Which abbreviation is used for specific altitudes established for obstacle clearance within 46 km?

The abbreviation that denotes specific altitudes established for obstacle clearance within a certain distance is known as MSA, which stands for Minimum Safe Altitude. This altitude is crucial as it provides a buffer above the highest obstacles in a given area, ensuring safe navigation for aircraft. The MSA is particularly important in mountainous or rugged terrain, where obstacles can be significant and pose risks to flight safety. It is established for specific segments of airspace, typically within a radius of 46 kilometers or 25 nautical miles from a navigational aid or an airway intersection, and allows pilots to maintain a safe altitude while navigating or in case of an emergency.

The other terms refer to different altitude requirements: MOCA (Minimum Obstacle Clearance Altitude) pertains to obstacle clearance in relation to a specific route segment but does not encompass a wider area like MSA. MEA (Minimum Enroute Altitude) is the lowest altitude that can be used for air navigation purposes that guarantees navigation signal coverage and obstacle clearance. MCA (Minimum Crossing Altitude) is the lowest altitude at which an aircraft must cross a fix in relation to a specified route. Understanding these distinctions is vital for flight safety and navigation.