How do you design autopilot mode annunciation to prevent mode confusion?

Mode confusion occurs when pilots misunderstand autopilot state, leading to accidents (e.g., AF447). Design principles: Clear mode annunciation - consistent location (typically top of PFD), distinct armed vs engaged indications, and visual hierarchy (active modes prominent). Mode transitions - announce all transitions aurally and visually, highlight unexpected mode changes, and minimize automatic mode reversions. Simplification - limit number of modes, consistent behavior across modes, and logical mode relationships. Alerting - flash annunciations for significant changes, use of amber for unintended states, and enhanced warnings for high-energy situations. Human factors evaluation - pilot-in-loop simulation to identify confusion scenarios. Training integration - realistic mode behavior in simulators. Standards: FAA Human Factors guidance, EASA certification specifications. Post-accident reviews inform best practices (Boeing MCAS lessons).