FAR 23.2405 — Automatic Thrust Control
FAR 23.2405 sets safety requirements for automatic power or thrust control systems on Part 23 airplanes, covering failures, crew override, and inadvertent operation.
In Plain English
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.
Regulation Text
14 CFR § 23.2405§ 23.2405 Automatic power or thrust control systems.
(a) An automatic power or thrust control system intended for in-flight use must be designed so no unsafe condition will result during normal operation of the system.
(b) Any single failure or likely combination of failures of an automatic power or thrust control system must not prevent continued safe flight and landing of the airplane.
(c) Inadvertent operation of an automatic power or thrust control system by the flightcrew must be prevented, or if not prevented, must not result in an unsafe condition.
(d) Unless the failure of an automatic power or thrust control system is extremely remote, the system must—
(1) Provide a means for the flightcrew to verify the system is in an operating condition;
(2) Provide a means for the flightcrew to override the automatic function; and
(3) Prevent inadvertent deactivation of the system.
Oral Exam Questions a DPE Might Ask
Q1What does FAR 23.2405 require regarding failures of an automatic thrust control system?
Per FAR 23.2405(b), any single failure or likely combination of failures must not prevent continued safe flight and landing of the airplane.
Q2If failure of the automatic power control system is not extremely remote, what features must it include for the flightcrew?
FAR 23.2405(d) requires a means to verify the system is operating, a means to override the automatic function, and a design that prevents inadvertent deactivation.
Q3How does the regulation address inadvertent crew operation of an automatic thrust system?
FAR 23.2405(c) states that inadvertent operation by the flightcrew must be prevented, or if not prevented, must not result in an unsafe condition.
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Related Sections in Part 23