By Vic Syracuse, EAA Lifetime 180848
This piece originally ran in Vic’s Checkpoints column in the August 2023 issue of EAA Sport Aviation magazine.
Last month I mentioned I would share more of the Hummingbird flight testing with you, and I promise I will. Overall, I have completed the Phase I testing, Carol got her first ride, and I think we are on track to bring it to EAA AirVenture Oshkosh 2023.
Next month I will share some more details of the Phase I testing, but this month I’ve decided to preempt that with some maintenance observations, which I think are more important to share. Some of them I have shared before, but I know we continually get new members, so in the spirit of both reinforcement and awareness, here are some findings on a couple of RV-9s that came to us recently.
I try to be present when a customer brings their aircraft to Base Leg Aviation, but it’s not only to meet them and discuss their airplane. I am carefully listening to the engine and airframe as they taxi up, as well as looking at the tread and ground track of the tires and other things such as spinner track.
I can quickly tell if the engine is idling properly. From the exhaust tone I can tell if it is too rich or too lean, or perhaps is missing a beat due to leaking intake gaskets or fouled plugs.
Sometimes I can’t be there as customers drop their airplane off on the weekends, so the first thing I do is run it up prior to doing any work. It not only gets the engine oil warmed up for draining, but also allows me to see how the other systems in the aircraft are working, such as the engine instruments and electrical system. We even have a checklist that we use to document all the readings both prior to and after the condition inspection.
The first RV-9 has been maintained by us for many years and comes to us all the way from Maryland. I always check the ignitions right after startup, and this one almost quit completely when one or the other ignition was checked. That was quite surprising since it had one electronic ignition.
It was so bad I was surprised the owner had not called and said he wasn’t coming. It got somewhat better and smoother once it warmed up, but it was still not to my liking. All other systems were good.
It piqued my interest. I removed the cowling and didn’t find anything amiss with the intake tubes or ignition wires.
The engine was approaching 1,200 hours so I was curious as to the condition of the spark plugs and cylinders. Upon removing the spark plugs I immediately discovered the problem — all of the lower plugs were full of lead deposits.
The plugs were Tempest HE REM37BY with the larger gap as used in the Electroair ignition system and are not usually prone to fouling. You can see in the photo how much lead was in them.
A couple of them did not pass the resistance test, and the center electrodes were beginning to “football,” so it was time to replace the plugs, which had almost 500 hours on them.
I know the pilot well, and I know he understands good leaning technique, so this warranted more scrutiny than just replacing the spark plugs. All the intake gaskets and hoses looked good, with no signs of brittleness, cracking, or blue stains.
When my flashlight settled on the airbox, I found what I was looking for. There were blue fuel stains all around the seam in the carburetor. That is usually evidence of a leaking or heavy float. This will initially cause an overly rich fuel mixture, which can lead to the excessive lead deposits I had discovered on the spark plugs.
I’ve seen this quite a few times over the years, and it’s usually around 1,000 hours and 10 years, which fit this scenario perfectly. We replaced the spark plugs, along with a new carburetor overnighted by Aircraft Spruce & Specialty Co., and the results were amazing.
The customer showed up as I was finishing, so I had him start the airplane. I like to be outside the aircraft, or at least have someone outside the aircraft, during the post-maintenance run-up to check for leaks, especially on the fuel system.
His immediate reaction was, “Wow! Night and day difference.” It started immediately and ran nice and smoothly, as it should. He later texted and said it ran wonderfully all the way home.
So, what’s the lesson here? The reality is that sometimes the performance of an engine can degrade so slowly that you may not notice it.
It’s kind of like that picture you hang so perfectly on the wall and notice it for a few days after you hang it up. Sometime later a visitor comes by and comments about the picture being crooked, and you never noticed it. Yet you know it was perfect the day you hung it.
A good idea is to have a “performance” checklist for your aircraft where you can make a note of all the engine parameters on day one, or when it comes out of maintenance. Then throughout the year, perform the checklist again and make note of the findings. I bet over time you will find things that you didn’t even notice were slowly degrading.
The second RV-9A had been purchased about a year ago and was coming for the first condition inspection with Base Leg Aviation. It ran quite nicely during the run-up, but I noticed the alternator was only charging at 13.4 volts. That’s not good. We typically look for 14 volts or higher.
A quick review of the logbooks revealed that some of the common items I often highlight were quite noticeably neglected, such as the 500-hour Slick magneto service bulletins (SB). Many owners in the amateur-built aircraft arena think that service bulletins don’t apply, but I’ve always begged to differ.
In the case of the Slick magnetos, I have seen them completely fail in flight as a result of not performing the 500-hour SB or the 1-15A SB pertaining to the rotor gear.
Just when I think we have stopped the plague of the loose jam nuts, we are reminded it is not totally eradicated. On this aircraft, all three jam nuts on the rudder were quite loose.
The K&N air filter was hard as a brick, quite shrunken in size, and had already damaged the airbox. Once a filter shrinks and hardens, besides not filtering the air, it vibrates in the airbox and begins to rub a hole through the bottom.
Repairing the airbox with some epoxy and/or aluminum sheet will fix the problem, along with installing a new air filter. I’ve mentioned this before — the K&N air filters are not “lifetime” when used in our aircraft. They shrink and harden over time due to exposure to fuel and excessive heat.
After removing the impulse magneto to perform the SB, I noticed quite a bit of rust on the impulse coupler housing. It was nothing major, and I was able to clean it up prior to reinstallation. It was, however, a reminder of what happens to the interior of these engines when they aren’t flown regularly or, even worse, when they are only run on the ground.
This aircraft had only 596 hours on it in 17 years. That’s not nearly enough — and we don’t know if it sat for any length of time during those years.
I often hear from owners that during periods of flying inactivity they will go out to the airport and run the engine on the ground periodically. That is one of the absolute worse things you can do to an aircraft engine. Unless you run the engine long enough to get it up to an oil operating temperature of 180 degrees and keep it there for at least 20-30 minutes, you are introducing a lot of moisture into the crankcase that does not evaporate.
Moisture is a byproduct of combustion, and some of the combustion gases blow past the piston rings into the crankcase. Besides being of high water content, it is also corrosive. When you shut the engine down, the moisture-laden vapor condenses back onto the engine components.
The camshaft and the components in the accessory case suffer the most. The cylinder walls will also experience extra wear and tear, especially during startup, as evidenced by the scoring on the cylinder walls I found during the borescope check.
Replacing the automotive alternator with an aircraft alternator showed a charging voltage of 14.3 volts during the post-maintenance run.
This aircraft has an Odyssey battery, which is probably the most common battery on RVs. That battery likes a higher charging voltage, such as 14.3-14.5. When charged at the lower voltages of 13.4-13.6, the life of the battery will shorten. Perhaps this one charged initially at the higher voltage but slowly decreased over time.
This RV-9A is another possible example of using a performance checklist throughout the year on your aircraft to prevent possible degradation from sneaking up on you.
No sense in having that battery failing to start your engine after you’ve landed for fuel on the first stop of your vacation trip. It could really put a damper on the fun factor!
Vic Syracuse, EAA Lifetime 180848, is a commercial pilot, A&P/IA mechanic, designated airworthiness representative, and EAA flight advisor and technical counselor. He has built 11 aircraft and has logged more than 10,000 hours in 74 different types. Vic founded Base Leg Aviation, has written books on maintenance and prebuy inspections, and posts videos weekly on his YouTube channel. He also volunteers as a Young Eagles pilot.