Which mode is prohibited for VOR approaches?

The correct choice indicates that use of the APPR (Approach) Mode is prohibited for VOR approaches. This is due to the fact that VOR approaches typically require the pilot to maintain manual control over the aircraft's navigation and altitude management. In normal operations with VOR approaches, there is a reliance on the pilot to interpret VOR signals and make necessary adjustments, as VOR approaches often include various procedural nuances that may not be effectively captured by an automated approach system.

In contrast, other modes like FMS (Flight Management System) Mode, IAS (Indicated Airspeed) Mode, and VOR Mode can allow the crew to utilize tools and systems to assist in managing flight path and navigation. However, they may not be specifically tailored for the requirements of a VOR approach in the same way that manual pilot control is needed. Thus, for VOR approaches, pilots are expected to disengage automated systems and rely on their training and instruments to ensure a safe approach and landing.