RV-8 and the 2023 Condition Inspection Pt. 1 (2/4/23 - 2/5/23)
Even though my Condition Inspection doesn't expire until the end of May, I am starting on it early. I got lucky last year and I didn't really miss any good flying days during that time period, but that may not always be the case. Also, I like to do it in segments so that the airplane is not down for too long at one time. Usually I start with the tail, then do the rear fuselage, then the wings, then the cockpit and firewall forward. It is the last section that takes the longest and usually has me down for a could of weeks (only getting to work on it on the weekends). I will often do a section on Saturday, put it back together and fly on Sunday, or at least do a section one weekend and fly the next weekend.
In this case, I also needed to replace the tires and inner tubes due to wear, well, due to wear on one tire anyway. For some reason, the left tire wears faster than the right one. Since the tires wear more on the outboard edge than the inboard one, I usually flip the tires on the wheels when the tread gets pretty low. So far, I have not been too good at judging when this is and don't get the longevity from the tires I would like. Also, I can gain extra life by swapping the left and right wheels/tires so that they can wear more evenly. Again, I usually wait too long to do that and don't get the desired benefit. This time, I plan to rotate them about every six months or so and see if that doesn't get me better tire life.
Carl used Goodyear Flight Custom III tires with Michelin Airstop Tubes. He also replaced the inner tube at each tire change, as recommended by the manufacturer of the tube. He got an average of 180 hrs out of them. I switched to Desser retreads because they are cheaper and supposedly have more tread depth and last longer than name brand tires.
In this case, the tire that spent most of its time on the left wore faster and drove the change while the tire that spent most of its time on the right still had lots of tread left. If I had rotated more frequently, I would have gotten more life out of them. The first set of Dessers only lasted me 79 hours. A lot of that was me, I was learning the airplane and particularly how to land it, so I wasn't as good to the tires as I could have been. Also, I missed the uneven wear and had to replace them to to chord showing in the worn area. The second set lasted 188 hours. If this set of Dessers doesn't wear any better, I may go back to the Flight Custom IIIs and see how they do. I thought I would have to replace these over the summer, as I had feared they wouldn't last with the uneven wear, but I got about 6 more months out of them than I expected, but it is time to replace them.
I didn't replace the inner tubes when I put the last retreads on because, well, they're expensive. As we all know, the cheapest thing in any airplane is the pilot. I had seen some pictures lately of some people having inner tubes chafe and cause leaks, so I figured I had probably pushed it as far as I dared with these tubes, and I installed new ones with these tires. It was nice to read the instructions and notice that they were telling me to do what I already did anyhow. I bought a can of Tire Talc from Aircraft Spruce almost 20 years ago and have used about half of it so far. Because of the moisture in the hangar, it is beginning to clump a little (yes, I just figured out that putting it in a Ziploc bag will help with this), but the clumps easily break down when touched.
I really hate working on landing gear, always have. Aside from being dirty and nasty, they are usually very close to the floor, which means a lot of bending, stooping, getting down on the floor, and then the inevitable, having to get back up again. When I was young(er) that didn't present too much of a problem, but as the years go by, it takes more of a toll, particularly the getting up part.
The other big thing I hate about landing gear is having the airplane jacked up. I got skittish about jacked airplanes in the Air Force. One of the most unstable things on jacks is an F-111. I almost had one fall off the jacks and I have been over cautious ever since.
The other problem is that there is no good way to jack the RV-8. There is a guy who makes beautifully machined jack points that mount to the axle, but my wheel pants fit so close there is no room to put anything under them and I really don't have the skills to modify the wheel pants so they will fit. In fact, the guy who did the maintenance for Carl had to grind down the bottom brake pad bolts because they were wearing a hole in the aft wheel pant.
Years ago, when I first got the RV-4, I bought a thing called, I think, a Handy Jack. It is a steel apparatus that goes over the wheel and has a cable that goes around the back side of the axle that sits on a floor jack to lift the wheel. It works, it actually works quite well, but with the cable holding the axle, it sways a good bit when it is off the ground. That, coupled with the fact that I never trust hydraulic jacks, once I get the wheel off, I spread the load between the jack and a pile of wood.
One issue I have had when jacking a wheel is that the tail wants to swing in the opposite direction of the wheel being jacked. In the past, I just chocked the tail wheel as tightly as I could and it seemed to limit the swing of the tail. I was always afraid that the tail would just keep swinging and make for a really bad situation. After some experimenting, I came up with a way to use the tow bar to keep the tail straight as I jack. This gives me a little more confidence while the wheel is off the ground.
The old tire was worn, but only in one small area. When I flipped the tire on the wheel last spring I tried to balance the wheel, but it didn't work out very well. With the one bald area, it would seem that the bald spot was the heavy spot and every time I landed, it came down on the same spot. There were no cuts and there was no chord showing, but its days were limited, so I changed them both.
Since everything was apart, I also inspected the brakes. I have been keeping an eye on the brake discs since I think they are original to the airplane. One was getting a little lower than the other and this year it was at .169' with a minimum of.167". About three years ago, that one was at .1719', so it isn't wearing that quickly, but I think I will replace them next year. I was also happy to see that the brake pads are in good shape. I had thought they would need to be replaced this year, but they still have a good bit of life left in them.
When I got the wheel reassembled with the new tire and tube installed, I went to balance them, but they were very close to perfectly balanced right out of the box.
Naturally, while I had the wheel apart I cleaned and repacked the wheel bearings. I have a bearing packer that makes relatively short work of the bearings. I just clean the old grease from the outside of the bearing and the bearing packer forces the old grease out while replacing it with new grease. I just clean the dirty grease off the top, run some over the rollers and stick it back in. I put new bearings in a couple of years ago and, fortunately, they are still good.
The instructions for the tubes say to let them sit and recheck the pressure after 24 hours, so I will leave the wheel pants off so that I can check them again tomorrow, then put the pants back on.
When I went back on Sunday, the tires had not lost any air, so I put the wheel pants back on. That part of the weekend's festivities is now complete. On to the the part that has me a little, but only a little, nervous.
At the end of January Van's came out with Service Bulletin (SB) SB-00036 that calls for the inspection of the outboard hinge brackets on the Horizontal Stabilizer (HS). If cracks are found, there are new brackets to be installed. There was a design issue with the originally intended SB brackets and they are being redesigned, so for the time being there is nothing to do but to inspect. Van's came out with SB-00036 Rev 1 last week, talking about the change in brackets but keeping the requirement for the inspection. I wasn't too concerned about finding cracks, but I wanted to get the inspection out of the way anyway. I ordered the original brackets, just in case, so that I would have them on hand if I did find cracks. Fortunately they halted shipments of the faulty brackets, so I never got them, but they will ship the correct brackets once they have them available.
The only reason that this is a little trickier than normal is that the forward side of the spar has to be inspected since the brackets are on the aft side and cover up the rivet holes. A crack would have to be pretty big to be seen from the aft side since it has to grow beyond the bracket to be visible. In order to inspect the forward side the aft tooling hole on the outboard rib has to be enlarged to allow a borescope to be inserted to see those rivets.
One of the things that really scares me about something like this is the possibility of scratching the paint. Carl took really good care of the airplane and the paint is in really good shape and I hate to do anything to ruin it. To that end, I placed some tape on the elevator counter weight skin as I drilled the hole out. There is just barely enough room to get an extension drill (12") without rubbing the skin. I used a layer of easy release painters tape covered by 2 layers of vinyl tape. It worked well.
Enlarging the hole turned out to be easier than I expected. It is fairly thin piece of 2024 aluminum, so it couldn't be that difficult. I was pleased with results. I was even more pleased with the fact that I didn't have any cracks.
I got a new Teslong Borescope last year. I used it to inspect my cylinders last year, but this was a good test for it and I am pleased with how it works. It is nice to be able to get into otherwise inaccessible places to inspect.
I didn't want to leave that big hole in there once the inspection was completed, so I covered it with a piece of vinyl tape. It isn't a perfect match, but from a few feet away, it is completely unnoticeable.
The SB calls for repetitive inspection every year until the new brackets are installed. Since it would be easy to scratch up the paint, not to mention potentially damaging a hole from drilling out rivets, I don't plan to do the terminating fix until and unless I find a crack. I would like to be able to say that since it went 21 years and 2,300 hours without a crack it probably won't crack, but, unfortunately, it doesn't work that way. I had been inspecting the hinge brackets and spar on the aft side at each condition inspection anyway, so adding the borescope doesn't add much difficulty to the inspection.
That pretty much covers what I did this weekend. Stay tuned for more Condition Inspection news in the near future, weather permitting.