Back to the wings

I’m working on preparing the wings for final installation, and one task that’s easier to perform now is installation of the Garmin GSA-28 autopilot roll servo. Nothing too tricky here, the G3x installation manual covers the process nicely. I’ve had this servo sitting around for a couple of years and it took a bit of searching to find the necessary parts.

Roll servo mostly installedOne gotcha…in the past, Garmin claimed that their servo was compatible with mounting brackets from other manufacturers but that turned out not to be the case. I had originally installed an Advanced/Dynon servo bracket, because way back when I built the wings I was planning to use their avionics.

Turns out that the Garmin servo *isn’t* compatible with Dynon’s brackets, so I had to swap it for the one from the GSA-28 install kit. This won’t be a big deal for anyone who’s installing a servo from scratch, but if you’re swapping from another manufacturer, be prepared for a little extra work.

Full flaps

Continuing on with avionics and cockpit wrap-up, I had to install a microswitch that tells the angle-of-attack (AoA) computer when the flaps are down. Flap deployment changes the coefficient-of-lift curve and so for the AoA computer to work properly, it needs to know when the flaps are down.

Where the flap-down switch resides

The only place I could think of for the switch was right at the front of the flap arm, which is at its lowest point when the flaps are up. I thought I’d do something really spiffy and adjustable…

Flap-down switch, first attempt

…but that didn’t work so well because the bracket (dark grey thing with the black switch attached) was too long and interfered with the elevator pushrod.

Flap-down switch finalGoing back to the drawing board, I put a 90-degree bend in the bracket and rotated the switch so that it’s activated by the flap arm clevis. Works great, and there’s enough play in the switch that I can adjust it later if necessary.

Turns out that was the easy part. This switch grounds a wire coming from the AoA computer, so I had to run a wire from it to the central ground block in the elevator pushrod tunnel. That took most of an evening, but it’s done and the AoA computer now shouts “flaps” through the intercom when the flap-down motor is activated.

Flap motor installed

And here’s the installed flap motor with a Deutsch DTM connector all ready for plugging in to flap power and position sensor inputs for the GEA-24 and GAD-27.

Tunnels and pumps

I found that all the wiring I’d run between the instrument panel and cockpit center section just wasn’t going to fit in the “tunnel” that covers up wiring, brake lines (for nosedragger RVs) and fuel lines running from the firewall and instrument panel to the fuselage center section. I had to modify the tunnel cover to relieve the 90-degree angle at its forward end and so create more room for wiring.

Tunnel angle

This bit of aluminum turns the tunnel’s 90-degree bend into two 45-degree bends and creates more room for wire.

Tunnel angle installed

Another picture? Sure!

Modified tunnel

That solved one problem in this area, but I still had another one – as I ran wiring from the tunnel to the center section I forgot to leave room behind the fuel selector for the J-shaped tube that connects it to the fuel filter/pump assembly. Oops.

OopsThe solution was to fabricate a bracket that moves the pump/filter up and forward enough to accommodate an L-shaped fuel line that doesn’t interfere with the wire bundles behind it.

Fixing the oopsThe bracket attaches to the existing pump mounting holes in the tunnel cover. This created a challenging fuel line run from the pump outlet to the firewall but Tom Swearingen at TS Flightlines solved the problem with a well-crafted flexible fuel line with a 90-degree fitting on one end.

Tom's fuel lineThe end result – a tunnel that fits nicely in the fuselage and a pump/filter that connects nicely to the fuel selector.

The finished tunnel

Trimming the starboard stabilizing ailertooters

I have an unfortunate tendency to communicate in movie quotes, so bonus points to you if you can identify the “starboard stabilizing ailertooter” reference without using Google, Bing or some other internet search megalith.

No, the Mighty RV doesn’t have ailertooters but it does have ailerons and that’s what prompted the title. One of the last bits of cockpit work is installing the aileron trim motor; I fitted the bracket way back when I was building the fuselage center section and all that was left was to install the motor and connect it to the flight controls.

Aileron trim installed

I didn’t take any in-process pictures, so all you get to see is the final product. The trim motor is under the square white bracket in the lower center of this picture. It drives a lever that’s connected to the control sticks with springs which are adjusted to be in just enough tension that the motor can move the sticks but not significantly affect roll control feel.

Drawing current

So after finishing almost all of the avionics wiring, I came across a little warning in the Garmin installation manual that their engine monitor unit may not be able to provide enough current to the boxes that determine the amount of fuel in the tanks – a bit of potential non-coolness. But I have a piece of parchment on the wall that says I know something about electrical engineering, so I decided to run a quick to check on Garmin’s warning.

Measuring fuel sender current

I popped the fuel level sender’s Deutsch connector apart, jumpered my multimeter into the power line and powered up the avionics. Voila…an accurate measurement of the sender’s current draw – 8 mA, which is significantly under the engine monitor’s max current level. Cool.

First RF

New telescopes have “first light”, the Mighty RV’s avionics had “first RF” today.

Pulling out for a clear view of the skyI powered up the panel – both GPS receivers came up in 3D differential, Sirius/XM is begging for a subscription, tower and ATIS on the comm radios, and there’s even ADS-B In traffic on the G3x to boot. Cool.

First RF

The end of Act 1

I decided that my time as an Air Force civilian was complete; it’s time to move on to Act 2. Lots of friends and family joined me for the retirement ceremony, including my friends and fellow QBs Don McPherson and Vince Orlando who joined me in a dram of the Blue Label.


My sister and her family flew in from Kentucky and we had a great time at a Sox game. The Sox obviously didn’t know that VIPs were in attendance and had the unmitigated gall to lose the game.

Jacob, Whits, Joshua and Elizabeth

A riveting partnership

My wife is awesome. And she rivets like a pro.

My riveting partner

We finished riveting the turtledeck…well, almost. There are three rivets left on each side that are gonna be a beeyotch to get, but that’s a problem to be solved tomorrow.

The riveted turtledeck

Looks good, doesn’t it? It was all Ellen.

Baggage bulkhead cover

We clecoed the baggage bulkhead in place because we could, and it looks cool.  Plus, it helps keep dirt and dust out of the tailcone.

Buttoning up the turtledeck

The tailcone avionics and electrical wiring are done and I really want to rivet the fuselage “turtledeck” skin – the one behind the cockpit. But I also don’t want to dive back there to fix wiring problems once it’s in place.

I’ve smoke-checked the ELT’s RS-232 data connection to the GTN-650, the tail nav/strobe light and even the elevator trim servo. But the last bit to be checked is the servo’s position indicator and the only way to know for sure is to configure the G3x Touch display to read and display position indicator signals. So that’s what I did.

G3x Pitch Trim 1

Configuring the Touch was a lot easier than I feared. All that’s required is to move the trim servo to full up, center, and full down and tell the display when the servo is positioned at each point.

G3x Pitch Trim 2

The Touch calibration page reads voltage coming from the position indicator and displays a gauge preview…very cool. That’s a good confirmation that the tailcone wiring is fully functional.

G3x Pitch Trim 3

And now Elevator Trim shows on the PFD…even more cool!

Turtledeck ready for riveting

A few more minutes and the turtledeck is clecoed into place for the last time and we’re ready to break out the rivet gun and bucking bars.