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What is ALTS in Aviation? (Altitude Select)

Updated: February 17, 2024

Understanding Altitude Select (ALTS) in Aviation

Altitude Select (ALTS) is a crucial term in aviation that refers to the capability of an aircraft's autopilot system to maintain a specific altitude. This functionality allows pilots to set a target altitude, which the autopilot will then maintain by adjusting the aircraft's pitch. In this article, we will delve deeper into the concept of Altitude Select, its importance in aviation, and how it impacts flight operations.

The Significance of Altitude Select

Altitude Select plays a vital role in aviation as it allows pilots to accurately control the aircraft's altitude. By setting a desired altitude, pilots can focus on other critical tasks, such as navigation and monitoring the aircraft's systems, while the autopilot system ensures that the aircraft maintains the selected altitude.

One of the key benefits of Altitude Select is its ability to enhance safety during flights. By utilizing this feature, pilots can minimize the risk of altitude deviations, which can lead to potential conflicts with other aircraft or airspace restrictions. Maintaining a precise altitude is especially crucial during instrument flight rules (IFR) operations, where adherence to assigned altitudes is essential for separation from other aircraft.

Moreover, Altitude Select allows for more efficient flight operations. By accurately maintaining a desired altitude, pilots can optimize fuel consumption and aircraft performance. This is particularly important during long-haul flights, where even minor deviations from the optimal altitude can result in significantly increased fuel burn and operating costs.

How Altitude Select Works

Altitude Select is typically controlled through the aircraft's autopilot system, which is designed to assist pilots in various aspects of flight. When engaged, the autopilot system uses a combination of sensors, such as altimeters and air data computers, to monitor the aircraft's current altitude.

Once the pilot inputs the desired altitude into the autopilot system, it engages the Altitude Select mode. The autopilot then adjusts the aircraft's pitch, either by controlling the elevators or using a fly-by-wire system, to maintain the selected altitude. If the aircraft starts to deviate from the desired altitude, the autopilot makes corrective adjustments to bring it back to the set value.

During climbs and descents, Altitude Select works in conjunction with the vertical navigation (VNAV) mode. VNAV allows pilots to set vertical profiles, specifying the desired rate of climb or descent, along with altitude constraints at different waypoints. The autopilot system then manages the aircraft's vertical speed and throttle settings to ensure the aircraft reaches each specified altitude at the designated waypoint.

It is important to note that Altitude Select does not absolve pilots from actively monitoring the aircraft's altitude and other flight parameters. Pilots must remain vigilant and cross-check the autopilot's performance against their own observations to ensure the system's accuracy.

Challenges and Limitations of Altitude Select

While Altitude Select is a valuable tool for pilots, it is not without its challenges and limitations. One of the primary challenges is the potential for altitude deviations due to external factors, such as turbulence or conflicting air traffic control instructions. In such cases, pilots may need to disengage the autopilot and manually control the aircraft to comply with immediate instructions or maintain safety.

Another limitation of Altitude Select is its reliance on accurate altitude measurement. If there is a discrepancy between the aircraft's actual altitude and the data provided by the altimeters or air data computers, the autopilot system may not be able to maintain the desired altitude accurately. Therefore, regular calibration and cross-checking of altitude instruments are essential to ensure the system's reliability.

In conclusion, Altitude Select is a critical feature in aviation that allows pilots to set and maintain a specific altitude using the autopilot system. By accurately controlling the aircraft's altitude, pilots can enhance safety, optimize flight operations, and improve overall efficiency. However, it is important to remember that Altitude Select is a tool that supports pilots and does not replace their responsibility to actively monitor the aircraft's performance. Understanding the capabilities and limitations of Altitude Select is essential for safe and efficient flight operations.

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