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  1. #1
    Todd copeland's Avatar
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    Constant speed prop question

    I just changed the prop on my glastar from a fixed pitch sensenich prop pitched more on the climb side for a hartzell constant speed prop. I have an io320b1a 160hp. My question surrounds the climb performance. While I have a minor adjustment to make on the governor to up the toms from 2610 to hit 2700, the climb performance of my plane is way down. I regularly saw 9-1400 fpm and now the most I can manage is 5-600fpm. The cruise is improved but I could have improved the cruise and sacrificed the climb by have my fixed pitch changed for a cruise pitch. Could that 90rpm adjustment make that much difference? What am I missing, this is really disappointing.Todd

  2. #2
    Chad Jensen's Avatar
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    Were the conditions the same for comparison? Really hot? 90rpm won't make a huge difference, but may be noticeable...though it won't make a 4-500fpm difference. Where do you pull your rpm indication from? Did something change there? Just thinking out loud here...
    Chad Jensen
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  3. #3

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    Did you happen to get the manifold pressure being produced by your engine while you had the fixed prop? How does it compare to the MP now? If the engine's putting out the same power, then I suspect that you're not getting the fine pitch you should be getting.

    One more thought: have you used a strobe-type tachometer on the prop during a static run-up to verify the aircraft's tach?
    Anxiety is nature's way of telling you that you've already goofed up.

  4. #4
    FlyingRon's Avatar
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    Also, that Hartzell prop weights a lot more than your fixed pitch. If your prop was pitched for climb before, all things being equal, you'd expect to see some decline. Also, if you did nothing else to fix the balance, you're using a lot more elevator down force (and hence drag) to counter hanging that additional weight pretty far out on the arm. When we hang big engines on Navions, we either move the battery back farther in the tail or add a few pounds to the very aft of the aircraft to counter.

  5. #5
    Jim Hann's Avatar
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    Another out loud thought, what RPM were you pulling in a climb with the fixed pitch prop? Was it greater than 2700?

    Jim
    Jim Hann
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  6. #6
    Todd copeland's Avatar
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    Thanks for the thoughts, the rpms were lower with the fixed pitch prop. We are investigating the cg further. While we haven't added that much to the nose, it is all at the nose! It also feels nose heavy, and if I can feel it it must be a factor. Reading the manual it states the glaster is very sensitive to the forward cg. I weighed the airplane today and I am working it out.Thanks,Todd

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