Date: 201311
Local time of day: 0001-0600
Location: LAS.Airport, NV
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Taxi
ATC / advisory: Tower LAS
Second aircraft: Commercial Fixed Wing
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness; Communication Breakdown; Confusion
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Person Air Traffic Control; Person Flight Crew
When detected: Taxi
Result: Flight Crew Took Evasive Action
Contributing factors: ATC Equipment / Nav Facility / Buildings; Human Factors
Primary problem: Human Factors

Narrative: LAS ATCT was on Configuration Number 1. This configuration consists of: departing Runway 25R; landing Runway 25L; departing and landing runways 19R and 19L. At the time of the incident; I was working Local Assist 1. One of my duties is to provide the sequence and departure priority to the Controller. Local Assist 1 monitors the Local 1 frequency. We have two different Local controls that control each side of the airport complex. The runways at LAS intersect at the departure end in this configuration. To remain compliant with the 7110.65; we must make sure aircraft are through the intersection before aircraft can land or depart safely. Essentially; each local has to 'take turns' departing their aircraft through the intersection. The Local Assist 1 determines who will depart. On this day and the day prior the ASDE-X (Ground RADAR) had been out of service and awaiting parts. Usually when the ASDE is in service; the Local Assist can look upon the ASDE and determine what each controller has without having to physically get up and walk to each side of the Tower to look at the pending departures that each of the two controllers have. I had to get up and walk to the opposite end of the cab away from my position to see what Local 2 had to depart while turning an extra set of eyes away from the Local 1 operation. When I got back to sit down; I noticed Air Carrier X holding short Runway 25R at Alpha 5 and Air Carrier Y rotating and airborne just pass Alpha 5 on Runway 25R. It seemed innocent enough until Air Carrier X questioned the Local 1 Controller; 'I am I still cleared to cross?' The Controller responds in the affirmative and Air Carrier X replied; 'Okay.' But Air Carrier Y was rolling.' At this point I'm still confident that nothing went wrong until I asked the controller did Air Carrier X have a point. The Controller was a bit rattled and that's when I realized he tried to cross Runway 25R with Air Carrier X; but cleared Air Carrier Y right afterwards. Luckily; Air Carrier X was well aware of the going on's and he didn't move until Air Carrier Y was well passed and airborne. One of the most used tools at the larger; busy airports is the ASDE-X Ground RADAR. The ASDE-X is not a substitute for the windows but we have come to rely on it as part of the routine scan. In this particular scenario; the ASDE-X being inoperable affected both the Local 1 and Local Assist. I had to get up and turn my back to the operation whereas when the ASDE-X is in operation I can stay engaged and control from one spot. Even though I have Local 1 frequency in my ear; I still could not equate what was going on without actually seeing and hearing the incident at the same time while it was unfolding. What good is an assist when I have to have my back turned.


Second narrative: It was a clear VFR day and the Captain had just landed on 25L in LAS and was exiting at Taxiway A5. Once clear of 25L; the Tower Controller cleared us to cross 25R on A5 then call Ground on 121.1. After repeating the clearance; I looked to my right to make sure 25R was clear. About 2;000 FT down the runway I see an Air Carrier Y rolling in our direction. At first I couldn't tell for sure if he was on the runway or a parallel taxiway; but I could tell he was moving faster than a normal taxi speed. I said to the Captain; 'Hold on; there's a plane. Wait; another carrier is on the runway. Stop; stop.' By now I could tell Air Carrier Y was on the runway gaining speed for takeoff. The Captain stopped our plane on A5 just past the intersection of A and A5 well short of the hold short line for 25R. A few seconds later another air carrier crossed us from right to left and rotates off 25R. I asked Tower if he had cleared us to cross 25R. He said; 'Cleared to cross 25R on A5; contact Ground .1 on the other side.' I said to the Controller that if we had crossed 25R when he told us the first time; we would have hit that other Air Carrier Y. His response was; 'We'll look into that.' We then safely crossed 25R and proceeded to the gate. Obviously had it not been for the actions of this crew; the results could have been disastrous. ATC never should have cleared us to cross the runway while another aircraft was in its takeoff roll. This goes to show why making sure runways and taxiways are clear before entering them is so important.


Synopsis: LAS Controller described a near runway intersection conflict event prevented by pilot action/s after noting a departure aircraft rolling.