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  • Steve

RV-8 and the 2021 Condition Inspection

Updated: Apr 26, 2021

Age: 20 Years Time: 2,172.0 Hours

4/9/21-- 4/12/21 - I started this years condition inspection with a brief hop to warm up the oil. The weather wasn't great, so it was a pretty short hop.

When I got back, Carl had just showed up to help me pull the bottom cowl. I can do it myself, but not without scratching something. As soon as we got the cowling off I pulled the top plugs to do a compression check. I don't use the tester but once a year and I always have to figure it out again. I thought I had the valve open, but both gauges read the same thing. Now open the valve, oh hey, that works better. I had 72/80 on cylinders 2, 3, and 4. On going back to retest #1, because the first number didn't make any sense, I got a much worse reading.

Initially it was reading 50/80, but moving the prop back and forth a bit got it up to 58. Not good. I could hear air escaping and it was was audible through the dip stick tube, so obviously blow by. I know my rings aren't in the best of shape, so I was only a little surprised.

Chris Klix, who maintained the airplane for many years before I bought it, had a trick to fix stuck rings. He would squirt some Marvel Mystery Oil (MMO) in the cylinder, let it sit for a half hour or so then run the engine. Most of the time this would unstick the ring(s) and give an acceptable reading. It was going to be a while before I had things to the point that I was ready for an engine run, so I made some notes and pressed on.

The next thing was to drain the oil and take an oil sample to send out for analysis. Once the oil was drained it was time to replace the oil filter. Once I had the new oil filter on it was time to check the finger screen, or oil pump suction screen.

Since I bought the airplane there has always been some carbon chunks in the finger screen as well as in the oil filter. This time though, there was much less than I usually see, which I'm pretty sure is a good thing. I'm not exactly sure what causes the carbon pieces, but they have been in the oil since before I bought the airplane and they don't seem to cause any harm. The finger screen and oil filter pick them up before they can be squirted into the internal oil passages.

Finger screen with carbon chunks.

Usually there would be about that much through the whole length of the screen. I change my oil between 25-35 hours. I don't generally fly enough to get more than that and still be in the calendar change interval. I extracted all of that and laid it out on a paper towel to get an idea of just how much it was. It wasn't much.

Carbo chunks.

There was also some very fine particles in the oil remaining in the oil filter after I cut it open.

Carbon particles in the oil residue.

I usually let the oil filter element drain for a week or so before cutting it out and laying it flat for inspection, so that will wait until next weekend, though I don't expect any problems.

The next thing I wanted to do was time the mags. I have a LASAR system on this airplane, so mag timing and maintenance is a little different than your usual Slick magneto. I started by checking the left mag it is seemed to be off by a couple of degrees so I went back to the beginning of the sequence, which is to set the left (sensor) mag to Top Dead Center (TDC). When I first got the Left TDC light to come on the crankshaft was a couple of degrees off of TDC. I didn't think that would be a problem so I adjusted it back to TDC.

Once TDC was set, you go back and look at the base timing position and it is supposed to be "near" the base timing position (25 degrees before TDC in this case). When I turned the propeller in either direction the "L Breaker Point" light would not go out, at all, ever. This seemed like a problem to me as it sounded like the points were closed all the time which would be a very bad thing.

I feared I would have to take it off and send it out for repair, which would put me behind by however long it took to get the mag fixed. I had sent them out for the 500 hr inspection 3 years ago shortly after I got the airplane and they have only accumulated 222 hours since then, so I hated to have to pull one out already. I started with a question on Vans Airforce, I got some information there. The full thread is here. There was another Steve on post #3 that had a similar situation and put in another mag and the problem went away, he never did send the offending mag out for repair so didn't know what the failure was.

I also sent an email to Progressive Aero which is also part of Aero Sport, since they are the outfit I sent them to before. Scott form progressive had some items to suggest, his response is below.

"I’m going to ask a stupid question but have you tried unplugging and reconnecting the 10-pin connector from the T-300 to the magneto? I was just wondering if the pin that connects to the points from the connector had a bad connection.

I’ve also included a drawing of the magneto plug so you can double check the connection at the plug to see if the points open and close. Just don’t hook an ohmmeter to this lead while rotating the magneto as it is connected to the points and coil and may give a voltage spike when rotating the mag.

If these checks still point to the magneto then you can try removing the mag from the engine and attaching the T-300 to it and checking if the Left BKR PT light & Left TDC light turn on and off when rotating the drive shaft.

If that still doesn’t work then the mag should probably come here to be checked out. It may be a broken wire that connects the points to the circuit board."

I pulled the offending left mag out and hooked it to the test box and sure enough, no matter how much I turned the shaft or in which direction, the L BKR PT light would not go out.

At this point I thought I was stuck. I figured it would take a couple of weeks. at least to get them up to Kamloops and back. Later that evening Carl emailed me saying that he forgot that he had a spare mag that he had bought as a spare and sent in for the 500 hr inspection. It had been sitting since 2015, but had never been installed. I figured that would allow me to ascertain if the problem really was my original mag or something else.

He dropped it off Monday morning and I looked it over and it looked OK. I had some difficulty sticking it in, but was able to get it in and timed. In order to get the TDC light to go out I had to rotate it as far as it would go counter clockwise, so there would be no more adjustment available for the future. I think I managed to get it off by a gear tooth.

I took out and tried to start it hoping that it would run and I could see if the problem was well and truly solved. It wouldn't start. Oh crap, why not? Again, the mag was obviously off by one tooth.

Left Mag first install attempt.

In the photo above you can see that the data plate on top of the mag is almost completely parallel with the ground, it should be angled inboard by about 20 degrees or so. It seemed to time OK, but it is definitely not right. Also, I had the fuel system open in a few places and drained pretty much all of the fuel out of the lines and I may not have primed it enough to get fuel in all of the lines.

It's late in the day and I'm pretty frustrated, not to mention having to go back to work tomorrow, so I will have to leave it until next weekend at which time I will pull the mag back out, reinstall it and try again.

4/16/21 -- 4/18/21 - First thing Saturday morning I pulled the mag back out and got set to put it back in. I futzed (technical term) around with the ground wire for a while. I had tried to get new ones last week, but couldn't find them anywhere. The big problem was that the hole in the large terminal had decreased in diameter due to the distortion of the terminal from the hold down nut. I wanted to at least put a new terminal on it, but I didn't have any the right size and kind, and neither did my Dad.

I ended up doing something that probably isn't too great, but I just enlarged the hole again so it would fit on the stud. In the end, it worked. It is only difficult to put in because there is absolutely no access back there. The bracket that holds the cable for the propeller governor is directly behind the mag and there are lines and wires going all over. I finally got it in, the right way, and timed.

How it should be installed.

Once that was done, I disconnected the injector lines at each cylinder and put a small cup under each one. I then turned on the boost pump until I got good fuel coming out. This ensured that I had fuel throughout the system and it did indeed take longer than I would have expected.

Next I squirted some MMO into the number one cylinder and let it sit for a while. After about half an hour I got all the oil I could out of the cylinder. Wanting to make sure there would be no hydraulic lock I pulled the engine through 8 blades and made sure it was past the compression stroke for #1 before pulling it out.

Now there was nothing left but to give it a try and hope that it would start and run correctly. It fired almost immediately, but ran rough for a minute or so. This happens when I have the fuel system drained. There also may have been enough residual MMO to cause some problem as well. After about a minute though, it settled down to a nice smooth idle.

I let it run for about 6 minutes and then shut it down and brought it back in. Once back inside I pulled the top plugs to recheck the compression on #1. When I first got it hooked up it was only showing 62, better than 58, but not by enough. I could still hear air hissing past the rings. I grabbed the prop and rocked it back and forth a few times and I heard the air hiss go away and the gauge shot up to about 77. Now that is an acceptable result.

Now I had my two main potential problems resolved. It should be all smooth sailing from here. I finished up the firewall forward by putting some mouse milk on the exhaust joints, installing the new spark plugs I had bought, and inspecting the propeller.

Before putting the new plugs in I managed to get some pictures of the exhaust valves that are almost legible.

Cylinder #1

Cylinder #3
Cylinder #2
Cylinder #4

I'm not particularly skilled at reading exhaust valve photos, but I think these are OK

This airplane had Tempest UREM38S Fine Wire spark plugs on it when I bought it. They have much less of a tendency to foul than massive electrode plugs and they typically last longer as well. Unfortunately, they are also about four times more expensive. I had been inspecting and cleaning the plugs at each annual and they look good and pass the resistance check, but I looked them up in the log book and they have been in there for 1,092 hours. I know they last a long time, but I was just nervous continuing to use them with that much time on them. So, for a mere $1,100, I was able to buy some peace of mind in the form of new spark plugs.

I bought the Tempest plugs because they are about $30 each less than the Champion plugs and for some reason my military discount at Aircraft Spruce on the Champions was 1% and on the Tempests it was 3.5%. The lower cost coupled with the fact that the old Tempests had lasted almost 1,100 hours made me think they were the right way to go.

With the firewall forward finished it was time to start on the fuselage. I pulled the seats and interior out and opened up the panels under the front seat. everything looked good so once I lubricated everything with a small amount of LPS-2 I put the big panel with the rear seat foot wells back in.

Next weekend I will finish up the fuselage at least, and maybe even finish up the whole thing.

4/24/21 -- 4/26/21 - The oil filter element has now had sufficient time to drain, so I started by taking a close look at it. As expected, there was some carbon in it, but a lot less than I had been seeing. All in all, it was a pretty good filter and that, combined with a glowing oil analysis report, makes me think that there is nothing imminently wrong with the internal workings of this engine.

This is pretty typical of what the whole filter looked like.

Once finished with the oil filter I went on to finish up the cockpit area. Since I had finished the forward cockpit last week, today I started by opening up the sidewall panels covering the flap actuator and flap control rod. Naturally, I want to inspect those items, not to mention the rear seat seat belt anchors, and I also need access for lubrication of the rod ends.

That lower panel, under the arm rest, covers the right side bearing block for the flap torque tube.
The same panel on the left side also houses the flap motor.

Once that was done it was time to do one of my least favorite tasks and that is to remove the rear baggage area panels. The top one is not so hard, but the bottom one is quite a pain. It is a little easier if the tail is lifted so the fuselage is near level, at least you don't keep falling down hill.

The top, curved, panel is relatively easy to get out. The rear shelf is all one piece and far more difficult.

It is possible to get to the bellcrank where the two push/pull tubes connect to lubricate the bearings for the top panel, but it is really not possible to do a good inspection of the battery, battery tray, solenoids, an all that stuff without removing the shelf. Because of its size and shape it is difficult to maneuver.

Of course, since I was in the area I also took this time to inspect and test the ELT. I still have an old 121.5 MHz ELT, but I also carry a 506 MHz PLB.

I managed to get everything inspected, lubricated and back together without undue difficulty. Once that was done, it was time to put the cockpit back together.

Once I had the cockpit cleaned and back together, including climbing in to clean the inside of the canopy, I was ready to tackle the tail. Inspecting the tail is very straight forward and not terribly difficult. There are a couple of service bulletins applicable for known tail area issues. One is SB 14-01-31 for Horizontal Stabilizer Spar cracks. This airplane had the terminating fix accomplished before I bought it, but I still continue to pay close attention to that area every year anyway.

The other is SB 14-02-05 for Elevator Spar cracks. I have not had any cracks in this area, so I have to inspect it every year per the SB, but I would inspect it anyway even without one.

Once everything was inspected and lubricated, I closed up the tail section.

The next area I worked on was the landing gear. Since the tail was still up on the stand making everything easier to get to I started with the tail wheel. Dissembling, cleaning, and inspecting these simple tail wheels is pretty straight forward. I really like sealed bearings, makes this process much easier.

Cleaned, lubed, and adjusted tail wheel.

From here I moved on to the main landing gear. It was pretty easy this month as I had replaced the tires and the caliper piston O-rings recently I have been through the majority of the system so I just needed a quick look and to clean the wheel pants and the caliper pins. Also, of course, I wanted to check on the wear of the brake pads. They were all good. In fact, with 140 hours on them, they show very little signs of wear. I'm not as gentle on them as Carl was, but now that I am used to the airplane (and it to me) I don't go through brake pads nearly as quickly.

Left Inboard
Left Outboard
Right Inboard
Right Outboard

I put new main tires on last May, Desser retreads that wear like iron. After 60 hours and 42 landings they still look brand new. And so concludes this round of landing gear maintenance. I really hate working on landing gears, particularly wheels and brakes (it's not hard, just messy and a lot of getting down on the floor, then back up), so this is a stage that I am always happy to have behind me.

The last thing on my list are the wings (OK, not last on the last, but last that I do). I usually save them for last as they don't usually take a long time and I don't usually find anything of great significance. The primary thing I am looking for here is SB 16-03-28 which is looking for cracks at the aft spar web at the inboard aileron hinge bracket attach rivets. Fortunately I have not not found any since the repair is rather intense and has to be performed very carefully. Once again this year, no cracks.

Left side looking aft from outer inspection panel.

While it's good that there are no cracks, there is some rust forming (again) on the bottom of the aileron push-pull tube. This has happened and been addressed before, before I bought the airplane, and it looks like it needs to be addressed again. I will have to pull that tube out to clean it up and repaint it. It doesn't have to be done right now, but I want to do it before next year's inspection.

Right side also looking aft from the outer inspection panel.

There is a little rust on the right side also, but it is not as much as on the left. Again, at least there are no cracks.

The outboard inspection cover is also where the aileron bellcrank is accessed and lubricated. It is a little difficult to get LPS-2 on all the joints, but not terrible.

Once the flaps and ailerons were lubricated and all the panels back on I was basically finished. I still need to clean the belly, but that can wait until next weekend (it's supposed to rain anyway).

Carl stopped by this morning and helped me put the cowling back on so it is back in one piece and essentially ready to go. I just need to get in an after maintenance test flight to make sure everything works properly and I am ready for new adventures.

In summary, I basically got this finished in the course of three weekends, with a few days off work thrown in. While I ended up with a few more finds than I would have expected, none of them turned out to be show stoppers. Primary findings were:

  1. Number one cylinder compression low (58) able to get up to 77 after another run.

  2. Left LASAR mag points closed continuously - Carl had a spare mag that I installed and appears to work, will send the original to the shop for repair.

  3. Two smoking rivets on vertical stab right side - need to fix but can wait for a rainy day.

  4. Small area of rust on left aileron push-pull tube - needs to be addressed but can wait for a rainy day.

  5. Small area of rust on right aileron push-pull tube - needs to be addressed but can wait for a rainy day.

I think I'm good for another year!

The checklist I use can be found here.

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