A B737 NG flight crew reported a false EGPWS predictive windshear warning on short final to BOS Runway 27.
Synopsis
A B737 NG flight crew reported a false EGPWS predictive windshear warning on short final to BOS Runway 27.
Narrative
On the descent into BOS; the First Officer mentioned the fact that on a previous flight landing Runway 27 in BOS he had experienced a predictive windshear alert (Go Around; Windshear Ahead). This occurred with a corresponding uncommanded system test of the windshear alerting system. He said that they went ahead and landed because they determined there was a malfunction of some kind; which caused the system to begin a test. They were called by a Company representative who asked why they didn't go around and they explained the malfunction. The Company representative was satisfied they had done the correct thing. Well; fast forward to yesterday. The same thing happened to us with the system going into the test mode and giving us the aural; 'Go Around; Windshear Ahead' alert. I don't know what is causing this; but we need to find out for two reasons. First; we need to preclude possible unnecessary missed approaches. Second; we need to prevent negative learning in that we are supposed to go around when we get a warning. Find out what is causing this and either fix the problem or at least alert crew to the possibility of the system going into the test mode and giving an invalid warning.
Second reporter narrative
On the prior approach; winds were calm with clear skies. There were no convective activity or windshear advisories on the ATIS. The radar was off. Approximately 200 FT AGL; we got the same indications as the previous flight: audio warning and the radar test display. I asked the Captain about continuing and he said to land. The radar test display stayed up until after landing and we selected terrain for the ND display on taxi in. Obviously there is something about this runway that is causing erroneous windshear warnings. There appears to be a power plant or radar site under short final that may be the source of erroneous signals. There are also some windmills in the vicinity.
NASA callback
The reporter stated that the EGPWS windshear warning test mode activates only on BOS Runway 27. The anomaly's cause is unknown; but windmills near the runway may be a factor.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.