Re: Turn onto xwind and final at 500' - why 500'?
From my experience of instructing in both NZ and the UK the 500' is just a function of the circuit height. I have used several airfields in the UK where circuit altitude is 1500 agl and therefore the turn onto x-wind and final is made at 800'. I would think that the general rule is that these turns are a function of half the circuit height i.e if circuit is 1000 then 500 is appropriate, it circuit is 1500' then 800 feet is the next appropriate level. This ensures that the circuit is evenly spaced and should allow glide back to the field should the donkey quit.