Narrative:

Air carrier X aircraft checked on frequency at the OM (5 mi final) for runway 27L (arrival runway) at atl. LLWAS alert aural alarm sounded and I informed the pilot of runway 28 windshear alert; 20 KT loss; 1 mi departure. Aircraft continued approach. About 2 mi final; I noticed that LLWAS display was now showing runway 28 microburst alert; 48 KT loss; 1 mi departure; however; there was no aural alarm associated with the update of the LLWAS display. Pilot was advised of microburst activity and aircraft landed normally. For yrs we have complained about LLWAS not producing a subsequent aural alarm when conditions deteriorate from the initial alarm. If I had not visually noticed the microburst alert and the aircraft had executed a missed approach; they would have unknowingly flown directly into the path of the microburst activity. The local controller for runway 27R (departure runway) was unaware of the microburst alert until I pointed it out. He took evasive action and vectored a rotating air carrier Y away from the microburst. The LLWAS aural alarm parameters must be adjusted so controllers are alerted to changes in windshear conditions.

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Original NASA ASRS Text

Title: ATL LCL CTLR EXPRESSED CONCERN REGARDING LACK OF SUBSEQUENT AURAL ALARM ON LLWAS EQUIP AFTER INITIAL WINDSHEAR NOTIFICATION.

Narrative: ACR X ACFT CHKED ON FREQ AT THE OM (5 MI FINAL) FOR RWY 27L (ARR RWY) AT ATL. LLWAS ALERT AURAL ALARM SOUNDED AND I INFORMED THE PLT OF RWY 28 WINDSHEAR ALERT; 20 KT LOSS; 1 MI DEP. ACFT CONTINUED APCH. ABOUT 2 MI FINAL; I NOTICED THAT LLWAS DISPLAY WAS NOW SHOWING RWY 28 MICROBURST ALERT; 48 KT LOSS; 1 MI DEP; HOWEVER; THERE WAS NO AURAL ALARM ASSOCIATED WITH THE UPDATE OF THE LLWAS DISPLAY. PLT WAS ADVISED OF MICROBURST ACTIVITY AND ACFT LANDED NORMALLY. FOR YRS WE HAVE COMPLAINED ABOUT LLWAS NOT PRODUCING A SUBSEQUENT AURAL ALARM WHEN CONDITIONS DETERIORATE FROM THE INITIAL ALARM. IF I HAD NOT VISUALLY NOTICED THE MICROBURST ALERT AND THE ACFT HAD EXECUTED A MISSED APCH; THEY WOULD HAVE UNKNOWINGLY FLOWN DIRECTLY INTO THE PATH OF THE MICROBURST ACTIVITY. THE LCL CTLR FOR RWY 27R (DEP RWY) WAS UNAWARE OF THE MICROBURST ALERT UNTIL I POINTED IT OUT. HE TOOK EVASIVE ACTION AND VECTORED A ROTATING ACR Y AWAY FROM THE MICROBURST. THE LLWAS AURAL ALARM PARAMETERS MUST BE ADJUSTED SO CTLRS ARE ALERTED TO CHANGES IN WINDSHEAR CONDITIONS.

Data retrieved from NASA's ASRS site as of May 2009 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.