Tnxs 'sector 3' for that.
I don't think it's needed to be shown that 3 legs are required to join a circuit(unless the other known rues apply) it's common knowledge that it's so or should be. From the first day I was taught to fly & the subsequent 30 yrs that has followed I at least join downwind & seeing as I have been checked by numerous person along they way by CASA & all their previous names etc ALL have expected this to be the case.
I hear/see the airlines doing at least a downwind join where practicable at non controlled AD's & if it where allowed I would bet my last dollar that these guys would be joining base where possible to save time/money, they don't so regs or nor regs that's good enough for me
CW