I have it on good authority that the selection dates are a tad later than specified above. No idea how many per year, but I'm interested to know. I thought there would probably be two per year for RAAF DEO and one for ADFA
Lets say an average course number of about 24 at BFTS with a new RAAF/RAN Alpha course every 12 weeks... Thats 4 courses a year which means about 96 people, plus whatever number of RAAF/RAN ended up with the primarily army Bravo courses. So lets go with something like 120 people? I'm gonna go with about half ADFA half DEO (I can't back those numbers up so don't get upset if i'm wrong). That gets reduced to 49 - 65 a year at the end of the sausage factory through various reasons... Mostly people failing.
The RAAF will always intake the same amount of people and if the requirement for people is less than usual they'll just scrub more to only get the cream of the crop but the bare minimum is 49. For DEO they'll usually intake in October, April with a smattering of people in between. Its not odd to have OTS courses with 20+ pilot candidates on it, nor is it odd to have courses with only 1 or 2.
Problem at the moment is demand is quite small within the ADF. There isn't the healthy speparation that used to happen so unfortunately there are too many O3 O4's clogging up the shute.
Hope thats some usefull information for ya. Fresh from Defence Recruiting and OTS/BFTS/2FTS
Edited: IOT add extra info and fix the numbers