Recently, Mxsmanic posted:

Blanche Cohen writes:

How is it possible to operate an aircraft without an engine that
is in operation?

You'll have to ask glider pilots about that.

On the other hand, no reply from anyone here will satisfy your
questions.

Quotations of regulations need to at least mention the subject of my
queries. Many people seem to believe that their own personal
interpretation of regulations has the same force of law as the
regulations themselves, but that is not the case.

The subject of your query was stated:
"I understand that one normally turns on beacons or anticollision lights
whenever an aircraft's engines are running. Is this a regulation, or just
a polite custom?"

Note that YOU were the one that set the parameters that the "aircraft's
engines are running", therefore, the regs quoted directly answered your
original question, as the PIC is always "operating an aircraft" if the
engines are running, and therefore it is not "just a polite custom". Once
again, you choose to argue rather than learn.

Neil