When Engines Go Bad
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My plane maxes out at about 164mph true, versus the book value of 176mph.
It needs to have a quart of oil added about every 5 hours of flying time.
Other than that, there is nothing external to tell me that there is something wrong with the engine.
The engine is a Lycoming O-360-A1A with about 1450 hours since major overhaul. That overhaul was done in 1974, and the plane sat for several years from 1992 to 1998 with no flight time at all. I suspected something was up with Cylinder #3 mostly based on the EGT vs Mixture graph (see below), but was not sure whether it was just an inconsistent fuel/air mixture or something more serious. The Blackstone oil analysis reports showed there was more wear than should be occurring, too. Below are the symptoms: |
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The last 5 oil analyses show high wear
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The EGT vs Mixture curve at 11,500 MSL shows Cylinder 3 has a problem(Leaner is to the left, Richer to the right).This might just as easily be diagnosed as a fuel/air mixture problem. Note that when the other 3 cylinders are operated 150 degree rich of peak for maximum power, cylinder #3 is right at peak. Could this exacerbate the self-destruction of that cylinder if done at a lower altitude with high power? 
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The Oil Screen at the 09/30/2006 oil changeA little non-ferrous carbon debris, and some ferrous slivers and powder show up in the ADC filter screen(Subsequent oil changes were not much different. This was the only oil change where I took photos.) |
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But none of all this is symptomatic of a bad engine! | |
June 22, 2007During my annual inspection, the mechanic discovered that cylinder #3 would occasionally only produce compressions of about 40/80. If you moved the prop a little, it would come up to 65. There is a bad spot somewhere in the cylinder. Cylinder 4 is also flaky. |
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July 2, 2007Overhauled cylinders are ordered and arrive a week later. |
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July 29, 2007Mechanic finally gets around to removing cylinder and discovers that the cam is worn and the lifters spalled. The choices are to either split the case and replace the cam ($6k) and the two cylinders already bought, or to go ahead and do a major overhaul on the whole engine. |
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August 7, 2007I choose a $19,000 major overhaul from Zephyr Aircraft Engines using all new ECI Titan engine parts, resulting in a nearly brand new engine. The generator, carb, fuel pump, and prop governor will be overhauled. The rest will be new, including Slick mags and Kelly eDrive inline starter. The old engine is removed from the firewall and shipped to Zephyr. |
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September 18, 2007New engine is shipped to Longview. |
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October 12, 2007New engine is mounted. |
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November 1, 2007First Flight. Left gear collapses. |
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November 20, 20075 months ago, I took my plane in for an annual inspection. Today, when I released the brakes to finally fly it back home, the right gear collapsed. I'm looking for a cheap source of hemlock. |
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December 28, 2007After 6 months and 30 AMU, N6030X is flying again. |
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The New Engine |
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The EGT vs Mixture curve at 11,500 MSLIf you compare this mixture graph on the new engine with the one at the top of this page for the old engine, you will notice that Cylinder 3 behaves similarly. That is, it peaks much earlier and much flatter than the other cylinders. Since the carburetor was overhauled and this engine has a completely new set of intake tubes and cylinders, this must be a design issue with the O-360-A1A.
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) The 2nd oil analysis on the new engine (far left column) All values are normal for a brand new nickel-cylinder engine |
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