CFII instructor as passenger (FAA)

It IS possible for an instructor to give dual instruction without
logging (or being) PIC.

In one instance, I did some instrument training in my aero-club's
Grumman Tiger. The instrument instructor I used was not yet checked out
in the aircraft type in the club. So, from a club insurance point of
view, he was unable to be insured as PIC in that aircraft at that time.

I HAD been checked out by another instructor, and on his suggestion, we
agreed that I was the PIC for the entire flight, and that he was
providing instrument instruction.

Dave

wrote:
Hello,

I can't find a reference for this in the FAR/AIM.

The question, in the context of FAA IR training, is whether

a) I (assume I am legally PIC in the airspace in question) can carry a
CFII as a mere passenger, and

b) can the instructor take over as an instructor at an agreed point in
the flight

c) can the instructor revert to being a passenger at an agreed point
after the training took place

I am sure the answer to a) must be yes - it would be silly otherwise.
It's b) and c) I am not sure about.

Any response would be very interesting - with references please if
anyone feels this is illegal.