Re: Aileron Trim Tabs
Posted: Wed Dec 02, 2015 3:21 pm
achesos wrote:At the risk of sounding foolish, I thought that once I fly my plane, simply adjusting the length of the combination of aileron push tubes would eventually 'balance' any roll tendency (if present)?
Adjusting the aileron pushrods will not correct a roll problem. The ailerons will always seek an aerodynamic equilibrim. Adjusting the pushrods will change where they trail in relation to the wing, but not where they trail in relation to each other. In other words, after an aileron pushrod adjustment you might find both aileron trailing edges trailing a little higher or lower in relation to the wing tip (or flap trailing edge), and you will find a lateral displacement of the control stick (as compared to where its neutral location was before the adjustment), but the roll tendency will still be there.
There are many ways to correct a roll problem. The problem likely is a result of slight rigging issues. These issues may or may not have to do with the wings. Some (more than what you may think) rigging issues have to do with the tail rather than the wings. I always start any rigging investigation with the tail, and then move to the wings. Now, on a Sonex there won't be much you can do about the tail rigging, or the wing for that matter, without remaking parts. Thus, we end up with either a trim tab on an aileron or a balance spring under the seat, as these are the least expensive (in terms of time and money) ways to fix the issue.
Another thing to remember is that, in an aircraft as light as a Sonex, lateral trim will be affected by loading. An airplane that might roll slightly one way or another with one person aboard will have a different roll tendency with two aboard. Depending on which way it wants to roll, adding a passenger may either fix the problem or make it worse. This being the case, it's important to trim the airplane for the flight regime it will most often be operated in, and then live with out-of-trim situations in other loading configurations. (Or put in an adjustable aileron trim system as one builder has described previously in this thread.)