Quick Qs about logging LCA time:

A LCA logs all time acting as a LCA from a required seat as PIC regardless of whether they were 'acting' as PIC bc they are the one signing for the A/C and the CA in IOE acting as PIC logs it as SIC, yes?

Do legacy interview logbook review boards want to see tallied time acting as LCA from a required seat?

They do not want to see anything about time acting as a LCA in the jumpseat, correct?

Probably just from a required seat, but you would have to ask each individual airline. If you think that time might be useful, log it in a separate column.

It's not quite like being the CA in the bunk with a relief pilot... he is still the PIC, but an LCA doing an observation from the JS is not the PIC. The LCA is clearly PIC when training a non-qualified CA on IOE (who logs SIC).

And the Captain doing upgrade/aircraft transition IOE needs to log it as SIC until they are signed off and flying with regular line FO's, yes?

Yes.
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Perfect, thanks Rickair.

On the FedEx app, it asks for instructor hours. I am not a CFI but am a regional LCA. Would you count time giving IOE etc as instruction? What about time spent giving line checks?

Yes and also yes.