WX reporting equipment ASOS symbology interpretation.

Attributes
ACN	323933
Time
Date	199512
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : csg
State Reference	GA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : cle
Operator	common carrier : air carrier
Make Model Name	SF 340A
Operating Under FAR Part	Part 121
Flight Phase	ground : preflight
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	oversight : supervisor
Qualification	controller : radar
Experience	controller radar : 7
ASRS Report	323933
Person 2
Affiliation	company : air carrier
Function	other personnel other personnel other
Qualification	other other : other
Events
Anomaly	other anomaly other
Independent Detector	other other : unspecified atc
Resolutory Action	other
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

I was the acting supervisor for the columbus, GA, tower/TRACON. The WX had been crummy all morning with no end in sight. The station manager for air carrier called to discuss WX for a departing aircraft which had been awaiting a 1400 ft RVR to takeoff. During the conversation, he indicated that the captain was planning to request a runway 23 departure, since runway 23 had no RVR, thus his requirement was 1/4 mi. I advised that the visibility was not 1/4 mi, and the tower visibility was 1/8 mi. He indicated that the situational awareness observation on his printout showed 1/4 mi. During our conversation we determined: ASOS will not report 1/16, 1/8, 3/16, only 'less than 1/4' which is transmitted as 'less than 1/4.' the air carrier computer system will apparently not print the 'less' symbol, so the printout which the pilot had displayed the visibility as 'percent 1/4' which the pilot interpreted as 1/4 mi. Had it not been for our conversation, this pilot would have taken off below minima.

Original NASA ASRS Text

Title: WX RPTING EQUIP ASOS SYMBOLOGY INTERP.

Narrative: I WAS THE ACTING SUPVR FOR THE COLUMBUS, GA, TWR/TRACON. THE WX HAD BEEN CRUMMY ALL MORNING WITH NO END IN SIGHT. THE STATION MGR FOR ACR CALLED TO DISCUSS WX FOR A DEPARTING ACFT WHICH HAD BEEN AWAITING A 1400 FT RVR TO TKOF. DURING THE CONVERSATION, HE INDICATED THAT THE CAPT WAS PLANNING TO REQUEST A RWY 23 DEP, SINCE RWY 23 HAD NO RVR, THUS HIS REQUIREMENT WAS 1/4 MI. I ADVISED THAT THE VISIBILITY WAS NOT 1/4 MI, AND THE TWR VISIBILITY WAS 1/8 MI. HE INDICATED THAT THE SITUATIONAL AWARENESS OBSERVATION ON HIS PRINTOUT SHOWED 1/4 MI. DURING OUR CONVERSATION WE DETERMINED: ASOS WILL NOT RPT 1/16, 1/8, 3/16, ONLY 'LESS THAN 1/4' WHICH IS XMITTED AS 'LESS THAN 1/4.' THE ACR COMPUTER SYS WILL APPARENTLY NOT PRINT THE 'LESS' SYMBOL, SO THE PRINTOUT WHICH THE PLT HAD DISPLAYED THE VISIBILITY AS 'PERCENT 1/4' WHICH THE PLT INTERPRETED AS 1/4 MI. HAD IT NOT BEEN FOR OUR CONVERSATION, THIS PLT WOULD HAVE TAKEN OFF BELOW MINIMA.

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.