Mercy! Mercy! That Dang Nabed PERCY!

Pre-Flight Preparations

I traded a nice old pattern-flying airplane (Carl Goldberg) for a trainer and early model Sport Acrobat (SA). The trainer was nice and will no doubt get a workout, but the SA was what really intrigued me.

When I got it from Al, it was covered in dust and looked like it had been sitting for a long time. There was a single servo in the tray however, the wing was still complete. What I noticed was that there were control horns on both sides of the elevator. “Hmmm,” I wondered, “How is that supposed to work?”

On the right rear elevator was a hole that Al had fixed and needed to be covered. So, I had an airframe less most of the electronics, but a good start on what promised to be a nice aircraft with traditional acrobatic performance.

I took the airplane to Wausau, Pope’s Hobby-Land, and showed it to Warren. He sold me an engine that was the right size. He even installed it. The engine was an OS 46 with ball bearings. There was no canopy in the store that would fit and he told me how to make one. There was another OS 40 engine I’d brought in from a crash and Dave repaired it while I waited.

When I got home the first problem was getting the control surfaces to working and the throttle linkage connected. This brought me back to the dilemma of the two horns on the elevators. My experience is, a dowel or other type of linkage, usually links the right and left side elevators mechanically. Thus, there is only one connecting rod going up to the elevator servo. Warren told me to join the two rods before they got to the servo and then connect the lead. I tried this but the rods and connectors were different and the flex did not allow for a synchronized lifting and lowering. So I called John and he explained how to use two servos, one for each elevator. He said it was just like using two servos in the wing ailerons. This confused me because while ailerons operate in tandem they move in opposite directions. I didn’t want this for the elevators and asked him to elaborate. He said the reason they operate in opposition is because they are mounted on opposing sides of the two servo actuators. If the horns are mounted both on the same side, they will operate in a synchronized manner moving in the same direction. Connecting them to a Y-harness allows them both to plug into the receiver slot.