What is the minimum aircraft battery voltage when using a GPU for start?

The minimum aircraft battery voltage when using a ground power unit (GPU) for starting procedures is critical to ensuring the aircraft's systems receive adequate power for a successful start-up. A voltage of 20 volts is recognized as the operational threshold that balances the need for sufficient power without risking damage or failure to the aircraft's electrical system.

At this voltage, the battery is able to provide enough energy to energize vital systems, such as avionics and ignition systems, while also facilitating the starter motor's operation. If the voltage were lower than this threshold, there could be an increased risk of insufficient power to the engine's starting mechanisms, potentially leading to start-up failures. Additionally, it is important for maintenance protocols to ensure the battery is within this operating range prior to initiating a start.

The other voltage options exceed the minimum requirement or fall short, making them inapplicable for this specific context. The choice of 20 volts reflects industry standards that have been established based on operational efficiency and safety considerations.