Dave’s RV-7A Building Log

I had some scrap .040 laying around that already had a 90 degree angle (from the old cabin frame support). I used that to secure the back of the GNS430 tray to the subpanel. I would have liked to secure the SL-40 as well, but none of the mounting holes lined up. I also cut some straps out of .063 to hold the middle of the stack in place. That will sandwich the other units around the GNS430 and should hold everything in place nicely. The angles at the back of the GNS430 also stabilize the subpanel quite a bit. Another nice side effect is that the whole panel is much sturdier. I’ve been debating about how to re-locate the ribs between the panel and subpanel, but am now thinking I may be able ditch them altogether. I’m going to leave them out for now and re-evaluate once the AFS units are installed.

I also finished fabricating the mount for the throttle quadrant. I put a slight bend in the angles at the back to match the subpanel rake and drilled holes for rivets to the subpanel and AN3 bolts to the quadrant mount angles.

I had to trim the hat section that holds the canopy release mechanism a little more. I think it’s still going to be workable. I should even be able to put the release handle above the avionics. I know lots of people leave it out, but I’m going to try to keep it if at all possible.

Good progress this weekend. I just need to prime some parts and I can rivet together the whole structure.

Went down to BFI to do my BFR (biannual flight review). We got the ground part done, but the clouds were too low for the flying we needed to do. Had to re-schedule the flight part.

Carefully marked and cut the subpanel where the avionics need to stick through.

Drilling the avionics trays to the mounting angles is a slow process. I did a lot of measuring and careful alignment. I used some .063 under the bottom tray for two purposes. First, the Garmin transponder has a cam at the bottom of the unit for securing it in the tray. If you mount the tray too close to the bottom of the opening, it’ll be tough to insert and remove. I also wanted to make sure there was no visible gap at the top of the stack.

Some people recess the trays so the bezels of the units don’t stick out so far. I went with the standard mounting. I made the front edge of the tray flush with the surface of the panel. I marked and drilled the trays one at a time, but I probably could have done them all at the same time. I drilled to #40 and then to #28 for #6 screws.

It looks like two of the trays use countersunk screws and two use pan head. Crazy. I temporarily installed countersunk screws in all of them just to test the fit. The SL40 fit great with one #6L washer on each side. There’s some slop in the PMA-8000B mount, but I’ll nail that down once I get the GNS-430 GPS. The stack looks really good. Now to cut the subpanel…

I pre-drilled the side angles for some rivets that will hold it to the panel. I found a combination of wood that would hold the trays at the perfect height to match the opening. The vertical dimension of the opening actually looks pretty good now. I drew some guide lines on the back of the panel and used that to center the trays and clamped the angles into place. I did lots of measuring to make sure everything was even and right where I wanted it. All of the trays except the SL40 are snug, as expected. I’ll have to use some thin washers for the SL40. I’ll sleep on it and drill the angles to the panel tomorrow.

I started looking more seriously at how to mount the avionics to the panel. The cutout Ross made in the panel is 6.25″ wide. The bezels on most of the avionics are 6.30″. The exceptions are the PMA 8000B audio panel which seems to be 6.33″ and the SL-40 radio which is about 6.27″. Also, the SL-40 does not leave a gap between the bezel and tray. The cutout must be at least 6.27″ wide for it to fit. So I spent the better part of an hour filing the edges of the avionics cut out. I’d like to actually have only half of the bezel stick out, but I’d have to make the whole cutout 6.33″ to fit the audio panel. That would leave a bit of a gap around all the other avionics.

The PMA tray is strange. Instead of securing the instrument via a cam at the bottom front like the Garmin units, it uses a weird screw/nutplate arrangement at the back. That would be fine except the tray is pretty loose at the front. I’m going to have to stick some UHMW tape in there or something to keep it from flopping around. (Edit 9/14/06: Mark from PS Engineering contacted me. Since the PMA8000B is plug and play replaceable with the GMA340, they have the exact same mount. I don’t have any doubt that the mount will be secure once everything is permanently installed. It’s just odd that Garmin hasn’t tried to standardize their equipment over time. I guess it’s an artifact of them buying up other products.)

I propped up the avionics at the back and did a dry fit in the panel. Looks like there’s a bit of a gap top to bottom. I’ll try to put most of that at the bottom where it’s less visible. I installed a couple switches under the avionics to make sure they were still accessible–no problem.

I cut a couple of lengths of 3/4″x3/4″x.063 angle to the height of the opening plus 1/4″. Now I just need to figure out how to hold the avionics in place so I can drill them to the panel. Mounting the trays to the panel is definitely not a plug-and-play process.

Between the Tour de France (kudos to Floyd) and the mid-80 temps in the garage, productivity has been very low lately. Both seem to be done, so hopefully I can crank on the plane again.

Some of the avionics arrived today. The autopilot is shipping direct from Trutrak, which I’ve read has been slow about filling orders lately. I also waited to order the GNS-430 GPS. Garmin, as expected, announced their WAAS-capable version of the 430 on Sunday. It’s only about a grand more than the old non-WAAS model, so I’ll get that for sure. Should be available in the Fall.

What did arrive was the GTX-327 transponder, SL-40 back-up radio, PMA 8000B audio panel, a tray for the GNS-430, and a mess of wires. The wiring looks to be pretty close to correct. For some reason Stark wired the ARCIN IN A and IN B together rather than the ARINC IN A and OUT A. That would have made more sense. I might have to snip and crimp a few things. Overall the harness looks good.

I spent some time looking at the harness, messing around with the trays, testing the fit in the panel, etc. The cutout that Ross made in the panel for the avionics is actually not wide enough for the trays or bezels to fit through. I’m not sure if that’s correct or not. Seems like it will work OK for the audio panel and transponder. There’s a bit of a gap between the bezel and tray that will hold the panel quite nicely. The SL-40 however doesn’t have a gap. This will take some head scratching to figure out.

I also received my order from Vans containing some miscellaneous hardware I needed, and some .040 sheet I’m going to use as a shelf for the fuse blocks and other modules. A lot of builders attach these to the subpanel or ribs, but they’ll be much easier to reach through the access hatches on the shelf. Thanks to JimP for that idea.

The good part is that I can move forward with a lot of stuff now. Many things were waiting on the avionics to arrive.

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

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.