Date: 201705
Local time of day: 1201-1800
Location: LAS.Airport, NV
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B LAS
ATC / advisory: TRACON L30; Tower LAS
Second aircraft: Commercial Fixed Wing
Aircraft component: TCAS Equipment
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction; Confusion
Second reporter function: Pilot Flying; First Officer
Anomaly: ATC Issue All Types; Aircraft Equipment Problem Less Severe; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Automation Aircraft TA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew FLC Overrode Automation
Contributing factors: Procedure
Primary problem: Procedure

Narrative: LAS was giving vectors for north landing and we were being vectored for 1R. A business aircraft was called out to us as traffic as they were being vectored on base leg for 1L. I do not recall hearing if the other aircraft was given a speed restriction but as we later discovered; that Crew's spacing awareness and control seemed to be greatly relaxed. As we rolled out on final; approach Control called them again as traffic and; shortly after we received a TA. When I finally spotted the traffic visually; I was surprised at how close it was. Shortly after being handed off to Tower we received an RA to descend. We discussed our options and agreed that; to comply with the descend RA; was the safest course and we continued the approach. I notified the Tower of the RA to let them know that the spacing left little to be desired. Tower asked our intentions and I let him know we were complying with the RA by continuing the descent. Somewhat unhelpfully; another on-air voice (possibly the other aircraft Pilot) interjected the assertion that the RA was a false indication. This presented a tempting opportunity for retort (not helping) but I declined to comment. While our approach continued; compliance with the RA seemed to force us below the PAPI and the RA continued to enunciate. I felt boxed in but to go around seemed like the least safe option. We discussed this and agreed to continue while opting to turn the TCAS to TA in order to silence one of the distractions. We landed uneventfully and taxied to the gate without incident or comment. I realized that by silencing the RA by switching to TA only; I was violating policy; but to do so seemed prudent under the circumstance. In addition I forgot to notify Dispatch of the incident but a report was filed upon completion of the trip.Despite violating TCAS policy; I am proud of our reaction as a Crew to the traffic threat. My First Officer did a great job keeping a cool head and flying precisely as we needed to mitigate the danger. We reassessed the situation at least three separate times to reach what I consider the safest course. ATC could have given safer sequencing and the other Crew could have opted not to push the margin so closely. In addition; unnecessary commentary over the frequency at such a critical moment is unhelpful.


Second narrative: LAS was giving vectors for north landing and we were on a base leg about 10 miles south of the airport. I was flying the aircraft. We had set up to fly the RNAV 01R; but had not yet been cleared for the approach or even told what runway we would be landing on.Approach informed us of our landing runway; gave us a vector to final approach course; and cleared us for the approach. After we intercepted final approach course; I used the MCP to fly the plane using LNAV and VNAV Path with autopilot and autothrottle engaged. Soon after intercepting VNAV Path; we received a TCAS TA alert from an aircraft about 600 ft above and behind us. ATC called out a business jet as traffic for us to be aware of. The Captain began looking for the threat while I continued flying the approach. After about 30 seconds; it became apparent to us that the business jet was flying an approach to LAS 01L and was sequenced too close behind us.Shortly after switching to LAS Tower frequency; the TA changed to a TCAS RA. I disengaged the autopilot and autothrottles and flew the aircraft to stay clear of the conflict by following the PFD guidance and commands. We were now VMC and the landing runway was in sight. The Captain and I agreed that the safest course of action was to continue the approach visually; using the RNAV approach guidance as able; as executing a missed approach would counter the TCAS commands and might fly us too close to the aircraft causing the RA.During the approach; the TCAS commands were going off the whole time because the other aircraft had continued to fly his approach to 01L behind us; maintaining an altitude of about 500-600 ft above and behind us. The aural commands were extremely distracting as we tried to configure the aircraft for landing; accomplish required checklists; ensure safe terrain separation; and attempt to coordinate with ATC. We were definitely in the 'yellow' as a crew; and I was probably in the 'red' as I was flying the aircraft approach to LAS 01R manually while attempting to maintain altitude separation from the aircraft above me while maintaining safe terrain separation below. The Captain asked me if I was comfortable with turning the TCAS switch to TA mode (as we can do in Denver when sequenced close to parallel aircraft) even though this was in violation of policy; and I agreed that this would reduce the level of stress in the flight deck and increase SA and overall safety.After completing this action; we accomplished the rest of the approach and landing without incident.


Synopsis: B737 flight crew reported continuing the approach to LAS Runway 1R despite a continuous RA due to traffic behind for landing on Runway 1L being too close.