What is the minimum required voltage for the aircraft battery when ground power is connected?

The minimum required voltage for the aircraft battery when ground power is connected is 24 volts. This standard is critical in aviation as it ensures that the electrical systems in the aircraft operate effectively and that there is sufficient power to support various functions such as avionics, lighting, and other essential systems.

A battery voltage of 24 volts provides a reliable and adequate power supply necessary for the aircraft's systems and helps in maintaining operational integrity. Lower voltages may not be sufficient to power the necessary components, thus risking operational failure or compromised safety.

While recognizing the attributes of the other choices, it's important to note that voltages below 24 volts would not meet the design requirements set forth for aircraft systems, meaning they may fall short of powering the necessary equipment efficiently or safely. Thus, the 24 volts specification is a basic standard in aviation safety protocols and operational requirements.