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Engine Break In and First Flight

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  • #31
    Hey all...question for those that have broken in their engine, but first some background info. My first flight was pretty exciting, new engine and airframe, flying at more than 75%. I was bumping between 145-150MPH. It wasn't a great feeling, especially not knowing what noises were normal and what weren't! Anyway, first flight was 1.3 and I used about one quart of oil. Second flight was 2.2 and I used about 1/2qt of oil. Third flight was only .9 (cut short by bad weather) and it appeared that I didn't use any oil. If I did, it wasn't much. CHTs have stabilized (I think) and I never saw anything above 428F on the first flight. Oil temp is stable at 187F. It helps having an OAT of 33F! I changed the oil yesterday and I'm ready to go back out once my RPM gauge comes back from repair.

    I have a grand total of 4.4 hours. Three takeoffs and three landings. Zero airwork, no slow flight, stalls, nothing...just flying really fast in circles above the airport. So the question is how long should I fly it at 75% and above before I can start exploring the flight envelope? The answers that I'm getting so far from other sources is anywhere between 10 and 25 hours. It is impossible to follow the EAA phase testing and breaking in an engine at the same time using successive flights as guidance . Any input is appreciated.

    p.s. I did get almost an hour doing pattern work in the left seat of Ken Frahm's Bearhawk and I am extremely grateful for the opportunity!. The time was invaluable and gave me the sight picture and airspeed "feel" that I needed for my flights, especially landing.

    IMG_20240606_111215.jpg
    Last edited by alaskabearhawk; 06-06-2024, 03:23 PM.

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    • Battson
      Battson commented
      Editing a comment
      Cool track - reminds me of Spirograph, assuming that kids toy was available where you live

  • #32
    AKBearhawk, I remember the main thing was running at or near full power until oil consumption stabilises. Everyone agreed on that, at least - you don't want to risk glazing the cylinder barrels. For some people, their engine needed 10 hours >75% power, others needed 45 minutes. It all depends on whereabouts in the engineering tolerance / fit of the somewhat random combination of different sized parts in your engine - as I understand it.

    That's the manufacturer's instruction too - from memory - run hard until oil consumption stabilises (not stops, stabilises - presumably at a level you are happy with). It sounds like you achieved that.

    I recall that if oil consumption doesn't stabilise in 10 hours, then you might have a problem on your hands. Worst case it means honing cylinders, I know one or two people who needed to do that.

    Beyond that, we maintained high power settings wherever possible for the first 20 to 25 flights (which we calculated would be roughly 25 hours) as a risk mitigation measure. Referring back to the flight plan we posted on the previous page (link below), you can see the 75% power requirement scattered through those flight plans.

    Obviously, it is necessary to reduce power settings for a range of flight tests, and of course for descent / approach / landing / ground running. Therefore, time spent operating at lower power setting does necessarily cause any problems, provided it's interspersed with extended running at high power settings, periodically. Again, you can see how we did this in the flight test plan.

    We didn't delay the flight testing schedule in the interests of running hard to break in for 10 or 25 hours. We designed our flight test schedule to minimise lower power operations, to what we felt was an acceptable level in the early stages. This was a balancing act. The risk of the engine glazing is one thing, but the risks associated with flying 25 hours with a relatively untested aircraft ranked higher in our risk assessment.

    We have had no problems with the engine, after following this plan. We have run around 1,100 hours now. We have been burning around 1 qt (or L) per 50 hours, until recently. We are now seeing a very gradual increase in the rate of oil consumption, with no other signs of engine wear increasing (oil filter particles normal, etc).

    Originally posted by Battson View Post

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    • alaskabearhawk
      alaskabearhawk commented
      Editing a comment
      That's great information...thank you!

  • #33
    Hi Paul, something that I have noticed that I'm sure you know too, is that it is hard to get really scientific about oil levels. The plane's parking attitude really matters, but also, immediately after a run, the oil level will be different than some hours after a run. It drains down into the sump from other places in the engine. Study the long term trends but expect lots of noise in the short term unless you are checking in a very consistent way.

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    • #34
      Fun stuff Paul! No doubt everyone will give you a somewhat different opinion. You’ll just have to settle on what you’re comfortable with.

      For me it was 5 hours. At that point the plane hadn’t used any oil in a couple hours, CHTs were cooler and I felt the risk of glazing the cylinders was now lower than the risk of flying an untested airplane.

      It sounds like you might be at the same point except you might need another data point or two to know if oil consumption has stabilized. Like Jared said, make sure you are checking the oil the same way every time. My engine will “make” about 3/4 quart if I check it the next day vs right after a flight.

      What type of cylinders did you go with: steel, chrome, nickel? If you went with steel or nickel I’d bet you are good to go. If chrome I would have been planning on 10 hours or more to break them in.
      Scratch Built 4-place Bearhawk. Continental IO-360, 88" C203 McCauley prop.

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      • alaskabearhawk
        alaskabearhawk commented
        Editing a comment
        Good points. I check the oil generally twice. Once after the flight when the dipstick is cool enough to remove, and when the engine has cooled down.I went with factory Lycoming cylinders, nitrided steel (blue stripe).

    • #35
      Good work there Paul. Another data point. I was given the same advice to run mine hard for 25 hours etc. At about 1.5 hours the CHT's showed a decrease, and there was very little oil consumption during the initial few hours, so I'm pretty sure that it could have been considered "run in" at that point. I did keep it running hard for about 10 hours mainly because the engineers were telling me to do so and I didn't have any experience to fall back on. Then, like Whee and Battson, I carried on with the test schedule, but continued to run it hard wherever I could. Now, with about 320 hours "airtime" on it, I typically add a quart at 35 hours between 50 hour checks.
      Nev Bailey
      Christchurch, NZ

      BearhawkBlog.com - Safety & Maintenance Notes
      YouTube - Build and flying channel
      Builders Log - We build planes

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    • #36
      Running "hard" to break in an engine is easy on most airplanes. But on a 540 powered BH or Harmon Rocket it seems a little dodgy. I built a cooling shroud to do it on the ground, and it looks like the local airport authority is going to let me do it. Hopefully video to follow in a couple of weeks.

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      • rodsmith
        rodsmith commented
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        I look forward to seeing that. I'm getting close to running my engine.

      • alaskabearhawk
        alaskabearhawk commented
        Editing a comment
        I’d be interested in seeing your setup as well. Test cells, at least the ones I have seen, seem pretty involved.

      • Battson
        Battson commented
        Editing a comment
        "A little dodgy" in what regard?
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