Narrative:

While on descent to land at msn, ATIS reported ILS runway 18 the approach in us and the tower closed. Green bay FSS and ZAU reported WX as winds calm and 1/4 mi visibility with freezing fog. While on descent prior to radar vector to final, ATC reported the tower WX observer said it looked better for us if we executed the ILS runway 36 approach instead of ILS runway 18. During descent approach, vector to final and final descent from 10000 ft MSL to surface and 15 mi from airport, we could see the approach lights, runway lights, centerline lights at msn. After landing, the patchy fog obscured some txwys from 1/4 - 1/2 mi visibility. The tower opened after we landed and reported the visibility up to 1/2 mi. We did the ILS runway 36 approach under good VMC with the last report of visibility at 1/4 mi. The required visibility for the approach is 1/2 mi. We had better than 7+ mi during all phases, descent, approach and landing. The question after we landed was 'were we legal to land when the last report given to ATC was 1/4 mi visibility?' contributing factors: the lack of true WX reporting of conditions for runway 36 versus what the person at the tower location is seeing or reporting. We, the crew, not being able to ask for a visual approach because ATC has to operate under the WX report given and unable to approve such a request. Corrective actions: have an AWOS report during hours the tower is not in operation. Allow to continue the approach and descend below FAF altitude when the landing surface or environment can be seen at the FAF altitude and in-flight visibility is greater than 7 mi reference far part 121-651.

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Original NASA ASRS Text

Title: FLC OF A DC9-30 LANDED DURING MINIMUM LNDG WX AS OBSERVED BY THE FLC DURING APCH AND LNDG.

Narrative: WHILE ON DSCNT TO LAND AT MSN, ATIS RPTED ILS RWY 18 THE APCH IN US AND THE TWR CLOSED. GREEN BAY FSS AND ZAU RPTED WX AS WINDS CALM AND 1/4 MI VISIBILITY WITH FREEZING FOG. WHILE ON DSCNT PRIOR TO RADAR VECTOR TO FINAL, ATC RPTED THE TWR WX OBSERVER SAID IT LOOKED BETTER FOR US IF WE EXECUTED THE ILS RWY 36 APCH INSTEAD OF ILS RWY 18. DURING DSCNT APCH, VECTOR TO FINAL AND FINAL DSCNT FROM 10000 FT MSL TO SURFACE AND 15 MI FROM ARPT, WE COULD SEE THE APCH LIGHTS, RWY LIGHTS, CTRLINE LIGHTS AT MSN. AFTER LNDG, THE PATCHY FOG OBSCURED SOME TXWYS FROM 1/4 - 1/2 MI VISIBILITY. THE TWR OPENED AFTER WE LANDED AND RPTED THE VISIBILITY UP TO 1/2 MI. WE DID THE ILS RWY 36 APCH UNDER GOOD VMC WITH THE LAST RPT OF VISIBILITY AT 1/4 MI. THE REQUIRED VISIBILITY FOR THE APCH IS 1/2 MI. WE HAD BETTER THAN 7+ MI DURING ALL PHASES, DSCNT, APCH AND LNDG. THE QUESTION AFTER WE LANDED WAS 'WERE WE LEGAL TO LAND WHEN THE LAST RPT GIVEN TO ATC WAS 1/4 MI VISIBILITY?' CONTRIBUTING FACTORS: THE LACK OF TRUE WX RPTING OF CONDITIONS FOR RWY 36 VERSUS WHAT THE PERSON AT THE TWR LOCATION IS SEEING OR RPTING. WE, THE CREW, NOT BEING ABLE TO ASK FOR A VISUAL APCH BECAUSE ATC HAS TO OPERATE UNDER THE WX RPT GIVEN AND UNABLE TO APPROVE SUCH A REQUEST. CORRECTIVE ACTIONS: HAVE AN AWOS RPT DURING HRS THE TWR IS NOT IN OP. ALLOW TO CONTINUE THE APCH AND DSND BELOW FAF ALT WHEN THE LNDG SURFACE OR ENVIRONMENT CAN BE SEEN AT THE FAF ALT AND INFLT VISIBILITY IS GREATER THAN 7 MI REF FAR PART 121-651.

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.