Put another 2.1 hours on the airplane, so we are up to 13.8 hours. The flight went well. I landed 25 minutes before the rain started, so I got the airplane inside just before things got wet. That should have been my first clue… The ying and yang of my luck would not allow me to get away with cutting it that close un-scathed.
Once in the hangar, I took the cowl off to do an inspection since this has now been the 4th flight since the last inspection. I have already and naively been lulled into confidence from the lack of squawks. Do more inspections on your new airplane people! I found something, and the airplane is temporarily grounded. I would imagine that I felt like what it feels like the first time a parent has to ground their kid.
Truth be told, I feel lucky to have found what I did. But I have learned from my luck. Here is what I found. The hose that connects the bleed air rail to the fuel injection nozzle for cylinder number 4 had fallen off. Come to find out that it is a good idea for me to check all my hose clamps as rubber changes as it gets heated and the clamps may tend to loosen. Also come to find out that I really need to clip the ends of the hose clamps so they don’t sit there and vibrate and create failures. So don’t install as I did here…
Normally not such a big deal because the bleed air isn’t truly required at this time. The engine will and did continue to run normally. However, when the bleed air fitting starts rubbing on something else….. something is going to act like sandpaper and something acts like rotten wood. After further investigation, I found that the hose fitting was rubbing on the CHT wire, and there was some chafing going on. This is superficial damage, and does not require anything other than preventing it from continuing.
However, when the now unsupported bleed air rail starts rubbing on your #4 cylinder fuel injector supply line, and it chafs nearly through the line, that is a bigger problem. The damage that I found appears to be a slot worn about half way through the wall of the injector nozzle line. I haven’t mic’d the notch yet, but I’m not too keen to know how deep it is…
I hesitate to say this so bluntly as I have family that read this blog, but for the sake of other builders and people who are or will be maintaining their own airplane, I will. I think I was within 1 hour of flight time of having a failure of that line. That would have caused a failure of the #4 cylinder as well as dumping fuel onto a 1500 degree exhaust that would have most certainly started a fire. The only solution would have been turning off the fuel and becoming a glider.
Now the good news out of all of this is two fold. One. Inspection caught a problem before it became a safety issue. Like I said, I learned something about inspecting. I got lucky finding this because something didn’t look quite right, and so I sat there and looked some more until I saw what was going on. It was lucky I saw it.
The better way is to be more methodical. When inspecting take one sub system and trace it from start to finish. Look for issues and complete one system before moving on to the other. If I would have visually traced from the fuel supply all the way to each cylinder, I certainly would have seen this issue. If that would have been how I found it, I would tell you it was through diligent inspection, and not luck. But like the old adage goes: we start with a bag full of luck and an empty bag of experience. Our job is to not use up our bag of luck before we fill our bag of experience. Needless to say, I went through each sub system in the engine compartment today and traced it from start to finish. Fuel, Oil, electrical, baffle, ignition, etc.
One i didn’t look too close at is exhaust. And two of my friends spotted a slight exhaust leak on photos I shared with them that I didn’t see. Not really a safety issue at this point, but still something that deserves the utmost attention. So I will verify torque on all exhaust pipe hold down nuts, and see if that fixes the problem. Can you see the exhaust leak in the following photo?
In the photo, on the left side, the discoloration and soot-looking substance on the top of the spring. I will clean it off so we can see if after the exhaust is re-torqued we still have a leak or not.
The second of the good news is a friend (Guru James) told me of a way of preventing this issue with the bleed air rail from happening. I need to fabricate a way of holding the bleed air rail. It currently is installed, i believe, per instructions and is solely supported by the hoses connecting the rail to the injector nozzles. But if I add a support in the way of an adel clamp and a crimped tube to a point on the baffle or cylinder, it will reduce vibration and lessen the likelihood of it becoming disconnected. If it does become disconnected, it won’t be chafing on the injector line.
While the Garaggio-Ez is temporarily grounded, it has been a good day. I have learned a lot. It is amazing to me how much building and now operating an experimental airplane is an educational process. I’m certainly learning a ton. The new injector line is already ordered, and I have a list of things to fix before flying again.
3 thoughts on “Grounded”
I should finish the thought…the worm clamps I am referring to are the larger ones on the EGT probes, intake tubes, and other places. It is a good idea to trim or bend down (so it touches the band to damp vibs) the ends of the small ones too. But, they are so small/short that the harmonic freqs are higher than your engine produces.
Also, the main reason for securing the injector bleed rail is to make the o-rings last longer. As the mass vibrates, it tears up the blue o-rings in the injector collar and gets progressively worse. The leaks will affect EGT balance once you get things tuned.
Pull those cowls and inspect no less than every other flight for quite some time…it will keep you and the plane safer. I still pull mine every 5hrs.
Glad it was a close call and nothing more, nothing less. 🙂