Experimenter is a magazine created by EAA for people who build airplanes. We will report on amateur-built aircraft as well as ultralights and other light aircraft.
Issue link: http://experimenter.epubxp.com/i/194874
F li g h t Te s t in g Te c hn i q u e s Long EZ Aileron control circuit Control System Freeplay Got slop? By Ed Kolano Got slop? You know, that tiny but annoying flight control system nuisance that renders your surgical flying precision to butcher shop cleaving? Let's talk about that, where it comes from, and how it affects your flying. Then we'll examine some other flight control bad boys and their contribution toward making an airplane harder to fly than it has to be. First, a demonstration. Pick up a pen and prepare to write. Notice how you're holding the pen between your thumb and at least one opposing finger? Draw a circle. Now move your thumb a tiny distance away from the pen, and draw an identical circle while maintaining that tiny gap. See the problem? That tiny gap is freeplay. You've probably already compared the two circles. Now compare your sense of control using each technique. Compare your frustration level between the two efforts. All together: Freeplay is bad. In the pen exercise, you had to move your fingers across the gap before the pen moved in the direction you wanted. The same thing happens in an airplane. 38 Vol.2 No.10 / October 2013 You have to move the control stick or pedals across the freeplay band before the control surface moves. Control system freeplay usually comes from looseness in the system. Worn components, loose cables, perhaps elongated holes in bell cranks, and a variety of other loose connections allow one component to move a short distance before moving the other. Even new, "tight" airplanes can have freeplay. The more linkage connections there are, the more opportunities there are for those tiny gaps. And they combine. Let's turn your arms into push-pull rods. Form an okay sign with your thumb and index finger. Now do the same with your other hand, but have that thumb and index finger meet in the circle formed by the okay sign of your other hand. I know, I know, but just get in touch with your silly self and bear with me. Your fingers should now form a loose chain link. Hold your arms in front of you so your forearms are horizontal. Let's say the elevator is connected to your left elbow, and the control stick to your right. As you move your control stick, notice your elevator doesn't move until Illustration courtesy of Rutan Aircraft Factory