Date: 201705
Local time of day: 0601-1200
Location: DFW.Airport, TX
Flight conditions: VMC
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class B DFW
ATC / advisory: Tower DFW
Second aircraft: Regional Jet CL65; Undifferentiated or Other Model
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Not Flying; First Officer
Anomaly: ATC Issue All Types; Conflict NMAC
Detector: Automation Aircraft RA; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: Captain flying. Normal flight. During descent; we were held at 4000 ft until turning a dogleg to final for Runway 35C. We had ILS frequency dialed in; and were on localizer when we were cleared to slow from 220 to 170; and cleared the approach. I immediately disconnected the autopilot; lowered the nose and continued configuring (we were at flaps 1 or 5). When we left 4000 ft; we were slightly above glideslope (about 1 dot) and centered on the localizer. At or near JOBBS; the final approach fix; with the aircraft configured with gear down and flaps 15 and the aircraft on both glideslope and localizer; we had a TA. I was busy flying the aircraft; but peaked at the TCAS and noticed an aircraft near our aircraft. It quickly became a RA and I was given the command 'Descend; descend' with the accompanying symbology. I was approximately 1500-1800 feet at the time and immediately pushed the nose over and looked at the TCAS. I saw the other aircraft exactly above our aircraft and only 300 feet separation. I descended to approximately 1200 feet AGL; as the symbology was moving up. Also; at the time of my level off; the non-flying pilot said he visually acquired the other aircraft and stated that we were clear. I then called for final flaps (flaps 25; flaps 30) as we approached the glideslope from below. I re-intercepted the glideslope and continued down. The landing was uneventful. On rollout; the Tower controller stated that he did not have a TA or RA; but that he had 'logged the event' or some wording similar to that.I am unsure of the cause of this event. It seems to me that Tower was not paying enough attention to traffic separation. I find it very hard to believe that ATC did not have a TA or RA. We had 300 feet separation. I also speculate that tower cleared the regional jet (RJ) for a visual approach even though the RJ was west of our localizer and cleared to land on 35R (to the east of our localizer); creating a situation in which the RJ either had to extend their downwind leg past our flight path; or cutting across our flight path. The FO told me that the RJ was in a steep descent and landed ahead of us on 35R. I cannot verify this as I didn't see the aircraft. Another question is what was the reaction in the other aircraft? If they received a RA; which they should have; why didn't they begin an immediate climb? If they did initiate a climb; how were they able to continue to land on 36R?Clearing an aircraft for a visual approach removes separation responsibilities from ATC; but clearing the aircraft for visual approaches when they were located as stated above is very poor judgement.


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


Synopsis: B737 flight crew reported receiving an RA on approach to DFW from another aircraft that was going over the top of them for a parallel runway.