Tail Assembly

From "Construction Notes" Falco Builders Letter, September 1994

Whenever anyone gets started on the Falco, they go through a period of adjustment to the realities of building. I think everyone starts out with the mental picture of that perfect airplane they are going to build, and somehow they get it in their head that every piece will be as immaculate, polished and perfect as the painted, polished and waxed airplane. And in that first couple of months, we frequently get calls from builders who are upset about something that looms very large in their mind. Dean Malstrom, for example, didn't care for the set of rudder pedal mounts. All of them were structurally fine and he recognized that, but they were from different machining batches and there were some slight differences in the appearance. No problem, we switched the parts with some we had on the shelf so he could have a cosmetically matched set.

There's also a typical period of adjustment while you come to understand what is important and what is not. The other day, for example, I got a call from a new builder who didn't like the appearance of some of the tail group ribs. In his case, he didn't like the appearance of the staples used in the construction of the ribs.

When we first made the tail group ribs, we used a ridiculously inefficient clamping method that allowed us to make exactly one rib a day. When we got into the wing ribs, we started using the staple-and-glue method that is used at the Pitts factory. It's a far superior way to make certain types of parts, and we use this method on many of the fuselage frames as well. And we're now making ribs for the tail group that way, using a laser-cut stapling template. I'll admit that staples detract from the appearance, but the parts are fine. You'd be amazed how many cosmetically perfect Falcos are flying with staples within them. All I'm saying here is that when that lump-in-the-throat feeling hits you in the early stages of construction, that it's something everyone has gone through.

Q: Now that I'm finished the tail group assembly, can I go ahead with fiberglassing the skin?

A: Yes, you can do this at any time.

From "Construction Notes" Falco Builders Letter, December 1994

Jack Lange asks if the MS21042 nuts can be cycled on and off without losing their safety grip. The answer is yes, and that is a basic part of the design. This is also true with elastic stop nuts, but there are always people who will swear that you can't, or shouldn't, do that. Since the safetying action of the nuts is caused by the nut pinching the bolt, the design would be defeated only by metallic wear, something you're not likely to do in the process of building a Falco.

It is possible, however, to wear the plating off the bolts, so most builders use plain nuts for temporary attachments and then install the MS nuts on final assembly-but if you have to remove and reinstall the MS nuts, then just do it.

From "Construction Notes" Falco Builders Letter, December 1990

We have had a little procurement boo-boo on P/N 775 elevator trim tab control arm. The last batch of fifty or so parts was made as drawn, not opposite-hand as noted in a revision. If they are made opposite-hand as intended, the flange that is screwed to the bottom of the elevator trim tab is inboard and mounts on the solid spruce rib that's 25mm wide, and that's why we changed it to an opposite-hand part.

As originally designed, the flange was outboard which worked fine on the wood elevator tab, which was made of solid spruce with a couple of lightening holes. We changed to the current construction of spar, ribs and trailing edge strip because it's lighter and easier to make. To use the current batch of parts, you'll need to glue in another block of wood outboard of the 25mm-wide rib at the inboard end. The weight penalty is negligible, and it's crazy to throw a couple thousand dollars worth of parts away because of the minor inconvenience of installing an extra block of wood.

From "Construction Notes" Falco Builders Letter, March 1988

John Kerosotas ran into an unusual problem by following our construction manual to the letter. Somewhere in the manual, I say to glue the phenolic upper elevator stop to the top of the stabilizer spar (see Sheet D3). Apparently everyone else has waited until later to do this. John found that when he did this, the phenolic block became trapped in the slot in the main fin spar, and he couldn't get the stabilizer out of the fin assembly. He is able to move things around enough to glue things in place, so it's not a complete disaster, but this little block keys things in place in a way that never occurred to me. I guess you'd better wait to install the elevator stop until you glue the stabilizer in place.

From Falco Builders Letter, March 1985

A number of builders have reported that the elevator balance weight was difficult to install since the lead compressed under the riveting pressure. If you wish, you may install the weight with a couple of No. 8 AN525 washer head screws and nuts.

From "Construction Notes" Falco Builders Letter, September 2001

Dave Brouchette asks about the elevator leading edge ribs at station 5.5. No vent holes are shown, and should there be? My wiseacre answer was "Do the drawings mean what they say when they say what they say?" Seriously, the idea is to vent the air internally into the trailing edge of the control surface. We don't put any vent holes in the leading edge ribs because we don't want to invite moisture into the control surface. And there are plenty of parts of the airplane where it's not necessary to vent the air at all because the volume is small or the compartment is rigid.

From "Construction Notes" Falco Builders Letter, December 2001

Charles Nutt asks, "We have a question on terminal block 5 located in the tail. There are only four terminals, but five wires (three for the strobe and two for the nav light). We didn't see anything in the plans regarding the hookup. Are we to assume that the black wires go together or is there something we're missing?"

I'm embarrassed to say that I don't remember. I remember I put the terminal block in there so you could hook up the tail light wires and disconnect them. You should not mix the ground wires of the strobe with the ground wire of the nav light, because they use dramatically different voltages. One is 12 volts. The other is a spike of very high voltage (over 1000 volts) of very short duration.

I think a simple solution would be to use one of the mounting screws as a terminal for the nav light ground wires. -- Scoti

Bob Brantley said he did this. "I used the shielded three-wire cable that comes with the Whelen hook-up kit for the tail strobe and the wiring kit wires for the tail light (black and yellow, I think). I used the four-wire terminal block on the front face of the forward fin spar and hooked the ground (black) wire from the three-wire cable to the right mounting screw (facing forward) through the Amp connections, the four wire terminal block can be used as a six using the mounting screws."