Date: 201308
Local time of day: 1201-1800
Location: BZN.Airport, MT
Flight conditions: VMC
Light: Daylight
Aircraft: Medium Transport; Low Wing; 2 Turbojet Eng
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class D BZN
ATC / advisory: Tower BZN
Second aircraft: Military Trainer
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Time Pressure
Second reporter function: First Officer; Pilot Flying
Anomaly: Conflict NMAC
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Clearance; Flight Crew Took Evasive Action
Contributing factors: Human Factors; Procedure; Environment - Non Weather Related
Primary problem: Ambiguous

Narrative: Descending into BZN; we had an extremely close near collision with a VFR antique military trainer. We joined a right 5 mile downwind for Runway 12 on a visual approach. We were aware of the radar outage at BZN both from the NOTAMS and verbally from ATC. While joining the downwind we heard the other aircraft call BZN Tower and state his estimated position of 10 miles west of BZN. I immediately began to scan the area for the other aircraft without any luck. The other aircraft was given instructions to line up straight in for Runway 12 and they would be #2 to follow us. I told my First Officer I felt uneasy since we did not have a visual on the other aircraft and apparently they did not have a transponder since the target did not show up on TCAS. We had the weather radar on as well but did not get any returns. I told my First Officer to keep it in tight to give us room inside the other aircraft; or where we thought the other aircraft would be from his position report. In the base turn we were both searching for the traffic; I was looking to the northwest and my First Officer was looking in the turn to the base. He then shouted '..it; there he is!' and started to steepen the bank. I saw the other aircraft on base to Runway 12 approximately 50-100 FT below us and about 300-500 FT right out in front of us. I came up on the yoke and banked to approximately 50 degrees to the right and pitched up a little; followed by telling my First Officer to lower the nose to not get into an accelerated stall. I can't say by how much we missed the other aircraft; but it wasn't by too much. I told the Tower we had a near miss/collision with the other aircraft. That was followed by a few seconds of silence. Tower responded with a roger. We continued the approach since we were stabilized by 1;000 FT AFE and still in a good position and landed without incident. Tower asked us to give them a call when at the gate. We did and discussed the incident and they said they'd send in some report. I gave a passenger announcement at the gate regarding the approach and the other airplane's position as not where it was supposed to be. That's why we took evasive action.Root cause was an inaccurate position report by the other aircraft and the other aircraft not entering a straight-in approach to follow us as instructed by the Tower Controller. Also; our inability to find the other aircraft because we were focused searching where he wasn't.All airplanes operating in and out of Class D airspace should be equipped with operable Mode C transponders so that even during times of radar outage; we will still be able to 'see' other conflicting traffic.


Second narrative: [This report contains no additional information].


Synopsis: An air carrier on a visual approach to BZN Runway 12 took evasive action during a near miss with an antique military trainer at about 1;000 FT above the airport.