Which of the following is required during inspections?

VOR inspections are required as part of ensuring that the navigation equipment complies with regulatory standards for reliability and accuracy. According to the Federal Aviation Administration (FAA) regulations, VORs must be tested for accuracy at specified intervals to ensure that they provide correct magnetic bearing information. This inspection helps maintain the safety and efficiency of navigation during instrument flight, as pilots rely on VOR signals for guidance. This is a critical aspect of maintaining instrument flight rules (IFR) operations, ensuring that pilots can accurately navigate and execute approaches based on reliable navigation aids.

The other choices, while they may have their importance in aircraft maintenance, do not fall under the category of routine inspections mandated by regulations specifically focused on navigation equipment functionality. Regular inspections of items such as propellers and cabin pressure are necessary for overall aircraft safety, but they are not subject to the same specific regulatory requirements for periodic inspections as VORs are. Therefore, VOR inspections stand out as a required item during inspections.