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    CLB power

    On most flights when calculating performance with the EFB, it gives me a derate takeoff with CLB 1 or 2 climb performance.

    I accurately enter all the details into the FMC and it shows me that either CLB 1 or CMB 2 is armed.

    After takeoff at 1000ft, CLB 1 or CLB 2 is correctly annunciated on the EICAS. However at roughly 12,000ft, it always changes to CLB. Is this correct?

    I assumed it would stay in CLB 1 or CLB 2 all the way up to cruise altitude.
    Ben Briscoe

    #2
    12,000 is the default washout altitude I believe
    Michael Sill

    Comment


    • DrJ1
      DrJ1 commented
      Editing a comment
      Its right there where it has always been for 140 posts Dan. Please take a look before you set out to comment in this manner

    • DDowns
      DDowns commented
      Editing a comment
      Man, it wasn't there when I made the comment. I mean it is now as plain as day, so much so that I couldn't have missed it. So, we're all good.

    • DrJ1
      DrJ1 commented
      Editing a comment
      Now if I didn't know any better, I would swear that was a backhanded comment seemingly indicating that I didn't add my name until after you posted your comment. Can't be true, cause surely I would have been asked to add it in one of my previous posts had it not been there prior... Yeah we're good now

    #3
    Originally posted by BWBriscoe View Post
    On most flights when calculating performance with the EFB, it gives me a derate takeoff with CLB 1 or 2 climb performance.

    I accurately enter all the details into the FMC and it shows me that either CLB 1 or CMB 2 is armed.

    After takeoff at 1000ft, CLB 1 or CLB 2 is correctly annunciated on the EICAS. However at roughly 12,000ft, it always changes to CLB. Is this correct?

    I assumed it would stay in CLB 1 or CLB 2 all the way up to cruise altitude.
    Yes, this is correct. As the air density decreases the engines create less thrust so nature takes over as the thrust limit. You also have an option on some types to transition at either 12,000 or 30,000 and that is usually just a company option not available to the pilot.
    Dan Downs KCRP
    i7-10700K 32GB 3600MHz 2080Ti

    Comment


      #4
      Originally posted by BWBriscoe View Post
      On most flights when calculating performance with the EFB, it gives me a derate takeoff with CLB 1 or 2 climb performance.

      I accurately enter all the details into the FMC and it shows me that either CLB 1 or CMB 2 is armed.

      After takeoff at 1000ft, CLB 1 or CLB 2 is correctly annunciated on the EICAS. However at roughly 12,000ft, it always changes to CLB. Is this correct?

      I assumed it would stay in CLB 1 or CLB 2 all the way up to cruise altitude.
      It’s commonly referred to to as the washout altitude and on the B777 family is either 12,000ft or 30,000ft (static port derived pressure altitude).

      The 12,000ft washout begins at 10,000 until thrust reference changes to full CLB at 12,000ft
      The 30,000ft washout begins at 10,000 until thrust reference changes to full CLB at 30,000ft

      GE and PW have typically been advocates of the lower washout as the shorter time to TOC and lower fuel burn required offset higher engine overhaul/maintenance costs.

      RR has typically advocated for the higher washout as the longer time to TOC and higher fuel burn are offset by lower engine overhaul/maintenance costs.

      Ultimately this all depends on the structure of engine ownership and overhaul costs etc.

      Off the top of my head below are some of the B777 operators with the 30,000ft washout.

      Cathay Pacific : B773, B77W
      Qatar Airways: B77L, B77W
      British Airways: -200ER G-YMMR/S/T/U only.
      Last edited by Calzonister; 20Mar2021, 02:37.
      Leo Cal

      Comment


        #5
        Thanks guys, really interesting.
        Ben Briscoe

        Comment


          #6
          If the climb performance is less than 500 fpm, the derate will be moved to one level up.
          Philip Kong

          Comment


            #7
            Originally posted by Calzonister View Post

            It’s commonly referred to to as the washout altitude and on the B777 family is either 12,000ft or 30,000ft (static port derived pressure altitude).

            The 12,000ft washout begins at 10,000 until thrust reference changes to full CLB at 12,000ft
            The 30,000ft washout begins at 10,000 until thrust reference changes to full CLB at 30,000ft

            GE and PW have typically been advocates of the lower washout as the shorter time to TOC and lower fuel burn required offset higher engine overhaul/maintenance costs.

            RR has typically advocated for the higher washout as the longer time to TOC and higher fuel burn are offset by lower engine overhaul/maintenance costs.

            Ultimately this all depends on the structure of engine ownership and overhaul costs etc.

            Off the top of my head below are some of the B777 operators with the 30,000ft washout.

            Cathay Pacific : B773, B77W
            Qatar Airways: B77L, B77W
            British Airways: -200ER G-YMMR/S/U only.
            Very interesting, especially the 777 operators off the top of your head, even specific airframes!

            I just took a dive into your other replies and answers on other threads. Awesome stuff.

            William Ezzell
            KATL

            Comment

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