What you're seeing is real world. The ILS Z Runway 16R uses RF legs from the HOBDA and KLOCK transitions. RF legs require specific capabilities from the auto flight system, for example a roll steering autopilot. Not all aircraft with the Garmin GTN have this equipment. Even if so equipped, the type certificate (TC) or supplemental type certificate (STC) holder may not have accomplished all of the certification requirements in AC 20-138D Change 2 to demonstrate the capability
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