General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

The statement indicating that the ADIRU is the primary source while the SAARU serves as a secondary source is accurate. The Air Data Inertial Reference Unit (ADIRU) is designed to combine both air data and inertial reference data to provide critical flight information, such as altitude, speed, and aircraft position. The system is essential for flight navigation and aircraft performance monitoring.

On the other hand, the Standby Air Data Reference Unit (SAARU) functions as a backup to the ADIRU. It is used to ensure that flight data remains available in case of an ADIRU failure. While the SAARU provides important data, it does not operate as the primary system and lacks the comprehensive data fusion capability of the ADIRU.

The other options do not hold true. The ADIRU provides a wide range of position and air data while SAARU does not exclusively provide speed data; instead, it can also present altitude and other essentials, although with less complexity compared to the ADIRU. This distinction of primary and secondary roles is critical in understanding their operational design in aircraft systems.