How is Ref 0 calculated when split markers are not available?

Ref 0, or reference zero, is a crucial parameter in flight operations that determines the point from which various distances are measured, particularly concerning takeoff and landing performance. When split markers that typically indicate this reference point are not available, it is necessary to calculate Ref 0 based on components of the takeoff performance.

The correct calculation involves adding the Takeoff Ground Run and the Takeoff Flare Distance. The Takeoff Ground Run refers to the distance required for the aircraft to accelerate down the runway before it becomes airborne, while the Takeoff Flare Distance represents the additional distance needed for the aircraft to transition from the ground to a climb after leaving the runway. By summing these two distances, you effectively establish a comprehensive reference point for the takeoff phase, which encompasses both the ground movement and the initial climb transition.

This methodology ensures a reliable estimate of Ref 0, especially in conditions where markers might be missing, thereby maintaining safety and performance standards during critical phases of flight. The other options, while incorporating relevant distances, do not combine the specific components needed for an accurate Ref 0 calculation focusing on the takeoff phase.