To operate properly, what must an RNAV be tuned to?

The correct answer is that an RNAV (Area Navigation) system must be tuned to a VORTAC station. An RNAV system is designed to allow aircraft to navigate without being directly over ground-based navigation aids. However, it does require certain inputs for operation, which can include signals from VOR (VHF Omnidirectional Range) stations and TACAN (Tactical Air Navigation) systems, collectively known as VORTAC.

When tuned to a VORTAC station, an RNAV system can utilize the precise bearing and distance information provided by the VORTAC to calculate the aircraft's position, enabling efficient navigation along predefined routes. This capability is particularly significant for en route navigation, approaches, and even departures, providing the essential data that informs the RNAV's navigation computations.

The other options—GPS, NDB (Non-Directional Beacon), and ILS (Instrument Landing System)—while related to navigation and aids, do not serve the specific function required for an RNAV operation in the same way as a VORTAC. GPS systems are independent navigation systems that can function without tuning into VORTACs, and while NDBs and ILS are useful navigational aids, they do not directly influence the RNAV's capability as