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what does the instructor log if the 'student' logs PIC?
From the Regulation AMC1.FCL.050
(iii) the holder of an instructor certificate may log as PIC all flight time during which he or she acts as an instructor in an aircraft;
FCL.010
"Category of aircraft" means a categorisation of aircraft according to specified basic characteristics, for example aeroplane, powered-lift, helicopter, airship, sailplane, free balloon.