ATPL Navigation Practice Test

The course deviation indicator (CDI) displays lateral navigation information and is essential for maintaining the intended course during flight. A full-scale deflection indicates that the aircraft is significantly off its intended track. When the CDI deflects from the center of the scale to either full-scale left or right, it signifies that the aircraft is more than the designated number of degrees off course. This is critical information for pilots, as it alerts them to make necessary adjustments to get back on the correct path. A deflection from the center ensures that the pilot knows exactly how far they need to turn to regain the intended course direction. In contrast, other options do not correctly define full-scale deflection. For instance, a full-scale deflection does not require the CDI to swing from one extreme to the other or flicker, as these would not provide accurate or clinically relevant information about the aircraft's position relative to the intended track. Understanding this concept is key for pilots in navigating effectively and ensuring they adhere to their planned flight route.