Narrative:

After takeoff from runway 24L at lax, we leveled at 3000 ft in compliance with the loop departure. When given our climb clearance, we started up and almost immediately received a TCASII RA directing us to 'monitor vertical speed' and 'descend.' the TCASII presentation showed an aircraft directly above us at 200 ft level. I clicked off the autoplt and manually descended the aircraft back to 3000 ft from 3300 ft. The RA stopped almost immediately upon descent and the target disappeared from the screen. The tower did not see any aircraft nor did we. We also had no targets on the TCASII screen until the RA came on. Previous experience with VFR aircraft transiting the VFR corridor without contacting anyone led me to believe that the RA was valid, and hazy sky conditions prevented visual sighting by us or tower/approach.

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Original NASA ASRS Text

Title: B757-200 FLC RESPONDED TO A TCASII RA DURING INITIAL CLB ON A SID DEP OVER ONE OF THE LAX VFR CORRIDORS. NO OTHER TFC OBSERVED ON THE ACFT TCASII SCREEN, AND NO CONFLICTING TFC WAS OBSERVED BY THE TWR CTLR.

Narrative: AFTER TKOF FROM RWY 24L AT LAX, WE LEVELED AT 3000 FT IN COMPLIANCE WITH THE LOOP DEP. WHEN GIVEN OUR CLB CLRNC, WE STARTED UP AND ALMOST IMMEDIATELY RECEIVED A TCASII RA DIRECTING US TO 'MONITOR VERT SPD' AND 'DSND.' THE TCASII PRESENTATION SHOWED AN ACFT DIRECTLY ABOVE US AT 200 FT LEVEL. I CLICKED OFF THE AUTOPLT AND MANUALLY DSNDED THE ACFT BACK TO 3000 FT FROM 3300 FT. THE RA STOPPED ALMOST IMMEDIATELY UPON DSCNT AND THE TARGET DISAPPEARED FROM THE SCREEN. THE TWR DID NOT SEE ANY ACFT NOR DID WE. WE ALSO HAD NO TARGETS ON THE TCASII SCREEN UNTIL THE RA CAME ON. PREVIOUS EXPERIENCE WITH VFR ACFT TRANSITING THE VFR CORRIDOR WITHOUT CONTACTING ANYONE LED ME TO BELIEVE THAT THE RA WAS VALID, AND HAZY SKY CONDITIONS PREVENTED VISUAL SIGHTING BY US OR TWR/APCH.

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.