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Thread: PA-22-160 climb vs cruise prop and speed?

  1. #11

    Join Date
    May 2019
    Location
    Kewanee, IL
    Posts
    40
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    Default Re: PA-22-160 climb vs cruise prop and speed?

    I have attached a spreadsheet showing RPM vs Airspeed. Do I have it correct?
    Just enter a new pitch to see the difference.
    Attached Files Attached Files

  2. #12

    Join Date
    May 2018
    Location
    Portland OR
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    78
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    Default Re: PA-22-160 climb vs cruise prop and speed?

    Quote Originally Posted by DaleLindstrom View Post
    I have attached a spreadsheet showing RPM vs Airspeed. Do I have it correct?
    Just enter a new pitch to see the difference.
    Well it's dead on for me if I use 85%.

    Sent from my LM-X210(G) using Tapatalk

  3. #13

    Join Date
    May 2019
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    Kewanee, IL
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    Default Re: PA-22-160 climb vs cruise prop and speed?

    Or, how about an RPM/MPH = PITCH chart.
    Attached Files Attached Files

  4. #14

    Join Date
    Mar 2016
    Location
    Merritt Island, FL
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    565
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    Default Re: PA-22-160 climb vs cruise prop and speed?

    Quote Originally Posted by Gilbert Pierce View Post
    Pick your desired pitch and rpm and figure it out

    Pitch x rpm x 0.0009 = miles per hour with no slip. Using my known numbers, 0.90 is a good efficiency number; 10% slip.

    58 inch X 2700 rpm X .0009 = 140.9 x .90 = 127 mph which is what I would see down low.

    Just adjust the pitch and rpm for what you want to do.

    Theoretically at 2500 rpm, 58 prop the math shows I should true out 117 miles an hour.
    That is exactly what I see.

    If anyone wants to see where I got the .0009 I will be happy show you the computation.
    inches x rev per min x 60 min per hour divided by (5280 ft per mile x 12 inches per ft.). The units then cancel to miles per hour. Hope you enjoy this as much as I did deriving it.

    By the way 61 inch pitch would give you 133.4 with the same conditions. An increase of 6.4 miles per hour. My prop is new. That variable 0.90 will change slightly with prop condition. Bear in mind this is theoretical. Your mileage my vary.

    I have doubts about many mph claims. I was getting 135 mph with a 54 prop until I redid my static system and calibrated it with a four course gps flight and some fancy math that camtom12 understands.
    Gilbert thanks for this post. I found a similar condition - My AI was optimistic, my original mechanical tach was erratic, I had no static system...I also didn't have a 61" prop as I was told upon purchase of the plane, etc. Garbage in... So, in the last year I got a good calibrated AI, hooked up a real static system per Piper dwgs, bought/installed an EI digital tach. Got prop overhauled and measured - 58". Now I get just about exactly what your calc indicates using 90% efficiency with wheel pants, and 2-3 mph less with them off. Just ordered new 60" Sensenich from Univair. (74DM6-0-60) That should get me another 4 mph at cruise.

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