Surely even as relief pilot the flying duty period commences at 'sign on'. That must be the point at which one becomes a member of the operating crew.
My company often positions crew in uniform and listed on the GD (apparently saves money on pax surcharges). Are they considered part of the crew ? What if they are on a type on which they are not rated ? Can they have a drink with their meals? I know what common sense would dictate but legally where do they stand?