Reporter states the ASOS is unreliable. Controller had to augment WX reports with visibility changes...

Narrative:

ASOS equipment continues to prove unreliable. On jun/mon/96 at XA50 local at cos ATCT WX deteriorated with typical convective activity. Thunderstorms were observed and manually entered into ASOS since the system cannot detect this greatest hazard to aviation safety. At XA47 local ASOS transmitted a special observation showing visibility 1 1/2 TR+. Actual visibility was much higher so the system was augmented to show 5 mi. The XA55 local WX observation was transmitted with a visibility of 5 mi but at XA57 local ASOS generated and transmitted another special with visibility 2TR. This occurred while the controller was attempting to make a new ATIS broadcast, control traffic and ensure that pilots received current WX information. ASOS visibility was again augmented to 5 mi and a special observation was transmitted at XB01 local showing visibility at 5 mi. For the next 45 mins ASOS continued to generate special observations with non-representative WX elements causing distraction and increased workload for the tower controllers. When convective WX is present it is difficult enough to provide ATC services and WX information to the users without the added distrs of making corrections to a system that cannot do what it was supposedly designed to do. ASOS in no way eliminates the need for trained WX observers. Problems with ASOS are frequent and continuing. Callback conversation with reporter revealed the following information: reporter stated the ASOS is basically doing what it is designed to do. Reporter indicated that when any of the ASOS sensor values are overridden, the particular sensor reverts to manual operations until the next scheduled ASOS WX observation. Reporter indicated that if there is an inaccurate reading of one of the elements, it is at this time the controller will augment the report and override the specific element(south). Reporter stated the ASOS system cannot detect types of cloud activity which then has to be input into the system by the controller. The reporter said that it is the responsibility of the FD/clearance delivery position to handle the ASOS changes but if the position gets busy, the other controllers will make the WX changes. Reporter implied that the software for the visibility element should be changed in order to provide more accurate readings. Reporter stated the workload/distraction of the ASOS varies with the WX and the time of day/traffic volume.

Original NASA ASRS Text

Title: RPTR STATES THE ASOS IS UNRELIABLE. CTLR HAD TO AUGMENT WX RPTS WITH VISIBILITY CHANGES AND TSTM ACTIVITY. RPTR CLAIMS ASOS GENERATED SPECIAL OBSERVATIONS WITH NON- REPRESENTATIVE WX ELEMENTS.

Narrative: ASOS EQUIP CONTINUES TO PROVE UNRELIABLE. ON JUN/MON/96 AT XA50 LCL AT COS ATCT WX DETERIORATED WITH TYPICAL CONVECTIVE ACTIVITY. TSTMS WERE OBSERVED AND MANUALLY ENTERED INTO ASOS SINCE THE SYS CANNOT DETECT THIS GREATEST HAZARD TO AVIATION SAFETY. AT XA47 LCL ASOS XMITTED A SPECIAL OBSERVATION SHOWING VISIBILITY 1 1/2 TR+. ACTUAL VISIBILITY WAS MUCH HIGHER SO THE SYS WAS AUGMENTED TO SHOW 5 MI. THE XA55 LCL WX OBSERVATION WAS XMITTED WITH A VISIBILITY OF 5 MI BUT AT XA57 LCL ASOS GENERATED AND XMITTED ANOTHER SPECIAL WITH VISIBILITY 2TR. THIS OCCURRED WHILE THE CTLR WAS ATTEMPTING TO MAKE A NEW ATIS BROADCAST, CTL TFC AND ENSURE THAT PLTS RECEIVED CURRENT WX INFO. ASOS VISIBILITY WAS AGAIN AUGMENTED TO 5 MI AND A SPECIAL OBSERVATION WAS XMITTED AT XB01 LCL SHOWING VISIBILITY AT 5 MI. FOR THE NEXT 45 MINS ASOS CONTINUED TO GENERATE SPECIAL OBSERVATIONS WITH NON-REPRESENTATIVE WX ELEMENTS CAUSING DISTR AND INCREASED WORKLOAD FOR THE TWR CTLRS. WHEN CONVECTIVE WX IS PRESENT IT IS DIFFICULT ENOUGH TO PROVIDE ATC SVCS AND WX INFO TO THE USERS WITHOUT THE ADDED DISTRS OF MAKING CORRECTIONS TO A SYS THAT CANNOT DO WHAT IT WAS SUPPOSEDLY DESIGNED TO DO. ASOS IN NO WAY ELIMINATES THE NEED FOR TRAINED WX OBSERVERS. PROBS WITH ASOS ARE FREQUENT AND CONTINUING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THE ASOS IS BASICALLY DOING WHAT IT IS DESIGNED TO DO. RPTR INDICATED THAT WHEN ANY OF THE ASOS SENSOR VALUES ARE OVERRIDDEN, THE PARTICULAR SENSOR REVERTS TO MANUAL OPS UNTIL THE NEXT SCHEDULED ASOS WX OBSERVATION. RPTR INDICATED THAT IF THERE IS AN INACCURATE READING OF ONE OF THE ELEMENTS, IT IS AT THIS TIME THE CTLR WILL AUGMENT THE RPT AND OVERRIDE THE SPECIFIC ELEMENT(S). RPTR STATED THE ASOS SYS CANNOT DETECT TYPES OF CLOUD ACTIVITY WHICH THEN HAS TO BE INPUT INTO THE SYS BY THE CTLR. THE RPTR SAID THAT IT IS THE RESPONSIBILITY OF THE FD/CD POS TO HANDLE THE ASOS CHANGES BUT IF THE POS GETS BUSY, THE OTHER CTLRS WILL MAKE THE WX CHANGES. RPTR IMPLIED THAT THE SOFTWARE FOR THE VISIBILITY ELEMENT SHOULD BE CHANGED IN ORDER TO PROVIDE MORE ACCURATE READINGS. RPTR STATED THE WORKLOAD/DISTR OF THE ASOS VARIES WITH THE WX AND THE TIME OF DAY/TFC VOLUME.

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.

Attributes
ACN	339158
Time
Date	199606
Day	Mon
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : cos
State Reference	CO
Environment
Light	Daylight
Person 1
Affiliation	government : faa
Function	controller : clearance delivery controller : flight data
Qualification	controller : radar
Experience	controller radar : 8 flight time total : 400
ASRS Report	339158
Person 2
Affiliation	government : faa
Function	oversight : supervisor
Qualification	controller : radar
Events
Anomaly	other anomaly other
Supplementary
Air Traffic Incident	other
Situations
ATC Facility	other physical facility procedure or policy : unspecified

Reporter states the ASOS is unreliable. Controller had to augment WX reports with visibility changes and thunderstorm activity. Reporter claims ASOS generated special observations with non- representative WX elements.