What is ALT2 in Aviation? (Altimeter)

The altimeter, abbreviated as ALT2 in aviation, is an essential instrument used by pilots to determine the altitude of an aircraft above sea level. It provides crucial information regarding the aircraft’s position in the sky, ensuring safe and efficient flight operations. In this article, we will delve into the details of the altimeter, its functionality, and its significance in aviation.

The Functionality of the Altimeter

The altimeter measures the barometric pressure of the atmosphere and converts it into altitude readings. It employs the concept of atmospheric pressure, which decreases as a pilot ascends into higher altitudes. This instrument features a sensitive aneroid barometer that responds to changes in pressure.

As the aircraft ascends, the atmospheric pressure decreases, causing the aneroid barometer in the altimeter to expand. This expansion triggers a series of mechanical linkages that translate the movement into a corresponding altitude reading on the instrument’s face. The altitude is typically displayed in feet or meters, depending on the unit setting chosen by the pilot.

To ensure accurate readings, the altimeter must be calibrated periodically. Pilots rely on regional pressure settings provided by air traffic control (ATC) to calibrate their altimeters. They dial in the current pressure, known as the altimeter setting, to account for variations in atmospheric pressure due to weather conditions and geographical location. This adjustment enables the altimeter to compensate for local differences in pressure, thereby giving pilots an accurate indication of their altitude.

The Significance of the Altimeter in Aviation

The altimeter plays a critical role in aviation for several reasons. Firstly, it allows pilots to maintain the desired altitude during level flight and adhere to assigned altitudes during instrument flight rules (IFR) operations. By continuously monitoring the altimeter, pilots can ensure their aircraft remains at the appropriate altitude, avoiding conflicts with other aircraft and potential collision hazards.

Additionally, the altimeter is crucial for navigation purposes. It assists pilots in determining their current position by cross-referencing altitude readings with known geographic features or waypoints. This enables them to identify their location on aeronautical charts and follow designated flight paths accurately.

Instrument meteorological conditions (IMC), characterized by poor visibility, often require pilots to rely heavily on their altimeters. In fog, clouds, or other low-visibility situations, pilots may not be able to rely on visual cues for maintaining safe altitudes. Instead, they depend on altimeter readings to navigate and avoid terrain or obstacles during the approach and landing phases.

Moreover, the altimeter aids in determining the aircraft’s rate of ascent or descent, which is crucial for precision approaches and stabilized climbs or descents. By closely monitoring altitude changes, pilots can ensure a smooth and controlled flight, adhering to published altitude restrictions and approach profiles.


The altimeter, denoted as ALT2 in aviation shorthand, is an indispensable instrument for pilots, providing vital information about an aircraft’s altitude. By accurately measuring atmospheric pressure changes, the altimeter enables pilots to navigate, maintain desired altitudes, and avoid potential hazards. Its role in aviation safety and precision cannot be overstated, making it a fundamental tool for every pilot. Understanding the altimeter’s functionality and significance is essential for those embarking on a journey into the exciting world of aviation.

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