Final answer:
The minimum voltage required to start an APU in an aircraft generally is around 24 volts, but it depends on the aircraft model and should be verified with the operating manual specifications.
Step-by-step explanation:
The minimum voltage required for an Auxiliary Power Unit (APU) start in an aircraft can vary depending on the specific aircraft model and its electrical systems. However, a general rule of thumb is that the aircraft battery voltage should be sufficiently high to ensure reliable starting and operation of the APU.
It is typically recommended that the battery has around 24 volts, but the exact minimum voltage requirement should be detailed in the aircraft's operating manual or by the manufacturer's specifications. Insufficient voltage may lead to a failed start or potential damage to the APU starting system.