Which approach requires DME or radar for execution?

The correct approach that requires DME (Distance Measuring Equipment) or radar for execution is the Localizer (LOC) approach. The Localizer is a type of electronic navigation aid that helps pilots align their aircraft with the centerline of the runway. For a LOC approach, DME may be necessary to provide distance information to the pilot, which aids in determining the aircraft's position and distance from the runway threshold. While radar can also be utilized for situational awareness and tracking, it may not always be essential for executing a LOC approach. However, the presence of DME or radar enhances the accuracy and safety of the approach.

In contrast, the other approaches listed do not have the same mandatory requirement. The VOR approach, for instance, relies on VHF Omnidirectional Range navigational aids and does not specifically necessitate DME or radar. The ILS (Instrument Landing System) approach typically combines both localizer and glide slope components, and while radar might be used for vectoring, it is not a requirement to execute the approach itself. The RNAV (Area Navigation) approach utilizes satellite-based navigational systems and is designed to be executed using GNSS (Global Navigation Satellite System) rather than relying solely on DME or radar.