Balancing the Controls

Questions from the field. Richard Clements called the other day and asked about the aileron balancing. There wasn't any difficulty on his part in understanding the instructions, but he said he was getting unmerciful grief from all the local 'experts'. Everyone told him that ailerons must be 100% balanced, and if not they say "I want to be there when you fly."

The simple answer is that the plans are right, and the self-appointed experts are wrong. One of the most popular fictions among homebuilders is the need for 100% balance on the ailerons. I don't know where it comes from, but most probably it grows out of ignorance and somehow the notion that 100% balance is some form of perfection.

Aileron balancing is just one of many considerations about aileron flutter. And that's a very complicated subject, because flutter is an aero-elastic phenomenum, and the principal factors are the stiffness of the wing, the resonant frequency of the wing, the speed of the airplane, the tension of the control cables and the balancing of the controls.

From the standpoint of the overall weight of the aircraft, and also for the best feel of the controls, it's desirable to have as little balancing as possible. So what happens is that designers like Dave Thurston and Stelio Frati build up a level of experience with aircraft so that they basically know what will be required and then you test the plane to make sure.

The amount of aileron balance that we have in the Falco was also specified by Dave Thurston for the Bellanca Skyrocket II-which once held a world's speed record at something like 320 mph-and Karl Hansen has twice bombed through our redline. So the next time some 'expert' starts forcing his opinion on you, just be polite, thank the guy for his advice... and ignore it all.

From "Construction Notes" Falco Builders Letter, September 1992

Another question from Australia came from Wayne Milburn, who is Tony Chamberlin's coworker building Guido Zuccoli's Falco. The airplane is almost ready to fly and when they were balancing the ailerons, they found they needed to add weight to the leading edge. With the plywood covering of the ailerons, this has been a fairly common experience, but there are some builders who have not needed to add weight.

I don't really see any point in doing much ahead of time to anticipate this, because there's no knowing for sure how you'll end up. It makes more sense to just balance them when they're finished. The method that Wayne used was to drill some holes in the ends of the aileron leading edge strip-from each end and at each opening-and then fill the holes with lead shot and epoxy. Since you know the weight that's needed, it's quite easy to figure out in advance how much lead shot you need.