D10 controller described a loss of separation event during parallel runway arrival operations when t...

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.

Original NASA ASRS Text

Title: 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.

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.

Data retrieved from NASA's ASRS site as of July 2013 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	1042464
Time
Date	201210
Local Time Of Day	1201-1800
Place
Locale Reference	DFW.Airport
State Reference	TX
Environment
Flight Conditions	Marginal
Aircraft 1
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	B737-800
Operating Under FAR Part	Part 121
Flight Phase	Final Approach
Flight Plan	IFR
Person 1
Function	Approach Departure
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Deviation - Procedural Published Material / Policy Deviation - Speed All Types

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.