Date: 201210
Local time of day: 1201-1800
Location: DFW.Airport, TX
Flight conditions: Marginal
Aircraft: MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Flight phase: Final Approach
Airspace: Class B DFW
ATC / advisory: TRACON D10
Second aircraft: B737-800
Reporter organization: Government
Reporter function: Approach; Departure
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Situational Awareness
Anomaly: ATC Issue All Types; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Air Traffic Control
Result: General None Reported / Taken
Contributing factors: Human Factors; Procedure
Primary problem: Human Factors

Narrative: The airport was in a North Flow configuration with simultaneous dependent ILS approaches to parallel runways in use (stagger; no monitors). MVFR conditions prevailed with low ceilings. There was also a strong wind shear around 3;000 FT; where the wind at altitude was strong from the southwest; but down low on the final; it was out of the northeast. This made for challenging 'turn-ons' to the ILS final. I was working the AR3 position; controlling the 36L final. Training was in progress on the adjacent AR position (Runway 35C). Arrival demand increased and I had one too many airplanes for the sequence. Both the Feeder Controller and the OJTI on AR2 advised that if I could get down below 2;500; I could get a visual approach and could put the extra airplane on their runway. I descended a MD80 to the minimum glide slope intercept altitude of 2;100; reduced the speed to 170 KIAS; and turned them in to the 35C localizer. I then descended a B737 to 3;100; reduced the speed to 170; and gave base-leg and intercept turns to the 36L localizer. I asked the MD80 to report the runway in sight; but they declined to do so. I then cleared the MD80 for the ILS approach. Once I had my required 2-mile stagger; I cleared the B737 for the approach to 36L. I then transferred communications on both aircraft to their respective tower frequencies. In watching the replay; it appears that the B737 did not slow down; and the stagger collapsed to 1.5 miles inside the FAF. I was also advised that the Quality Assurance Office did not consider the MD80 established on the localizer (dead center on the ILS) when vertical separation was lost. My biggest mistake was letting other controllers talk me into filling a tight hole with hopes of getting a visual approach clearance; especially considering the great difference in wind speed during and after the ILS turn on. The conservative nature of the airline involved should have also been a 'red flag.' I should have extended the B737 on the downwind; gone into the next slot; and let the feeder re-sequence subsequent aircraft. This could have also been avoided if the supervisors opened Final Monitor positions and implemented independent ILS approaches instead.




Synopsis: D10 Controller described a loss of separation event during parallel runway arrival operations when trying to fill a tight hole on final in hopes of a visual approach; the reporter's indication of opening the Final Monitor position may have prevented the occurrence.