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  • V Speed questions

    While I doubt that anyone has Companion speeds, I figure that a 180-200hp Patrol will have similar numbers. I am just curious what to expect

    So looking for the following specifically:
    Vx
    Vy
    Best Glide

    Thanks
    N678C
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  • #2
    There's a little to this. Here's more reading.
    You say your airplane's POH doesn't have some performance numbers you need? Or, because of airframe or powerplant modifications, your factory-original POH performance section is out of date? Or perhaps you need numbers for your one-of-a-kind homebuilt? Don't despair ... and don't guess! Now there's an easy way to calculate accurate light aircraft V-speeds, rates and angles of climb, thrust, drag, and much more. Aviation physicist and private pilot John T. Lowry shows you how. (This first installment deals strictly with simple fixed-pitch-prop airplanes; a follow-up article deals with constant-speed props and other complications.)


    https://www.kitplanes.com/predicting-performance/

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    • #3
      Originally posted by Utah-Jay View Post
      While I doubt that anyone has Companion speeds, I figure that a 180-200hp Patrol will have similar numbers. I am just curious what to expect

      So looking for the following specifically:
      Vx
      Vy
      Best Glide

      Thanks
      VX - lots.
      VY - ehhhh....who's looking inside when trying to clear the trees?
      Best Glide - like a rock.

      lol.... lots of helpful data from the snarky Vermonter.

      Comment


      • Utah-Jay
        Utah-Jay commented
        Editing a comment
        Thanks Peter

    • #4
      The Bootstrap spreadsheet has a ton of options, I plugged numbers in it yesterday and came up with some interesting/helpful results
      N678C
      https://eaabuilderslog.org/?blprojec...=7pfctcIVW&add
      Revo Sunglasses Ambassador
      https://www.youtube.com/channel/UCQ0...tBJLdV8HB_jSIA

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      • #5
        The theory is very simple, but the engine/prop throw that off. An EFIS makes it simple to measure. Max climb angle you can get off the Flight Path Marker. You trim for the highest FPM angle. Best Glide same. You are minimizing the glide angle and measure it with the FPM. Absent prop effects, fixed vs constant speed, AOA rules uber alles. But the prop type throws the math off.

        Without an EFIS you can take some measurements.

        The basic airplane has an AOA that maximizes those values. The type of prop effects it. A feathered CS prop you can probably just calculate V speeds. If you can't feather it will change a lot.
        Last edited by svyolo; 04-07-2023, 12:19 PM.

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        • #6
          I am sure my EFIS will be a huge help, as for props I have a Sensenich GA prop that I will do testing for all 6 pitches. I reckon I will primarily run it in #4. Pitches are 2, 3, 4, 5, 6, and 7, there is another pin you can get that is marked 0 and 1

          2 is finest pitch, 7 most course for cross countries
          N678C
          https://eaabuilderslog.org/?blprojec...=7pfctcIVW&add
          Revo Sunglasses Ambassador
          https://www.youtube.com/channel/UCQ0...tBJLdV8HB_jSIA

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          • #7
            Here's a few below to get you started in the general direction, applicable to my 4-place at 2200lbs. I imagine the Companion may be extrapolated to a lighter weight.

            In testing there are a lot of variables. For climbing I generally use full power ROP (although I did test all speeds LOP as well). For best glide etc, I use 70 kts now because it provides energy/airspeed for the flare. If airspeed is reduced to 50 KIAS, the resulting high descent rate is difficult to recover from and can take several hundred feet. For a normal cruise, I always fly LOP and tend to use either 22" MAP for around 110 KIAS (36LPH), or 26" 120 KIAS (42LPH).

            Rates of climb were tested at different airspeeds - all through to 8000ft. Also many different cruise scenarios, mixture settings, speeds etc. For example I can cruise at 130 KTAS with an eye watering fuel burn, or 115 KTAS at a wallet friendly fuel consumption. Rates of climb always settle back to around 1700 FPM once averaged out, although initial indications can be spectacular on a cold day, low altitude, light weight etc.

            80B28E0D-59B1-474B-87F8-FF8D05FA9E1F.jpg
            Last edited by Nev; 04-07-2023, 04:03 PM.
            Nev Bailey
            Christchurch, NZ

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            • Nev
              Nev commented
              Editing a comment
              Yes those speeds are in knots. I got a band of 70-80 kts for Vy where the results were similar so you're probably correct as well.
              Early on there was no chance of me doing a climb like that without engine cooling issues. The cooling is much better now and not an issue. However I would seldom do a climb at 80 kts - usually it would be 100kts or so - a compromise between time to climb and efficiency - and cooling if necessary.

            • Utah-Jay
              Utah-Jay commented
              Editing a comment
              80mph type climbs always bother me as I can’t see over the nose. Good to know what the plane will do if needed, but no need for those kind of hit pitch angles in my opinion, just silly youtube stuff

            • Utah-Jay
              Utah-Jay commented
              Editing a comment
              Let me correct, 80mph does in fact not bother me, the 55mph cling is pretty steep for my taste

          • #8
            Jay, 80 bothers you? ??
            That’s a pretty fast climb speed around here. 50,60 mph gets her up off the ground nice. ? Of course I am 0-500 msl…. Most of the time. Until I hit 500 agl…

            pb

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            • Utah-Jay
              Utah-Jay commented
              Editing a comment
              500AGL
              80 does not bother me, but the pitch angle of 55ish mph is a bit high for my liking
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