Most RNAV systems include a ____________ that uses a large database.

The correct answer is that most RNAV systems include a flight management system, often referred to as an FMS. This system integrates various data inputs from onboard navigation sensors and external sources to manage the aircraft's flight path.

An FMS uses a large database to facilitate the operation of RNAV (Area Navigation), which enables aircraft to fly on any desired flight path within the coverage of ground- or satellite-based navigation aids. The database contains critical information such as waypoints, airways, and airports, allowing the FMS to compute optimal flight routes based on inputs from the crew and flight plan requirements.

While a navigation database is a crucial component within the flight management system, it is the FMS that encompasses a broader range of functionalities, including route calculations and performance management. This comprehensive integration of data and control capabilities is essential for modern navigation and efficiency in air traffic management.