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What is A/F in Aviation? (Autofeather)

Updated: February 15, 2024

Understanding Autofeather (A/F) in Aviation

Autofeather (A/F) is an essential feature in aviation that helps ensure the safety and efficiency of aircraft operations. It is a system designed to automatically feather the propeller blades of an aircraft's engine in the event of an engine failure or during certain flight conditions. This article will delve into the details of autofeather, its purpose, operation, and significance in aviation.

The Significance of Autofeather in Aircraft

Autofeather plays a crucial role in enhancing the safety and performance of aircraft. In the event of an engine failure during takeoff or landing, the autofeather system automatically adjusts the propeller blades to feather position. Feathering refers to the process of aligning the blades parallel to the airflow, thereby minimizing drag and allowing for a controlled descent. By reducing drag, the autofeather system helps the aircraft maintain stability during critical phases of flight.

Additionally, autofeather also contributes to the overall efficiency of an aircraft. When an engine fails, the thrust imbalance can cause the aircraft to yaw or roll, which can be challenging to control. By feathering the propeller blades, the autofeather system reduces the thrust imbalance, making it easier for pilots to maintain control of the aircraft. This feature is particularly crucial in multi-engine aircraft, as it helps pilots to safely manage engine failures and maintain balanced flight.

How Autofeather Works

The autofeather system relies on several components to function effectively. These include sensors, actuators, and control units. The system continuously monitors the engine parameters and compares them to predetermined thresholds to determine the need for autofeathering.

When certain conditions are met, such as low oil pressure, excessive engine torque, or a sudden loss of power, the autofeather system activates. It sends a signal to the propeller's feathering pump, which rapidly moves the propeller blades to the feather position. This movement is achieved through the use of hydraulic or pneumatic pressure.

Once the propeller blades are feathered, the aircraft experiences reduced drag, allowing for a controlled descent or climb, depending on the flight phase. The system also alerts the flight crew of the autofeather activation through visual and aural warnings, ensuring they are aware of the change in propeller configuration.

The Importance of Regular Autofeather System Maintenance

As with any aviation system, regular maintenance is vital to ensure the proper functioning of the autofeather system. Routine inspections, testing, and maintenance procedures help identify and address any potential issues that may compromise the system's reliability.

Regular maintenance tasks for the autofeather system include checking the system for leaks, inspecting the condition of the propeller blades, and verifying the integrity of the sensors and control units. Additionally, functional tests are conducted to ensure the system responds appropriately to simulated engine failures.

It is worth noting that the autofeather system's reliability is paramount, as it plays a critical role in mitigating the risks associated with engine failures. Therefore, aviation authorities and maintenance personnel adhere to strict guidelines and regulations to ensure the autofeather system is kept in optimal condition.

To maintain the safety and operational efficiency of the autofeather system, aircraft manufacturers provide detailed maintenance procedures and schedules. These procedures outline the specific tasks, intervals, and equipment required for proper autofeather system maintenance.

By following these guidelines and conducting regular maintenance, aircraft operators and maintenance personnel can ensure the autofeather system remains reliable, contributing to the overall safety and performance of the aircraft.


Autofeather (A/F) is an essential feature in aviation that enhances the safety and efficiency of aircraft operations. By automatically feathering the propeller blades in the event of an engine failure, the autofeather system helps maintain stability and control during critical flight phases. Its significance in multi-engine aircraft cannot be overstated, as it aids in managing thrust imbalances and allows pilots to maintain balanced flight.

Understanding the operation of the autofeather system and the importance of regular maintenance is crucial for aviation professionals. By adhering to maintenance schedules and conducting routine inspections, aircraft operators can ensure the autofeather system remains reliable and contributes to the overall safety and performance of the aircraft.

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