What is VX in Aviation? (Best Angle Of Climb Speed)

What is the Best Angle of Climb Speed in Aviation?

In aviation, the best angle of climb speed, also known as Vx, is a critical parameter that pilots consider during takeoff and climb phases of flight. It refers to the airspeed at which an aircraft achieves the greatest gain in altitude per unit of horizontal distance traveled. Understanding the concept of Vx is crucial for pilots as it directly affects the aircraft’s performance and safety. In this article, we will delve deeper into the best angle of climb speed and explore its significance in aviation operations.

Factors Affecting the Best Angle of Climb Speed

The best angle of climb speed, Vx, is influenced by several factors. Let’s examine some of the key elements that impact the determination of this critical airspeed:

Fuel Efficiency

One important aspect to consider when determining the best angle of climb speed is fuel efficiency. Pilots aim to climb at an airspeed that allows them to gain altitude rapidly while minimizing fuel consumption. By flying at the optimal Vx, pilots can strike a balance between achieving the desired altitude and conserving fuel, ensuring an efficient climb.

Aircraft Performance

Another crucial factor affecting Vx is the performance characteristics of the aircraft. Different aircraft types have varying capabilities when it comes to climbing efficiently. Factors such as engine power, weight, wing design, and aerodynamics play a significant role in determining the optimal best angle of climb speed. For example, an aircraft with a high power-to-weight ratio and efficient wing design can achieve a steeper climb angle at a lower airspeed compared to an aircraft with less favorable performance characteristics.

Air Density and Temperature

Air density and temperature also influence the best angle of climb speed. As altitude increases, air density decreases, which affects an aircraft’s performance. High-altitude airports or hot weather conditions can reduce the air density, making it necessary for pilots to adjust the Vx accordingly. In denser air, an aircraft can achieve a steeper climb angle at a higher airspeed, while in less dense air, a lower airspeed will be required to maintain the best angle of climb.

How to Determine the Best Angle of Climb Speed?

Knowing how to determine the best angle of climb speed is essential for pilots to maximize the performance of their aircraft during takeoff and climb. Several methods can be used to calculate Vx, including:

Performance Charts

Many aircraft manufacturers provide performance charts in the aircraft’s flight manual or operating handbook. These charts describe the aircraft’s performance characteristics at different weights, altitudes, and temperatures. By referencing these charts, pilots can find the specific best angle of climb speed for their aircraft based on the prevailing conditions. It’s important to note that these charts are specific to each aircraft model and should be used accordingly.

Flight Computer or Electronic Flight Bag

Pilots can also use flight computers or electronic flight bags (EFBs) to calculate the best angle of climb speed. These electronic devices have built-in performance calculators that consider various factors such as aircraft weight, air density, and temperature. By inputting the necessary data, pilots can obtain the optimal Vx quickly and accurately, enhancing flight planning and decision-making.

Flight Testing

In some cases, particularly for aircraft without easily accessible performance charts or electronic flight bags, flight testing may be required to determine the best angle of climb speed accurately. By conducting flight tests at different airspeeds and recording the rate of climb, pilots can identify the airspeed that yields the steepest climb angle. It’s important to note that flight testing should only be performed by experienced and qualified pilots in a safe and controlled environment.

Importance of the Best Angle of Climb Speed

Understanding and adhering to the best angle of climb speed is crucial for several reasons:

Obstacle Clearance

During takeoff and initial climb, pilots must clear any obstacles within the aircraft’s flightpath. By climbing at the best angle of climb speed, pilots can ensure maximum clearance over obstacles such as buildings, trees, or terrain. Using Vx allows pilots to minimize the distance required to reach the desired altitude, reducing potential risks associated with obstacle avoidance.

Performance during Engine Out Situations

The best angle of climb speed also plays a vital role in scenarios where an aircraft experiences an engine failure during takeoff or climb. In such cases, pilots need to maximize the aircraft’s climb performance to ensure a safe outcome. By maintaining the Vx, pilots achieve the steepest possible climb angle, which allows them to clear obstacles and potentially find a suitable landing spot within a shorter distance.

Range and Endurance

Efficiently climbing to the desired altitude by using the best angle of climb speed can have a positive impact on an aircraft’s range and endurance. By minimizing the time spent in the climb phase, pilots can conserve fuel and increase the aircraft’s overall endurance. Additionally, reaching the desired altitude more quickly allows for longer and more efficient cruise segments, enhancing the aircraft’s range capabilities.


The best angle of climb speed, Vx, is a vital parameter in aviation that significantly influences an aircraft’s climb performance and safety. By understanding the factors affecting Vx and knowing how to determine this critical airspeed, pilots can optimize their aircraft’s performance during takeoff and climb. Adhering to the best angle of climb speed ensures obstacle clearance, enables effective decision-making in engine-out situations, and enhances overall range and endurance. Pilots should always consult their aircraft’s performance charts, utilize flight computers or EFBs, and conduct flight testing when necessary to obtain the most accurate and reliable Vx values for their specific aircraft.

For More: What is VRS in Aviation? (Vortex Ring State)