Taxi Test

Posted on by Neal

Today I arrived at the airport early to prepare for and conduct a taxi test. In my test card, I planned to check steering operations on the ground – braking action, differential braking, and tail wheel steering. I also planned to calibrate the magnetometer on the compass rose. Everything went well, and I learned a few things along the way.

The compass rose is at the other end of the runway, and I am trying to minimize the amount of engine run-time at low RPM. Because the engine is brand new and needs to be broken in, the recommendation is to run it at high power for the first few hours of it’s life. Since I can’t do that on the ground, I don’t want to be running the engine longer than I need to before it’s flying. However, I need to calibrate the magnetometer, and it’s a sensitive instrument. Calibration requires slowly taxiing in a circle in an area free from any magnetic interference, which is what the compass rose provides. I decided it was worth the extra 5-6 minutes to taxi there and back to give the calibration the highest chance of success.

The engine started nicely, and I started the taxi test right away. Since the tower was operating by the time I was ready, I also had a chance to test my Com1 radio, tower gave me a 5/5 rating – loud and clear. With the cowling on I could check my visibility while taxiing. By sitting up straight I can see over the top of the cowl, although the first 200 feet in front of the plane is obscured. Moving my head to the left I had a nice view down the side of the cowl, and I found that to be the easiest way to monitor the taxi way ahead. Engine instruments showed the engine was running well – consistent CHTs, EGTs, and oil temp & pressure.

Arriving at the compass rose, I positioned the aircraft on the left side, facing due north, as described in the Garmin manual. I needed to boot the PFD into Calibration mode which required shutting down the G3X system, and booting it back up. I shut off the standby battery first, then the main battery. For a moment I was surprised that all the avionics were still operating. Then I remembered the alternator was still on, and was powering the system. I shut off the alternator, and the engine started to shut down! I immediately realized what had happened, but didn’t have the reaction time to stop it. I pulled the mixture to complete a normal engine shutdown. The e-mag ignition system depends on main buss power at low RPM. The mags have internal Alternators to provide power, but only about ~1200 RPM. I was idling the engine when I shut off the power, and the ignition system stopped igniting.

While the engine was shutdown I booted up the G3X into calibration mode and get the magnetometer test ready to go. The engine started right up again, and I followed the on-screen instructions to slowly turn in a circle to the right, holding position every 30 degrees. The whole process took about 10 minutes, and thankfully passed at the end. I taxied safely back to the hangar and shutdown. The total engine run time was 18 minutes, a bit longer than I hoped.

Analyzing the engine data again, everything appeared normal.

Post taxi inspection. Exhaust is starting to change color. No sign of oil leaks, a track of splatter from the exhaust joint lubricant.

Here is some of the engine and flight data. Note, the data between the vertical bars is interpolated, since I only had data from the beginning and end of the test, and not while performing the magnetometer calibration (the time between the bars).

Not sure why the airspeed is indicating 18 MPH before and after the test, and why it’s so much higher than the ground speed. There was approximately 5 knots of wind, and no other reason I can think of that would cause it to read high. Prop blast could be a factor after engine start, but the pitot tube is well outside the prop blast area.

First Engine Run

Posted on by Neal

Today was a major milestone – the engine ran for the first time! My friend Donnie met me at the airport at 7am to help advise and provide a second set of eyes on the process. It was early enough to be very quiet, allowing us to focus. After a few preparatory steps, we pulled the airplane out onto the taxi way and started the test. I had a test card written that covered everything I wanted to test – engine instruments, ignition, prop governor, alternator etc.

Everything performed completely as expected, and I was very happy and relieved to complete the test successfully. After verifying everything engine-related, I also took the chance to test the brakes. Donnie removed the chocks and I rolled forward a couple of feet and confirmed the brakes worked well.

After shutdown, I did find an oil leak. I traced it back to a loose oil hose fitting, and was able to torque it up and resolve the issue. It was one of the oil lines connecting the oil cooler, and I must have just plain forgotten to torque it. I added torque seal and checked all the other fluid fittings on and around the engine while I was at it.

The engine ran well. I let it idle for several minutes until the oil temperature reached 100 degrees F, then performed a run-up by slowly increasing RPM to 1800. That’s where I checked the mags, cycled the prop, and double-checked the alternator output. I collected the engine data from the G3X system and uploaded into an analysis tool on my laptop. There was nothing that looked out of the ordinary to my untrained-eye.

First start!
First start from inside the cockpit
CHT data
EGT data
Fuel flow data
Oil temp data
RPM data

Fuel flow test

Posted on by Neal

Today I tested the fuel system for the first time, running the electrical fuel pump and testing fuel flow. Everything worked well, and I was happy to see no obvious leaks.

I started by disconnecting the fuel line leading into the fuel servo, and redirected it into a large measuring jug. Then I poured approximately three gallons of gas into the left fuel tank, and turned the fuel selector to the left tank. I wanted to make sure I had fuel in the fuel pump before starting it the first time, so I used the shop vac and some clear tubing to prime the system – drawing fuel through the fuel lines, all the way to the fuel servo.

I powered up the panel and switched on the pump, and was happy to see fuel flowing into the jug. I ran the pump for a minute and measured 92 fluid ounces pumped, which translates to 43.125 gallons per hour. I repeated the test on the right tank, measuring 94 ounces pumped, about 44 gallons per hour. During the second test the fuel flow gauge was measuring 43.7 gallons per hour, which is very close to the amount I measured.

I repeated the test in a level flight attitude, and then tested for unusable fuel. With the plane in a level attitude, I pumped all the fuel out of the tank, and then drained the leftover fuel from the fuel tank drain port. I measured 6 ounces of unusable fuel per tank, for a total of 12 ounces.

Note the fuel flow of 43.8 G/H. Fuel PSI is low at just 1.5, but I expect that is because the fuel line is simply draining into a jug
Disconnected fuel line pouring fuel into a jug
Left tank test results after a minute of pumping fuel
Right tank fuel flow test
Total unusable fuel left, just 12 ounces

Weight and Balance

Posted on by Neal

Today Donnie helped me with a weight and balance. The airplane weighed in at 1257 pounds, which is right about what I expected. The center of gravity is a very important datapoint too, and after crunching some numbers the empty CG was 81.54 inches aft of the datum. The datum is a point 72 inches forward of the wing leading edge.

The process started by loading up the airplane with all the panels, screws, interior panels, carpet, literally everything that will be part of the airplane. I didn’t bother installing everything, in some cases I just placed the parts in their correct position.

With that done, the next task was to level the airplane. The weight needs to be calculated on level flight condition, so I needed to raise the tail up about 3 feet. To facilitate this I brought my standing desk from home, and was able to easily raise and lower the desk to find level. Using a desk instead of a saw horse allowed room for the scale to sit under the tailwheel. A digital level on the canopy rail was sufficient to identify level.

With that done, I moved the desk out of the way and Donnie set up the scales – one under each wheel with a WiFi controller giving a digital readout for each scale. We then rolled the mains up onto the scales. Then we raised the tail and positioned the desk and scale under the tailwheel. With that done we wrote down the weights, and the weighing exercise was complete.

To get an accurate arm for each scale, I used a plumb bob to make a mark on the floor identifying the wing leading edge. Then I carefully measured the distance to the center of each wheel. The plum bob came in handle at the tail too so I could measure the distance while the tail wheel was still elevated.

With those calculations done, I created a spreadsheet to plot W&B and played around with a few scenarios.

Configuring the standing desk to attain level flight attitude
The numbers. Interestingly, the right main wheel is a quarter inch aft of the left main wheel, relative to the wing leading edge.

Assembly Tasks

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This week I made multiple trips to the hangar to work on various tasks.

Wing attach bolts

I finally torqued the wing attach bolts. The night before, I tested out my torque wrenches to ensure they were reading correctly, and they were both very close. I used a vice to hold the wrench, and then secured a weight over the arm and measured the distance from the fulcrum. For weight I used a 1 Gallon plastic jug filled with carefully measured amounts of water. The nuts were easy to torque, I only found one where it took a second to figure out how to torque it. I ended up using a socket extension that allowed some movement, so I could torque the nut without fear of bending small bits of aluminum that were close by.

Pitot tube:

I finalized the wiring and install of the pitot tube. I used butt splices to connect the pitot heat wiring, replacing the original molex connector. In the process I included a service loop to help with any future maintenance.

I also trimmed the pitot and AOA pneumatic lines at the wing root, inserting them both into the connectors under the seat. I still need to test the system for leaks, and to verify I didn’t switch Pitot and AOA at any point in the system.

Strobe lights:

I did some troubleshooting on an issue with the wing tip strobe lighting. Both sets of strobes are flashing, but weakly. There is only 6.6V at the wingtip, so I’m losing half the voltage somewhere in the system. I tried the easy tasks such as unplugging and reconnecting connectors, but no luck.

VOR Antenna

I completed the VOR antenna wiring, and was happy to tune in a nearby VOR and see a positive ID and a needle on the CDI. The reception seemed good, even though the antenna isn’t well grounded (I don’t have all the screws in the wingtip, and they provide the ground path). The job was quite simple, I just needed to cut the cable to length and install a BNC connector, then plug it into the fitting I had previously installed under the passenger seat. I added a service loop, for ease of maintenance. At the right wingtip I connected the ring terminals to the antenna and torqued them up. I also tidied up the wing tip wiring and then secured the wingtip fairing. I then fired up the instrument panel, turned in the Julian VOR and was happy to see the reception, even on the ground in a metal hangar at 20 miles, and without a properly grounded antenna.

The main spar wing attach bolts, final torqued
One of the aft wing attach bolts
Signs of life from the VOR antenna. The Nav radio is tuned to 113.75, and the green line on the left hand screen (PFD) is pointing to the VOR station
The VOR antenna connection under the passenger seat
Right wingtip wiring. With the wingtip off, I found I could rotate it and set it on its aft edge, balanced against the wing. This made working on the wiring much easier.
Service loop for the pitot heater wiring. Insulated butt splices are visible here and would be the recommended place to disconnect the pitot wiring for any maintenance
Another angle of the pitot tube install. Note, the pushrod is disconnected to allow more room to access the pitot tube wiring.

Light Check and Pitot Tube install

Posted on by Neal

Over the course of a couple of evenings this week I checked out the lights and installed the pitot tube, checking the heater function. I’m trying to fully test the electrical system so I can start troubleshooting and addressing any issues.

The pitot tube installation went mostly according to plan. The Vans plans include a simple, unheated pitot tube, and a lot of builders opt for an upgraded pitot tube with AOA and heat, as I have done with the Garmin pitot tube. One of the considerations for the builder is how to bend the pitot and AOA aluminum tubes coming out of the top of the pitot unit to avoid interference with the aileron push tube. My bends were good, and no changes were needed. Installing the 90 degree aluminum fluid fittings was a bit challenging as access is somewhat limited. I was able to torque them sufficiently so hopefully they won’t leak.

The pitot mast and tube during installation. You can see the end of the pushrod emerging from the darkness directly above the pitot mast
A blurry picture of the aluminum pitot and AOA tubes bending around the pushrod and connecting to the flexible tubes via 90 degree fluid fittings
I had chatGPT clear up my blurry photo above. Not too bad, although it’s added some details that aren’t in the original

The wiring was where I ran into a problem. I had previously set everything up, and all I needed to do was insert the crimped pins into a molex connector, then plugging it in. Unfortunately, the pins were slightly too large for the molex connector, and in the process of trying to make it work, one of the pins pulled off the wire. I’m going to need to redo the wiring, so I’ll be looking into other options. I may just use butt splices and ditch the molex connector. I was able to rig it temporarily so I could test the heater unit using the panel switch, and everything worked as expected.

The rest of the aircraft lighting mostly worked as expected, although I had a list of squawks to troubleshoot and resolve. The first issue was the FlyLED Combo spotlights on the right wing were not illuminating. This was a lost connection, and fully seating the molex connector resolved the issue.

The second problem was the tail light not working. This turned out to be an inadvertent switching of the wiring polarity, and switching the pins in the tail fixed the issue. I had previously wired up a small molex connector and successfully tested the tail light. What I hadn’t considered at the time was that the wires need to pass through a small hole in the Vertical Stabilizer, and I had to remove the molex connector. Rather than messing with a molex connector (just another possible point of failure), I used d-sub pins and insulated the pins with heat shrink. This is when I had switched the wires and introduced the issue. The biggest pain was the lack of access to wiring. With the tail spring right under the forward end of the tail fairing, the fairing can only be moved about half an inch, and I had to flex the side of the fairing to reach in and grab hold of the service loop and then remedy the issue.

That leaves two lighting issues to troubleshoot, 1. One row of red LED position lights isn’t illuminating and 2. The wing tip strobe lights are very dim.

I reached out to Paul at FlyLED and he has pointed me in the right direction to start troubleshooting to isolate the problem. Hopefully some investigation will identify the issue and I can get these problems resolved.

With the navigation and landing lights on, the lighting is extremely bright.

Next I’ll be testing the trim system, and eventually the magnetos.

I also heard back from Vans about an interference issue I’m seeing between the fuel tank bracket and the fuselage side skin. I’m planning to trim the corner off the bracket, which I hope to do with some careful use of a small cutoff wheel.

The red circle indicates the area where the tank bracket is contacting the fuselage. It’s the same on both sides, so it doesn’t appear to be caused by a wing alignment issue. I plan to trim the corner off the bracket to create some space

Wing Attach

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Today my friends Jeremiah, Trey, and Sam helped me mount the wings onto the fuselage. Everything went well, and it’s now looking like a real airplane!

I arrived at the hangar early, and spent time preparing for the event. Jeremiah drove down from LA, and within 5 minutes of his arrival, Trey and Sam landed after flying in from Carlsbad. We got started right away, and things went according to plan.

To prepare for the operation, I had laid out all the necessary hardware, plus the lubricants needed, and the tools I planned to use. I chocked the wheels and raised the tail into a level attitude, and set up some sawhorses to support the wing.

We started by lifting the left wing onto the saw horses and fine tuning the height by removing layers of padding. I then applied Boelube and we gently moved the left wing into position. The drift pins went in with some gentle tapping, as did the larger bolts. Then the remaining bolts were driven through, and the job was complete. It was a fun moment of truth to remove the sawhorses and marvel at how simple the attachment was, and how much load the bolts will carry.

We then moved onto the right wing and repeated the process. Generally it was easier the second time, because we had the process down, and knew where to position everything. It took slightly longer to align the right wing, but there were no issues installing everything.

The only potential issue I observed were there tank attach brackets. The aft corner of the bracket is contacting the fuselage side skin. Items the same on both sides, and it could be “as designed”, but I sent an email to Vans to check.

I haven’t final torqued the bolts yet, but this can wait for a day or two, as the bolts are loaded in shear vs tension.

Raising the tail. It ended up even higher than this picture shows.
Lining up the left wing
Lining up the left wing
The 2×4 helped tremendously to tap home the bolts. Not a lot of force needed, just some gentle bit firm taps
This time on the right wing, Trey applying some pressure to keep the spar web from flexing as the bolt threads pass through.
Both wings attached!
Amazing to see the airplane almost completely assembled now. Certainly a huge milestone today
The tank attach bracket. The aft corner of this bracket it touching the fuselage side skin

Finished Tail Attachment

Posted on by Neal

Over the last week I finished up the tasks needed to mount the tail components. This included removing and modifying the Vertical Stabilizer fairing, connecting the tail wheel, final torque for the rudder attach bolts, and installing the rudder bottom fairing.

I popped the Vertical Stabilizer fairing off, and took it home for modifications. I needed to shave about 1/8th off the back edge, which necessitated adding some layers of filler and glass inside the fairing, to build up the aft edge. Then using a curved sanding block, removing the required amount of material from the back edge. I did all the glassing and sanding at home, then test fit the fairing, made another adjustment, then primed and riveted it back into position.

Then I installed the rudder attach hardware and torqued the nuts on the attach bolts. There’s no easy way to get a torque wrench onto the nuts, so I did the best I could to achieve the right torque.

I hooked up the tail wheel using sash chains and springs, and then adjusted the length of the chains to get about the right amount of tension. I found using zip ties to compress the springs, and to hold the tension on the chain helped to hook everything up.

I then wired up the tail light, and coiled the slack cable into the fairing. This is when I discovered that the rudder bottom fairing can’t be installed with the rudder in final position. After some Vans Airforce research, the advice was to remove the bottom two rudder attach points and swing the rudder sideways and aft to allow the fairing to fit, then reassemble. So at midnight on Saturday I felt like I was starting again, undoing the attach points, taking off one of the sash chains, installing the fairing, then putting it all back together.

Anyway I eventually got it all done and headed home in the early morning hours.

The rudder attach hardware is hard to access
Sash chains and springs
The forward edge of the rudder bottom fairing can’t be attached due to tail wheel spring (the white steel tube) interference
Everything finally in place on the tail

Vertical stabilizer and rudder install

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Today I was able to install the Vertical Stabilizer and the rudder. Before I started that task, I spent time filing down the elevator horns stops. That is, the deck angle on the aft end and the deck doubler on the forward end.

The filing was tedious as I was carefully working to get the correct amount of elevator travel. I was able to get the prescribed 25 degrees of down travel, but not the full 30 degrees of up. I’m at 27.5 degrees up, and not comfortable removing any more material from the aft deck angle before hearing back from Vans. From what I can tell, I’ll have to remove a significant amount more to gain the addition 2 degrees. All of the dimensions appear to be correct, so I’m not sure why I’m having an issue.

Update: tech support at Vans concur that it’s not worth any further filing to gain a couple more degrees of up travel. I’m going to leave this as-is.

The VS install is easy, and I’ve done it so many times now, I was able to complete the task quickly. I had to torque the bolt heads on the bottom 3 bolts (vs the nuts) due to no real access for a torque wrench, so I added some additional torque to account for the bolt movement.

I did run into an issue with the rudder, there’s some interference between the forward edge of the rudder counterweight arm and the aft edge of the Vertical Stabilizer fairing. Not sure how I didn’t find that earlier, but I’m hoping some light sanding will resolve the issue.

The rudder can pass through it’s full range of motion, but it’s rubbing and binding between the fairings
The area of interference that I’ll need to resolve
Looking good with the tail installed

Elevator Final Assembly

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With the airplane at the hangar, I took some time today to visit and do the final install of the horizontal stabilizer and elevators. The most time consuming g apart was finding the right hardware, and I found I was short one bolt. I’m installing the tail section with all new hardware, as these prices have been installed and uninstalled a number of times.

Without all of my tools at the hangar, I ran into what will probably become a frequent problem – the tool(s) I need are not there when I need them. I need to file off some aluminum to allow the elevator horns to make their full range of travel. The elevators need to deflect 30 degrees up and 25 down, and right now it’s 25 up and 23 down. I’ll have to tackle this next time.

It was fun to get the pushrods connected and be able to move the elevators with the stick for the first time!