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Thread: catastrophic failure of the XP-400 engine

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    www.SkupTech.com mike mcs repair's Avatar
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    catastrophic failure of the XP-400 engine


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    skywagon8a's Avatar
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    Interesting, they don't say what the propeller was. There is a note at the end of every propeller TC which says which engines the propeller is approved vibrationwise on. There is a reason for this. Perhaps the reason this crankshaft failed was because the propeller/crankshaft combination set up a certain vibration at a certain rpm? These vibrations can have the same effect as aerodynamic flutter on the airframe. Sudden, bzzz, snap, bang!.
    Just because the airplane was "experimental", it doesn't mean the vibration doesn't matter. There have been many failures over the years of propellers which are outside their certified limits on "experimental" airplanes.

    I wonder if there have been any engine/propeller vibration analysis done on the XP-400 engine? Just because they look like a Lycoming, it doesn't mean that they are exactly the same.
    N1PA
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    It wasn't a propeller problem. I asked when I was there to see my engine. When I was there they were looking at a detonation problem. One of their engineers showed me how he was studying the flame shape during combustion. The decision to scrap all the motors came several days later. They told me the problem wasn't found in every engine they tore down and they couldn't explain why, so they bought them all back to be safe. The accident in the lawsuit was well known among us owners. It wasn't the first crank failure I knew of, either. My engine production had been delayed for crankshaft QC problems so obviously Superior was already paying close attention to cranks when they built my motor.
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    skywagon8a's Avatar
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    I know you do a lot of research stewart. As you have indicated, they really are not sure what caused the failure. The resonance developed between the engine and prop is what I was referring to. This is the wikipedia explanation without going into the complex engineering studies. https://en.wikipedia.org/wiki/Resonance One of the advantages of a wood or carbon fiber prop as you have, is their ability to absorb the destructive resonance vibrations.

    Perhaps it was detonation? My comments were based upon the information in mike's article's report.
    N1PA

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    They were sure it was detonation but not sure what caused it. That's what they told me. The detonation article is linked in Mike's attachment. Mike and I witnessed an unexplained detonation event before my plane ever flew. And I was concerned with my unusually high EGTs. All interesting looking back.

    I'm pleased Superior got a reasonable settlement. My opinion of them hasn't changed. Great company.
    Last edited by stewartb; 02-12-2020 at 11:19 AM.

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    BC12D-4-85's Avatar
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    Electronic adjustable ignition and pre-detonation sensors (both vibration or spark ion sensing) have been around for many years. Takes an engine control unit and pre-engineering. Something Stone Age engines lack.

    Gary

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    Failures happened with electronic ignitions and conventional magnetos. Superior had issued a bulletin to retard timing, too. I'm pretty sure they'd have rather fixed the engines than buy them back. When Scott Hayes called me to talk about the buy back he told me he wouldn't fly behind my engine because it was dangerous, even after my crank passed inspection. I thought that was a pretty strong statement considering the source. It's all history now. Some day I hope to hear the rest of the story.

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    www.SkupTech.com mike mcs repair's Avatar
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    Article updated to include some O-360 from superior


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    skywagon8a's Avatar
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    Quote Originally Posted by mike mcs repair View Post
    Article updated to include some O-360 from superior
    https://www.aopa.org/news-and-media/...m_medium=email
    N1PA
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    Different cranks than the 400s. Likely from the same foundry in Germany, though.

    I wonder if this will be similar to the metallurgy problems that Continental and Lycoming had in their cranks in the past.The crankshaft business must be difficult.
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    Quote Originally Posted by stewartb View Post
    Different cranks than the 400s. Likely from the same foundry in Germany, though.

    I wonder if this will be similar to the metallurgy problems that Continental and Lycoming had in their cranks in the past.The crankshaft business must be difficult.
    Lycoming was the last AD, due to a change in the molydebym (spelling?) which caused a brittle condition. It gets real quiet when the propeller leaves the airframe.

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    I thought it was chromium. Not that it matters in this context. I didn't pay much attention to the Lycoming problem. I lost a summer for the Continental problem and now a year plus for the Superior problem.
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    aktango58's Avatar
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    Quote Originally Posted by astjp2 View Post
    It gets real quiet when the propeller leaves the airframe.
    Only outside. Inside I bet gets really loud!

    Really, it is great that today we have the ability to step and discover what these problems are. Look back in history and many planes went down for 'unknown' problems; some were discovered later, other's not. Usually it was by accident they were discovered.

    Stratocruiser's prop blade cracking is one I can think of.
    I don't know where you've been me lad, but I see you won first Prize!
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    www.SkupTech.com mike mcs repair's Avatar
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    the broken cranks(continental 520?) I head of/work on from my stepfather's experience.. the one we flew 3 times trying to diagnose it as it cracked more AFTER pilot radioed and sat it down on sand blow at bible camp.... prop never left, but overspeeded and threw alternator belt as crack opened on 3rd test flight....

    the other he was a passenger in, somewhere between naknek and king salmon....

    props didn't depart, but you could pull props fore and aft and visuals see/flex crank afterwards....

    happy endings all considered, other than tore up engines... and packed oil screens... fun loading extra new engine into a 185 by hand, and loading broken engine.... that darn lift strut makes it a challenge!!

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    wireweinie's Avatar
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    So what was the fix for the 520? Metalurgy or mechanical?

    Web
    Life's tough . . . wear a cup.
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by wireweinie View Post
    So what was the fix for the 520? Metalurgy or mechanical?

    Web
    We bought the plane with LOST engine logbook. Probably had a prop strike logged. This happened 200 hours later. Lawyer owned it before us.... so we bought another prop strike engine from “wild bill” that had been flipped when he caught a set net rope down in Bristol bay. And tore it down and took it and installed it. Not much left of old engine. I gave/sold/ never got paid the case half’s to mad mike almost 30 years ago. Not sure they were any good after the events...


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  17. #17
    wireweinie's Avatar
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    Prop strike or other mechanical damage, I can understand. But the problems like in the XP-400 seems like weird voodoo stuff. Hope they share the knowledge when they figure it out.

    Web
    Life's tough . . . wear a cup.
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    www.SkupTech.com mike mcs repair's Avatar
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    Quote Originally Posted by wireweinie View Post
    Prop strike or other mechanical damage, I can understand. But the problems like in the XP-400 seems like weird voodoo stuff.

    Web
    Or falsified inspection/tests from manufacturer.....


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    I tend to see part of the issue in these crankshafts with the radius of the journal fillet is too small. But the very poor combustion chambers are a major part of the problem.
    I find it interesting that I am criticized in that I might not use an aircraft engine in my plane. This is because I am afraid to fly behind any "new" aircraft engine since they are proving they can no longer produce what they built 50 years ago, which was designed 80 years ago and has not seen even a modicum of technological improvement since.
    Can not one of these companies hire a 25 year old who can do some FEA work,allow him to utilize modern methods and materials and give him a chance to start fresh. He would get rid of these sand cast cases and rear cover and produce far stronger ones that are ˝ the weight. Every other industry utilizes pressure cast components with great results. Can they not utilize a crankshaft with proper balance weights which will be lighter than what they have now.
    If these recent crank failures are attributed to detonation, one, how the hill did they ever come to market?
    And why has no one ever changed the port shape ab combustion chamber in these engines.

    Back in '93-94 Continental did a development project with Honda engineers on port design and combustion technology. The results were never released. 1994 was just the beginning of higher velocity port design that is used in most every engine built today other than aircraft.

    It would be interesting to see what an engineer from Lycoming would think if he ever looked at the insides of a modern outboard motor.
    Actually he would just be bewildered and confused, call it Jap crap even if it was designed in this country, and walk away.

    I would love to see today what Mazda, Mitsubishi or Honda would build for an aircraft engine today. Or Yamaha, Mercury, Suzuki.
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    Quote Originally Posted by wireweinie View Post
    So what was the fix for the 520? Metalurgy or mechanical?

    Web
    My own Continental crank problem was metallurgy. Mine was a factory reman 0-470 back around the year 2000. Continental sent a rep to Birchwood to core a hole in the prop flange of mine and a few other factory engines I knew about using a roto broach. He sent the samples back to the factory for analysis. I don't know of a single engine that was tested that didn't have to be torn down and the crank replaced. 135 operators got priority so private guys had to wait, and then they ran out of crankshafts. Not a fun year. I recall lots of criticism from Lycoming owners but a few years later they had the same problem. And now Superior. Three for three.
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    Quote Originally Posted by CharlieN View Post


    It would be interesting to see what an engineer from Lycoming would think if he ever looked at the insides of a modern outboard motor.
    Actually he would just be bewildered and confused, call it Jap crap even if it was designed in this country, and walk away.

    I would love to see today what Mazda, Mitsubishi or Honda would build for an aircraft engine today. Or Yamaha, Mercury, Suzuki.
    I'm sure those engineers know more about other types of engines than most of us do. My 4-stroke Yamaha outboard and snowgo spin at high RPMs. That offers a whole nuther problem. Not insurmountable. Watch internet videos of Steve Henry's Highlander using a Yamaha Apex motor. It's a popular engine with the Highlander and Super STOL crowd. Suitable for very light planes. Bigger planes not so much.

    https://youtu.be/FiOFtul8gu8

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