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Typical cruise altitude

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    Typical cruise altitude

    Hi,
    What is a typical cruise altitude for the DC6? Using simbrief, it usually calculates 12,000 - 14,000 ft as optimal, and if I will manually select 20,000 for example, significantly more fuel will be required.
    What was realistic typical cruise altitudes for a DC6? I read somewhere is was in the 12-14k ft indeed as that was more fuel efficient, and it would fly higher to overfly weather.
    But then again, I WANT to shift the super chargers!
    What are the rules of thumb here?
    Oren Geva

    #2
    The rule of thumb is that as you go higher the fuel consumption per nm increases. However, it is a balance between fuel cost and time that is now called the cost index (CI) but that came later in FMS equipped aircraft. The only reason to go above 14000 is terrain avoidance or favorable tail winds (which MSFS cannot simulate yet), and the significance of 14000 is that on a standard day this is where the density of the air is half that of sea level. It's a nice compromise between economy and speed.

    My PAA Operations manual lists routes and optimum power settings and back then they used 1100 BHP and pretty much stayed below 16000. A Canada Air youTube video was posted here yesterday of a DC-6 flight Vancouver-Tokyo and that Captain said they fly West at 8, 10 ,12 or 14,000 and the video indicate power setting of about 1200 BHP.

    The significant limitation is supercharging. Unlike a turbocharger, the supercharger takes power directly from the engine and the power required goes up significantly as the density of the air decreases. The typical critical altitude where you change from LO to HI speed blower of 16000, you are literally shifting gears and taking a lot more power from the engine.

    As far as over-flying weather, the consideration is more about avoiding ice and turbulence or of course CB's than staying in clear air. Simply put, not even jets avoid CBs by going higher, you go around them.
    Dan Downs KCRP
    i7-10700K 32GB 3600MHz 2080Ti

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    • bobsk8
      bobsk8 commented
      Editing a comment
      This info should be a sticky.

    • Bolton
      Bolton commented
      Editing a comment
      Brilliant post !!!!

    • Swagger897
      Swagger897 commented
      Editing a comment
      Why exactly can’t msfs simulate tail winds now?

    #3
    In many old accident reports regarding the DC-6, the cruise altitude was 18.000/21.000ft.
    http://www.baaa-acro.com/search-resu...ne=dc-6&page=0
    Claudio Rampini

    Comment


      #4
      Interesting reading............thanks for posting this link.

      Also thanks to Dan for his interesting post.
      Last edited by Hollister56; 13Sep2021, 17:50.
      Ed Grabel

      Comment


        #5
        Thanks DDowns , that was enlightening.
        Oren Geva

        Comment


          #6
          in addition to Dan's explanation:

          If the temperatures are low you can use auto lean fuel without overheating your engines which allows higher altitudes using the high blower and still getting the fuel flow down to 580 gph/engine with a still satisfying ground speed. But if it's warm there is no benefit in climbing higher and heating up yor engines, keep the fuel rich and your engine temps at 200. Fly slower at 160-180 kias at FL140-150 but save money by saving engines. I found 31MAP/140BMEP a perfect power setting.
          i7-6700k, GTX 1080TI, 32GB DDR4 RAM @2666MHz, 4k
          Marc Ehnle

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            #7
            Originally posted by Claudius View Post
            In many old accident reports regarding the DC-6, the cruise altitude was 18.000/21.000ft.
            http://www.baaa-acro.com/search-resu...ne=dc-6&page=0
            What a treasure trove of information. Thanks for the link
            I can see myself spending quite some time going over all the DC6 accidents.

            Lance Gomes
            Lance Gomes

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