What is A/T on Boeing 777? (Autothrottle)

The Boeing 777, one of the most widely used commercial aircraft, has revolutionized the aviation industry with its advanced technology and safety features. Among its many systems, the Autothrottle, also known as A/T, plays a crucial role in ensuring the aircraft’s optimal performance and efficiency. In this article, we will delve into the details of what the Autothrottle is and how it functions on the Boeing 777.

How Does the Autothrottle Work?

The Autothrottle system on the Boeing 777 is designed to automatically control the thrust output of the aircraft’s engines, primarily during the different phases of flight. It works in tandem with the Flight Management Computer (FMC) and other flight control systems to maintain a target thrust setting, eliminating the need for constant manual adjustments by the pilots.

During takeoff, the Autothrottle ensures that the engines provide the necessary power for a smooth acceleration and climb-out. The pilots input the desired takeoff thrust setting into the Flight Management Computer, which then commands the Autothrottle to maintain that specific level of thrust. This not only standardizes the takeoff procedures but also minimizes the likelihood of human error when setting the thrust manually.

Once the aircraft is in the air and cruising at a certain altitude, the Autothrottle continuously adjusts the engine thrust to maintain a predetermined speed or Mach number. The pilots can select various modes, such as speed or Mach hold, enabling the Autothrottle to automatically adjust the thrust to achieve the desired airspeed. This feature allows for optimized fuel efficiency and ensures a stable flight, even in changing atmospheric conditions.

During the descent and landing phases, the Autothrottle assists the pilots in achieving a smooth and controlled approach. By entering the desired approach speed into the Flight Management Computer, the pilots can rely on the Autothrottle to adjust the engine thrust accordingly, providing the necessary power for a safe descent and landing. This helps reduce pilot workload and allows for more precise speed control, especially in challenging weather conditions.

Benefits of Autothrottle on Boeing 777

The Autothrottle system on the Boeing 777 brings several significant benefits to both pilots and passengers. Let’s explore some of these advantages:

1. Enhanced Safety: The Autothrottle system ensures that the aircraft operates within safe boundaries by providing precise control of engine thrust. This helps prevent overspeed or underspeed situations, especially during critical flight phases.

2. Fuel Efficiency: By automatically adjusting the engine thrust based on the desired speed or Mach number, the Autothrottle system optimizes fuel consumption. This results in reduced fuel costs for airlines and contributes to a more sustainable aviation industry.

3. Pilot Workload Reduction: The Autothrottle system lightens the workload for pilots during high-workload phases of flight, such as takeoff and landing. By automating the thrust control, pilots can focus on other crucial tasks, maintaining situational awareness and ensuring a smooth flight for passengers.

4. Consistent Performance: With the Autothrottle system, the aircraft can consistently achieve the desired speed, allowing for a smoother and more comfortable flight experience for passengers. This contributes to customer satisfaction and strengthens an airline’s reputation for reliability.


The Autothrottle system on the Boeing 777 is a vital component that enables precise control of engine thrust, contributing to the aircraft’s overall performance, efficiency, and safety. By automating thrust adjustments throughout various flight phases, the Autothrottle system enhances safety, reduces fuel consumption, lightens pilot workload, and ensures consistent and reliable performance. With its advanced technology and numerous benefits, the Autothrottle system on the Boeing 777 continues to play a crucial role in modern aviation.

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