AIN has learned that FAA officials are considering the introduction of TCAS-III to meet collision-avoidance needs when large unmanned aircraft start to operate in civil airspace. TCAS-III, which would add lateral resolution advisories (RAs) to the vertical commands current-generation TCAS-II offers, was proposed during TCAS development in the 1980s but was not taken further after investigations showed that its development would be technically challenging and could delay the implementation of the system, both in North America and elsewhere.
The renewed interest in TCAS-III comes from the expectation that future unmanned aerial vehicles (UAVs) would be unlikely to have the climb capability required in a current RA vertical avoidance maneuver. Sources have told AIN that should the FAA eventually adopt the system, it would necessarily require an airworthiness directive mandate to upgrade all TCAS-II units to TCAS-III standards to maintain airspace compatibility.
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