High Speed Taxi Disaster

Don't do this!!!

Before I took to the air, I wanted to try and verify the engine was behaving well, and I thought I could learn more on a high speed ground run than I could doing static tests.  Well, it was a bit too windy to spend an extended amount of time on the runway at medium speed, and I ended up catching a gust of wind that was way stronger than whatever rudder authority and tailwheel traction that I had, and it pushed me right off the side of the runway into the grass.  Tragically this was also in the same place as the only taxiway sign within a couple thousand feet, and I collected that sign with the left wing leading edge.

I inspected the whole plane according to instructions from Sonex, and found no damage beyond the left wing.  Unfortunately the main spar received a dent as well, which means this whole wing is compromised.

Luckily my insurance just went into effect, so I'm going to do an insurance claim and buy a quick-build left wing box from Sonex, re-rig it, transplant the control surfaces, lights, and wiring, and then I think I can have it fixed.  Still, this is definitely going to take a while and set me back a few months!

Airworthiness!

I got my airworthiness certificate!  I did all the paperwork following the EAA guide, and it all went smoothly.  No issues with the DAR, he pretty much liked everything that he saw.  The only recommendations he gave me was to think about adding some doublers where I mounted avionics items directly to the skins, and eventually add a fuel drain so I can check for water in the fuel.  For now though we're good to go!

Engine Tweaks

This plane is nearly ready to go!  I'm just chasing down a few engine quirks.

I spent quite a bit of time adjusting the secondary ignition timing.  I started with the static setting which ran okay, but my RPM drop when I checked the two systems was still a little high.  I tried checking and adjusting the secondary timing with a timing light and a helper, but that didn't make much of an improvement, as didn't really seem all that safe either.  Finally I settled on just running the engine, moving the trigger cap a tiny bit, running it again, and repeating that until it stopped running better and started to run worse.  Then I moved it back to where it seemed the best.  I think that's the best I can do on the ground!

The other thing was an oil leak at the turbo outlet.  I've sealed the oil sump to the turbo at least twice, and it'll stay sealed for a while but it seems to spring a leak if I do a high power runup.  I think it's probably more of a high temperature issue than pressure related.  Sonex sent me a little adapter plate to put between the turbo and the sump, and I also bought the highest temperature sealant I could find, and so far it's been good!  Sonex also asked me to check the ports in the oil pump as some had been setup wrong, but mine was all good.  I guess that could have stopped the pump from scavenging oil correctly and cause oil pressure to increase in that return line, but I don't think that was the problem anyway.

We'll see if it leaks again!

Fuel Level Probe Calibration (3)

3 hours

This was simple but it just took a while.  In order to calibrate the fuel level probe, I had to start with an empty tank and then add fuel in known amounts and record the sensor's output on the G3X, at both a level flight attitude and with the tail on the ground.

I just added two gallons at a time and then calibrated it in each attitude, until the tank was full!

More Cowl Adjustments (9)

9 hours

OK, now I'm really getting down to the last few things (I think).  I can not fathom any way to get the upper cowl on and off, the way the plans have it attach, with the prop installed.  So, I decided to slightly modify the aft edge of the cowl so it doesn't have to be wedged under the lip on the front of the windshield skirt.  Then hopefully it can be installed and removed vertically and stay out of the space that the prop is occupying.

Here is my inspiration.  This is an RV-8, and this picture is from the Skybolt website (which is where I got all my cowl fasteners anyway):

So, I will cut the aft 1/2" or so off of the fiberglass, remove the female Skybolt receptacles, install a bunch of those little tabs, put the receptacles on the tabs, and then the cowl will just sit on top of the tabs with the fasteners holding it down.

First, I removed the prop so I could get the cowl on.  Then I traced the front edge of the windshield skirt onto the cowl, and removed it.  Then I drilled out all of the receptacles, and then cut along my line to remove the aft edge of the cowl.

The little pins that hold the clip out on these fasteners while they're adjusted were all long gone, so I made some replacements out of safety wire.  I later found out that these fell out a little too easily, and the stems from 3/32" rivets actually worked much better.

Next I made a bunch of tabs, and drilled them for the receptacles.

I went across the windshield skirt, and attached a tab at each spot that previously had a receptacle.

It was tricky to drill the cowl to the existing holes in the tabs.  I located some of them by putting a flashlight underneath and spotting the hole through the fiberglass, but I had to do a few by just measuring and hoping I hit the hole in the tab when I drilled through my mark.  Eventually I got all of them though.

I don't have a good picture of it, but I ended up making little 1/16" thick strips as spacers to put between each tab and the underside of the skirt.  That brought the upper surface of each tab down enough to make the top of the fiberglass pretty close to flush with the skirt.  It was also totally required in order for all the fasteners that held the upper and lower cowl pieces together to still fit!

The only real issue remaining is this gap in each corner.  I don't think there's any way I can flex the cowl enough to follow that contour.  I think I will just add some filler or something later to build up the fiberglass enough to cover these gaps.

After many, many iterations, I got all the fasteners to line up correctly, and now the cowl can be dropped straight down into place without needing any extra room at the front.  I reinstalled the prop and called it good enough for now!

Here's a good depiction of the extremely minimal space between the cowl and prop.

I will come back later and address these little gaps in the corners.

Weight & Balance (2.5)

 2.5 hours

***NOTE!  I later found that all the weights I measured here were totally wrong, when I re-weighed the plane in June 2022.  But this is still a good overview of the process at least.***

I've been waiting to get this done for quite a while; it's one of the last "admin" items I needed to do in order to get the plane inspected, and I was also very curious to find out what my plane weighs!

Once the prop was installed, the next task was to measure the plane.  I propped up the tail to put it in a level flight attitude, and then got to work.  The datum, as far as W&B is concerned, is the tip of the spinner.  I taped a plumb bob to it and marked a spot on the floor directly below.  Then I marked the following points, on each side of the plane: the wing leading edge, main gear axles, wing trailing edge, and the tailwheel axle.

For each pair of points, I connected my marks with a laser level so I could mark where along the centerline that fuselage station was.  Since I had marked the spinner tip and the tailwheel, I had two good points to also connect with the laser, so I knew where the centerline was.

Finally, I measured from my spinner tip (datum) mark, along the centerline, to each of the other points.

Here are the measurements I came up with:

Leading Edge: 52.2"

Main Gear: 55.1"

Trailing Edge: 106.2" (so the wing chord was 54.0" which matches the plans)

Tailwheel: 217.1"

Next was to weigh the plane.  I was not able to get my hands on any kind of official certified aircraft scales anywhere, so I bought three scales on Amazon instead.  They have a capacity of 440 lbs each, and as far as I can tell they're accurate.  My wife and I each weighed ourselves on a calibrated scale, and then both stood together  on each of these scales to see if our combined weight showed up correctly.  It was within 1.5 lbs on each scale, and our combined weight is about 290 lbs, which is pretty close to the weight on each main gear tire.  So based on all that I'm confident that these scales were good to go for this task!

Anyway, long story short here are the results (with the tail raised so the plane was level):

Left Main Gear: 291 lbs

Right Main Gear: 308 lbs

Tailwheel: 38 lbs

Total: 637 lbs

I'm pretty happy with that total weight!

Next came the W&B report.  Here's what I wrote up to submit with my airworthiness paperwork:

Propeller (2)

 2 hours

Finally, after just over a year since I ordered it, I have my Prince P-Tip propeller!  I think in the long run I will say it was worth the wait; it looks awesome!

I removed the Sterba loaner prop and the 1/2" spacer I had temporarily installed, and bolted the new prop on.  Here's where it got exciting.  As I mentioned a couple posts ago, with the spacer gone and the prop all the way back at the prop flange face, it is MUCH harder to get the cowl on and off.  I found I was able to round off some edges and do some strategic filing to make the lower cowl possible to install without interfering, however the upper cowl appeared to be totally impossible to install with the prop there.  The aft edge of the upper cowl is supposed to go under the front edge of the windshield skirt, and then you rotate the front down until it meets the front of the lower cowl.  But, until it's all the way in position, the front face of the upper cowl protrudes forward 1/4" or 1/2".  With the prop taking up that space, there's no way to get the cowl on!

I scratched my head over this for a while and finally decided it would be worth it to change how the upper cowl mounts.  For now, I left it perched where it was, just sitting on top but not fastened down.  At least now I can do my weight and balance while I ponder how to fix this issue!