Why must I have a slip and turn indicator?
I'm currently studying up for my CPI. Today we were discussing the minimum equipment requirements as per CAO 20.18.
Appendix 1 tells me in need an air speed indicator, altimeter, compass and as accurate time piece for PPL flights. If it is charter flight I need to add a turn and slip indicator and outside air temperate indicator.
Can any one tell why I need a slip and turn indicator? All the other items make a lot of sense to ensure a safe flight but I can't see why the logic behind the slip an turn.