I did a quick search of the archives and found plenty of references to this subject but the were all scattered about as tangents to the original thread subject. So I thought I'd start a new thread that could be found easily with the search function ma\king it easy to reference in the future - thus the odd title. This thread is not to be confused with approach control devices that are pretty well covered here - Precision approach control My Duster has flaps that rotate to a 90 degree position and limit the maximum speed in a dive to the gliders Vne. It looks like I'm going to have a few pounds to play with on my part 103 project and am considering adding a similar device, but set to automatically deploy at some predetermined speed, maybe in the same way that an automatic leading edge flap does. My questions are: Has this been done in the past? (assuming yes) If so, how? Can anyone point me to a web source, or other source, where I can study up on ways to do what I'm considering? Hazards, other than unwanted deployment or asymmetrical deployment, that I may not have considered?