B737 flight crew reported conflict with a pipeline inspection aircraft on short final to runway 35L ...

Narrative:

While on short final for runway 35L we got a traffic alert at our 10 o'clock position. We assumed since tower did not inform us of any traffic that it was a helicopter orbiting off our left. To our surprise we saw a small high wing general aviation aircraft in our 10 o'clock position heading directly for us on a base leg. The aircraft appeared to be making an attempt to avoid us by starting a climb. We slightly lowered our nose to also avoid the aircraft but we were limited on how much altitude we could lose since we were already so low to the ground. Once we were sure we would not hit the aircraft; we returned to the correct glideslope angle and landed the aircraft. We questioned tower about the encounter and that was the first time we heard anything from ATC about the fact that it was a pipeline aircraft that we had gotten close to. We commented to tower that we had gotten a TCAS traffic alert and that it would have been nice to have been told of the pipeline aircraft's position. It did not seem that the tower controller was very concerned about the event so I requested a phone number of the tower supervisor. I contacted the tower supervisor from my hotel room and she said it was the tower controller's duty to inform of us of the traffic.

Original NASA ASRS Text

Title: B737 Flight Crew reported conflict with a pipeline inspection aircraft on short final to Runway 35L at AUS. Conflict was announced by TCAS but not reported by AUS Tower.

Narrative: While on short final for Runway 35L we got a Traffic Alert at our 10 o'clock position. We assumed since Tower did not inform us of any traffic that it was a helicopter orbiting off our left. To our surprise we saw a small high wing general aviation aircraft in our 10 o'clock position heading directly for us on a base leg. The aircraft appeared to be making an attempt to avoid us by starting a climb. We slightly lowered our nose to also avoid the aircraft but we were limited on how much altitude we could lose since we were already so low to the ground. Once we were sure we would not hit the aircraft; we returned to the correct glideslope angle and landed the aircraft. We questioned Tower about the encounter and that was the first time we heard anything from ATC about the fact that it was a pipeline aircraft that we had gotten close to. We commented to Tower that we had gotten a TCAS Traffic Alert and that it would have been nice to have been told of the pipeline aircraft's position. It did not seem that the Tower Controller was very concerned about the event so I requested a phone number of the Tower Supervisor. I contacted the Tower Supervisor from my hotel room and she said it was the Tower Controller's duty to inform of us of the traffic.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	862312
Time
Date	200911
Local Time Of Day	1201-1800
Place
Locale Reference	AUS.Airport
State Reference	TX
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	Small Aircraft
Flight Phase	Initial Approach
Person 1
Function	Captain
Experience	Flight Crew Last 90 Days 210 Flight Crew Type 15000
Person 2
Function	First Officer
Experience	Flight Crew Last 90 Days 194
Events
Anomaly	Conflict Airborne Conflict

B737 flight crew reported conflict with a pipeline inspection aircraft on short final to runway 35L at aus. Conflict was announced by TCAS but not reported by aus tower.