Narrative:

TCAS failure. Shortly after takeoff and before reaching 1400 ft; we got a descending RA. Skies were clear with good visibility and both pilots had scanned the departure area. We saw no traffic but responded to the RA. Shortly afterwards; the RA changed to a climbing RA with a red target X mi at 12 O'clock position displayed within 100 ft of our altitude and then level with us. We saw no traffic but again responded to the RA. ATC was informed and they too saw no traffic or knew of any traffic in the vicinity. About 15 mins later we got a TCAS fail message. Entering congested airspace; we turned off the RA function to avoid more false RA's. We did get a false TA and; therefore; turned the TCAS system off. The disturbing part of this malfunctioning system was that it guided us towards the ground at a low altitude. Further; there was no reason to think that it could not also guide us into other traffic. I have seen malfunctioning TCAS system before; but never one like this that gave RA guidance that was not only false but also clearly affected safety of flight negatively.

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Original NASA ASRS Text

Title: B757-200 FLT CREW RECEIVES TWO APPARENTLY FALSE TCAS RESOLUTION ADVISORIES DURING INITIAL CLIMB; FOLLOWED SHORTLY BY A TCAS FAIL MESSAGE.

Narrative: TCAS FAILURE. SHORTLY AFTER TKOF AND BEFORE REACHING 1400 FT; WE GOT A DSNDING RA. SKIES WERE CLR WITH GOOD VISIBILITY AND BOTH PLTS HAD SCANNED THE DEP AREA. WE SAW NO TFC BUT RESPONDED TO THE RA. SHORTLY AFTERWARDS; THE RA CHANGED TO A CLBING RA WITH A RED TARGET X MI AT 12 O'CLOCK POS DISPLAYED WITHIN 100 FT OF OUR ALT AND THEN LEVEL WITH US. WE SAW NO TFC BUT AGAIN RESPONDED TO THE RA. ATC WAS INFORMED AND THEY TOO SAW NO TFC OR KNEW OF ANY TFC IN THE VICINITY. ABOUT 15 MINS LATER WE GOT A TCAS FAIL MESSAGE. ENTERING CONGESTED AIRSPACE; WE TURNED OFF THE RA FUNCTION TO AVOID MORE FALSE RA'S. WE DID GET A FALSE TA AND; THEREFORE; TURNED THE TCAS SYS OFF. THE DISTURBING PART OF THIS MALFUNCTIONING SYS WAS THAT IT GUIDED US TOWARDS THE GND AT A LOW ALT. FURTHER; THERE WAS NO REASON TO THINK THAT IT COULD NOT ALSO GUIDE US INTO OTHER TFC. I HAVE SEEN MALFUNCTIONING TCAS SYS BEFORE; BUT NEVER ONE LIKE THIS THAT GAVE RA GUIDANCE THAT WAS NOT ONLY FALSE BUT ALSO CLEARLY AFFECTED SAFETY OF FLT NEGATIVELY.

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.