Dave’s RV-7A Building Log

Made two backing plates for the COM antennas, drilled them to the fuselage bottom skin just aft and outboard of the sticks, and deburred everything.

I finished cutting the last two ignition wires and putting the coil end connectors on. I installed one of the ignition wire baffle seals, but it really needs AN3-3 bolts which I’m out of. Other than that the seals will work great.

Tinkered around with a few other things before deciding to work on something from the task list. Modifying the harness 5th point (aka crotch strap) attach bracket for the Hooker harnesses sounded easy. The brackets are tailored for the Vans harnesses, but the Hookers are larger while using a smaller bolt. I drilled a hole for an AN4 bolt a little further down on the bracket.

Another issue is that the Hooker harness has a rather long bushing for the attach bolt. I installed the brackets according to Vans directions, which specify a gap of 1/8″ between the brackets. I suppose if you knew ahead of time that you were going to use Hooker harnesses, you could space them apart more. Instead I just ground down the bushing so that it’s almost flush. Much easier solution than trying to move the brackets.

I also had to enlarge the hole in the seat pan with a file a little bit so the strap adjustment buckle would fit through. Sounds like a lot of work, but it didn’t take long to do. Yay, another item crossed off the list. It would be great to get the list mostly done. Then I can concentrate on wiring, panel, and avionics.

I wasn’t feeling well today. Don’t know if it was a bug or simply being over-tired. I had reserved a plane for 1pm to practice some landings and maneuvers. The weather was absolutely perfect, but I just didn’t feel up to it. I spent time with the family and messing around on the plane instead.

I finally came to terms with the control cable quandry. I read through the entire section in the Spruce catelog and didn’t find any information that would have prevented me from mis-ordering. I did find one helpful thing, an optional polyolefin covering for the cables. I’ll get that on the next ones.

I also decided to double (and maybe triple) check that the lengths were correct. I placed all of the various arms and adjustments to their mid-position. I mounted the panel and quadrant back in the plane and placed the levers to their mid positions. While I held the cable roughly where I wanted it to be routed, Julie measured the difference between the end of the cable and the mounting hole in the quadrant lever. Adding on 7/8″ for the clevis end, I then calculated the correct length for each cable: mixture 51″, prop 48″, throttle 50″. There’s a fair amount of adjustability at each end and in the routing, so +/- 1″ would even work OK.

The mixture cable especially has a lot of flexibility since the arm angle can be changed to any position and the end on the lever arm can be adjusted. I put everything at its mid-position and mounted the mixture arm so the lever arm doesn’t hit the bracket. Hard to describe, but you’ll understand when you get here.

I got some great responses from the Yahoo Lycoming group. The standard mag wiring is right mag to upper-right and lower-left spark plugs, left mag to upper-left and lower-right spark plugs. This is to balance out the RPM drop when doing a magneto test. Dan also suggested just wiring one side to all upper and the other to all lower just to make troubleshooting easier, which was a good idea. In the end, I decided to go with the standard wiring. EmagAir provides all the parts, a crimper, and great instructions for making the ignition harness. I put on 6 of the 8 coil ends onto the wires. It’s time consuming work, but I’m going very carefully.

I also ran down to the hardware store and picked up a couple parts for a poor-man’s prop torque extension. I wish I could claim that I thought of this, but I got it off the VAF forum. Buy a bolt and nut (and washer for good measure) that are the same size as the prop nut. In my case this was 3/4″

With my 3/4″ wrench on the prop nut, I put the bolt/nut “adapter” in the other end and then attached the torque wrench to it. I used the formula that came with the torque wrench to de-rate the torque value appropriately for the extension. Unfortunately, my good torque wrench doesn’t go high enough for the prop bolts. I’ll have to borrow one.

I worked further on the throttle quadrant control cables, the time hooking up the mixture cable. Again, I wasn’t able to get the full swing out of the mixture arm. No matter how I adjusted things, it just wasn’t working. And then it dawned on me what the problem was. The bulkhead nuts are not located in the same position relative to the end of the cable as the standard Vans cables. In the picture, the top cable is the end of Vans standard push/pull knob cable. The bottom cable is the standard Spruce A-1550.

When I figured that out, I was at first furious and then frustrated. I tried to think of how I can remedy the problem. I could fabricate new brackets for all the cables. But that would be a huge hassle, especially for the prop governor. The Aircraft Spruce catalog doesn’t mention this dimension anywhere. There are some mentions of the “travel” for a control cable, but now how that affects the bulkhead nut placement. I figured more travel was a good thing, but not in this case. It puts the bulkhead nuts further back on the cable. In the end I decided to just order new cables. They’re not cheap at $50 each, but I’d rather get them right as controlling the throttle, mixture, and prop pitch are kinda important. My main concern is that Spruce took 2 months to make them last time. Hopefully I can get that expedited somehow.

I wasn’t feeling much like working on the plane at this point. I looked around for the Pmag manual, but couldn’t find it in the usual piles. I decided to clean up the paperwork. Every little part for the plane comes with it’s own instruction manual. I grabbed a big 3-ring binder, a 3-hole punch, and some plastic Postit tabs and got it all organized by major category. Much better.

I eventually found the Pmag manual in the electrical pile and started figuring out how to wire up the spark plugs. Aircraft engines have two spark plugs for each cylinder. I know each cylinder should be fired by two separate sources, but I wasn’t sure if there was a standard approach to that. I asked the Lycoming Yahoo group.

Since I had the panel out, I decided to rivet the vent brackets in place. Turned out great.

I fabricated a couple angles to hold the throttle quadrant in place at the subpanel. I’m going to wait for the avionics stack to arrive before I final drill those in case there’s some interference problem.

My final task for the day was to install the prop control cable. One strange thing was that I wasn’t able to make the prop governor arm swing from one stop to the other. I adjusted the retaining nuts and the end terminal, but it just wasn’t working right. (See tomorrow’s entry for the reason.)

Adele had her last swim meet of the season, but I still managed a little time on the plane. I went back to working on the throttle quadrant. I clamped it to the panel and climbed into the plane to check the ergonomics. I wanted to make sure the quadrant wasn’t crowding my legroom, was easy to reach, and that I could still easily get to the switches mounted above it. With the mounting bracket’s peaking out from under the panel by about 3/4″, it was a perfect balance. Found myself involuntarily making engine noises while moving the stick around. I can’t wait to fly this thing some day.

I took quite a bit of time finding the perfect location for drilling the panel flange and quadrant attachment bracket, and drilled them out to #12. It looks like the bracket will be about 1″ below the subpanel. I’ll use some large angle there. That will actually work out well as the cables tend to angle up a bit. I also figured out a way to make a bulkhead for the cable housings to attach to. It’s all very difficult to explain, but hopefully it’s clear from the picture.

I also spent some considerable time figuring out the avionics interconnections. I was sort of just leaving it up to Stark to connect everything correctly, but then I started to get worried. Since the CDI interface to the EFIS isn’t completely figured out yet, he was waiting to get more details. Rob at AFS said the ARINC interface won’t be sorted out until Fall, so we can’t wait for that. Those wires will just have to end in a pigtail for now. This is the list I sent him today:

PMA8000B
pilot/co-pilot stereo headphones
pilot/co-pilot mic plus PTT
speaker output
COM1 < --> GNS430
COM2 < --> SL40
NAV1 < --> GNS430
4 unswitched inputs and 2 entertainment inputs < --> 3′ pigtails
Swap line
Lighting lines wired for 14V

GTX327
RS-232 IN & OUT < --> GNS 430 (to get groundspeed from GPS, and to send altitude data)
RS-232 IN < --> pigtail (for EFIS altitude output)

GNS430
RS-232 IN & OUT < --> GTX327
RS-232 OUT < --> autopilot
RS-232 IN & OUT < --> pigtail for EFIS (just in case)
VOR/ILS ARINC 429 IN & OUT < --> pigtail for EFIS
GPS ARINC 429 IN < --> pigtail for future traffic device
GPS ARINC 429 OUT < --> autopilot
COM & VOR/ILS < --> PMA8000B

SL40
Serial data input pigtail. (I’ll eventually hook this to a Garmin 396 for radio freq download.)
COM < --> PMA8000B

Digitrak II Autopilot
ARINC < --> GNS430 (this is in case I ever upgrade to GPS steering)
Serial input < --> GNS430
Control wheel disconnect switch
Roll servo
Pitch servo

When I soldered the red position light together, I wasn’t reading far enough ahead in the instructions. Since the forward face of the cutout in the wingtips is angled back a bit, the LEDs need to be angled forward 10 degrees or so. When I soldered in the red LEDs, I didn’t leave enough of the lead above the board to bend the LEDs. I asked Bill for some replacement LEDs and he sent them out free, which was very cool.

I removed the old LEDs, sucked out the solder with a bulb, and re-soldered the LEDs in place. I still tried to screw it up by putting some of the LEDs in backwards. I really shouldn’t work on something so technical when I’m tired. I managed to get it all straightened out and the unit works great. These position lights are very cool, but it’s definitely not an easy soldering job. I’d buy the pre-made ones next time.

Now I just need to seal the board. I’m thinking of painting it with a white epoxy paint to really make it blend in.

Decided to install the seals I bought a long time ago from Aircraft Spruce. These seals allow the ignition wires to pass through the baffle. I could have used snap bushings, but these seals look cool and cover a larger area that will allow the wire to be installed/removed while keeping the bulky terminals intact.

The big drawback is that the seals have a really odd-shaped cut out. It took quite a while to figure out how to do it. In the end, it was fairly easy. Drill four holes in a line. The two outer ones get drilled to #10 for the AN3 bolts. The two inner ones get drilled out to 3/4″ each. I was worried about using the Unibit to enlarge the overlapping holes to 3/4″, but it ended up not being a problem. I just applied sideways pressure on the drill to keep the Unibit from catching in the overlapping area. I made a template out of stiff paper of the desired cut out shape and used that to draw an outline on the baffle. That helped quite a bit for coaxing the Unibit in the right direction. A little bit of filing to clean up, and they turned out great. Another item crossed off the list.

I spent a few hours while watching TV trying to figure out the innerconnects between the avionics. Talking to Carl down in NZ kind of confirmed my worries that Stark only hooks up what you tell him to. I’m figuring out what each line on each unit does and whether/where I want it connected to something else.

I wanted to knock another item off the task list, so I worked on the fuel pump overflow. I guess there’s a pressure relief valve within the pump. If the pressure gets too high for some reason, fuel will spill out the port. I hooked it up almost exactly per the Vans plans. I just moved it a little inboard so it wouldn’t interfere with my relocated breather tube. The plans call for a #12 hole in the bottom skin for the outlet, but I had to go #10 for the tube to fit. Safety wiring each end is much more secure than I would have guessed.

With that done, I turned to something more interesting. I started working on the mount for the throttle quadrant. I cut two pieces of .063 x 3/4 x 3/4 angle to about 11″ each. I then carefully located and drilled holes in one end of each to attach the quadrant. This end will be visible from the cockpit, so I want it to look good. I did a lot of clamping and double checking while drilling out to #10 for AN3 bolts.

These angles will attach to the bottom of the panel. I’m not exactly sure yet how I want the quadrant positioned, but now I can try a couple of scenarios with these angles attached. It’s nice to be moving from the head-scratching stage to the implementation stage with this quadrant. I’ve put a lot of thought and research into how to install this thing.

Arlington always gets me inspired to get this project flying. Even though it was a beautiful day outside and the temps hit 80 in the shop, I spent most of the day working on the plane.

I finished up my replacement brackets for the vents. I fitted, drilled, and dimpled to get it fitted just right. I used the fly cutter to make the 2-1/4″ hole for the vents.

With the vents positioned much better, I trimmed the template for the side panels and took some new pictures to send to Classic Aero.

I decided to try out the crimper that I borrowed from Steve. There’s a dial on the top for the wire size, which I set to #2. Strip some insulation off, put the terminal on and squeeze away. There ain’t nothing that is going to pull that terminal off the wire.

With some careful measuring and making sure the angle between the terminals was right, I finished up the positive battery cable. I’ll need to secure this wire somehow. It flops around way too much. I touched a wire between the negative battery terminal and the control terminal on the contactor. I was wearing gloves and safety glasses in case the whole thing sparked and blew up. Click, click. Woohoo, it works!!

Time to attack some stuff on the punch list. The crankcase breather tube has been bugging me for way too long. I figured out a place on the firewall to install a nut plate and went for it. I trimmed the end of the breather so it’s right above the left exhaust pipe and at an angle that will prevent air from being forced up into the tube. I had to bend the tube slightly so it wouldn’t hit the engine mount. Done deal, looks great. I just need to read up on how to make the “whistle slot,” a hole that prevents pressure from building up in case the end of the tube freezes shut (very unlikely).

This picture is a little harder to figure out, but shows the top view of the breather tube routing.

A neighbor stopped by and chatted for a little while. His family owns a 172 and a wrecked 210 that they hope to restore some day. He also has a friend building an RV-6. I think he’s the first visitor to actually crawl around under the engine and check things out. I can see how you could kill a whole day talking down at the airport. Another good reason to keep the plane in the garage as long as possible.

Last thing for the day was to paint the cabin vent brackets. Long, productive day.