Piper Pilot 100 — Systems Description

This document is an ACAS II Bulletin focusing on the operations of the Traffic Alert and Collision Avoidance System (TCAS II) at low altitudes. It discusses how TCAS II functions differently when the aircraft is close to the ground, particularly regarding the use of radio altimeter data to inhibit certain resolution advisories (RAs). The bulletin outlines several operational events that illustrate the limitations of TCAS II in low-altitude scenarios, including encounters with non-altitude reporting aircraft and drones. The document aims to educate pilots and air traffic controllers on the importance of understanding TCAS II's operational parameters to enhance safety during low-altitude operations.

• RAs are inhibited below 900 feet AGL.
• All TCAS aural announcements are inhibited below 500 feet AGL.
• TCAS will only generate RAs against altitude reporting intruders.
• Non-altitude reporting aircraft may still generate TAs under certain conditions.
• GPWS/TAWS alerts take precedence over TCAS RAs.