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Thread: Let's talk propellers

  1. #31
    tjlebaron's Avatar
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    Default Re: Let's talk propellers

    Quote Originally Posted by Wag-builder View Post
    Oops, left out some critical information! Cruise power is 2300 RPM and 115 MPH indicated airspeed.
    Thanks! This was helpful!

  2. #32
    tjlebaron's Avatar
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    Default Re: Let's talk propellers

    Quote Originally Posted by andya View Post
    for those with apple products, there is an app by James Petty, called AircraftPower which
    runs the graphs after you put in Manifold Pressure, RPM, Altitude,Temperature.
    Neat app. I used coming home from Steve's AC to be sure I ran above 75%
    as much as possible to get good seating of the rings on the fresh ovhl
    the app covers engines from the O-235 thru many of the O-320 and O-360 engines
    Hey thanks. I just downloaded this app and it is great! Note: it is for iPad and not iPhone

  3. #33
    Brian's Avatar
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    Default Re: Let's talk propellers

    Quote Originally Posted by andya View Post
    for those with apple products, there is an app by James Petty, called AircraftPower
    Thanks for the heads up about this App Andy! Way easier than eyeballing the chart in the POH.
    Brian
    Brian
    Monrovia, CA

  4. #34
    dbudd's Avatar
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    Default Re: Let's talk propellers

    I put a 50" on my 150hp pacer to get out of my dads short strip . At 4000 ft msl it made a big difference in take off but suffered in cruise. I burn less fuel though, flatter prop less manifold pressure I guess.

  5. #35
    tjlebaron's Avatar
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    Default Re: Let's talk propellers

    A few number from today's flight with a 150 HP and 58 pitch prop. To figure airspeed I documented ground speed at three headings each 90 degrees from the other, added them together and divided by 3.

    OAT was 20 deg. Pressure altitude was 5,500 feet, MAP 2300, Tach 2500

    At 78% power, airspeed = 117 mph.

  6. #36

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    Default Re: Let's talk propellers

    Finally got to fly again in similar conditions with prop repitched to 58”. On this day Temp was 79F with DA of 1337’. It’s performing as expected. Pleased I’d say.

    Pitch 58”
    Static rpm 2300
    Takeoff rpm
    (30 mph). 2375

    80 mph climb
    Rpm. 2400
    Fpm up. 1000

    1000’ Full throttle
    Rpm. 2525
    IAS. 120

    1000’ 24” x 2350
    IAS. 113

  7. #37

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    Default Re: Let's talk propellers

    So here's an idea I have. There is a sensenich M74DM7 63 inch for sale right now cheap with only 300 hours on it. What do you think about having it repitched to 62 inches for use on my PA-22-150? What I have read in the TCDS requires it to be able to static a minimum of 2150 RPM. Please comment. My goal is to get all the practical speed I can out of my plane.

  8. #38
    andya's Avatar
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    Default Re: Let's talk propellers

    If you were to buy it, I would try it at 63 inch just to see if it will turn the min static.
    Then try it in the air to see what it will turn WOT at your typical cruise altitude.
    I had a 62" pitch on my O-320 for a short time, it seemed to give me extra speed, +4-5 mph ias
    but coming out of a nice grass strip took a while to break ground and climb performance
    was not what I wanted. Settled on a 60" pitch. what is your present pitch prop?

    Out west I have to fly high (8.5-9.5) and I like the 60 as I could fly WOT leaned to about 75 rich of cruise
    and turn 2650-2670 rpm. Never tried that with the 62" pitch as never had a reason to be that
    high before moving west.
    "Progress is our most important problem"

  9. #39

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    Default Re: Let's talk propellers

    I currently have the original M74DM6-0-61 on my '56 TP. There are no logged records of any changes or modifications so I assume its the original pitch. 2720 TT hours, and a few shallow rounded areas on the back face indicate it's had some nick blending touch-ups done over time. I was considering having it overhauled - just because...and was looking at some for sale adds and spotted the 74DM7-63 and had a similar thought to yours, about "try it", but so many on this forum seem to go with shorter gearing. Another thought is, no down time while I get my 74DM6 overhauled. My TP will easily rev to 2730 RPM with the current prop at 1500 feet, flat and level flight over Monterey Bay, any day I try. AI shows about 132 - 133 mph with wheel pants and 126 without. I'm just wondering if a 63" might be too hard to pull to full RPM and power. Might be worth a try like you say, and who knows, maybe at 7,500', and leaned just ROP, it might be a great cruise prop at 2450 RPM. Thanks for the comment, Andy. I think I'll give the guy a call and see if its in pristine shape.

  10. #40
    Administrator Steve Pierce's Avatar
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    Default Re: Let's talk propellers

    Prop pitches flatten out over time so I would keep that in mind if you have no history on your prop when comparing it to one with 300 hours.

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