Narrative:

ASOS commissioned at fsm aug/94. System consistently reports incorrect sky and visibility conditions which are required to disseminate on ATIS and use for determining status of air traffic area. On oct/fri/94 ASOS reports ground visibility of 1 1/2 mi. Tower visibility is 3 mi. Because we have to use the lower report to determine air traffic area status, control zone IFR and VFR flight curtailed completely. After calling the NWS on the field, they took a visibility reading, determined it was 3 mi, and amended the WX to 3 mi. The NWS is scheduled to be closed down the first of 1995 which will force us to rely solely on the ASOS for WX reporting. This is a continuing problem with the ASOS and we find it is severely curtailing VFR flight because of incorrect readings. Without a human backup to the system an aircraft incident is possible. If the ASOS incorrectly reports visibility, pilots may be executing approachs below safe minimums putting the pilot in a precarious situation.

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Original NASA ASRS Text

Title: WX RPTING EQUIP PROB ASOS RPTING WRONG VISIBILITY. ONGOING PROB.

Narrative: ASOS COMMISSIONED AT FSM AUG/94. SYS CONSISTENTLY RPTS INCORRECT SKY AND VISIBILITY CONDITIONS WHICH ARE REQUIRED TO DISSEMINATE ON ATIS AND USE FOR DETERMINING STATUS OF ATA. ON OCT/FRI/94 ASOS RPTS GND VISIBILITY OF 1 1/2 MI. TWR VISIBILITY IS 3 MI. BECAUSE WE HAVE TO USE THE LOWER RPT TO DETERMINE ATA STATUS, CTL ZONE IFR AND VFR FLT CURTAILED COMPLETELY. AFTER CALLING THE NWS ON THE FIELD, THEY TOOK A VISIBILITY READING, DETERMINED IT WAS 3 MI, AND AMENDED THE WX TO 3 MI. THE NWS IS SCHEDULED TO BE CLOSED DOWN THE FIRST OF 1995 WHICH WILL FORCE US TO RELY SOLELY ON THE ASOS FOR WX RPTING. THIS IS A CONTINUING PROB WITH THE ASOS AND WE FIND IT IS SEVERELY CURTAILING VFR FLT BECAUSE OF INCORRECT READINGS. WITHOUT A HUMAN BACKUP TO THE SYS AN ACFT INCIDENT IS POSSIBLE. IF THE ASOS INCORRECTLY RPTS VISIBILITY, PLTS MAY BE EXECUTING APCHS BELOW SAFE MINIMUMS PUTTING THE PLT IN A PRECARIOUS SIT.

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.