In the context of your post, we know that when you say "trainer", that your talking about your flight "simulator". If you can aford it, I would say buy Real Flight G-5.5 for $199. Its really good. But it will let you push your boundary's and try things that you would never try with your real planes. Even after you are up and flying, you can use the flight sim at night, when its too windy, too much snow or rain. Its not just to learn to fly, but to progress after your flying. It really helps with muscle memory. Now, here on RCU, you are going to get the "join a club, dont buy a sim". Ignore them, do them both (Sim & Club) Joining a club is a GREAT way to learn the right way to do thing and to save you some money from your stupid little thumbs trying to kill your plane all the time. Joining a club also gives you a chance to meet a lot of cool guys (and 3 asssholes) that like to talk and teach RC flying. Oh ya, they will teach you and you son to fly for free, if you join.

Now to you losing your plane in a turn on your SIMULATOR. Your just starting out so "coordinated" turns are not what you need to learn first. You need to learn to "yank and bank" just so you can get through the turns and more advanced skills can come at a later date.

When you BANK using your planes ailerons, it will bank the plane but also make it lose altitude. You bank the plane and then pull back on the elevator to tighten the turn a bit. Dont bank over 45 deg. The more you bank and pull on the elevator, the tighter the turn gets. Once you get this VERY basic turn down, start doing figure 8's.

Hope you have fun. Oh ya, join a club!!