FAR 23.2405 — Automatic Thrust Control

FAR 23.2405 governs how automatic power or thrust control systems must be designed on Part 23 airplanes (normal category). The rule is about making sure that automation managing your engines doesn't create a hazard — either through normal use, failure, or accidental crew interaction.

Key requirements:

• Normal operation must be safe. The system, when working as intended in flight, cannot produce an unsafe condition.
• Failure tolerance. A single failure — or any likely combination of failures — must still allow continued safe flight and landing.
• No inadvertent activation. The design must prevent the flightcrew from accidentally engaging the system, or if accidental activation is possible, it must not create an unsafe condition.
• Crew awareness and authority. Unless system failure is extremely remote, the design must let the crew (1) verify the system is operating, (2) override the automatic function, and (3) prevent inadvertent deactivation.

Operationally, this is why automatic thrust systems include status indicators, disconnect switches, and guarded controls — the pilot must always know what the automation is doing and be able to take command.