Anonymous

Regarding the statement under “Discussion” of “We have received reports of anomalies with the Aviation Communication & Surveillance Systems (ACSS) Traffic Alert and Collision Avoidance System (TCAS) units during a flight test over a high density airport.” ACSS believes it relevant to note that the initial such report was provided to the FAA by ACSS in late 2009, and that the FAA then reportedly did manage to reproduce the scenario during another flight test in early 2010. However, with over 35 million flight hours of ACSS TCAS systems in field operation no operator has ever reported to ACSS any such anomalies being observed, nor is ACSS aware of any such reports having been provided to the FAA (reference Section 1.4 of ACSS document 8008352-001,“ACSS Continuing Operational Safety Probability Assessment of the Interference Limiting Function”, included with this comment submittal). This fact would indicate that the probability of such an event is low enough that an Airworthiness Directive to address the potential situation is unnecessary.