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  • Anyone actually getting 150kts?

    Just curious if anyone is getting the advertised 150kts true airspeed in their 260se?

    I have finally gotten the chance to fly some longer trips and according to the aspen I get more like 142-144. I have tried altitudes between 8 and 12k as well as different rpm and power settings but nothing gets me to 150.

    Typically I have been cruising at 2450rpm full throttle leaned to about 13gph. This gives me speeds mentioned above with temps in the 340-360s


    On another note I've put about 10 hours on it this month and i think I finally have everything about figured out. Just need to see why the verticle speed on the stec 60 isn't stopping at the altitude I enter into the aspen. Maybe it's not supposed to so if anyone has an aspen feel free to chime in.

  • #2
    Re: Anyone actually getting 150kts?

    You may have to go ROP to get something nearer to 150. Todd would be the best reference.

    I got pretty much the same as you now with 5PX at similar power settings. That was before stripping, new paint and a lot of fairing body work. I'll let you all know what I get when I get the wheel pants back on.

    Blue skies,

    Tom
    Attached Files

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    • #3
      150 knots

      The power setting you indicated is not fully ROP (at optimum altitude). In fact, depending on the altitude (you didn't indicate which altitude this was at), this could very well be in the "red fin" territory that's potentially damaging.

      Running ROP at about 6000-7000 here in hot Florida, pumping about 15.5 gal/hr gets me just above 150 kts in my airplane.

      I only do this to demonstrate it's possible.

      In cruise, I am always running lean of peak and at best altitude for speed, I see about 142-144 kts true in this regime and save a few gallons an hour.

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      • #4
        Tom the plane looks great! Quite an improvement from when I sold it to you!

        I never cruise below 8500 since my field elevation is at 5500. Typically I cruise at 9500-11500 I've read most everything I can find on leaning the io470 and it seems 13gph is about where I should be. Not sure what you mean by in the red zone. I've never seen chts over about 360 even in climb. In cruise they typically are 340 ish.

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        • #5
          Originally posted by nworth View Post
          The power setting you indicated is not fully ROP (at optimum altitude). In fact, depending on the altitude (you didn't indicate which altitude this was at), this could very well be in the "red fin" territory that's potentially damaging.

          Running ROP at about 6000-7000 here in hot Florida, pumping about 15.5 gal/hr gets me just above 150 kts in my airplane.

          I only do this to demonstrate it's possible.

          In cruise, I am always running lean of peak and at best altitude for speed, I see about 142-144 kts true in this regime and save a few gallons an hour.
          My Katmai presently performs exactly like Norm's, almost to the knot. In cooler temps I can sometimes achieve 152 or 153 but that's with light-to-moderate load, prop and throttle all forward and leaned to ~150 deg ROP. That's more fuel than I care to use for sure.

          Load also matters. At or near MGTOW (2950 lb, or 3100 lb with Tom Storli's STC) the plane is hard-pressed to get to 150 KTAS.
          Kevin Moore
          Former 260se/stol Katmai with BRS owner; planeless for now
          sigpic

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          • #6
            Originally posted by nworth View Post
            In cruise, I am always running lean of peak and at best altitude for speed, I see about 142-144 kts true in this regime and save a few gallons an hour.
            Originally posted by kwmoore View Post
            My Katmai presently performs exactly like Norm's, almost to the knot. In cooler temps I can sometimes achieve 152 or 153 but that's with light-to-moderate load, prop and throttle all forward and leaned to ~150 deg ROP. That's more fuel than I care to use for sure.
            Here's an example, full throttle, 2400 rpm, lean of peak, 142 KTAS over San Francisco a week ago.



            Here's the view out the right side window:



            And out my window:



            It was a beautiful day in the SF Bay Area!
            Kevin Moore
            Former 260se/stol Katmai with BRS owner; planeless for now
            sigpic

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            • #7
              151 KTAS cruise today

              Here's an example from today: 6500 feet near Novato (KDVO, Gnoss Field); OAT 64 deg F (~8100 ft density altitude), full throttle, 2530 rpm (my plane's smoothest rpm setting), leaned to ~150 deg ROP for best power. This is likely somewhere between 70-75% power based on the IO-470 %power tables taking into account both altitude and temperature. A bit over 16 gph coursing through the injectors--I might have gotten it to 152 or 153 had I used full rpm (2620) but at the cost of another gph or so. This is more fuel than I want to use, considering that 140-142 KTAS was subsequently realized at the same altitude at full throttle, 2400 rpm, 20-25 deg LOP at 12.3 gph. In both cases CHTs were at or below 360 degrees even though it was a rather warm day.

              Kevin Moore
              Former 260se/stol Katmai with BRS owner; planeless for now
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              • #8
                One more data point

                I was flying on Saturday to Madison, WI and back with light winds at 5000.

                24", 2400rpm, 14 gph = 141-142 knots in my 260se.

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                • #9
                  Originally posted by russe View Post
                  I was flying on Saturday to Madison, WI and back with light winds at 5000.

                  24", 2400rpm, 14 gph = 141-142 knots in my 260se.
                  Hmm, lessee here, 24" would be full throttle at 5000 feet, I think. Assuming something like 60 deg F OAT, 141-142 KTAS would be ~130 indicated airspeed. OAT was...? Not sure what I would get in such circumstances but I can have a look next time the opportunity presents itself.

                  2400 rpm vs. my 2530 would likely make at least a 1 gph difference, perhaps a bit more. Moreover, I suspect you lean more aggressively than I. At these settings you're definitely rich of peak, but I'm not sure how much rich of peak. I'll WAG and say 75-100 degrees ROP. Based on my past experience, were I full throttle, 2400 rpm rich of peak at ~5000 feet I'd be pumping at least 15, maybe 15.5 gph through the engine. Norm, what's your experience?

                  Another thing to consider, about three years ago I had my Katmai's rigging adjusted by a CPA-trained rigger. It made a difference in cruise speed as described here.
                  Kevin Moore
                  Former 260se/stol Katmai with BRS owner; planeless for now
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                  • #10
                    Yes but no pretty pictures like Kevin's.

                    Glen

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                    • #11
                      Some examples from today

                      Originally posted by russe View Post
                      I was flying on Saturday to Madison, WI and back with light winds at 5000.

                      24", 2400rpm, 14 gph = 141-142 knots in my 260se.
                      I went out for a Mental Health Flight today and enjoyed converting about 120 lb of dinosaur reduction to noise and carbon dioxide. It felt good.

                      I took the opportunity to try to approximate russe's power settings at 4500 and 5500 feet (VFR). As you can see from the OATs it was a warm day aloft.

                      At 5500 feet (density altitude ~6800 feet) I used full throttle, 2400 rpm, and leaned to ~150 deg ROP for best power (hottest EGT was ~1380). CHTs were all 370 or below. This resulted in a higher fuel flow than I expected, a few tenths over 16 gph! At this ROP setting, I was getting 146-148 KTAS, see below for representative data:



                      Without changing anything else, I dialed back to 15-20 deg LOP, fuel flow was only 12.2-12.3 gph and 140-142 KTAS. I like this better...



                      On the way home I set it up at 4500 feet (density altitude ~5900 feet) along the same lines. Now ROP was just a few tenths under 17 gph for 147-149 KTAS:



                      Once again LOP (12.5-12.6 gph) was a much nicer place to be:



                      Not sure what to make of russe's 14 gph fuel flow, in my airplane today that would have been ROP but much closer to peak than my 150 deg ROP and would not have been the optimal mixture setting for best power ROP for sure. It may be that russe's engine is running differently from mine in some way (mag timing?) but that's just ignorant speculation on my part. In any case his reported speeds are similar to what I saw today (and usually) when running lean of peak.
                      Kevin Moore
                      Former 260se/stol Katmai with BRS owner; planeless for now
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                      • #12
                        A few things to remember.

                        Flying higher reduces drag so one almost never gets max cruise speed down low. Fly as high as you can while still pulling around 75% power, normally this seems to be around 7,000 ft. Everyone is also right in that fuel equates to speed. I don't think I've seen an IO-470 being run hard that doesn't take 15 - 16 gph at 7,000 ft on a warm day. One could run with the cowl flaps open and lean more aggresively but then again that creates drag and also lowers cruise speed. Of course rigging comes into play and without the airplane being properly rigged it will never achieve its best speed. The biggest factor is one we have no control over. That is how the airplane was originally built at the factory. Some airplanes just come out faster than others and there really isn't anything one can do about it. It's all in how the airplane was built and some are just a little straighter than others. I've had two superb airplanes neither of which were all that fast but they were really great airplanes.

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                        • #13
                          Lean of peak in coldish temps

                          From this past Sunday: 4500 feet, 35 deg F, 2530 rpm, full throttle, 30-35 deg LOP, about 13.2 gph.



                          A really beautiful day with occasional light chop!



                          Kevin Moore
                          Former 260se/stol Katmai with BRS owner; planeless for now
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                          • #14
                            Katmai/King Katmai spec sheet

                            From my article in the Jan. 2010 issue of CPA magazine. The full article is available as a pdf in the downloads section of Todd's website. Stated useful loads are conservative; useful loads of up to 1300 lb and full-fuel payloads near or above 800 lb can be realized on lightly or moderately optioned airframes.

                            Kevin Moore
                            Former 260se/stol Katmai with BRS owner; planeless for now
                            sigpic

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                            • #15
                              With all of the excitement surrounding PPP's King Katmai & Kenai with 300 hp IO-550, this thread shows that the IO-470 in the older 260se/stol and Katmai models is no slouch either and a very efficient performer.
                              Kevin Moore
                              Former 260se/stol Katmai with BRS owner; planeless for now
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