crew Took Evasive Action
Procedure; Environment - Non Weather Related; Airspace Structure
I was flying Aircraft X. I was incoming to SQL from the north for [a] full stop landing; exiting the SFO Bravo; heading south towards the airport. SQL Tower initially asked me to enter a left downwind for Runway 30; keeping 101 freeway to my left; and they would call my left base for Runway 30. A couple of minutes later they asked me to turn left; overfly the runway and enter a right base for Runway 30. I crossed the runway at 1200 feet and began to descend to pattern altitude. SQL Tower told me to follow Aircraft Y that was on an extended right base for 30. As I was searching for Aircraft Y; I began to turn right downwind for 30 right as I noticed Aircraft Z cross in front of me....both of us executing an evasive maneuver. I told Tower that I had a near miss with Aircraft Z....and Tower responded that this aircraft was not on frequency. I was able to land safely.   Upon reviewing ADS-B data and ATC recording of the event; it appears that Aircraft Z took off from Runway 30 and was asked to follow Aircraft A; Aircraft A was told to proceed to KNBR [radio station] antenna and then proceed on course; which they did. Aircraft Z however did not follow Aircraft A and turned too early into downwind. The tower also gave Aircraft Z a very early frequency change so they were not on frequency at the time of [the] near miss. It seems to me that the failure of the Tower to verify that Aircraft Z had Aircraft A in sight was a factor in this near miss; as well as the Tower's early frequency change for Aircraft Z.
Pilot of a single engine aircraft reported an NMAC occurred during traffic pattern entry; resulting in evasive action.