Date: 201902
Local time of day: 0601-1200
Location: LAS.Tower, NV
Light: Daylight
Aircraft: Small Transport
Operating under: Part 91
Flight plan: IFR
Flight phase: Taxi
Airspace: Class B LAS
ATC / advisory: Tower LAS
Second aircraft: B737-800
Reporter organization: Government
Reporter function: Local
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Workload; Time Pressure; Human-Machine Interface; Communication Breakdown
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Less Severe; Conflict Airborne Conflict; Ground Excursion Runway
Detector: Person Air Traffic Control
When detected: In-flight; Taxi
Result: Air Traffic Control Provided Assistance; Flight Crew Executed Go Around / Missed Approach
Contributing factors: Human Factors; Aircraft
Primary problem: Aircraft

Narrative: I was working LC2 (Local Control) so only the arrivals and departures off 19R. Aircraft X was inbound for RWY 19R. Everything appeared normal on the approach and landing. As it appeared the aircraft was at taxi speed; I instructed Aircraft X to turn right at Taxiway T; they advised unable. I instructed them to turn right at the next Taxiway W and they said they were going to miss that one too and said something unreadable about the brakes. I though the pilot had said they didn't want to hit the brakes too hard. I asked Aircraft X if they could make Taxiway B as there were aircraft waiting to depart RWY 26R and a tight gap with my next 19R arrival. They said they could. And then I asked if they could make the high speed exit off their left side just so I could get them off the runway a bit quicker and LC1 could depart. Aircraft X said they could make the high speed Taxiway Y so I instructed them to turn left on Y and then left on the center Taxiway E and gave up the intersection to LC1. Once Aircraft X was on Taxiway E; I gave them instructions to cross RWY 19R at W and contact ground on point 1. They read that back correctly. I observed Aircraft X going too fast by Taxiway W and keyed up to inform them that they were missing W and might be turning up the high speed. Aircraft X said they were turning back and appeared to do a left 270 and ended up stopped in the dirt. Aircraft X advised that they had lost steering capability and brakes and would need a tow. They were off the runway but 100% in the RSA (Runway Safety Area).My next arrival was about 3 mile final and I sent that aircraft around with no issues. Aircraft Y was also inbound for RWY 19R about 8 miles out. When Aircraft Y checked in; I told them to expect a go around due to a disabled aircraft on the runway but to just continue on the approach for now. At about 5-6 miles from the airport I told Aircraft Y to go-around and maintain 4;500 feet and just fly the profile for the 19's. I believe I also mentioned that I was going to take him over the airport and out the other side. Not sure exactly how I worded it. Aircraft Y asked if they could expect 26L and I told them that they could. At approx. 3 miles from the approach end of 19R; Aircraft Y advised they could no longer fly the RNAV and requested a vector. I told Aircraft Y to fly runway heading and maintain 6;000 originally and then changed it to 5;000 for overhead traffic. Aircraft Y appeared to be in a right turn away from runway heading so I instructed them to turn back left heading 175 and called traffic of the departure end of Runway 26R; Aircraft Z that had departed on the STAAV departure. That departure should not have been a factor for Aircraft Y's go around but once Aircraft Y turned out to the west it was. Aircraft Z and Aircraft Y saw each other and I instructed Aircraft Y to maintain visual separation with Aircraft Z. The heading I gave him was going to take Aircraft Y behind Aircraft Z. Once the conflict was clear; I climbed Aircraft Y up to 7;000 and switched him to Departure.Reference Aircraft X - I thought it was unusual for such a light aircraft to miss taxiway T and W off 19R. Next time instead of assuming everything was ok; I should double check to make sure.Reference Aircraft Y - I need to find better phraseology to take an aircraft on the base to 19R over the airport and on runway heading for the 19's. I feel like Aircraft Y may have gotten confused after asking if they can expect 26L and then flew runway heading for 26 instead of 19. Better phraseology and emphasizing everything a couple times may have helped here.




Synopsis: LAS Tower Controller reported a runway excursion with one aircraft and a poorly planned missed approach with following aircraft.