Narrative:

The WX in denver was marginal VFR to complete IFR conditions. The base of the clouds were hovering in the 900-1000 ft range (6000-6200 MSL). The tops were around 7300 MSL. We were running simultaneous ILS approachs to runways 35R and 36. These runways are separated by 1 mi. This operation requires the use of a final monitor position in the TRACON to ensure that aircraft remain on the localizer due to the close proximity of other aircraft conducting approachs on the other runway. For reasons unknown to me the TRACON said they were going to use visual separation as well when conducting these approachs. This was okay above the clouds, but what about when they went into them. This operation also requires that aircraft be on the local control frequency 18 mi out on final. The tower complained again because they weren't getting them until the OM (5 mi). When the complaints were issued we were told they needed to keep the aircraft in order to apply the visual separation. There are no procedures for this. The end result was about 3 hours after beginning this operation, the final monitor position noticed an large transport closing the distance behind a heavy widebody transport. Realizing that if something wasn't done that soon he could not maintain the required minimum of 5 mi separation. He asked the large transport pilot if the less than standard wake turbulence separation would be acceptable. The pilot replied 'no problem.' hence, he did not pull the aircraft off of the approach. The tower supervisor in the tower cabin attendant did not like what he saw and called an operational error on the final monitor controller for not applying proper wake turbulence separation. There are some serious questions here as to the proper use of wake turbulence separation. The problem is the controller was applying separation standards that could not possibly be assured because of the awkward position this operation put him in. The real culprit in this scenario is trying to put too many airplanes into an airport that the WX conditions did not allow. We pushed the envelope too far. The rules were written and flow rates adjusted because of the airport limitations. Then the rules were bent to squeeze in a couple more aircraft. The end result was an operational error which could have been avoided if only the procedures for simultaneous ILS approachs were followed as written. Unfortunately, this practice happens all too often. If this trend continues, someday more than an operational error will occur.

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Original NASA ASRS Text

Title: TWR CTLR IS CRITICAL OF APCH CTLR HANDLING OF A HVY INBOUND ACFT AND ANOTHER ACR. CTLR CLAIMS THAT LTSS OCCURRED.

Narrative: THE WX IN DENVER WAS MARGINAL VFR TO COMPLETE IFR CONDITIONS. THE BASE OF THE CLOUDS WERE HOVERING IN THE 900-1000 FT RANGE (6000-6200 MSL). THE TOPS WERE AROUND 7300 MSL. WE WERE RUNNING SIMULTANEOUS ILS APCHS TO RWYS 35R AND 36. THESE RWYS ARE SEPARATED BY 1 MI. THIS OP REQUIRES THE USE OF A FINAL MONITOR POS IN THE TRACON TO ENSURE THAT ACFT REMAIN ON THE LOC DUE TO THE CLOSE PROX OF OTHER ACFT CONDUCTING APCHS ON THE OTHER RWY. FOR REASONS UNKNOWN TO ME THE TRACON SAID THEY WERE GOING TO USE VISUAL SEPARATION AS WELL WHEN CONDUCTING THESE APCHS. THIS WAS OKAY ABOVE THE CLOUDS, BUT WHAT ABOUT WHEN THEY WENT INTO THEM. THIS OP ALSO REQUIRES THAT ACFT BE ON THE LCL CTL FREQ 18 MI OUT ON FINAL. THE TWR COMPLAINED AGAIN BECAUSE THEY WEREN'T GETTING THEM UNTIL THE OM (5 MI). WHEN THE COMPLAINTS WERE ISSUED WE WERE TOLD THEY NEEDED TO KEEP THE ACFT IN ORDER TO APPLY THE VISUAL SEPARATION. THERE ARE NO PROCS FOR THIS. THE END RESULT WAS ABOUT 3 HRS AFTER BEGINNING THIS OP, THE FINAL MONITOR POS NOTICED AN LGT CLOSING THE DISTANCE BEHIND A HVY WDB. REALIZING THAT IF SOMETHING WASN'T DONE THAT SOON HE COULD NOT MAINTAIN THE REQUIRED MINIMUM OF 5 MI SEPARATION. HE ASKED THE LGT PLT IF THE LESS THAN STANDARD WAKE TURB SEPARATION WOULD BE ACCEPTABLE. THE PLT REPLIED 'NO PROB.' HENCE, HE DID NOT PULL THE ACFT OFF OF THE APCH. THE TWR SUPVR IN THE TWR CAB DID NOT LIKE WHAT HE SAW AND CALLED AN OPERROR ON THE FINAL MONITOR CTLR FOR NOT APPLYING PROPER WAKE TURB SEPARATION. THERE ARE SOME SERIOUS QUESTIONS HERE AS TO THE PROPER USE OF WAKE TURB SEPARATION. THE PROB IS THE CTLR WAS APPLYING SEPARATION STANDARDS THAT COULD NOT POSSIBLY BE ASSURED BECAUSE OF THE AWKWARD POS THIS OP PUT HIM IN. THE REAL CULPRIT IN THIS SCENARIO IS TRYING TO PUT TOO MANY AIRPLANES INTO AN ARPT THAT THE WX CONDITIONS DID NOT ALLOW. WE PUSHED THE ENVELOPE TOO FAR. THE RULES WERE WRITTEN AND FLOW RATES ADJUSTED BECAUSE OF THE ARPT LIMITATIONS. THEN THE RULES WERE BENT TO SQUEEZE IN A COUPLE MORE ACFT. THE END RESULT WAS AN OPERROR WHICH COULD HAVE BEEN AVOIDED IF ONLY THE PROCS FOR SIMULTANEOUS ILS APCHS WERE FOLLOWED AS WRITTEN. UNFORTUNATELY, THIS PRACTICE HAPPENS ALL TOO OFTEN. IF THIS TREND CONTINUES, SOMEDAY MORE THAN AN OPERROR WILL OCCUR.

Data retrieved from NASA's ASRS site as of July 2007 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.