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CS Prop questions

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  • CS Prop questions

    Good Day-

    I did my first 2.5 hours in an O-470 CS prop. I've read the basics, and tried to learn as much as I could before the first flight.

    All went well flying, and nothing too overwhelming.

    What are the main things to NOT to do with that CS prop and vice versa? For example, manifold pressure reduction first, then RPM's when reducing power and RPM increase first then manifold pressure for increase are the main things that I've read.

    What do you all think? What do you suggest for the main things I should/shouldn't to keep my engine strong and healthy?!

    Thanks for the expertise.

  • #2
    watch your cylinder head temp. plan you power reductions far in advance and step it down as opposed to just yanking the power and dropping it in like a rental.


    • #3
      Disclaimer: This info is worth exactly what you paid for it.

      CHT's and power reduction: An "inch a minute" is conservative and what I try to do every time. (Look at your gps and start reductions about 10 minutes out or so depending on power setting........that'll take you from 24 to 14 for example) Cylinders are expensive.

      Speaking of cylinders, run it on the rich side. A half gallon an hour isn't that expensive when you have to buy a jug.

      Cycle the prop several times while taxiing in the winter to get some warm oil through the hub prior to first runup and TO.

      Probably alot more I am forgetting but remember "prop on top" and keep the tach higher than MP.

      Likely get alot of good tips to follow. Good question.


      • #4
        The PPONK site used to have different prop settings for maximum thrust on takeoff. Maximum prop efficiency, I guess

        IE 2850 RPM is not always the most efficient depending on density altitude. Worth a read.


        • #5

          Oh I see AK-Hunt beat me to it..
          C/S props are a neat thing as long as you treat them well and throw money at them occasionally. Warm oil is their friend and they like slow changes whenever possible.

          I used to have access to a C-210 for doing commercial ratings, but the owner insisted on saving a few dollars in gas by running it lean of peak all the time. He may have save a few hundred dollars in gas but it eventually cost him a few thousand when he roasted the valves.

          I learned to never move the prop up on landing until I am out of governing range. You will know you are out of governing range when rpm is lower than set rpm. At that point engine is not producing enough power to reach the set rpm. When you move the the prop knob forward (going flat pitch) you will not hear anything. If you set it while in governing range you will get an increase in RPM and all that extra strain on your prop and engine. You see non-owner pilots doing that because they think it is cool to slam in the prop and use it as a brake.

          More light reading

          Float-CFI, Photo Guide, Fishing Guide, Remote Kayaking
          Guest Cabin, Flight Reviews, Aerial Tours


          • #6
            Constant speed props are usually under maintained. The longer you wait the more expensive it'll be. Private guys aren't required to comply with the 5 year inspection standard but with my MaCauleys it's been a good idea to plan for hub tear down at or near 5 year intervals.

            Take it easy pushing the throttle in. When the prop winds up it'll suck gravel into the blades. I make power increases as slowly and smoothly as the situation allows.

            I never pull power rapidly but I disagree with the previous warnings about power reductions unless you like to fly high. Most Alaska guys don't fly high enough to worry about shock cooling on descent. My 6 point monitor has alleviated any shock cooling concerns I ever had. I manage my approaches with focus on speed. If you're coming into Hood you need to be slowing down well before Pt Mac. Engine settings are what they are. Airspeed is my primary concern and surrounding traffic may dictate that. The real shock cooling comes when you shut it down.

            Make sure you flatten the pitch on short final so you're ready to go-around should the need arise. I always push the prop to flat and the carb heat to cold before touch down.

            You have green arcs for MP and RPM. As long as you keep the needles in the green you're good. Let the plane tell you what power settings to use. For me that's 24 squared or even a bit higher. My old engine/prop liked 23/2350. A dynamic balance is always a good idea, by the way.

            At take-off I apply power, get into the air, retract flaps, reduce MP, reduce RPM, trim for desired airspeed. Once at cruise altitude I'll re-trim, adjust power/prop, close cowl flaps, and re-trim as necessary.


            • #7
              Thanks for the replies.

              That link Float Pilot posted with the prep.pdf was a good read. It goes into great detail of the why's and how's. I didn't/don't want to only learn when and what to do but why. I think it will serve the engine better in the long term and give me the knowledge (hopefully) to get the most out of the plane.

              I must add, after about 10 hrs of working a CS prop, it isn't as big and bad as I anticipated. A little more work doing splash and goes but I feel like a real pilot now turning all these fancy levers and buttons .



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