Which instrument does the ADC NOT control?

The correct answer is the tachometer, as it is not controlled by the Air Data Computer (ADC). The ADC is responsible for processing data from various sensors to provide information such as outside air temperature (OAT), vertical speed, and indicated airspeed. Each of these parameters relies on data related to the aircraft's environment and performance measurements, which the ADC interprets and displays.

In contrast, the tachometer measures the engine RPM and operates independently of the air data systems. It instead relies on the engine's own sensors to monitor performance metrics. This separation is crucial in understanding how flight instruments are categorized and organized in aircraft systems, highlighting the unique roles that different instruments play in flight operations.