Narrative:

Aircraft X was northeast direct pmd level at 090; aircraft Y was southeast on the hollywood park route; a VFR route through lax class B; level at 095. Traffic was exchanged and aircraft Y reported aircraft X in sight. Their targets merged with standard 500ft. Separation. After target resolution was obtained I climbed aircraft X to 110; the pilot responded that they were already responding to TCAS/RA. I asked the pilot to advise when the RA was complete and he could start his climb assuming that the TCAS/RA told him to decent for aircraft Y. He responded that the RA was for a climb and he was climbing to 110. Due to the quick climb in response he was near 095 with only about 1/2 mile of target resolution. There was no other aircraft in the vicinity within several thousand feet below him. I asked if his TCAS was showing an aircraft below him because I couldn't see anything. He responded that it was due to the aircraft that was at his 9 o'clock; the only aircraft in that vicinity; before they crossed paths was aircraft Y. If he had responded to this incorrect RA a few seconds sooner he would have been within no more than a few hundred feet; maybe less; with the targets merged. This is not a rare occurrence. Over the past few years I have observed several RA's that told the pilot to climb or descend into the traffic that set them off causing unsafe proximity. Recommendation; address programming errors with TCAS equipment. Instead of requiring pilots to comply with ras immediately every time; even when they have just been issued traffic that conflicts with the RA; instruct pilots to use common sense when deciding on a proper response to RA's. Allow controllers to issue instructions that contradict RA's when they see it will result in an unsafe situation. TCAS/RA's are far from perfect; we need to stop treating them like they are infallible.

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Original NASA ASRS Text

Title: SCT Controller described a TCAS RA event between a VFR and IFR aircraft after the VFR reported the IFR in sight; the reporter indicating that TCAS alerts are far from perfect and sometimes result in closer conflict situations.

Narrative: Aircraft X was NE direct PMD level at 090; Aircraft Y was SE on the Hollywood Park route; a VFR route through LAX Class B; level at 095. Traffic was exchanged and Aircraft Y reported Aircraft X in sight. Their targets merged with standard 500ft. separation. After target resolution was obtained I climbed Aircraft X to 110; the pilot responded that they were already responding to TCAS/RA. I asked the pilot to advise when the RA was complete and he could start his climb assuming that the TCAS/RA told him to decent for Aircraft Y. He responded that the RA was for a climb and he was climbing to 110. Due to the quick climb in response he was near 095 with only about 1/2 mile of target resolution. There was no other aircraft in the vicinity within several thousand feet below him. I asked if his TCAS was showing an aircraft below him because I couldn't see anything. He responded that it was due to the aircraft that was at his 9 o'clock; the only aircraft in that vicinity; before they crossed paths was Aircraft Y. If he had responded to this incorrect RA a few seconds sooner he would have been within no more than a few hundred feet; maybe less; with the targets merged. This is not a rare occurrence. Over the past few years I have observed several RA's that told the pilot to climb or descend into the traffic that set them off causing unsafe proximity. Recommendation; address programming errors with TCAS equipment. Instead of requiring pilots to comply with RAs immediately every time; even when they have just been issued traffic that conflicts with the RA; instruct pilots to use common sense when deciding on a proper response to RA's. Allow controllers to issue instructions that contradict RA's when they see it will result in an unsafe situation. TCAS/RA's are far from perfect; we need to stop treating them like they are infallible.

Data retrieved from NASA's ASRS site as of April 2012 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.