Date: 201409
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Second aircraft: Small Transport; Low Wing; 2 Turbojet Eng
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Human factors: Communication Breakdown; Time Pressure; Situational Awareness; Confusion; Distraction
Second reporter function: First Officer; Pilot Flying
Anomaly: ATC Issue All Types; Conflict Airborne Conflict; Deviation - Altitude Overshoot; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued Advisory / Alert; Flight Crew Took Evasive Action; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Clearance
Contributing factors: Airport; Procedure
Primary problem: Procedure

Narrative: While on approach; we were cleared down to 2000 Feet; direct an intersection to join the localizer; cleared the visual approach; and maintain 210 knots until the initial approach fix (IAF). We were on the localizer; after IAF and prior to interception of the Glideslope level at 2000 feet. We were in the process of slowing and configuring the aircraft for Glideslope Intercept. My First Officer was the pilot flying. Just prior to interception of the Glideslope; the approach controller told us we had traffic at our 11 o'clock; 1.5 miles; which was a FAA flight Check aircraft who had us in sight and was maintaining visual separation. At first; being night I could not visually see the traffic. I saw on TCAS that the traffic was only a mile away; 300 feet below us and heading right toward us. I then got a visual on the landing light of this traffic and it was indeed heading toward us at nearly our assigned altitude. We then received a resolution advisory (RA); the First Officer did a great job of turning off the autopilot and hand flying the RA to keep us away from this traffic that appeared to be on a collision course with us as well as climbing toward us. We were on the localizer as instructed flying our visual approach when to our surprise; this FAA Flight Check Aircraft was cutting across the localizer in a perpendicular fashion heading toward us. We climbed and missed the Flight Check aircraft by about 300 feet vertically. Thank God for TCAS! I informed ATC that we were responding to an RA. When the conflict was over; we had more that enough distance from the airport to reestablish a stabilized approach and landing and we landing without further incident. After landing I asked the Tower to give me the phone number to the TRACON. I spoke with the Approach Control Supervisor who said it was indeed unusual and he would have their quality control people look into it.


Second narrative: As the captain told ATC; their reply was that yes I said they have you in sight. After clear of conflict I was able to descend back down and get stabilized on the PAPI. I do not think the other aircraft had us in sight. I do not know why they would be allowed to cross final approach at approach altitude.


Synopsis: A B737 at 2;000 FT on an ILS approach took evasive action after a TCAS RA from a FAA Flight Check aircraft while both were under ATC control. The other aircraft reported the B737 insight but took no evasive action.