What may happen if an aircraft with a flat battery is started by hand?

Starting an aircraft with a flat battery by hand can lead to the alternator remaining off line after the engine starts. This occurs because the engine relies on adequate electrical power from the battery to initiate the alternator's operation. A flat battery may not provide sufficient voltage to activate the alternator, which means the aircraft’s electrical system won't be supported by the alternator's output.

In such a situation, the electrical systems may be compromised or may not function as intended. While all attempts would be made to start the engine, without adequate battery assistance, the alternator's engagement may fail, impacting the overall functioning of the electrical systems once the engine is running.

Other options suggest that the electrical systems would work normally or that the battery would charge immediately; however, these are not accurate reflections of what occurs in the case of a hand-started aircraft with a flat battery.