FLIGHT CONTROL BALANCING
This is an area that affects what seems to be all general aviation airplanes from the various manufacturers. We have found numerous flight controls out of the specified balance range. Some of these were not in balance from the factory or rebuilding facility. Others were within balance when the aircraft was bare aluminum but subsequent painting placed them out of range.
Most of these aircraft have been flying for years with no flutter problems. Of the ones that have had problems, especially the faster airplanes, many have had tragic results. As stated above the 190/195's are only one type out of, should I dare say all, that display the results of neglect in the area of balancing. Of the 20 elevators in the first test group, 13 were out of balance and 3 more would have been out of tolerance with paint. These numbers are still about the same on average.
Anytime a flight control is altered in any way it has to be balanced. In our opinion it would be a good idea to have them checked with or without any work performed to them.
On this note, there has been at least one instance of elevator flutter on a 195 that is believed to be caused from slop in the elevator trim system from excessive bushing play.
February 18, 2001
We had completed an engine change from an R-915 back to the original R-755 on a customers airplane that I have flown many hours in the past 3 years. I was breaking the engine in at higher power settings than I normally run, and as a result higher indicated airspeed (about 168 mph). I noticed some un-commanded movement in the control column, which, when left alone, would begin to develop a definite rhythm and increase in intensity. I could make it stop by applying back pressure to the controls. I have heard first hand stories of encounters with flutter (SCARY) so of course I did not experiment with this situation much although I did allow this sequence to initiate itself 3 times to make sure it was not just an isolated occurrence.
Upon inspection all bushings and hinges had no excessive play however both elevators were well out of balance specifications. This was corrected and on subsequent test flights the scenario could not be duplicated.