Do you get to pick what air frame you want to work on when you get out of AET a school? Or do you just get picks with a certain air frame you will be assigned to?
Where you are stationed "picks" the airframe for you. For stations with more than one airframe, you may state your preference, but the "needs of the service" may trump your desires.
It all starts with where you are assigned for the Airman Program, if you return to that same station after "A" School, and/or what you put on your dream sheet.
Fret not too much if you do not get your first choice. It's all good!
If you do have a strong preference to fly on a specific airframe, then know what airframes are at what units and put those on your dream sheet. If you want to go helo's and put a dual airframe unit, your not helping your cause very much.
Picks out of "A" school depend on your placement in the class. You no longer fill out dream sheets. If you have a strong desire to go somewhere in particular, study your butt off and volunteer for everything.