What is TRA on Boeing 777? (Thrust Resolver Angle)

The Thrust Resolver Angle (TRA) is an important concept in aviation, specifically related to the Boeing 777 aircraft. The TRA refers to the angular position of the thrust reverser target in relation to the engine core. This angle plays a crucial role in determining the direction of the engine’s exhaust gases during thrust reverser deployment. Understanding the TRA is essential for both pilots and engineers as it directly affects the aircraft’s overall performance and safety. In this article, we will delve deeper into the significance of the TRA and its implications on Boeing 777 operations.

Understanding the Thrust Resolver Angle

The TRA is primarily used during landing to assist in decelerating the aircraft on the runway. When the pilot engages the thrust reversers, the engine’s exhaust gases, instead of flowing straight out of the back of the engine, are redirected forward, creating a reverse thrust force. This helps the aircraft slow down more efficiently, allowing for shorter landing distances. The TRA is responsible for determining the direction in which the exhaust gases are directed.

On the Boeing 777, the TRA can have various angular positions, depending on the specific requirements of the landing. Typically, the TRA is set by automated systems based on factors such as aircraft speed, aircraft weight, runway conditions, and pilot input. However, pilots also have the option to manually adjust the TRA to cater to specific landing scenarios where automated settings may not provide optimal performance.

It is important to note that the TRA is not a fixed value throughout the descent and landing phase. The angle is constantly adjusted by the aircraft’s systems to ensure that the reverse thrust force is effectively directed for maximum deceleration. The continuous adaptation of the TRA allows for precise control over the aircraft’s speed during approach and landing.

The Influence of TRA on Aircraft Performance

The TRA has a significant impact on the overall performance of the Boeing 777 during landing. The angle affects several key parameters, including the braking distance, reverse thrust efficiency, and runway surface conditions. Let’s explore each of these aspects in detail:

1. Braking Distance

The TRA plays a crucial role in determining the braking distance of the aircraft. By redirecting the exhaust gases forward, reverse thrust generates a backward force, aiding in deceleration. A well-optimized TRA ensures that this force is effectively utilized, resulting in shorter braking distances. This is particularly important in scenarios where the runway length is limited or when landing on a wet or icy surface, where maintaining maximum control is essential.

2. Reverse Thrust Efficiency

The efficiency of reverse thrust is directly impacted by the TRA. An optimal TRA allows for the maximum redirecting of the exhaust gases to facilitate efficient deceleration. If the TRA is not set correctly, the effectiveness of reverse thrust could be compromised, resulting in reduced braking efficiency and longer landing distances. Therefore, it is critical to ensure the TRA is set accurately to achieve the desired reverse thrust efficiency.

Additionally, the TRA also helps minimize the potential damage caused by debris on the runway. By directing the exhaust gases forward, any loose objects on the runway are pushed away from the aircraft, reducing the risk of foreign object damage.

3. Runway Surface Conditions

The TRA takes into account the specific condition of the runway surface, allowing for optimal deceleration in various scenarios. For example, when landing on a wet or slippery surface, a lower TRA may be selected to maximize traction and prevent hydroplaning. On the other hand, when landing on a dry surface, a slightly higher TRA can be employed to ensure efficient deceleration without compromising tire performance.

By adapting the TRA to the runway surface conditions, pilots and automated systems can enhance the aircraft’s overall safety during landing.


The Thrust Resolver Angle (TRA) is a critical factor in the operation of the Boeing 777 aircraft during landing. It determines the direction in which the engine’s exhaust gases are redirected during thrust reverser deployment, consequently impacting the aircraft’s braking distance, reverse thrust efficiency, and ability to handle different runway surface conditions.

As pilots and engineers, understanding the significance of the TRA allows for optimal utilization of reverse thrust, ensuring safe and efficient landings. By continuously adapting the TRA based on factors such as aircraft speed, weight, and runway conditions, the Boeing 777 can achieve maximum deceleration and control during the landing phase.

Therefore, it is crucial for aviation professionals to have a comprehensive understanding of the TRA and its implications on aircraft performance. By considering the factors discussed in this article, pilots can make informed decisions and utilize the benefits offered by the Thrust Resolver Angle to enhance overall safety and efficiency.

For More: What is DADC on Boeing 777? (Digital Air Data Computer)