I didn’t have much time this week, but I was able to get the trim system working correctly.
Using the laptop and a long Ethernet cable I was able to use the VPX configurator tool on my laptop to send power to the trim motors. I was pleasantly surprised that both the roll and pitch servos worked correctly. I carefully verified that the orientation was correct. It would be easy to reverse either one. For example, the elevator trim tab moves up and down just like the elevator, but it has the opposite effect from the elevator itself. Pitching “up” causes the elevator trailing edge to move up. Trimming “up” causes the elevator trim tab to move down, not up. It moves opposite the elevator, providing a force that moves the elevator to change the aircraft’s pitch.
After confirming the motors were working, I was able to set the correct max, min, and midpoint settings for both servos.
I then worked on mounting the aileron trim brackets on the right wing aileron pushrod. These connect the springs from the servo control arm to the pushrod, actuating the aileron.
Aileron trim servo. The servo mounts onto the access panel at this point. Springs will attach to the holes in the end of the arm, and extend to the brackets on the pushrod. Diagram of the aileron trim system showing the springs and how they connect to the pushrod and servo armUsing the laptop to run the trim motors and to set the trim limit parametersVPX config tool. The whole electrical system can be configured and activated from the laptop. The blue Ethernet cable is a 50 foot cable that plugs into the VPX box behind the panelDue to interference between the springs and the pushrod, I bent the servo arm to gain some clearance Springs attached to the servo arm.One last picture before closing this up. Note, the d-sub connector is safety wired together
This week I’ve continued with various assembly tasks.
Lighting:
I resolved the issue with the strobe lights, finding I had mis-pinned a molex connector on the wingtip. Once I corrected the pins, everything worked just fine. It took longer than I care to admit to troubleshoot and find the problem. I learned that it’s useful to start by validating assumptions around where your wires are going by measuring impedance and verifying there is a good electrical connection. Then start measuring voltage drop, once you know your wires are going where you thought they were going.
Comparing this picture to the diagram below, you can see the difference in the pinout. This is actually how I left the connector. Previously the female molex connector actually had the correct pins, but the male was incorrect. Rather than switching the male pins, I just changed the female. How it’s supposed to be wired. I had the right hand side of this correct, and the left hand side incorrect. I changed the right hand side to match the left .Lights are all working as expected now.
Aileron Attach:
With help from a saw horse with adjustable leg height, I was able to quite easily install the ailerons. I used new hardware, except for the bushings, since I’ve had these on and off a few times. I was wondering if the install would be more difficult than when the wings were in the stand, but I found it the same, or maybe slightly easier.
I installed and final torqued the aileron pushrods, verified they were correctly rigged using the templates. The templates allow for the pushrod between the aileron and the bell crank to be correctly sized to establish the correct neutral point. Later in the week I rigged the stick-to-wing root pushrods per chapter 41, and adjusted pushrod length until I had the neutral point on both ailerons aligned with a level stick base. I was then able to test the stick clearance, and found I need to trim more off both sticks to avoid hitting the throttle (pilot side) and mixture (passenger side).
I hung the flaps and connected the pushrods, adjusting them to get both flaps all the way up, then verified they have enough clearance from the fuselage.
I also secured the wiring for the magnetometer. I had installed this a couple of years ago but hadn’t finalized the wiring. I had plenty of length so I created a large service loop and secured it out of the way of the pushrod.
Flap pushrodsCalibrating the pushrods took an iterative approach but I eventually got itWing tip template helps keep the aileron neutralFlaps on and configuredGetting the washes onto the bolt that secured the pushrod at the stick base was a challenge. Note, this picture was taken before I torqued up the nutPassenger side stick interferencePilot side stick interference
Tonight I finished a couple of wing-related jobs. I wired a connector onto the Trim Servo, and corresponding right wing wiring harness. Then I worked on a wing cradle modification in preparation for moving the wings to the airport.
For the servo, I installed a 9-pin d-sub connector. I contemplated different arrangements, and eventually settled on a d-sub connector. I plan to safety-wire the two connector halves to prevent them from loosening, and to keep the wiring secure I glued a zip-tie holder onto the servo housing using some epoxy glue.
I still haven’t installed the tabs onto the pushrod, which is what the servo attaches to via a couple of springs. I need to do that before the wings are attached, but I’m slightly concerned I may end up needing to adjust the pushrod length when I rig the ailerons, and that might require a rotation of the pushrod.
On the wing cradle, I made a fitting to hold the wing spars in position on the cross beam. I’ll add a padded “cap” to the fitting to grip the spars and prevent any movement.
Amongst other things, today I installed the magnetometer in the wing, and wired up the circular connector. I didn’t gab any photos unfortunately. There are just a couple of rivets to set in order to make the mount, then the unit screws into the mount, and the mount slides into the bracket in the wing.
With the aircraft outside, we took the opportunity to test the lights and other systems. I tested the landing lights, taxi lights, navigation lights, strobe lights, wig-wag function, magnetometer, satellite reception, canopy fans, canopy flood light, comm radios, and GPS receivers.
There were some issues with the lighting which I’ll need to investigate and fix: one row of red nav LED lights were intermittent, the wing tip strobe lights were weak, and the right side, leading-edge, landing lights were in-op.
Aside from that, everything else worked as expected.
In order to test everything I made a wiring harness that was 7 feet long and allowed me to connect the wing lighting from both wings while they remained in the wing cradle. I positioned a couple of workbenches behind the fuselage so I could plug in the tail light, and the wingtip lights. It’s possible the extra 7 feet of wiring had an adverse effect on the lighting voltage, contributing to some of the problems, but I didn’t attempt to troubleshoot.
G750 receiving GPS signalGPS signal from the GA-35 antennaMagnetometer connected, but not yet calibrated. Note, all lights are on, and current draw is 16.5AThe wing connection setupI had to drop the left wing down out of the cradle to connect the wiring Nav light test. The intermittent LEDs are on the bottom left of this image, which is actually the top side (the top is upside down here)Right wing nav lights looking good
I spent time securing the right wing wiring today. Zip ties along the length, and some RTV in some places to help secure everything and keep it from rattling around in places where the wiring bundle was loose within the snap-bushings.
Today I installed the autopilot roll servo. Having done this on the previous set of wings, this went quickly. I also installed the bell crank, the adel clamps, and torqued all the bolts.
Installed and wired upInstall finished except for wiring tidy up.
Today I spent time running the wiring harnesses through the right wing, and installing the spare wiring molex connector bracket. This is my own (Vans approved) modification to make it easier to add more electrical devices in the future.
Riveting on the spare wiring bracket. Look at that grey hairBracket installedAutopilot roll servo wiring
Tonight I enlarged one of the wing systems holes to 5/8ths to allow two pneumatic tubes to fit through the first 4 ribs. Then I installed my additional spar wiring molex bracket, ran all of the wiring in the left wing, and installed adel clamps in the area where the wiring runs along the spar.
The additional molex connector bracket is supporting the two additional molex connectors, one for the pitot heater, and one for spare wiring. The red and clear tubes are protruding from the enlarged 5/8th holesAt all stations on the main spar, I have an adel clamp like this one installed. These have slightly longer AN bolts, and right now they are not torqued. The clamp keeps the wires from moving, and protects them from chafing on the spar waffle plate edge
Today I started installing the wing systems. I ran some of the cables out to the wing stops, but then discovered I made one error on the routing and had to undo some work. Unfortunately I ended up snapping some molex crips, so I need to order some replacements from Vans to finish the wing tip lighting runs.
Fuel sender wired. I tested the connection, seems okOne of the left wing wiring harnesses installedThe first, and incorrect, routing of these wires. These need to run along the spar one more bay before stepping aft (up). I fixed the issue
