Date: 201701
Local time of day: 1201-1800
Location: LAS.Airport, NV
Light: Daylight
Aircraft: B737 Next Generation Undifferentiated
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Descent
Airspace: Class E L30
ATC / advisory: TRACON L30
Second aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Confusion; Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: ATC Issue All Types; Conflict Airborne Conflict
Detector: Automation Aircraft RA
When detected: In-flight
Result: Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Human Factors
Primary problem: Human Factors

Narrative: Descending into LAS in the vicinity or IPUMY fix; we received a 'traffic; traffic' TCAS TA warning. The associated traffic showed 3500 feet below our current altitude and climbing. Neither Captain nor I could visually acquire the traffic. Sometime later we received a 'Climb' RA and the Captain disconnected the autopilot and complied with the RA. During this time I visually acquired the aircraft in question passing our 3 o'clock at a distance I would assess between 1/2 mile to a mile slightly below our altitude and by the time it reached my 4 o'clock it was co-altitude and still climbing. The radios were busy and I couldn't get an advisory call to ATC yet. At this point the RA audibly gave another command I believe was 'monitor Vertical Speed' quickly followed by clear of conflict. At this point we told ATC of our maneuver and they responded that aircraft had violated their clearance and wasn't answering. I assume they were on a different Approach/Departure frequency than we were. We were given a new descent clearance; the Captain reengaged the autopilot; and the flight proceeded uneventfully the rest of the way to the gate.We were never advised by ATC of the conflict due to multiple frequencies and congestion on the radios. I also am unaware of the assigned altitude that the other aircraft violated; but altitude closures happen quickly when one is descending in idle; and another is climbing at climb thrust! TCAS worked as advertised.


Second narrative: While descending on the KEPEC3 Arrival we got a Traffic Alert for an aircraft at our 12 o'clock; 3400 feet below us. The alert became an RA requiring a climb of 1000 FPM. I immediately complied and initiated the climb. The First Officer (FO) told ATC that we were performing a TCAS maneuver. ATC responded that the other aircraft busted his clearance. We were between 9000 feet and 10;000 feet when the maneuver began and received 'clear of conflict' at about 10;500 feet. The FO saw the other aircraft pass by at our altitude 'no more than one mile.' Opinion: We suspect this Crew busted their 7000 feet restriction at ROPER. We were cleared to 8000 feet and our paths could have crossed. They were climbing like a missile. It's careless and reckless to be climbing so rapidly in crowded airspace. It leaves no room for error. No one can anticipate or react to what they are doing fast enough to get out of the way. It's only by luck that we had some lateral separation; their error and arrogance almost cost many lives. I would prefer to not share airspace with that Crew ever again. Let them check out the rodeo; a profession for which they seem especially well suited.This event shakes my faith in TCAS. It's only luck that our paths did not cross like our altitudes did. Next generation of TCAS should provide lateral as well as vertical guidance. This happened so fast and unexpectedly that I don't think ATC could have provided a turn to help maintain separation. Also; we could not see him with our nose in a climb attitude. We couldn't have known which way to turn. Perhaps arrivals and departures should be on the same frequency. We heard nothing from or about the other aircraft. Increased situational awareness may have helped us maneuver more effectively to avoid a midair collision.


Synopsis: B737NG flight crew reported that while descending into LAS they received and responded to an RA with a climbing resolution. Shortly after; ATC came on to advise them the other aircraft overshot their altitude causing the conflict.