Tail Assembly

From "Construction Notes" Falco Builders Letter, March 1995

A builder wrote the other day. He's starting the tail group assembly and wants to install an electric servo to operate the elevator trim tab, using a Mac trim servo mounted in the fuselage and with a push-pull cable to the tab as per our plans. He asks for my advice.

From what I've seen of it, the Mac trim servo is a well-made device that has built-in stops. It's been used on lots of homebuilts, and I'm not aware of any horror stories. That's the good part.

Unlike other modifications, the idea of an electric trim system does not upset me greatly, but I worry about a number of things. The first question is why bother at all? People who have not flown a Falco frequently become interested in the idea of installing electric trim because the airplanes they have flown require a lot of trimming. Electric trim seems like a nice feature.

As any Falco pilot can tell you, the elevator trim wheel on a Falco is more lonesome than the Maytag repairman. You just don't trim a Falco that much, and it's so easy to do with the wheel. The manual system is very light and infinitely more reliable than the electric device. What happens if you lose electrical power? What if the motor fails? What if an electrical fault causes the motor to run to the end of its travel and then burn out? Electric trim systems in production airplanes are always in addition to manual systems, and that's certainly not true with this sort of system.

I'm also bothered whenever anyone, early in the construction, starts becoming a re-designer of things to solve imagined problems. It's a worrisome syndrome that often leads to other, more adventuresome and dangerous modifications. In general, my advice is don't do it. Instead, try to get religion on doing things exactly according to the plans. After all, you don't hear a single finished-and-flying Falco builder out there bemoaning the lack of electric trim, and there's a great benefit to having everyone doing the same thing. That way, when there are problems, we can all learn from them. There's safety in numbers in this sort of thing.