TCAS feil kan føre til forvirring - AIN

Operators Report Errors with TCAS Advisories

TCAS has proved to be effective in reducing collision potential between aircraft, but the system has also caused confusion in the cockpit, according to a recent Aviation Safety Reporting System (ASRS) Callback newsletter. Reports of false TCAS indications and invalid resolution advisories (RAs) have resulted in reduced separation and safety between aircraft, ASRS said. “RA climbs have been reported that either should have been issued as RA descents or should not have been issued at all,” it noted. “Dangerous aircraft flight paths have resulted from ghost target intruders. Near-[collision] incidents without any TCAS warnings have been reported as well.” This issue of Callback shares reported incidents of illogical TCAS and RA indications and some resulting problems. “Several lessons may be gleaned,” ASRS said. “Chief among them is the notion that safety, judgment, and common sense may temper procedural obedience when evaluating and responding to TCAS advisories.” Although these latest reports have yet to result in a new ASRS special study on the TCAS issues raised, a previous study on near midair collision incidents—updated through August 2017—contains 50 ASRS reporting database sets, many of which deal with TCAS errors reported by both corporate and airline pilots.