Avionics

First, let's visit the letter bag:

J.R. Willett said...
Hi Dave,

I work for Dynon, and while I obviously can't comment on what Vans is planning, I can assure you that you will be well-supported no matter which Dynon product you end up with. We work hard to make sure that users of even our oldest products are fanatically happy. As you can probably imagine, our word-of-mouth reputation among our existing users is critically important to our future success.

Skyview has many improvements over the D180 generation of products (and many more Skyview software features are on the way), but if you are happy with what the D180 offers, you don't need to worry about the availability of support and repair.

Dynon is thriving, and we'll be there for you!

This is in response to something I said in my posting about biting the bullet and going ahead with placing my order for the finishing kit despite a small degree of market uncertainty regarding the emergence of the Dynon SkyView as an option for the RV-12.

To wit:

The SkyView has a number of advantages and it is arguably a better piece of equipment, but I remain unconvinced on the merits that the additional capabilities are really necessary in a plane as simple as the RV-12. What is inescapable, though, is that it will be well supported by Dynon for a much longer time horizon than the soon-to-be considered obsolete D-180.

This is great reassurance that I can safely choose to stick with the D-180 and be able to count on continued support from the manufacturer. I find this kind of service/support of aging products to be the exception rather than the rule in my line of work and it's gratifying that Dynon has a more customer friendly outlook. I have to say that I'm impressed with J.R. taking the time to pass along these assurances; customer service is a big deal to me and I love to see it done well. Thanks, J.R.!

Speaking of world-class customer service, I just spent more than an hour on the phone with a Van's Aircraft employee trying to figure out why Capt. Rush's autopilot won't work with his Dynon D-180. This is more of a Van's issue than it is a Dynon issue because the problem is clearly in the wiring. We worked on it for four hours straight and were completely at a loss as to what was wrong, but Ryan J. at Van's patiently stayed on the phone with us and talked us through some trouble shooting steps. It looks like the problem has been narrowed down to the connector that carries the wires from the back of the switch panel out to the autopilot disconnect switch. We both thought that there was something wrong with the switch, but Ryan was able to help us prove that the switch was working okay. The wiring inside of the switch box was also verified as functional. That leaves the connector. When I left, Capt. Rush was struggling to get the wires out of the connector to see if he could isolate the problem.

Once the autopilot problem is solved (assuming!!), we'll move on to trying to figure out why the GPS is also refusing to communicate with the Dynon. Ryan was able to give use some tips for working on that problem as well. All of this work on Capt. Rush's plane kept me from getting out to the hangar to rivet wing skins onto my own wings, but it will be worth it when it comes time to install my own avionics. I have a much better feel now for how all of the wiring and components interact and that can only benefit me when it comes time to install my own stuff, whether it be a SkyView or a D-180.

On the topic of my own wiring, I decided to test the continuity between the stall warning switch and the terminals on the wing root, figuring it better to find a problem now than later. Checks good!

I also ran a length of fishing line from the terminal panel out to the wing tip in case I decide to add the lighting kit later. The fishing line will assist in pulling the required electrical wire through the wing. The RV-12 doesn't have inspection ports or easily removable wingtips, so it seems prudent (and the plans suggest it) to make preparations now rather than suffer later.

Progress Stalled

Progress on the airplane has been stalled for a couple of days due to the nagging lower back injury sustained earlier this week. I've been to the chiropractor a couple of times and he, normally a veritable miracle worker, has only been able to move the pain point around to new locations. It started in my lower back, he moved it to a shooting pain down the length of my right leg, and finally got it cornered in an area I can live with. Not to put too fine a line on the final location, but let's just say that I had to cancel family plans to go to a two and a half hour movie because I didn't think I'd be able to sit through it. Emphasis on "sit."

That's all just fine with me since I can now stand and walk around almost as if nothing had happened to my back. The timing was perfect for getting back to work on the plane as we have been the appreciative recipients of a wonderful warm air mass sent up to us from the deep south. Can you imagine a temperature of 67F on New Years Eve? Well, of course you can; you live in Australia. But to us winter sufferers in Central Ohio this is a heat wave! I'm never one to waste good weather, so I ended up spending most of the day and evening out at the hangar.

I was working on the stall warning switch, so in effect my stalled progress became progress on the stall warning. What nice linguistic symmetry, albeit somewhat forced.

It started easily enough. Nearly all of the parts were located in a single brown bag.

The stall warning switch is essentially a micro switch sandwiched between two mounting plates. A metal vane is installed - this vane will protrude out through a slot cut into the leading edge of the left wing. When the angle of attack on that wing gets high enough to indicate that the wing will soon stall, the airflow that normally presses down on the vane will instead force it upward. This will cause the arm of the vane to activate the stall warning switch, thus closing an electrical circuit that will sound a warning horn in the cockpit.

The two mounting plates need to be final drilled to the sizes required for the two screws that will hold them together and for the screw that the vane will pivot around.

I just noticed that my Harbor Freight vise is "Made in Ching." I always knew that tool sizes at Harbor Freight were only approximations; now I know that spelling is too! (Cruel Karmic irony - I'm in here fixing the spelling of "vane" - I had used "vain" instead.)

This was still fairly early in the morning. We had yet to attain our eventual high of 67F, so a Thermos of coffee was still welcome.

Plus, I needed a little caffeine fortification before tackling the job of sorting out the washers that would be used as spacers when building up the switch mechanism. There were five different sizes all tossed into the same bag. There were three actual screw diameter sizes, with two of those three sets each having two separate widths. I separated them into piles by using visual inspection.

Then I ran into a problem with the plans. I know it might seem as if I'm being churlish when I call Van's to task on these minor problems with the normally industry-leading, excellent plans, but it is inarguably the case that these plans need to be as close to perfect as they can be made. The reason for that is the way the kit is certified in the eyes of the FAA. As an E-LSA, I am actually building this airplane on behalf of Van's. When it's done, I will certify that I followed the plans to the letter, and Van's will then inherit the liability for the safety and certification compliance of the completed aircraft. With that in mind, one would think that Van's would want to ensure that the thing is being built 100% correctly.

So here's why I bring this up. Do you see the washers labeled NAS1149FN432P, NAS1149FN416P, and NAS1149FN832P on the drawing? Well, you won't find any washers labeled that way in the kit inventory. What you will find instead are washers labeled AN960-4, AN960-4L, and AN960-8. Through a little intuition and detective work I was able to cross-identify those specs, but it would seem that Van's could correct that mismatch pretty easily and avoid any potential problems. On the other hand, the inventory had notes that pointed out the the AN960-4 is .032" thick, while the AN460-4L is .016" thick. My intuitive leap was that the #4 size rivet that was .032" think was probably the NAS1149FN432P. And so on. So the information is there, you just have to work for it.

Once I had that straightened out, it was a simple job to build the stack of parts into the final assembly.

With that done, a drilling template gets prepared. This template will be used to locate the holes that will be drilled in a rectangular piece of plastic. That piece of plastic will get mounted in the wing root where it will mate with a similar piece of plastic embedded in the side of the fuselage. The point of this exercise is to create a set of electrical terminals that will make contact when the wing is installed onto the airplane. This will allow the electrical current to flow out to the stall warning switch. The reason for this relatively complex way of making the electrical connection is that the wings are intended to be removable. You wouldn't want to have to connect and disconnect wires every time you wanted to remove or replace the wings. There would be too much risk of forgetting to do it, and there would be a lot of recurring stress on the connectors that would eventually lead to their failure.

There are two halves to the drilling template, so I marked the cut line with a Sharpie and separated the halves with the band saw.

The template gets clamped to the piece of plastic, the holes are drilled with #40 pilot holes, and are then final drilled to #19 or #30, depending on location.

The plastic terminal block then gets riveted to the mounting bracket that will hold it in place on the wing. A washer gets put on the shop head of the rivets, presumably to spread the pulling load of the rivet to keep it from simply pulling through the soft plastic.

Then it's time to start on the actual wiring. The first piece of wire is a short connector that will attach to the wing rib and provide a ground connection to the switch.

After fabricating that wire, the switch assembly gets mounted to the wing. The plans described what was going to happen. One screw would go through the hole at the bottom of the switch assembly and provide both a post for the ground wire and a pivot point for the switch assembly. The top screw would go into a slot; this would allow the switch assembly to pivot to so it could be precisely adjusted to just the right position. This triggered a recollection of a similar arrangement on the airsickness detectors (air vents) on the fuselage. Those too work by means of a screw running through a slot, and I remembered that the slot needed quite a bit of filing to make it work smoothly. I tested the switch assembly with a screw and sure enough, it needed some work with the file.

Quite proud of myself for proactively preventing the need to remove the switch after the hassle of installing it, I confidently proceeded with the installation.

Inexplicably forgetting that pride invariably goeth before the falleth, I blithely struggled with fitting the wing skin in place to ensure that the vane moved freely in the slot, assured in my knowledge that all would work well and there would be no reason to undo all of this effort. What could go wrong? After all, I had surmounted the difficulty in breaking the washer identification code, I had detected the slot trap and rectified the misfit problem, and really, it's just a simple switch, right?

And verily came the inevitable falleth. The vane was hard against the edge of the slot and would not move at all.

I removed the top clecoes on the wing skin and was able to remove the switch without having to completely remove the skin. Visual inspection of the switch assembly showed two things: the screw that was acting as a pivot for the vane was slanted, and the vane could do with moving inboard by one washer width. Both problems were addressed by loosening the two main screws, removing the pivot screw, changing the order of the washers from "two washers - vane - one washer" to "one washer - vane - two washers," and making sure the pivot screw didn't pick up any slant while re-tightening the main screws. In truth, I probably would have gotten away with just taking the slant out of the vane pivot screw.

Screwed back in place, the short ground wire is attached and a second wire, this one 68" long, is attached to the switch and run back to the wing root through the bushings in the ribs.

At the wing root terminal block, the 68" wire is bolted into place and another short ground wire is fabricated and attached to the terminal block.

The terminal block and second ground wire are mounted to the wing. Now we know why we needed nutplates on that rib.

The stall warning switch was the last thing from keeping me from installing the wing skins. It was getting dark and I wouldn't be able to work much longer, but there were a few folks hanging around the airport enjoying the temperate clime and I was going to need help flipping the wing in order to start skinning the bottom. I grabbed the help while it was available and couldn't resist the urge to get the first piece of skin clecoed on.

Being as it was New Years Eve, an impromptu party broke out in one of the neighboring hangars. There was champagne, munchie/snacks, and eventually two large pizzas acquired from the local biker's bar. As it got chilly, "Tool Junky" Al (his words!) pulled out a heater that delivers something like 12,500,000 BTUs and we all sat around trading friendly insults. Even Puppy Cabot joined in!

One thing you simply can't get away from on New Years Eve is the declaration of resolutions. My experience has taught me that the easiest resolutions to keep are the self-destructive ones, so my resolution for 2011 is to further my goal of becoming an International Man of Mystery and Intrigue by acquiring a taste for single malt Scotch whiskey. Dr. Doctor D, himself owning a gorgeous and impeccably maintained Piper Warrior in a hangar across from mine, was able to provide some fine practice materials.

I'm not sure that I will be able to keep my resolution (to me, Scotch still tastes like something I should be using to wipe on my arm before getting a shot), but I am 100% sure that I have never had a more enjoyable or more satisfying New Years Eve.

Left wing agitation

As if the hangar wasn't crowded enough already, I had co-pilot Rick come down and help me move the wing skins out there. I tried to move them myself, but it turned out that my Subaru isn't big enough for them to fit. I didn't find that out until I had hauled one of them up out of the basement, wrenching my back in the process, and found that there was no way to get it in there short of folding it up. Stacking them in the hangar in the gap between the RV-6's wing and tail was the only good place to put them. Unfortunately, it's going to make it prohibitively difficult to get the plane in and out of there on the off chance that we get some decent flying weather.

At least the chiropractor was able to get my back fixed up. He's getting used to airplane-building related injuries.

Despite the bitter 14F chill factor, I got back out to the shop this afternoon to get the left wing caught up to the right wing. The primary structural difference between the two is that the left wing has the nose ribs' back flanges riveted into the web of the spar rather than the back ribs' front flanges having that honor. That's a bit more awkward to do since the ribs aren't pointing up at the ceiling with the spar sitting flat on the work bench as they had been with the right wing. With the left wing, I had to get the rivet puller into the gap between the ribs and rivet into the horizontally orientated spar. It's a slightly less comfortable way to do it, but it went well enough right up until I got to the inboard ribs.

The plans go to pains to insist that the manufactured head of the rivet (the flat part, or 'top' of the rivet) be placed on the rib side of the rib/flange equation. This is intended to keep the larger 'shop head' out of the way when trying to put the rivets through the rib flange and into the spar. That looked to be pretty near impossible to me when I got to the inner ribs. There was no way I could fit that big rivet puller into that tiny gap. I was flummoxed for a few minutes, then I just decided to do the rib-flange-to-wing-spar rivets first. Doing it that way mooted any concern of the shop heads getting in my way.

I was pretty proud of the pragmatic problem-solving brilliance I had demonstrated with that technique, and I was still glowing with self-awe as I was performing the final step of inserting snap bushings into each rib. These bushings will guide and protect the wires that are run out to the wing tips to carry electricity for the wingtip lights that I'm not buying. ($1,300 for lights on a plane that I won't fly at night? Not worth it to me!) It's a simple matter of just snapping the bushing into the pre-drilled hole in the rib. It couldn't be simpler. I was dumbfounded, then, when I got to the last rib and there was no hole! Impossible!! All of the ribs are the same!

Well, that's true. As long as you install all of them right side up, that is.

The very last rib needed to be drilled out and replaced with the right side up.

So much for brilliance!


** in case you're wondering, PITA stands for Pain In The A$$

Finishing Kit ordered

As usual, I think I waited too long. The estimated lead time on receiving a finishing kit is eight weeks. Doing the complex mathematical conversion, that works out to roughly two months. At this point, I would be surprised if I was still working on the wings two months from now. That said, it won't take too many days with temperatures in the teens (or less!) to burn through those days, so it may turn out that I timed it just right.

The 'Finishing Kit' is comprised of almost all of the little bits and pieces that converts a piece of aviation-themed sculpture into an actual airplane. Amongst the major components are things like the seat cushions, seat belts, engine cowling, wiring harness, landing gear components (including wheels, inner tubes, tires, and brakes), and fuel tank components. I have a few comments on a couple of those items.

First, the wiring harness. This is a wonderful thing! While there will be wiring tasks such as pushing pins into connectors, stripping wires and splicing them to other wires, and crimping on terminals, there will be none of the truly difficult work like planning and laying out the entire electrical system on a blank page of paper. That said, there is a potential cost to ordering the finishing kit right now. It comes down to the avionics; by ordering a wiring harness today, I have virtually committed to the Dynon D-180 as my major avionics component.

Dynon D-180

There's nothing inherently wrong with that; the D-180 is a wonderful piece of equipment. The problem (such as it is) is that there are strong rumors floating around that Van's will soon offer the newer Dynon SkyView as either a replacement for, or an alternative to, the D-180. The SkyView has a number of advantages and it is arguably a better piece of equipment, but I remain unconvinced on the merits that the additional capabilities are really necessary in a plane as simple as the RV-12. What is inescapable, though, is that it will be well supported by Dynon for a much longer time horizon than the soon-to-be considered obsolete D-180. For that reason alone I would consider it as an upgrade, although it would have to be very competitively priced in comparison to the D-180 for me to opt for it.

Why do I have to decide now? Well, there will undoubtedly be changes to the wiring harness. After spending hours installing the current harness, I will not be likely to want to pull it back out again to install a new one, particularly as it will be much harder to do in a completed airplane. And, as you would expect, I would take a bath on the dollars already invested in the D-180.

This uncertainty is one of my beefs with Van's. They keep things like this very close to the vest, making it impossible to make well-informed decisions. I'd say they could announce the availability of the SkyView option tomorrow, but they won't. I say "they won't" with such confidence because of an even more irritating thing, which is the cagey way that they announce new options. Which is to say, they don't. The first you'll know about it is when the option suddenly appears on the order form. This is exactly what happened with the optional prefabricated fuel tank.

You have to understand that I have read a lot about other builder's difficulties with various parts of the construction process and from what I've read, there is no more painful process than building the fuel tank. More precisely, the difficulty seems to be more in the building of a non-leaking fuel tank. The tank is assembled from components in much the same way that the map box was. Because it is comprised of bent aluminum parts, there are large holes and gaps that need to be sealed to make it air/fuel tight. Having had the unhappy experience of using the tank sealant on other parts of the kit and reading about the numerous failed attempts on the part of others that have gone before me, and considering that the fuel tank in question is going to be sitting right there in the cockpit with me, I opted for the now-available prefabricated tank. It was exorbitantly expensive at $445, but I think it's worth it for the peace of mind that comes with it.

My argument isn't with the price, though. What bugs me is that there was no announcement of a newly available product. Van's, oddly enough, is not run like a business. They don't seem to market to existing customers at all, relying instead on word-of-mouth. That works out okay for people that spend a lot of time online, but I wonder how less connected people ever find out about this stuff.

Anyway, I opted for the prefab fuel tank, decided to bite the bullet on the D-180, and decided what color the seat cushions will be. I went with plain old tan cushions to match the interior paint and to guarantee that the colors won't clash with whatever exterior paint design I finally come up with.

Winter Blues

I haven't left the house for two days. The grey, dispiriting Columbus winter weather that has blanketed us for over a week now has shown only sporadic and short-lived efforts to move along. Yesterday was Christmas, and that meant spending the day at home enjoying the holiday. Today provided ample time to work on the airplane but it would been at the cost of going out to a very frigid hangar. The long and short of it is that I lacked the motivation to get decked out in my heavy winter duds. It seemed easier and far more comfortable to stay in and park myself on the couch with soon-to-be-dog (his 1st birthday is in two days) Cabot. He slept, I read a book on my new Kindle.

Still, the nagging thought at the back of my brain was always present: "You really should do something productive today."

So I did.

The next time that I go to the hangar, it's highly likely that I'm going to go ahead and put the wing skins on the right wing. That wing is going to have to be moved out of the way so I can go back to working on the left wing and it will be better to do so only after accomplishing what would have been the next steps on that particular wing anyway, which is to skin it. As it stands right now that wing is especially vulnerable to damage. Once the skins are on, it will be much more rigid and the ribs will be protected.

To put the skins on, the blue protective shipping plastic has to be removed first. That seemed to be a perfect indoor job. The removal of that plastic is by far the most onerous job of the entire build. It's normally hard to remove but I was told recently that it will come off much easier if heated with a blow dryer. I thought that might be worth a try. It turns out that the plastic does come off easier when heated, but the hand required to hold the blow dryer is also needed to hold down the aluminum while the other hand pulls on the plastic.

I enlisted some help.

Co-pilot Egg volunteered to operate the blow dryer while I pulled off the plastic, but she soon decided things would go quicker if the old man just moved out of the way. I did nothing to discourage her from going it alone. After all, I'm normally the first in line to let someone else do the dirty work - why should this be any different?

Within half an hour she had followed my lead and enlisted her own helper.

Here are a few observations about building an airplane with teenage girls:

• They enjoy comparing their boo-boos.
• You hear things you aren't used to hearing. In this case, "You smell nice. Is that your new perfume?"
• They're fine with using power tools, as long as you are willing to call a hair dryer a power tool.
• They can't work for more than two minutes without sending or receiving a text message.

It took almost two hours, but all of the skins are now denuded of their blue cladding. I handed the helpers a $10 bill and sent them to the mall to hang around for the afternoon.

I went back to the Kindle.

Well, it just keeps getting better!

I'm only mildly annoyed at myself for using the wrong rivets while putting in the ribs yesterday, and drilling all twenty-eight of them back out and replacing them with LP4-4s wasn't that big of a deal in the long run, but it's still nagging at me. I was out at the hangar this morning putting the nose ribs onto the right wing and as long as I was there I looked at the directions again.

Now, we all know that Van's tells you to read the page through before starting on anything and that is good advice, but they could meet us halfway. If I was to describe the way that particular page was laid out, it would go like this:

1) Cleco and rivet some ribs.
2) Cleco and rivet some more ribs.
3) Cleco and rivet some different ribs.
4) Cleco and rivet one more rib and I promise we're done.

Note: use a different size rivet in steps 1 thru 4.

I'm thinking the placement of that note might have contributed to my mistake.

Still, I own this one. Purely my fault and I'm willing to let this just be water under the bridge.

But then....

I came home to find this message from Bill, The Oregon Kid:

I was just looking at the Blog. I made the same error you did on the LP4-3, 4-4 rivets. Van's told me no problem just leave them in there.

Sigh. While misery loves company, it remains the fact that the only thing I had going for me in this entire incident was the feeling of having done the right thing by biting the bullet and correcting the problem.

Well, that's not entirely true. I also got a reminder about how important it is to fully understand what's going on with each and every page/section of the manual. I put that to good use this morning when I was riveting in the innermost flaperon hinge brace. I found that this brace uses the LP4-4 rivets:

Oddly enough, the top and bottom rivets that go through the doubler and into the ribs look like they would also use LP4-4s, but they don't:

I then went through the normal angst about whether or not I'm interpreting the woefully inadequate picture that shows which side of the flange the ribs go on. I got the first three wrong and had to go back and move them over to the other side.

The nose ribs go in quite easily, although it gets a little tricky as you get to the root area. It's a tight fit and requires the use of the wedge thingy, and the second to last rib is an 'R' instead of the normal 'L' type which caused a little confusion.

Finally, the front spar stub gets riveted on - that was completely uneventful.

Now I have a problem. I'm not sure where I'm going to put this big wing when my loaned-out rib gets returned this afternoon and I go back to get caught up on the left wing. Space is getting really tight!