Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Conflict NMAC
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification
Aircraft; Human Factors
While descending on the 25R into LAX crossing LYCOM fix at 10;500'; we [experienced] a near miss from a small single-engine aircraft that appeared to be a Piper Cherokee type. TCAS was functioning normally and did not alert us of any conflict. We believe the aircraft was not in compliance with ADS-B requirements. Our descending path took us underneath the small aircraft; missing by less than 300'. His starting position was to our left and below moving slowly to our right above. We cleared conflict below and to his left. We queried LAX Approach Control about the aircraft. They had no target on their screen of any kind and they don't believe he was in radio contact with any controlling agency. Our track was on the ILS on profile tracking 235 from CRCUS and turning to 251 track crossing LYCOM. His track appeared to be between 270-290 degrees. Once we were at a lower altitude; Control allowed us a side step visual to 24R and flight landed successful with no further incident.
Air carrier Captain reported an NMAC with a light aircraft on approach to LAX.