What is V in Aviation? (Magnetic Variation)

In the world of aviation, there are numerous terms and concepts that pilots and navigators need to be familiar with to ensure safe and efficient flights. One such term is magnetic variation, often referred to as V. Magnetic variation plays a crucial role in aviation navigation, and understanding its significance is essential for every pilot.

Magnetic variation, also known as magnetic declination, is the angular difference between true north and magnetic north. In simple terms, it describes the variance between the direction indicated by a magnetic compass and the actual geographic or true north. This variation arises due to the complex nature of Earth’s magnetic field, which is generated by its molten core.

Understanding Magnetic Variation

The Earth’s magnetic field is created by the movement of molten iron and nickel in the planet’s outer core. Just like a bar magnet, this magnetic field has both a north and south pole. However, the Earth’s magnetic field does not align perfectly with its geographic axis, resulting in a deviation between magnetic north and true north.

Magnetic variation is not constant and changes over time. In fact, the magnetic north pole of Earth is continuously moving at an average rate of 10 kilometers per year. This movement can have a significant impact on aviation navigation, as it means that the magnetic variation at a specific location will change over time.

Significance of Magnetic Variation in Aviation

Magnetic variation is of utmost importance in aviation because it affects the accuracy of navigation systems that rely on magnetic references. Although modern aircraft navigation primarily uses GPS (Global Positioning System) for precise positioning, magnetic directions are still used in various flight instruments, such as magnetic compasses. Since these instruments indicate magnetic north, pilots must account for magnetic variation to determine true headings and navigate accurately.

Failure to account for magnetic variation can result in navigational errors, leading to incorrect flight paths, missed waypoints, or even deviation from prescribed airways. These errors can have severe consequences, posing risks to both the safety of the aircraft and those on board. Therefore, pilots must consistently update and adjust their flight plans to account for the changing magnetic variation.

In addition to navigation, magnetic variation also affects other aspects of aviation, such as runway numbering. Runways are assigned numbers based on their magnetic alignment, allowing pilots to easily identify their orientation. For example, a runway aligned with a magnetic heading of 150 degrees would be designated as runway 15. As magnetic variation changes, it becomes necessary to periodically update runway designations to reflect the current magnetic alignment.

The Calculation and Effects of Magnetic Variation

Calculating magnetic variation involves determining the angular difference between true north and magnetic north at a specific location and time. This information can be obtained from various sources, including aeronautical charts, navigational databases, and specialized software.

In the Northern Hemisphere, if magnetic north is to the west of true north, the variation is considered “positive” or “westerly.” Conversely, if magnetic north is to the east of true north, the variation is considered “negative” or “easterly.” For example, if the magnetic variation at a specific location is +5 degrees, it means that the magnetic compass will indicate a direction 5 degrees west of true north.

The effects of magnetic variation become particularly significant during long-distance flights. As an aircraft traverses across different regions, the magnetic variation can change, affecting its heading and track. Pilots must account for these changes and update their navigation accordingly to maintain course accuracy.

Furthermore, magnetic variation can also impact instrument approaches, which are critical during low visibility or poor weather conditions. These approaches rely on precise navigation and must account for any existing magnetic variation in order to provide accurate guidance to pilots during landing.


Magnetic variation, denoted by the abbreviation V, is a significant factor in aviation navigation. It represents the angular difference between true north and magnetic north, and its correct consideration is paramount for safe and accurate flight operations. Pilots must continually update their navigation systems to account for the changing magnetic variation and ensure that their flight paths remain on track. By understanding and accounting for magnetic variation, pilots can navigate the skies with precision and confidence.

For More: What is THS in Aviation? (“Trimmable Horizontal Stabilizer)