Narrative:

Our flight took off with the last update on the WX 100 ft obscured, 1/4 mi visibility. 15 mins prior, the update was 200 ft, 1 mi visibility. I called the tower at destination airport and they said it was fluctuating up and down. We departed and upon arrival we were given a heading to intercept the localizer, advised that the RVR was 1200 ft. We needed 200 ft and 2400 ft RVR according to the approach plate. I decided to shoot the approach, the missed was briefed and at the decision ht the runway environment was in sight. The aircraft landed in a safe, normal manner. The question when we got on the ramp was whether or not we were at fault for accepting the approach clearance when I knew the RVR was reported as less than what was needed as prescribed on the approach plate. The FARS in part 91 say that descent below decision ht and no landing may be made if the 'flight visibility' is less than that prescribed on the approach. Flight visibility is the forward horizontal distance from the aircraft, which would be a visibility only the pilots could see or determine. We accepted the approach, landed, it was uneventful but the question remains as to whether we were ok to accept the clearance in the first place. We are part 91. I am currently consulting the instrument flying handbook, the aim, the FARS and employees 'controllers' in my local control tower for this answer. Most people don't shoot approachs to 100 ft obscured and 1200 ft RVR everyday. When cleared for the approach, this was clearly no time to decide whether or not we were legal to do it. The answer is not easily found, but I will keep looking.

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Original NASA ASRS Text

Title: FLC OF A CORP JET MADE AN ILS APCH AND LNDG WHEN THE WX WAS RPTED BELOW PUBLISHED MINIMUMS. HOWEVER, THE FLT VISIBILITY MET VISUAL REFS FOR GOING BELOW THE DECISION HT.

Narrative: OUR FLT TOOK OFF WITH THE LAST UPDATE ON THE WX 100 FT OBSCURED, 1/4 MI VISIBILITY. 15 MINS PRIOR, THE UPDATE WAS 200 FT, 1 MI VISIBILITY. I CALLED THE TWR AT DEST ARPT AND THEY SAID IT WAS FLUCTUATING UP AND DOWN. WE DEPARTED AND UPON ARR WE WERE GIVEN A HDG TO INTERCEPT THE LOC, ADVISED THAT THE RVR WAS 1200 FT. WE NEEDED 200 FT AND 2400 FT RVR ACCORDING TO THE APCH PLATE. I DECIDED TO SHOOT THE APCH, THE MISSED WAS BRIEFED AND AT THE DECISION HT THE RWY ENVIRONMENT WAS IN SIGHT. THE ACFT LANDED IN A SAFE, NORMAL MANNER. THE QUESTION WHEN WE GOT ON THE RAMP WAS WHETHER OR NOT WE WERE AT FAULT FOR ACCEPTING THE APCH CLRNC WHEN I KNEW THE RVR WAS RPTED AS LESS THAN WHAT WAS NEEDED AS PRESCRIBED ON THE APCH PLATE. THE FARS IN PART 91 SAY THAT DSCNT BELOW DECISION HT AND NO LNDG MAY BE MADE IF THE 'FLT VISIBILITY' IS LESS THAN THAT PRESCRIBED ON THE APCH. FLT VISIBILITY IS THE FORWARD HORIZ DISTANCE FROM THE ACFT, WHICH WOULD BE A VISIBILITY ONLY THE PLTS COULD SEE OR DETERMINE. WE ACCEPTED THE APCH, LANDED, IT WAS UNEVENTFUL BUT THE QUESTION REMAINS AS TO WHETHER WE WERE OK TO ACCEPT THE CLRNC IN THE FIRST PLACE. WE ARE PART 91. I AM CURRENTLY CONSULTING THE INST FLYING HANDBOOK, THE AIM, THE FARS AND EMPLOYEES 'CTLRS' IN MY LCL CTL TWR FOR THIS ANSWER. MOST PEOPLE DON'T SHOOT APCHS TO 100 FT OBSCURED AND 1200 FT RVR EVERYDAY. WHEN CLRED FOR THE APCH, THIS WAS CLRLY NO TIME TO DECIDE WHETHER OR NOT WE WERE LEGAL TO DO IT. THE ANSWER IS NOT EASILY FOUND, BUT I WILL KEEP LOOKING.

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.