question: can I usefully log it?

A Commander as in single engine or multi?
If it was single engine, and you are at least a Private Pilot SEL, then you
can log any time you were "sole manipulator" of the controls.
If you are Instrument rated, you can log that time that you were sole
manipulator in IMC.

If it was a Multi engine commander (AC690B) etc, and you do not have a multi
rating, unless he wants to sign your logbook as "dual given", then other as
a nice entry in the logbooks, it does not count for much. Same for the IMC
if you are not instrument rated.

Otherwise, an enjoyable trip. An ATP may instruct other pilots in air
transportation service (61.167b), most ATPs maintain a CFII rating, many may
not.

BT

wrote in message
oups.com...
So I flew recently in a Commander. I was not a required crew member in
this part 91 flight. I flew right seat and an ATP was PIC. He's not a
CFI and I'm not instrument-rated.

Can I log the time in some way to count the time towards experience in
IMC or my total time? Of course I can stick it in my logbook if I feel
like it, but could it count towards anything?