Medium large transport crew was issued LLWAS warning. Crew executed a go around.

Attributes
ACN	419797
Time
Date	199811
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : ord airport : ord
State Reference	IL
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : ord
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Flight Phase	descent : approach landing : go around landing other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 12000
ASRS Report	419797
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	other anomaly other
Independent Detector	other controllera other flight crewa
Resolutory Action	other other
Consequence	Other
Supplementary
Primary Problem	Airport
Air Traffic Incident	other
Situations
ATC Facility	other physical facility
Airport	other physical facility

Narrative:

During a VMC approach to runway 22L at ord, tower reported surface winds of 230 degrees 25 KTS gusting to 39 KTS and issued a microburst alert for runway 22L. A missed approach was executed during which we overflew runway 22L. No evidence of microburst activity was encountered and conditions normally associated with microbursts were not present. There was no convective activity in the area and the winds for approach and landing were the same. The tower reported that the alert had persisted for over 20 mins and no aircraft had landed. We remained in the traffic pattern for another 10-15 mins and decided that due to lack of evidence for microburst activity and winds at the surface equal to the winds on the approach path that the LLWAS was giving a false alert. We made an uneventful approach and landing encountering light to moderate turbulence normal for the gusty wind conditions but experienced no windshear.

Original NASA ASRS Text

Title: MLG CREW WAS ISSUED LLWAS WARNING. CREW EXECUTED A GAR.

Narrative: DURING A VMC APCH TO RWY 22L AT ORD, TWR RPTED SURFACE WINDS OF 230 DEGS 25 KTS GUSTING TO 39 KTS AND ISSUED A MICROBURST ALERT FOR RWY 22L. A MISSED APCH WAS EXECUTED DURING WHICH WE OVERFLEW RWY 22L. NO EVIDENCE OF MICROBURST ACTIVITY WAS ENCOUNTERED AND CONDITIONS NORMALLY ASSOCIATED WITH MICROBURSTS WERE NOT PRESENT. THERE WAS NO CONVECTIVE ACTIVITY IN THE AREA AND THE WINDS FOR APCH AND LNDG WERE THE SAME. THE TWR RPTED THAT THE ALERT HAD PERSISTED FOR OVER 20 MINS AND NO ACFT HAD LANDED. WE REMAINED IN THE TFC PATTERN FOR ANOTHER 10-15 MINS AND DECIDED THAT DUE TO LACK OF EVIDENCE FOR MICROBURST ACTIVITY AND WINDS AT THE SURFACE EQUAL TO THE WINDS ON THE APCH PATH THAT THE LLWAS WAS GIVING A FALSE ALERT. WE MADE AN UNEVENTFUL APCH AND LNDG ENCOUNTERING LIGHT TO MODERATE TURB NORMAL FOR THE GUSTY WIND CONDITIONS BUT EXPERIENCED NO WINDSHEAR.

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.