I realise 0 & 1 is the on off switches but what does the child_3d=1 control. There must be an additinal line in the aircraft.cfg that it controls and this is missing or damaged. It works on the default aircraft but when you create a new panel in a new aircraft it doesn't seem to work. Why is it so?
Im confused about what your asking?
Are you trying to add this line in a new panel?
If so then maybe the panel you are adding it too doesn't contain a mini panel (which is what we belive this line controls) and if that is the case I would think that you would have to also add a mini-panel to the aircraft you are modifying in order to have this work.