Final answer:
When using an external power unit on an aircraft, the battery master should typically be in the 'OFF' position to prevent damage. This is crucial as it avoids problems that can be caused by power surges or voltage mismatches. The correct answer to the question is 'True.'
Step-by-step explanation:
The question pertains to the correct procedures for using an external power unit in relation to an aircraft's battery master switch position. When connecting an external power source to an aircraft, it is generally true that the aircraft's battery master should be in the "OFF" position. This is to prevent potential damage to the electrical system and battery from power surges or mismatches in voltage when connecting or disconnecting the external power unit. Additionally, it is important to consider the aircraft's manual or specific procedures as they may vary slightly based on the type of aircraft or the systems in use.
Batteries are a critical component for stand-alone operation of an aircraft's electrical systems. When relying solely on batteries, the cost is increased due to the necessity for multiple batteries and the associated maintenance or replacement that will be needed over time. During the recharging process, some of the energy used will be dissipated as heat due to the internal resistance of the battery, which is an unavoidable part of the charging process.
Given the information provided and standard safety procedures, the correct option for the question is 1) True. The battery master should indeed be in the "OFF" position when connecting an external power unit.