What is the minimum altitude for autopilot engagement during Category 1 ILS operations with glideslope angles of 3.5° to 4.5°?

For Category 1 Instrument Landing System (ILS) operations with glideslope angles between 3.5° and 4.5°, the minimum altitude for autopilot engagement is typically set at 160 feet above ground level (AGL). This allows for a stable platform to ensure that the aircraft can safely transition from autopilot to manual control as it approaches the minimum decision height, thereby enhancing safety and precision in the landing phase.

This altitude is important because it balances the need for effective autopilot assistance during critical phases of flight while maintaining enough altitude to ensure that corrective actions can be performed if necessary. In Category 1 ILS procedures, pilots are skilled with the expectation that they will take over manual control at heights where the autopilot may no longer reliably manage landing conditions due to weather or other factors. Hence, the designation of 160 feet AGL serves as a regulatory guideline to support safe operational practices in varied conditions associated with such approaches.