Narrative:

Filed IFR flight from bis to far. WX forecast was 5000' overcast, 2 mi with snow and fog. Upon reaching about 25 NM west of far VOR the WX went down to 200 obscured, 1/2 mi with snow and fog. Upon reaching 10 mi from far VOR WX was reported as 300 3/8, RVR 1800. Far approach was informed that I needed a minimum of RVR 1800 or 1/2 NM official WX to shoot the ILS to 35 at far. Upon reaching the hold at 5 the far 35 localizer, far approach informed me I was ok to shoot the ILS to 35 with 1/2 mi visibility. I crossed the OM and started to descend on the ILS. Approximately 1/2 NM inside the OM approach reported RVR 1200, varying to 1600' visibility, less than 1/2 NM as allowed per the regulation for far part 135. Since I was already inside the OM, it was ok to shoot the missed approach. Or, if visibility and ceiling would allow, to do a landing. Upon reaching the decision height. The missed approach was initiated as advised by ATC. The problem here is this: the tower allowed me 1/2 mi to shoot the approach, but did the official WX show at the time of shooting the approach that the flight visibility was good enough to initiate the approach? According to a copy of the NWS/FAA FSS report for that time period, the WX was still below minima allowed. In fact, it was 300 and 1/8 with snow and fog. I shot the approach on good standing with approach control that officially I needed at least 1/2 mi to shoot the approach. As cleared for approach I understood my WX minimums had been met. From now on I'll definitely ask if the WX is official or not.

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Original NASA ASRS Text

Title: PLT OF SMA ATX IS UNCERTAIN OF LEGALITY OF HAVING MADE AN APCH IN MINIMUM WX CONDITIONS.

Narrative: FILED IFR FLT FROM BIS TO FAR. WX FORECAST WAS 5000' OVCST, 2 MI WITH SNOW AND FOG. UPON REACHING ABOUT 25 NM W OF FAR VOR THE WX WENT DOWN TO 200 OBSCURED, 1/2 MI WITH SNOW AND FOG. UPON REACHING 10 MI FROM FAR VOR WX WAS RPTED AS 300 3/8, RVR 1800. FAR APCH WAS INFORMED THAT I NEEDED A MINIMUM OF RVR 1800 OR 1/2 NM OFFICIAL WX TO SHOOT THE ILS TO 35 AT FAR. UPON REACHING THE HOLD AT 5 THE FAR 35 LOC, FAR APCH INFORMED ME I WAS OK TO SHOOT THE ILS TO 35 WITH 1/2 MI VISIBILITY. I CROSSED THE OM AND STARTED TO DSND ON THE ILS. APPROX 1/2 NM INSIDE THE OM APCH RPTED RVR 1200, VARYING TO 1600' VISIBILITY, LESS THAN 1/2 NM AS ALLOWED PER THE REG FOR FAR PART 135. SINCE I WAS ALREADY INSIDE THE OM, IT WAS OK TO SHOOT THE MISSED APCH. OR, IF VISIBILITY AND CEILING WOULD ALLOW, TO DO A LNDG. UPON REACHING THE DECISION HEIGHT. THE MISSED APCH WAS INITIATED AS ADVISED BY ATC. THE PROB HERE IS THIS: THE TWR ALLOWED ME 1/2 MI TO SHOOT THE APCH, BUT DID THE OFFICIAL WX SHOW AT THE TIME OF SHOOTING THE APCH THAT THE FLT VISIBILITY WAS GOOD ENOUGH TO INITIATE THE APCH? ACCORDING TO A COPY OF THE NWS/FAA FSS RPT FOR THAT TIME PERIOD, THE WX WAS STILL BELOW MINIMA ALLOWED. IN FACT, IT WAS 300 AND 1/8 WITH SNOW AND FOG. I SHOT THE APCH ON GOOD STANDING WITH APCH CTL THAT OFFICIALLY I NEEDED AT LEAST 1/2 MI TO SHOOT THE APCH. AS CLRED FOR APCH I UNDERSTOOD MY WX MINIMUMS HAD BEEN MET. FROM NOW ON I'LL DEFINITELY ASK IF THE WX IS OFFICIAL OR NOT.

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.