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Thread: catastrophic failure of the XP-400 engine

  1. #1
    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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  4. #4
    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.

  6. #6
    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.

  8. #8
    www.SkupTech.com mike mcs repair's Avatar
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    Article updated to include some O-360 from superior


    Sent from my iPhone using SuperCub.Org

  9. #9
    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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  10. #10

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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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