At one time ,as we all know,all the g/slopes were 2.5(ICAO).Then over the last few decades 3degrees is the accepted stndrd.As has been pointed out low on the Vasi puts one on the end -to use the longer runway dis available.(3 degrees touches one down about a 1000' into the runway dis.)..2.5 touchdon closer to the end ,but faster ergo one uses the extra dis.
(a 90 degree g/slope provides the least rollout)
Getting on the step stems from the 'heavy metal' days of the piston era,trim it level???and get the 'cruise' speed up...Even the DC8 needed some tlc on initial cruise..
In Canada the policy is to only establish Vasi/papi on Non precision approaches(some have with the ILS),but they very rarely align themselves-there just provide slope guidance once Visual.
Cheers..(is it my round??)
