Narrative:

WX reported as 1/16 mi, sky obscured. Except for airport area, WX was clear. Apparently, a runway maintenance vehicle was on runway during second low approach, and the driver was not aware of approaching aircraft. Based on previous experience at this airport, I believed that the official WX report lagged the changing WX situation, and was not accurate although approach control was informed that a low approach only was requested. They issued an IFR approach clearance, but did not explain why a clearance for a low approach was not, or could not, be given. Neither approach nor tower gave me any WX information, such as a PIREP, to help determine the likelihood of the fog dissipating quickly, nor frankly did they seem very interested in that information. Visibility observations are apparently only taken from a single point, and are of limited value when the obscuration does not cover the entire landing area. Under those conditions, controllers should understand the pilot's need to view the landing area in order to make a reasonable decision concerning waiting for improvement or proceeding to an alternate. Some provision should be made to allow WX observations to be updated more quickly during rapidly changing conditions, including when the conditions are improving. Sometimes 5 or 10 mins can make a critical difference.

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Original NASA ASRS Text

Title: PART 135 OPERATOR STARTED INST APCH PROC WHEN THE WX WAS RPTED BELOW AUTHORIZED IFR LNDG MINS.

Narrative: WX RPTED AS 1/16 MI, SKY OBSCURED. EXCEPT FOR ARPT AREA, WX WAS CLR. APPARENTLY, A RWY MAINT VEHICLE WAS ON RWY DURING SECOND LOW APCH, AND THE DRIVER WAS NOT AWARE OF APCHING ACFT. BASED ON PREVIOUS EXPERIENCE AT THIS ARPT, I BELIEVED THAT THE OFFICIAL WX RPT LAGGED THE CHANGING WX SITUATION, AND WAS NOT ACCURATE ALTHOUGH APCH CTL WAS INFORMED THAT A LOW APCH ONLY WAS REQUESTED. THEY ISSUED AN IFR APCH CLRNC, BUT DID NOT EXPLAIN WHY A CLRNC FOR A LOW APCH WAS NOT, OR COULD NOT, BE GIVEN. NEITHER APCH NOR TWR GAVE ME ANY WX INFO, SUCH AS A PIREP, TO HELP DETERMINE THE LIKELIHOOD OF THE FOG DISSIPATING QUICKLY, NOR FRANKLY DID THEY SEEM VERY INTERESTED IN THAT INFO. VISIBILITY OBSERVATIONS ARE APPARENTLY ONLY TAKEN FROM A SINGLE POINT, AND ARE OF LIMITED VALUE WHEN THE OBSCURATION DOES NOT COVER THE ENTIRE LNDG AREA. UNDER THOSE CONDITIONS, CTLRS SHOULD UNDERSTAND THE PLT'S NEED TO VIEW THE LNDG AREA IN ORDER TO MAKE A REASONABLE DECISION CONCERNING WAITING FOR IMPROVEMENT OR PROCEEDING TO AN ALTERNATE. SOME PROVISION SHOULD BE MADE TO ALLOW WX OBSERVATIONS TO BE UPDATED MORE QUICKLY DURING RAPIDLY CHANGING CONDITIONS, INCLUDING WHEN THE CONDITIONS ARE IMPROVING. SOMETIMES 5 OR 10 MINS CAN MAKE A CRITICAL DIFFERENCE.

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.