Date: 201707
Local time of day: 1801-2400
Location: AUS.Airport, TX
Flight conditions: VMC
Light: Night
Aircraft: Large Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground AUS
Second aircraft: Small Aircraft; High Wing; 1 Eng; Fixed Gear
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Communication Breakdown; Confusion; Distraction
Second reporter function: Pilot Flying; Captain
Anomaly: ATC Issue All Types; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Took Evasive Action
Contributing factors: Airport; Environment - Non Weather Related; Human Factors; Procedure; Staffing
Primary problem: Human Factors

Narrative: We were following the 17L Approach path to Runway 17L at AUS. We were handed off to Tower and it was immediately evident that the Tower Controller was very busy handling multiple aircraft on approach to both south runways as well as handling Ground Control on the same frequency. There were multiple air carrier aircraft on approach to both runways and shortly after switching frequencies; we heard a general aviation helicopter [advise ATC of] heavy vibrations and request immediate landing. Tower cleared the helicopter in distress to land on Taxiway Bravo; one of the two parallel taxiways to our landing runway. There were multiple transmissions to the helicopter about his status as well as to other aircraft on the field and approach while we were on final. Tower broadcast a request for all aircraft to be on 121.0 Tower frequency. The helicopter was subsequently cleared to hover-taxi on Bravo to the FBO. Tower instructed us to plan to turn onto Taxiway Alpha after clearing the runway; which is the parallel closest to the runway. After landing we turned off the runway at Kilo and could see that the helicopter was at the intersection of Kilo and Bravo turning into the FBO. The Captain took this turn slowly as it was hard to tell in the dark exactly what the helicopter was doing and how far away he was. Tower instructed us to taxi to the ramp via Alpha; Golf; Golf 1. After getting established northbound on Alpha; I proceeded to do my After Landing Flow and called Operations on the number 2 radio. The Captain had briefed the likelihood of parked aircraft and congestion in the ramp area and I planned to have my attention outside at that point; but in my mind while on Alpha we would be free of traffic conflict threats. The helicopter was now behind us; other carrier aircraft landing after us would likely roll out to the same intersection we had; and would also be behind us. I also thought I noticed the lights of an aircraft taking off on 17L to our right and so I did not think any aircraft were currently on or would be exiting the runway. My attention was on the After Landing Flows and calling Operations on the number 2 at that time; so I did not hear all transmissions taking place on Tower frequency (which the number 1 radio was still on as instructed). As we approached the turn to Taxiway Golf; I had just switched back to the number 1 radio and told the Captain that we were still going to Gate XX and that Operations requested the APU be left running for tow off the gate. The Captain was slowing for the turn and suddenly braked hard to a stop while turning our aircraft left off of center line. He said something like 'where did that guy come from?' I looked right and saw the beacon of a GA aircraft high wing general aviation aircraft stopped just in front of and to the right of our right wing on Taxiway Golf reverse runway exit. This aircraft was extremely hard to see in the dark. His position and beacon lights blended in with the airport lighting and he did not have any taxi or landing lights illuminated. The GA aircraft Pilot queried Tower for instructions and said something about 'the air carrier'. The Tower replied that he had been instructed to give way to the air carrier. I don't know how far into the taxiway from the hold short line the GA aircraft was but I could see that we didn't have room to pass. The Tower transmitted that he couldn't see the GA aircraft. From the Tower's perspective the GA aircraft was directly to our right; close; and shorter and so not viewable over our fuselage. I transmitted that the GA aircraft would need to move first and that he had room to do so. Tower instructed the GA aircraft to go ahead and join Bravo and we were still cleared into the ramp. At no point during approach; landing; and taxi to the gate were we issued traffic alerts by the Controller. We were aware of the helicopter because we heard the transmissions. I never heard a GA aircraft receiving instructions to give wayto us. The Captain noticed something about the GA aircraft that grabbed his attention and his quick reaction avoided a potential collision. I believe the single controller in the tower cab was overloaded and that there was too much traffic in the terminal area for single Controller operations to be safe.


Second narrative: [Report narrative contained no additional information.]


Synopsis: Air carrier flight crew reported taking evasive action from a GA aircraft while taxiing at night after landing at AUS. The very busy Controller was apparently handling all ATC communications on multiple frequencies and failed to alert the crew about ground traffic.