How long prior to a VOR check is the logbook endorsement valid?

The valid window for a VOR check logbook endorsement is indeed 30 days. This timeframe is specified to ensure that the VOR equipment is checked for accuracy and reliability within a reasonable period before its use for navigation. A VOR (VHF Omnidirectional Range) check ensures that the navigation signal is being received accurately, which is crucial for maintaining safety in IFR operations.

If a pilot performs a VOR check and logs the results, that endorsement remains valid for 30 days, meaning the pilot can use the VOR system for navigation within that time frame without needing to perform another check. This 30-day limit emphasizes the importance of regular checks to maintain the integrity of navigation systems during flight operations, aligning with the expectation of precision and safety in IFR flying.