Date: 201708
Local time of day: 1801-2400
Location: ONT.Airport, CA
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class C ONT
ATC / advisory: Tower ONT
Second aircraft: Small Aircraft
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Situational Awareness; Workload; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Unstabilized Approach
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action
Contributing factors: Weather; Human Factors; Airspace Structure
Primary problem: Human Factors

Narrative: We were on the ILS 26L to ONT. At 1500 AGL; ATC advised of VFR traffic north of us. Simultaneously we got a TCAS RA to descend. I was the PF and I followed the TCAS guidance. I felt boxed in because the traffic was above us and we were being given commands to descend towards the ground at low altitude. I thought that the only way out was to turn left. As I descended I started a turn to the south. It was hazy and we were landing into the setting sun. Neither of us saw the traffic but the FO did see the red RA at +100 and less than 1 mile. We got the TCAS 'descend' aural alert but no 'clear of conflict'. We got the 'glideslope' aural warning but no GPWS terrain warning. We were not stable at 1000 since we were below the glideslope. We were VMC and I remember thinking that if we weren't stable at 500 we would go around. We were stable and continued to a normal landing.This is a challenging approach for the B737. At TAKOE you are required to be at 210 kts 3300 AGL and only 12.7 miles from the field. I noted on the 10.7 pages that this is a high density VFR traffic airport and there is poor visibility in haze especially at dusk. This was certainly the case for us. The sun was directly in front and just below the top of the window frame. The glare made the approach difficult. Twice ATC asked us if we would prefer runway 26R. Both times we declined because we were already setup for 26L. The VFR traffic on final approach at low altitude added exponentially to the task load. The controller seemed unconcerned with the conflict. Meanwhile we were getting a TCAS RA to descend into the ground. I remember thinking: 'What's VFR traffic doing out here on final approach at this altitude?'


Second narrative: I was the FO PM. On the ILS to 26L. Conditions were VMC but approximately 10 miles visibility due to haze and low sun angle in front of us. Ontario Tower called out traffic as a light 'traffic watch' aircraft that would be north of our approach; low altitude; and no factor. We responded searching but never saw the aircraft. The aircraft's track was on TCAS. Configured and approaching approximately 1300-1400 AGL we got a TCAS aural of 'traffic' then 'descend'. The captain followed the descent command and I was looking for the traffic outside. I did see the aircraft's TCAS track around a mile from us and co-altitude. The track quickly drifted past our 3 o'clock and we leveled around 700-800 AGL and below the glide path. We flew level until re-intercepting the glide path and continued a normal landing. After landing; the tower was adamant that the aircraft was no factor and our TCAS must be 'overly sensitive'.


Synopsis: B737 flight crew reported a traffic conflict while on final approach at ONT. While complying with TCAS commands the flight became temporarily destabilized on the approach; but recovered and made an uneventful landing.