In fact the Hangar 9 series of PTS Trainers use flaps exactly for the purpose RCKEN states. They are fixed position items the way they come but you can add a flap servo and explore the interesting and often misunderstood world of flaps. The Hobbico Nexstar, another trainer, also comes with the ability to add flaps and all the Telemasters trainers have them, well all the glow ones I've ever seen do.