When conducting a dual VOR cross-check, what is the acceptable tolerance?

The acceptable tolerance when conducting a dual VOR cross-check is +/- 4°. This means that when comparing the indications from two VOR receivers, the readings should be within 4 degrees of each other for the equipment to be considered functioning correctly. This tolerance is important for ensuring that the navigational data being used is accurate enough to guide the aircraft safely. A smaller tolerance of +/- 4° is deemed sufficient in aviation to maintain an appropriate level of safety and reliability while navigating, ensuring that pilots can effectively discern their position and course relative to navigational aids.

In contrast, larger tolerances would allow for more significant discrepancies between readings, which could potentially lead to navigational errors. Thus, maintaining this specific 4-degree threshold helps pilots operate confidently within the necessary precision required for safe flight operations.