Complied with SB 14-01-31

While inspecting the plane for this year’s condition inspection, I discovered the dreaded crack near the bend of the forward horizontal stabilizer spar. You can see the crack emanating from the bottom of the u-shaped notch at the top of the spar.

I came over bright and early one Saturday morning and disassembled the empennage in about 2 hours. I didn’t get any pictures of the process or the naked empennage, but you can imagine what it looks like.

I brought the horizontal stabilizer home since it will be much more convenient to work on here. My buddy Greg dropped by and helped me drill most of the structure. He brought some handy drill guides that helped us hit the center of each rivet (though we still buggered a few).

I didn’t get too many pictures during the process, but I did do a few things differently than the SB specifies. The SB asks you to drill out only the first two rivets along the forward spar so that you can slide a thin stainless steel shim between the skin and spar to protect the skin when trimming the spar. I decided to drill out a couple of additional rivets.

This allowed me to wedge in a thin (1/4″) wood piece to space the spar away from the skin. Not only does that help protect the skin, it makes it far easier to smooth out the cut after trimming the spar.

I also cleco-clamped a putty knife to the spar web at the bend to protect the spar from the Dremel wheel. I’m really glad I did this as I bumped it several times during the cut and I know I would have damaged the spar.

There were a handful of holes that were unfortunately elongated slightly. I decided to step these up to -5 rivets and drilled the holes out with a #20 bit. It was a slightly different set between the left and right side, so I decided to drill out some additional holes so that the -5 rivets were symmetric between each side. Fortunately, all holes turned out nice and round after doing so. I thought I might need to install cherrymax rivets in these holes, so I calculated the grip length for each hole based on the material stackup. I ended up shooting a bucking solid AN470 rivets in every holes.

After carefully finding the end of the crack, I stop drilled it with a #40 bit and deburred it.

I didn’t get a picture, but I elongated the hole toward the crack slightly and then smoothed everything out.

Greg dropped by a couple more times to help me rivet the structure and reassemble it. The plane was down for about a week, but I’m glad to have this behind me and know that it’s far more robust than it was before.

Added Oil Cooler Quick Drain

Saf-Air recently released an adaptor that allows you to add a quick drain to an AN fitting. My oil cooler has a tee fitting at the lowest point that I installed a cap on, but draining the oil from this point was always a bit of a pain. The adaptor lets me replace the cap with a quick drain that I can attach a hose to.

Unfortunately, my oil cooler was too close to the firewall for me to install it directly on the tee, so I needed to add a 90º fitting to point the assembly downward. I assembled the pieces on the bench since it was much easier to safety wire this way.

I then installed the assembly to the tee on the lower port of the oil cooler.

The quick drain points slightly forward and nicely clears the engine mount and brake line.

Inspection after Over G

During the flight back from Oshkosh, my buddy and I hit some massive clear-air turbulence west of Salt Lake City. We slammed our heads on the canopy and then the plane pitched up nearly 45º. It was a little hard to tell how much of the diversion from level flight was caused by the turbulence vs. my instinctual response of pulling on the stick when we hit the initial negative-G, but we ended up reading a peak of 6.1 on the G meter. Fortunately, we were low on gas since we were near the end of our leg, so we only weighed about 1,670 lbs.

A quick call to Van’s technical support confirmed what I was already assuming: these planes are strong and I’m unlikely to have damaged anything. They asked me to remove the wing-root fairings and empennage fairing and look for any wrinkled metal. Assuming none was found, fly on!

I pulled both wing-root fairings (unfortunately stripping two phillips screws in the process), and gave everything a thorough inspection. Everything looked a perfect as the last time I have the fairings off, so I buttoned everything back up. The structure here is really beefy, so I really wasn’t expecting to find anything in this area.

While the tail is certainly quite strong, is needs to be quite light. That necessitates using much thinner structure back here. While I wasn’t too worried about the wing roots, I was a little more concerned about the tail. I spent extra time here just to be safe, but like the wings, everything here looked perfect.

I buttoned everything back up and took off for a formation flight with a couple of buddies. These really are amazing aircraft, and it’s good to have reassurance of just how strong they really are!

Fixed Sticking Heater Valve

I had an IPC & BFR the other night and my new heater valve was stuck slightly open. It was a warm night, and hot air blowing on my feet was pretty miserable. Since I’m leaving for Oshkosh in less than a week, I really wanted to fix this before flying across the hot midwest.

Unfortunately, getting to the heater valve requires pulling out most of the forward interior, seat pans, doghouse and tunnel cover. Once I was in there, it was about a two minute fix to determine what was sticking and fix it. The corner of the lower door flange was digging in to the bottom of the heater valve. A very slight bend of the lower flange fixed the issue nicely.


Replaced ADS-B Module and Wrapped Up Maintenance

I wrapped up the heater valve swap by reconnecting the SCAT tubing and control cable and then reinstalled all of the interior aluminum covers and seat pans. Before reinstalling the cowl, I checked the breather vacuum valve in case I needed to clean it. I’ve been checking this every oil change and it never seems to get worse than this.

Before reinstalling the interior, I needed to swap the ADS-B module. Dynon recently contacted me about swapping this because they apparently found a hardware defect and they want to replace all of the units in the field. Although I don’t relish removing all of the interior and baggage wall to get to this, I don’t mind since I really appreciate how proactive Dynon is about resolving issues like this.

The new unit is identical from the outside, so it’s a trivial swap (unlike when I swapped from the SV-ADSB-470 to the SV-ADSB-472).

Replaced Heater Valve

I recently noticed that my cabin heat wasn’t working. After a quick inspection, I realized the control arm on the heater valve had broken off of the flapper valve. The valve is a stainless steel unit from Plane Innovations which I upgraded to because I wanted to keep all steel components on the firewall.  I emailed the company about the best way to repair the valve and they rushed out a new one free of charge. I wish more companies had this kind of customer service.

Unfortunately, getting the old valve out requires pulling a substantial amount of the interior out. The heater valve is behind the tunnel cover which is under the fuel pump cover. The fuel pump cover sits under the forward seat pans, so the seats and carpets need to be removed.

My son helped me remove the nuts holding on the heater valve. This is one of the few items that regrettably I didn’t attach to the firewall with nutplates. It would have made replacing it far easier. Unfortunately, adding nutplates now is virtually impossible, so we just bolted the new one on the same way.

Here’s the failed heater valve. The spot welds simply failed due to the high vibration around the firewall. The new valve has five spot welds instead of four, but I’m not optimistic this will prevent this from happening again.

Finished Repairing Gear Leg Fairings

Fortunately, I was able to pop off the extra glass and flox mixture I used for the gear leg fairing attachment.

I then fabricated and epoxied some 0.063″ aluminum strips onto the fairings. I curved the upper ends to follow the curvature of the gear legs.

I drilled some extra holes in the strips and then countersunk them so that the epoxy would flow through and help lock the strips to the fairings. After the glue cured, I sanded everything flush with the strips.

Repaired Gear Leg Fairings and Replaced Tailwheel Control Arm

One of the fiberglass ears at the top of the gear leg fairings broke off on the left fairing.

The one on the right is cracked all the way through and is likely to break soon.

I had used electrical tape to hold the brake hose to the gear leg. This broke in most of the spots, so I took it all off. I didn’t get a picture of it, but I just wrapped the electrical tape around the gear leg and then used some zip ties to secure the brake hose.

I pulled the tailwheel fork off to clean and lubricate it. While it was off, I swapped the control arm with one that has a hole for a tie-down hook.

Continued 2016 Annual

I cleaned out the coking that occurs in the check valve that dumps into the exhaust pipe. It was maybe 20-30% blocked and is easily scraped out.

Since I added the tee into the breather line to add an extra check valve as a safety measure, the hose clamp on the upper side of the tee was rubbing against the engine mount. I shortened the hose below the tee to get the hose clamp to clear the mount.

This allowed me to just use the adel clamps to secure the check valves to each other and to the hose. You can also see that I painted the place on the engine mount that was scratched.

One of the two welded brackets for the heat shield near the alternator also broke. I’ll have to order another one of these.