What is A/THR on Airbus A330? (Auto Thrust)

Auto Thrust, also known as A/THR, is a critical feature of the Airbus A330 aircraft that plays a significant role in maintaining optimal performance and enhancing flight safety. As the name suggests, auto thrust automates the thrust management during various phases of flight, relieving pilots from the task of manually controlling the engine thrust. With advanced computer systems and sensors, the A/THR system adjusts the engine power to ensure the desired speeds and performance parameters are achieved. In this article, we will explore the workings of auto thrust on the Airbus A330 and understand its importance in modern aviation.

The Role of Auto Thrust in the Airbus A330

The auto thrust system on the Airbus A330 is designed to provide pilots with increased control, efficiency, and safety throughout the flight envelope. By relieving the pilots from manually managing engine thrust, auto thrust allows them to focus on other critical aspects of flight, such as navigation, communication, and monitoring the overall aircraft systems. This automation not only reduces workload but also enhances precision in maintaining the desired speeds, minimizing performance deviations, and improving fuel efficiency.

During takeoff, the A/THR system helps pilots achieve the necessary engine power automatically. As the throttles are advanced to the takeoff position, the auto thrust system takes over and adjusts the thrust based on the aircraft’s weight, center of gravity, ambient conditions, and other factors. This ensures that the aircraft accelerates smoothly and reaches the desired takeoff speed in a controlled manner. By eliminating the need for manual adjustments, auto thrust provides a standardized and consistent takeoff procedure across different flights.

During climb and cruise phases, the auto thrust system maintains the desired airspeed by controlling the engine thrust. The A330 continuously receives inputs from various sensors, including the air data reference system (ADIRS) and the flight management and guidance computer, to adjust the thrust accordingly. The auto thrust system compensates for changes in altitude, air temperature, air density, and aircraft weight, ensuring that the aircraft operates within the predetermined flight envelope.

One of the key advantages of the auto thrust system is its ability to handle abnormal and emergency situations effectively. In the event of an engine failure or a scenario requiring a rapid descent, the A/THR system adapts the engine thrust to meet the desired performance requirements. This ensures that the aircraft remains under control even in challenging situations, providing pilots with greater confidence and reducing the likelihood of manual errors.

It is important to note that although the auto thrust system aids pilots in various flight phases, the ultimate responsibility for the safe operation of the aircraft lies with the flight crew. Pilots are continuously monitoring the aircraft’s systems and flight parameters, ready to intervene and manually control the engine thrust if necessary. This human-machine interface ensures a well-balanced approach to flight operations, combining the benefits of automation with human decision-making capabilities.

How Does Auto Thrust Work?

The auto thrust system on the Airbus A330 comprises several components and sensors that work together to automate thrust management. Let’s take a closer look at the key elements and how they contribute to the seamless operation of the A/THR system.

The first component is the flight management and guidance computer (FMGC), which receives inputs from various sources, including the pilot’s inputs, the air data reference system (ADIRS), the aircraft’s weight, and speed. This information is processed to determine the appropriate thrust required for a given flight phase. The FMGC calculates the target thrust based on the programmed flight plan and desired performance parameters.

To achieve the target thrust, the FMGC sends commands to the auto thrust computer (ATC). The ATC processes these commands and sends appropriate signals to the aircraft’s engine control system. The engine control system interprets these signals and adjusts the engine thrust accordingly, ensuring that the desired performance parameters are achieved.

The auto thrust system continuously receives feedback from various sensors, such as the air data reference system, the engine control unit, and the flight control computers. These sensors provide real-time data on the aircraft’s speed, altitude, weight, and other important parameters. The A/THR system compares this data with the target thrust and makes necessary adjustments to maintain the desired performance.

In addition to the primary thrust control, the A/THR system also incorporates several protection features to enhance safety. These features include engine anti-ice protection, stall prevention, overspeed protection, and wind shear detection. By integrating these protections within the auto thrust system, the A330 ensures that the engines operate optimally and the aircraft remains within safe operating limits.

It is worth mentioning that the auto thrust system on the Airbus A330 is designed with redundancy in mind. This means that there are multiple independent systems and sensors that cross-check each other to ensure accurate thrust control. In the event of a failure or discrepancy, the system is capable of adapting and reverting to alternate modes, allowing the pilots to maintain control and safely complete the flight.


Auto Thrust, or A/THR, is a crucial automation feature on the Airbus A330 aircraft that enhances the performance, efficiency, and safety of flight operations. By automating the thrust management process, the A/THR system allows pilots to focus on critical tasks while ensuring optimal engine performance. From takeoff to landing, the auto thrust system adjusts the engine power based on various inputs and sensors, maintaining the desired speeds and performance parameters. Its ability to handle abnormal and emergency situations adds an extra layer of safety to flight operations.

The seamless operation of the A/THR system is made possible by the integration of components such as the flight management and guidance computer, the auto thrust computer, and various sensors. These components work together to calculate the target thrust, process commands, and adjust engine power as required. The system incorporates protection features to prevent stalls, overspeed, and other potential hazards.

As with any automation system, it is essential for pilots to have a thorough understanding of the auto thrust system’s operation and limitations. They must be ready to manually intervene if necessary and continuously monitor the aircraft’s systems and performance. The combination of automation and human decision-making ensures a safe and efficient flying experience for both passengers and crew.

For More: What is EFOB on Airbus A330? (Estimated Fuel On Board)