Which sources provide system initialization data for each IRU unit?

The correct choice states that GNSS (Global Navigation Satellite System) and ADCs (Air Data Computers) provide system initialization data for each Inertial Reference Unit (IRU).

This is because GNSS contributes critical positional data that helps the IRUs establish their initial position within the Earth's coordinate system. GNSS offers highly accurate geographical coordinates, which are essential for the initialization of an IRU as they need a good reference point to function effectively.

ADCs play a crucial role in supplying data related to the aircraft’s airspeed, altitude, and other critical environmental parameters. This data complements the positional information from the GNSS, allowing the IRUs to calibrate and refine their measurements accurately. By integrating information from both GNSS and ADCs, the IRU can better calculate its own orientation and position.

In contrast, the other options do not provide the required initialization data specific to the IRUs. GPS and altimeters, while related to navigation, do not encompass the full integration of data needed. Flight computers and sensors tend to use the data generated by IRUs rather than providing initialization data. Pilot controls and feedback primarily contribute to aircraft operation and handling but are not used for initializing the IRU system.