thanks for the all the answers.
I was more wondering : " does a FI need to sign all the flight he has done with a trainee, for the trainee to gain his PPL"
or does a FII need to sign all the hours he has flown with a trainee FI. The CAA is checking the logbook to issue a FI rating, do they need to see every flight made to obtain a FI countersign by the FI instructor?
thx