What action should be taken if more than one component of an ILS is unusable?

The rationale behind using the highest minimum required by any single component when more than one component of an Instrument Landing System (ILS) is unusable lies in maintaining safety and ensuring that the pilot operates within the best available parameters. Each component of the ILS provides specific guidance and information that supports the safe descent and landing of the aircraft.

If multiple components are not operational, it is crucial to adhere to the most conservative minimums available, which is why the highest minimum from any functioning component is selected. This approach reduces the risk associated with operating under potentially unstable or incomplete guidance, ensuring that pilots have the clearest understanding of the conditions required for a safe landing. By maintaining the higher standards, it ensures the aircraft can still navigate safely, reducing the likelihood of complications during the approach.

Choosing a VOR approach, continuing the approach at a lower altitude, or aborting the approach may not address the critical guidance necessary for a safe landing. These actions could lead to unsafe flying conditions if the pilot does not have the appropriate information to make informed decisions about the landing.