okie... lemme clear things up a little... okie, i've done all
these in 2001, so whether if there had been any changes to the
system, i do not know... 
Pre-enlistment: (if you expressed your interest in joining when you
are in JC or Poly)
1st stage - CPSS
this is the stage where you go down to CMPB to get your
computerised pilot thingy done...
the test is mainly on your IQ, psycho-motor skills. the test is
roughly ard 4 hours long...
Pass or fail, they'll send you letter...
2nd stage - Health Examination
You'll be asked to go down to Aeromedical Centre at PLAB. A series
of body checkups will be done... Things include an X-ray of your
spine, heartbeat rate, eyesight, ears and nose checkup, dental
checkup. They will ask you to go into a room to measure the length
of your legs and hands. The height when you sit down. Roughly thats
abt it.
If you fail, you'll probably hear from them. If you pass, the next
stage would come during your BMT.
During enlistment: (if you indicated your interested in joining
during BMT when the AFRC ppl come down for a recruitment
talk)
Okie the first and second stage are the same, just that the order
has been switched. You'll go for your health examination first
before the CPSS
3rd Stage: (same for both pre-enlistment and during
enlistment)
Okie this is the interview stage where you'll be asked to to sit in
front of a panel of interviewers which include a LTC (prob from
FTS), a CPT (prob from AFRC) one more member and then 2
psychologist.
typical questions like tell me more abt yourself and why you wanna
join the Air force will be asked... 
Immediately, you'll be notified whether you are selected as a pilot
trainee...
after which, those who has to go to OCS first will go to OCS, those
that is selected but din make it to OCS will go to Air Force School
to wait for their chance to go to Tamworth for their
airgrading.
Hope this helps to clear the air 