How can you calculate your base turn without inputs for your angle of bank and your speed. This will affect your radius and thus your distance flown. Your ROD will be equally affected. It is not a simple task. And throw wind into the mix.
Many years ago I had to calculate the turning radii with different winds to intercept a lat/lon at a time to the second. Even in level flight, it is complex with many variables, and that was clean, level without changing config or speed...
As I said above, manoeuvre into position laterally on downwind, then turn in looking out the window. Reduce or increase the AoB depending on how tight you are. Pull / push sidestick/yoke/throttle as appropriate if you are low or high.
It's a visual manoeuvre, using your eyes and judgement.
If you can't, there's an app for that. It's called the ILS or RNP AR. The button's on the FCU.
Last edited by compressor stall; 31st Aug 2016 at 11:45.