Don't be lazy, read the guides. I'll leave this one for you to start. There is plenty of information out there :D

http://www.trainworld.us/NF2/English/SS_Class_Manual_v5.pdf

Thanks never bothered to look :P

But in CASE you're lazy:

Planesmen essentially increase the air replenishment rate when you're surfaced... in other words, it makes it so you can spend less time above water!

Ya i got that :P
But why are they called PLANESmen.. You think they would be used on a CV with that name :P

what air flow .... its WATER FLOW that the planes are using .....

'plane' .. and .. 'AIRplane' ... are NOT the same exact word ...

submarine planes let it move up and down through the water
an AIRplane's wings let it move up and down through the air
a HYDROplane has planes that lift the boat out of the water

the word plane referes to a surface that PLANES .. regardles of if the medium is air or water or whatever

Ok i get that But if so wouldent that make the sub dive and surface faster?

not sure but it sure does seem like you can dive/surface/critical faster as you progress, but not sure if it the sub tier or the planesman