How frequently must a VOR be tested for accuracy?

The correct frequency for testing a VOR (VHF Omnidirectional Range) system for accuracy is every 30 days. This requirement is established to ensure the reliability and precision of the navigational aid for pilots using it for instrument navigation. VOR testing involves checking the equipment's accuracy against known references to ensure that the signal received by an aircraft's navigation system is accurate enough for safe operation.

Regular testing every 30 days helps to mitigate potential errors that can arise due to equipment malfunction or degradation, which can occur over time. By adhering to this requirement, flight crews can maintain confidence in their navigational capabilities, particularly under instrument flight rules where precise navigation is critical.

Options that suggest longer intervals, such as every 60 days or 90 days, do not meet the regulations set by the FAA for VOR accuracy checks, which could compromise operational safety. The critical nature of maintaining accurate navigational aids is why a more frequent testing schedule is mandated.