Narrative:

At XX36 on may/xx/95 I noticed a microburst alert go off for runway 35R, indicating a 40 KT loss. This alert caused an air carrier to execute a missed approach. The winds throughout the entire airport never got higher than 6 KTS. The LLWAS indicated the alert, while the terminal doppler WX radar screen had a red 'X' on it indicating it was OTS. The alert went away within a short period of time. We continued to use this unreliable equipment regardless. The missed approach was logged, the malfunction in the equipment was not. This is a constant problem. At XX45, the wind indicators on the LLWAS went blank again for about 30 seconds. The terminal doppler WX radar appeared normal. Again, this is a continual problem. At YY55 a gust front passed over the airport. A gust or microburst was obvious because of the blowing dust. Nothing of note was ever displayed on the terminal doppler WX radar. This equipment is dangerous for flight and should be logged OTS permanently until it can become reliable. Most controllers have no confidence in it at all. It is prematurely being certified despite known problems. Callback conversation with reporter revealed the following information: reporter stated since moving to new den airport ATC equipment problems have been ongoing with no corrective action, ucr's filed with no response. LLWAS-3 will not interface with terminal doppler WX radar and causes false microburst alerts. Reporter stated FAA was told prior to installation of the terminal doppler WX radar that it would not interface with LLWAS-3. Reporter stated den was a test facility for another manufacturer terminal doppler WX radar and LLWAS-3 which did interface correctly. Equipment has been de-interfaced and is now worked independently. Equipment still does not work properly.

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Original NASA ASRS Text

Title: ACFT GAR DUE TO FALSE MICROBURST ADVISORY. ATC EQUIP PROB LLWAS-3 TERMINAL DOPPLER WX RADAR.

Narrative: AT XX36 ON MAY/XX/95 I NOTICED A MICROBURST ALERT GO OFF FOR RWY 35R, INDICATING A 40 KT LOSS. THIS ALERT CAUSED AN ACR TO EXECUTE A MISSED APCH. THE WINDS THROUGHOUT THE ENTIRE ARPT NEVER GOT HIGHER THAN 6 KTS. THE LLWAS INDICATED THE ALERT, WHILE THE TERMINAL DOPPLER WX RADAR SCREEN HAD A RED 'X' ON IT INDICATING IT WAS OTS. THE ALERT WENT AWAY WITHIN A SHORT PERIOD OF TIME. WE CONTINUED TO USE THIS UNRELIABLE EQUIP REGARDLESS. THE MISSED APCH WAS LOGGED, THE MALFUNCTION IN THE EQUIP WAS NOT. THIS IS A CONSTANT PROB. AT XX45, THE WIND INDICATORS ON THE LLWAS WENT BLANK AGAIN FOR ABOUT 30 SECONDS. THE TERMINAL DOPPLER WX RADAR APPEARED NORMAL. AGAIN, THIS IS A CONTINUAL PROB. AT YY55 A GUST FRONT PASSED OVER THE ARPT. A GUST OR MICROBURST WAS OBVIOUS BECAUSE OF THE BLOWING DUST. NOTHING OF NOTE WAS EVER DISPLAYED ON THE TERMINAL DOPPLER WX RADAR. THIS EQUIP IS DANGEROUS FOR FLT AND SHOULD BE LOGGED OTS PERMANENTLY UNTIL IT CAN BECOME RELIABLE. MOST CTLRS HAVE NO CONFIDENCE IN IT AT ALL. IT IS PREMATURELY BEING CERTIFIED DESPITE KNOWN PROBS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED SINCE MOVING TO NEW DEN ARPT ATC EQUIP PROBS HAVE BEEN ONGOING WITH NO CORRECTIVE ACTION, UCR'S FILED WITH NO RESPONSE. LLWAS-3 WILL NOT INTERFACE WITH TERMINAL DOPPLER WX RADAR AND CAUSES FALSE MICROBURST ALERTS. RPTR STATED FAA WAS TOLD PRIOR TO INSTALLATION OF THE TERMINAL DOPPLER WX RADAR THAT IT WOULD NOT INTERFACE WITH LLWAS-3. RPTR STATED DEN WAS A TEST FACILITY FOR ANOTHER MANUFACTURER TERMINAL DOPPLER WX RADAR AND LLWAS-3 WHICH DID INTERFACE CORRECTLY. EQUIP HAS BEEN DE-INTERFACED AND IS NOW WORKED INDEPENDENTLY. EQUIP STILL DOES NOT WORK PROPERLY.

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.