Narrative:

I fly for a scheduled regional airline and was repositioning from alb to iad. Runway 19R was in sight 30 mi out, with the ATIS calling clear skies and 10 mi visibility. Very localized fog (ground) was forming and the TDZ RVR was dropping rapidly to below landing mins for 19R. At a 10 mi final we were vectored off that approach, to 1R. We then became #3 for the approach when the patchy fog relocated to the approach end of 1R. Outside the marker the latest WX report indicated RVR for 1R TDZ 1400 ft, mid 3000 ft. Rollout greater than 6000 ft. Because of our part 91 status we continued the approach and landed uneventful never losing sight of the runway and doing it in VFR conditions at all times until rolling out in the midfield section, where we penetrated a portion of the fog bank. Because of the very localized nature of the fog that night, the TDZ RVR transmissometers, due to their off runway locations, indicated fog at the side of the runway but not actually on it. The jet that landed previous to us in effect also 'plowed out' the runway of the very scattered fog. RVR values for landing are often very accurate and helpful but that night in dulles they were only good for that specific area, between the meters. In my 14 yrs of flying I never saw conditions like I did that night.

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Original NASA ASRS Text

Title: COMMUTER CAPT ON FERRY FLT RPTS LNDG AT IAD WHEN RVR VALUES ARE BELOW MIN. FLT WAS OPERATING UNDER PART 91 SO ONLY FLT VISIBILITY VALUES ARE PERTINENT TO THE DECISION TO LAND. RPTR SAYS PATCHES OF FOG WERE LCLIZED BTWN THE TRANSMISSOMETERS AND NOT ACTUALLY OBSCURING THE RWY.

Narrative: I FLY FOR A SCHEDULED REGIONAL AIRLINE AND WAS REPOSITIONING FROM ALB TO IAD. RWY 19R WAS IN SIGHT 30 MI OUT, WITH THE ATIS CALLING CLR SKIES AND 10 MI VISIBILITY. VERY LOCALIZED FOG (GND) WAS FORMING AND THE TDZ RVR WAS DROPPING RAPIDLY TO BELOW LNDG MINS FOR 19R. AT A 10 MI FINAL WE WERE VECTORED OFF THAT APCH, TO 1R. WE THEN BECAME #3 FOR THE APCH WHEN THE PATCHY FOG RELOCATED TO THE APCH END OF 1R. OUTSIDE THE MARKER THE LATEST WX RPT INDICATED RVR FOR 1R TDZ 1400 FT, MID 3000 FT. ROLLOUT GREATER THAN 6000 FT. BECAUSE OF OUR PART 91 STATUS WE CONTINUED THE APCH AND LANDED UNEVENTFUL NEVER LOSING SIGHT OF THE RWY AND DOING IT IN VFR CONDITIONS AT ALL TIMES UNTIL ROLLING OUT IN THE MIDFIELD SECTION, WHERE WE PENETRATED A PORTION OF THE FOG BANK. BECAUSE OF THE VERY LOCALIZED NATURE OF THE FOG THAT NIGHT, THE TDZ RVR TRANSMISSOMETERS, DUE TO THEIR OFF RWY LOCATIONS, INDICATED FOG AT THE SIDE OF THE RWY BUT NOT ACTUALLY ON IT. THE JET THAT LANDED PREVIOUS TO US IN EFFECT ALSO 'PLOWED OUT' THE RWY OF THE VERY SCATTERED FOG. RVR VALUES FOR LNDG ARE OFTEN VERY ACCURATE AND HELPFUL BUT THAT NIGHT IN DULLES THEY WERE ONLY GOOD FOR THAT SPECIFIC AREA, BTWN THE METERS. IN MY 14 YRS OF FLYING I NEVER SAW CONDITIONS LIKE I DID THAT NIGHT.

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.