Quote:
If it is agreed or implied that one pilot will intervene, or take over, if he deems it necessary, at any time during the flight, then that pilot is PIC. Is this defined in regulation some where?
Yes:
EASA Part-FCL November 2011
‘Pilot-in-command’ (PIC) means the pilot designated as being in command and charged with the safe conduct of the flight.
UK CAP 393 Air Navigation: The Order and Regulations January 2015
‘Commander’ in relation to an aircraft means the member of the flight crew designated as commander of that aircraft by the operator, or, failing such a person, the person who is for the time being the pilot in command of the aircraft;
‘Pilot in command’ means a person who for the time being is in charge of the piloting of an aircraft without being under the direction of any other pilot in the aircraft.
Of course Canadian definitions may differ somewhat.
Generally before renting out an aircraft to a pilot to take away a Group/Club would want to assure themselves that the pilot is both qualified (a paperwork check) and competent (a practical check ie the check flight). The check flight is a club requirement, not a regulatory one, so there is no requirement to even be qualified to fly it - eg medical just ran out but want to get the check done so can rent in a few days once restored.
Since satisfactory completion of a check flight is a requirement
before the Group/Club would hand over the aircraft it seems very odd to me that any checkee would even expect to log PIC for the check flight itself.
Many times I have flown as a passenger, who once airborne, by prior agreement, will take over flying the plane for a specific purpose (like assessing a change to the aircraft, or demonstrating a newly installed feature, or equipment) I hardly think of myself as PIC for the flight, and do not log that time.
You were never PIC so you were correct not to log anything. You took over the actual flying of the plane with the permission, and under the supervision, of the PIC. They could take back the controls at anytime they liked and if you put the aircraft in a situation outside of their competence/experience level, but within yours, all you could (legally) do would be to offer advice which the PIC could accept or reject as they saw fit.