新机设备交验后，前三个月要检查次

A. It is a navigation mode that ensure the aircraft follows a desired flight path in the range of navigation signal coverage. or within the capacity limits of the airborne navigation equipment, or a combination of both.
B. It is required NAV performance.
C. It Regulates the system performance requirements of the aircraft flying in the designated airspace or along the ATS route. flight instrumentation procedure