Narrative:

Departed off runway 34R and cleared to 9;000 feet. Upon reaching nearly 8;000 feet ATC advised us of traffic descending to 10;000 feet. We attempted to slow our ascent; but the aircraft had already entered 'altitude acquire' mode. At approximately 8;500 feet a TCAS resolution advisory (RA) was aurally and visually annunciated; with 'level-off' commanded. The captain complied with the RA; but due to system lag and utilizing flight director TCAS RA cues; the airplane's climb was not fully arrested until about 8;700 feet. In order to comply with the TCAS RA flight director cues; the aircraft then descended to approximately 8;400 feet. Due to some confusion between interpretation of seemingly conflicting commands from the TCAS system ('level-off' aural vs. Slightly descending FD cue); ATC was not notified until the conflict had already cleared. No unusual maneuvering was required; and ATC seemed to be surprised by the report of the RA.the TCAS resolution advisory system is outdated and does not contain logic for level-offs. Today's high-performance aircraft safely maintain steady higher-rate climbs and descents with programmed level-offs that the TCAS system is incapable of compensating for. This decades-old technology; which is designed as an added safety layer; is creating false positives in the already crowded modern airspace environment. These false positives then become a safety risk in and of themselves; due to deviations in ATC clearances that are required; and yet could create even more dangerous loss of separation.

Related reports:

Google
 

Original NASA ASRS Text

Title: Air Carrier flight crew reported receiving conflicting instructions from a TCAS/RA Alert for traffic above them that was not a factor.

Narrative: Departed off Runway 34R and cleared to 9;000 feet. Upon reaching nearly 8;000 feet ATC advised us of traffic descending to 10;000 feet. We attempted to slow our ascent; but the aircraft had already entered 'altitude acquire' mode. At approximately 8;500 feet a TCAS Resolution Advisory (RA) was aurally and visually annunciated; with 'Level-Off' commanded. The Captain complied with the RA; but due to system lag and utilizing Flight Director TCAS RA cues; the airplane's climb was not fully arrested until about 8;700 feet. In order to comply with the TCAS RA Flight Director cues; the aircraft then descended to approximately 8;400 feet. Due to some confusion between interpretation of seemingly conflicting commands from the TCAS system ('Level-Off' aural vs. slightly descending FD cue); ATC was not notified until the conflict had already cleared. No unusual maneuvering was required; and ATC seemed to be surprised by the report of the RA.The TCAS Resolution Advisory system is outdated and does not contain logic for level-offs. Today's high-performance aircraft safely maintain steady higher-rate climbs and descents with programmed level-offs that the TCAS system is incapable of compensating for. This decades-old technology; which is designed as an added safety layer; is creating false positives in the already crowded modern airspace environment. These false positives then become a safety risk in and of themselves; due to deviations in ATC clearances that are required; and yet could create even more dangerous loss of separation.

Data retrieved from NASA's ASRS site 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.