Replaced Tailwheel

On one of my fuel stops on my recent trip back to TX and OK, I felt a weird vibration on landing, and it turned out that a chunk of the rubber from the tailwheel had broken loose. There had always been a defect in the rubber from the time the tailwheel was new, but I thought it was cosmetic. It lasted over 8 years and nearly 500 hours of flight time though, so I can’t complain too much.

In the meantime though, FlyBoy Accessories started selling this 4″ lightweight tire that is 13.5oz lighter than the 5.5″ tire above. That moves my CG an additional 0.13″ forward which should further help with the aft CG issue I’ve always had.

Replaced Pitch Servo Shear Screw

Sometime in the last couple of weeks, I noticed that the pitch servo wasn’t controlling the plane. I did some ground diagnosis and determined that the shear screw had sheared or some reason. I don’t recall any forces that would have caused this, so I can’t say why it happened. Dynon sent out a shear screw replacement kit a few days ago and I stopped by the airport this morning to install it and put the plane back together.

It’s amazing that this tiny cross section of brass is critical to the autopilot being able to control the aircraft.

I reassembled the control arm and tested the autopilot servo. Everything worked as expected, so I reinstalled the interior and updated the logbook.

Swapped Propellers

The RV-7 was designed before the days of composite constant-speed propellers, and was further designed for the 200hp, angle-valve IO-360 motor. Taking Van’s advice to build the lightest plane possible, I opted for the WhirlWind Aviation 200RV composite prop and the much lighter IO-375 motor. This meant I was approximately 70lbs lighter in the nose than the plane was designed for. This put my C.G. much farther aft than typical, and it was in fact easy to load the plane aft of the aft C.G. limit.

I spoke with Van for a bit at a party last year, and he indicated that the easiest change to make (short of just bolting on some weight) would be to switch to an aluminum constant speed propeller. When my 200RV prop started slinging grease back in the spring, it seemed like the perfect time to do the swap.

I ordered the Hartzell C2YR-1BFP/F7497 through Van’s. This is a 74″ prop and not normally recommended for the RV-7 due to being 2″ longer than the 72″, recommended prop. However, I spoke with someone at Hartzell, and he indicated that there were advantages in thrust with the 74″, and the extra weight only helped my situation. The only downside for me is reduced ground clearance. The 200RV had 8 3/8″ under normal gear compression in a level attitude, so this prop should have 1″ less, or 7 3/8″. In a hard landing, or if I inadvertently raised the tail too far, this would be reduced. However, I virtually always fly off hard surface runways and generally do tail-low wheel landings, so I’m not particularly worried about the reduced clearance.

The prop shipped 4-6 weeks later and pretty quickly landed at the UPS hub in San Jose, CA where I live. Unfortunately, UPS then lost track of it for three weeks! Eventually, it turned up in a trailer full of packages that apparently sat unopened that whole time. I dropped by their hub and picked it up and brought it to the hangar where I opened it and got it ready to mount on the plane.

The first step is fitting the rear spinner bulkhead. This needs to be cut to match the doubler and then relieved further to fit on the propeller without touching the hub itself.

My buddy Michael was kind enough to let me drop by his place and shoot some of the Stewart Systems primer on the front and rear bulkheads, then I riveted the two parts of the rear bulkhead together.

When everything was ready with the new prop, I pulled the old prop from the plane.

I’ve had some back pain recently, so I used this lifting sling with my shop crane to get the old prop off and install the new prop on the plane. This was far easier that trying to hold the prop with one arm while manipulating the bolts with my other hand.

I taped the new bulkhead to the flywheel while installing and safety wiring the new propeller.

I then installed the rear bullhead to the hub retaining bolts and torqued them to spec.

I temporarily installed the front bulkhead so that I could begin fitting the spinner.

I needed to be able to turn the engine freely when fitting the propeller, but I needed it to be fairly stable. I used the same technique I did when fitting the wheel pants, and jacked the plane up by the engine mount. I then removed the lower spark plugs so that the engine could spin freely.

When fitting the spinner, I also needed to be able to cycle the blade from the fine pitch stop to the coarse pitch stop. I ended up using some padding and one of my Bessey clamps which worked perfectly. Here is the propeller at the fine pitch stop.

By just pushing down on the clamp (and holding the propeller tip to prevent it from rotating the engine), it was easy to twist the blade to the coarse pitch stop.

I’m using the Cummins Spinners spinner for this propeller. I emailed Alan back in the spring to inquire about purchasing one of these, but there was no response. Others online said that hadn’t been able to get ahold of him for over a year and a half! I gave up hope and ordered the spinner kit from Van’s, but just before install, I received an email out of the blue from Alan saying he had a spinner ready to ship! It took a couple of weeks to get here from Australia, but it’s worth it for the look of a polished spinner on the plane.

To ensure the spinner was centered, I used a combination of a marker at the tip and a dial indicator on the side to measure wobble. I think it’s impossible to get this to 0″, but I feel like I got pretty close. You couldn’t see any deviation with the marker tip and the dial indicator showed +/- 0.003″ deviation. Since the spinner is 0.065″ aluminum, that’s only about 5% of the thickness of the spinner!

After drilling all of the holes, I set the nut plates on the front bulkhead.

…then safety wired it in place.

My buddy Greg found a metal polishing place about 45 minutes from my house, so I dropped the spinner off and had them polish it to a mirror finish.

Interestingly, the prop clocks at a different location when the engine’s stopped. The old prop would be level after shutdown.

It looks like I’m going to need to raise the prop a small amount due to engine mount sag. You can see the misalignment of the spinner and cowling clearly here. The spinner sure does look sharp though.

I also need to fabricate filler pieces to fit behind the blades, but that can happen down the road a bit.

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.