If the pilots alternate flying the aircraft by handing off the
controls to the other person, do they also alternate pilot-in-command
responsibilites?


Not automatically. Assuming both are rated, current, and in all ways able to
BE pilot in command, then they must agree who is to =be= the top dog in charge
of the flight. They can agree that one will be, the other will be, the pilot
flying will be, the pilot NOT flying will be, but whoever they agree is PIC for
the leg in question is the final authority and the one upon whose wrath the FAA
(in theory) will fall should there be an incident.

Of course, in fact the FAA may well come after both and the question may become
moot.

But this all has to do with who IS the Top Dog of the flight. Who IS the PIC.

Now who gets to LOG PIC time ("Hands On Time", or HOT) is governed by different
rules, as you pointed out. The FAA confuses things by giving these two
DIFFERENT CONCEPTS the same name. Being Top Dog is different from logging HOT.
BEING PIC is different from LOGGING PIC.

Thus (among other things, you can log PIC time when you're HOT but not Top Dog.
Many long threads about this exist, try google.


On a slightly different topic, is it legal by FAA standards to let a
passenger take the controls of an aircraft?


I don't know of a rule against it, and I don't know of a ruling saying no. I
personally consider the passenger to be an organic autopilot, and have no
problem letting them manipulate the controls. I remain Top Dog, and continue
to log HOT (just as I would using an inorganic autopilot). If there were an
incident, it would be my responsibility, and I'd expect the FAA to try the
"careless and reckless" rule against me, so I am careful to not let the
passenger get us into a situation which would cause an incident. (besides
which I like being alive). I believe it is not inherently "careless and
reckless" to allow a passenger to manipulate the controls, although it might be
careless and reckless for me to let them go too far afield without my
intervention.

Jose

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