Variation, abbreviated as VAR, is an important concept in the field of aviation. It refers to the angular difference between true north and magnetic north at a particular location. This variation is caused by the Earth’s magnetic field, which is not aligned perfectly with its geographic north pole. Understanding variation is crucial for pilots and navigators as it affects the accuracy of their flight planning, navigation, and instrument readings. In this article, we will explore the concept of variation in aviation and its significance in ensuring safe and efficient flight operations.
The Importance of Variation in Aviation
Variation plays a vital role in aviation as it directly influences the accuracy of magnetic compasses, navigation systems, and instrument readings. It is crucial for pilots to account for variation when planning their flight routes and interpreting the information provided by their instruments. Failure to properly consider variation can lead to navigational errors, which can be potentially dangerous during flight.
One of the primary uses of variation is in determining the correct heading for a flight. The heading is the direction in which an aircraft is pointed with respect to true north. However, since magnetic compasses are used for navigation, the magnetic heading needs to be calculated by adjusting the true heading based on the local variation. This ensures that the aircraft is flying in the intended direction.
For example, let’s say a pilot plans a flight with a true heading of 090 degrees. However, at the departure airport, the variation is determined to be 10 degrees west. To calculate the magnetic heading, the pilot subtracts the variation from the true heading, resulting in a magnetic heading of 080 degrees. This is the direction the aircraft needs to follow based on the magnetic field of the Earth at that particular location.
In addition to navigation, variation also affects runway naming conventions. Runways are usually numbered based on their magnetic heading rounded to the nearest ten degrees. For example, a runway facing true north (heading 360 degrees) may be designated as Runway 36. This takes into account the magnetic variation at that airport, allowing pilots to align their understanding of runway orientation with their instruments.
Calculating Variation
Calculation of variation involves understanding the current magnetic deviation at a specific location and the annual change in variation over time. The magnetic deviation refers to the short-term fluctuations in the Earth’s magnetic field, which can affect the accuracy of compasses and other instruments. On the other hand, the annual change in variation accounts for the gradual shift in the Earth’s magnetic field over time.
Aviation authorities and organizations provide aeronautical charts, known as magnetic variation charts or isogonic charts, to help pilots determine the variation at different locations. These charts display lines called isogonic lines, which connect points with equal variation values. By referencing these charts, pilots can accurately adjust their navigation systems and instruments to account for the variation at their specific location.
It’s important to note that variation can vary significantly depending on the geographical location. Various factors such as the distance from the Earth’s magnetic poles and the local magnetic anomalies can influence the amount of variation experienced at a particular place. Therefore, pilots must refer to up-to-date information and consult reliable sources to ensure accurate calculation of variation for their flight planning.
Conclusion
Variation, or VAR, is a crucial concept in aviation that affects flight planning, navigation, and instrument readings. Pilots and navigators must understand and account for variation to ensure accurate and safe flight operations. By properly calculating and adjusting for variation, pilots can maintain the correct heading and navigate along their intended flight routes. Additionally, the use of magnetic variation charts helps pilots determine the variation at specific locations, taking into account both magnetic deviation and the annual change in variation. Overall, variation is an essential consideration in aviation to ensure precise and efficient flights.
For More: What is XPDR in Aviation? (Transponder)