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BLEED TRIP OFF during the "pack off" takeoff

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    BLEED TRIP OFF during the "pack off" takeoff

    Hi all,
    I have a question about the 737.

    I took of today with a rather full plane so I have decided for a "packs off" takeoff. During the takeoff roll, I recieved the "Bleed Trip Off" master caution, hence I have rejected and by QRH pressed the "Trip reset" button - the light extinguished, checklist done. I lined up for another try - and again (this time I just ignored it). It was rather hot outside (33 degrees).

    My question is - is this a usual (or at least expected, given the conditions) thing? Should I not use the "packs off" takeoff at hot weather? Is there something to prevent this? Finally - is this a reason to reject the takeoff (apriori it should be - it is a master caution, right?)

    Thanks, Jan



    Jan Vysoký


    #2
    How fast were you going when the warning came up. Looking at another website, somebody said above 80 knots and prior to V1, you would only stop for fire or fire warning, engine failure, predictive windshear warning, or if the Captain doesn't think the plane's going to fly, so it sounds like if you were above 80 knots, this wouldn't be a reason to reject the take-off.
    Captain Kevin

    Kevin Yang

    Comment


      #3
      Originally posted by vysous View Post
      Hi all,
      I have a question about the 737.

      I took of today with a rather full plane so I have decided for a "packs off" takeoff. During the takeoff roll, I recieved the "Bleed Trip Off" master caution, hence I have rejected and by QRH pressed the "Trip reset" button - the light extinguished, checklist done. I lined up for another try - and again (this time I just ignored it). It was rather hot outside (33 degrees).

      My question is - is this a usual (or at least expected, given the conditions) thing? Should I not use the "packs off" takeoff at hot weather? Is there something to prevent this? Finally - is this a reason to reject the takeoff (apriori it should be - it is a master caution, right?)

      Thanks, Jan


      Hi.

      This is a rather nuisance warning that is more likely to happen on a bleeds-off takeoff. It is caused by an over pressure sensed at the bleed air valve which trips the valve off. When reducing the power and doing a trip reset this warning will most likely immediately be reset. Below 80 knots you should stop for any reason including this issue, however it is likely to happen on any of your bleeds off takeoffs so if you are aware of this light coming on it is probably safe to just continue your takeoff. When configuring your pressurization panel after departure and running your non normal checklist (trip reset) the fault should clear.
      Balint

      Comment


        #4
        There's no such thing like packs-off takeoff on 737. Incorrect aircraft configuration was likely the cause of the master caution. Please share how did you configure aircraft for takeoff.

        Pack trip off is rather common issue on 737, especially during engine start in hot conditions. Only way to prevent the issue it provide cooled air so temperature in duct won't exceed 90degrees celsius *.
        As Balint said, you should reject takeoff below 80 kts for any reason (for example master caution light comes on) and above 80 only if engine fire/failure or aircraft is unable or unsafe to fly (up to your interpretation what unable or unsafe means).

        Worth reading: http://www.b737.org.uk/airconditioning.htm
        Last edited by Dzosef; 19Feb2021, 00:41.
        Matthew Chalupniczak

        Comment


          #5
          I believe you intended to do a no bleed take-off
          Regards,
          Eric Hill

          Comment


            #6
            What you wanted to do was, I believe, Engine Bleeds off, Apu on, Apu bleed on, packs on/auto, isolation valve open. This is from memory, could be I mix it up with other aircraft, but I believe that‘s how it‘s done. Packs off is 747.
            Ryzen 9 5900X, RX 6900XT, 32GB DDR4 RAM @3600MHz, 4k
            Marc Eland
            GFO Beta

            Comment


              #7
              Originally posted by Dzosef View Post
              There's no such thing like packs-off takeoff on 737. Incorrect aircraft configuration was likely the cause of the master caution. Please share how did you configure aircraft for takeoff.

              Pack trip off is rather common issue on 737, especially during engine start in hot conditions. Only way to prevent the issue it provide cooled air so temperature in duct won't exceed 90degrees celsius *.
              As Balint said, you should reject takeoff below 80 kts for any reason (for example master caution light comes on) and above 80 only if engine fire/failure or aircraft is unable or unsafe to fly (up to your interpretation what unable or unsafe means).

              Worth reading: http://www.b737.org.uk/airconditioning.htm
              And this is precisely the reason why there are type ratings, right? :-)) I got the warning under 80, so definitely I should have stopped.
              Jan Vysoký

              Comment


                #8
                Originally posted by Ephedrin View Post
                What you wanted to do was, I believe, Engine Bleeds off, Apu on, Apu bleed on, packs on/auto, isolation valve open. This is from memory, could be I mix it up with other aircraft, but I believe that‘s how it‘s done. Packs off is 747.
                Yeah, you are almost right, except (see FCOM SP 2.7) the isolation valve should be closed. But thanks anyway - I did it wrong aaaaall the time (I just turned off the packs, as you would do on A320, for example). This is the downside of flying so many different types
                Jan Vysoký

                Comment


                • Ephedrin
                  Ephedrin commented
                  Editing a comment
                  Haha thx...

                #9
                If you follow the FCOM Supplementary Procedure for the No Engine Bleed Takeoff and Landing it won't happen again. Be careful during the after take off part of the procedure and do every step slowly to avoid discomfort (Changing bleed source in flight in the real airplane makes a pop).
                Omar Josef
                737 FO
                757/767 rated
                Spain

                Comment


                  #10
                  Originally posted by Aeromar View Post
                  If you follow the FCOM Supplementary Procedure for the No Engine Bleed Takeoff and Landing it won't happen again. Be careful during the after take off part of the procedure and do every step slowly to avoid discomfort (Changing bleed source in flight in the real airplane makes a pop).
                  I did see it one or two times in the PMDG BBJ when taking off at high altitude airports like Quito or Jackson Hole though when using the 27k bump and a No Engine Bleed takeoff.
                  Never had it in real life but maybe there's a difference between our 26k engines and the 27k bump engines.

                  Anyway Jan, if you know it's coming you can anticipate it and cancel the warning, reset the system in the air and keep going. Personally I have a feeling the NGXu might be a bit oversensitive, but as my airline has different engine ratings and we don't fly to high altitude airports I can not make any definitive comment as to whether you might expect this or not.

                  Comment


                    #11
                    Originally posted by Emi View Post

                    I did see it one or two times in the PMDG BBJ when taking off at high altitude airports like Quito or Jackson Hole though when using the 27k bump and a No Engine Bleed takeoff.
                    Never had it in real life but maybe there's a difference between our 26k engines and the 27k bump engines.

                    Anyway Jan, if you know it's coming you can anticipate it and cancel the warning, reset the system in the air and keep going. Personally I have a feeling the NGXu might be a bit oversensitive, but as my airline has different engine ratings and we don't fly to high altitude airports I can not make any definitive comment as to whether you might expect this or not.
                    I did a couple no bleeds takeoffs during line training and I don't remember master cautions.
                    Omar Josef
                    737 FO
                    757/767 rated
                    Spain

                    Comment


                      #12
                      Originally posted by Aeromar View Post

                      I did a couple no bleeds takeoffs during line training and I don't remember master cautions.
                      On our fleet I did a couple as well already and never got master cautions, but since we don't have the 27k bump, which I could imagine to play a role here, I don't really want to comment on that part.

                      Comment


                        #13
                        I am having this issue right now. on the engine 2 bleed.. The only way I can remedy it and get rid of the bleed trip warning is to shut off the bleed for Forums in flight.. How can I fix this?
                        Jason Saucier

                        Comment


                          #14
                          It's not real uncommon for us to do a bleeds off takeoff, especially full out of Maui or Lihue. Typically these will be 27k bump takeoffs in an -800, since our priority order for achieving good takeoff data is to use bleeds off as a last resort, so we'll bump the thrust first. (They're usually flaps 25 as well.) I've never once seen a master caution associated with the procedure.

                          My teaching slogan for high-speed abort reasons has always been "fire, failure, shear or fear." (Fear being any concern that the airplane may not fly.)
                          Andrew Crowley

                          Comment


                            #15
                            Originally posted by Stearmandriver View Post
                            My teaching slogan for high-speed abort reasons has always been "fire, failure, shear or fear." (Fear being any concern that the airplane may not fly.)
                            Shear being windshear or something else.
                            Captain Kevin

                            Kevin Yang

                            Comment


                            #16
                            Originally posted by Stearmandriver View Post
                            It's not real uncommon for us to do a bleeds off takeoff, especially full out of Maui or Lihue. Typically these will be 27k bump takeoffs in an -800, since our priority order for achieving good takeoff data is to use bleeds off as a last resort, so we'll bump the thrust first. (They're usually flaps 25 as well.) I've never once seen a master caution associated with the procedure.

                            My teaching slogan for high-speed abort reasons has always been "fire, failure, shear or fear." (Fear being any concern that the airplane may not fly.)
                            What about all the numerous flights out of PHX where it stays so hot.. And its not sea level.. Do you guys do packs off takeoffs there ?
                            Jason Saucier

                            Comment


                            • DDowns
                              DDowns commented
                              Editing a comment
                              PHX has long runways, neither PHOG nor PHLI do. Just a couple thousand feet makes a difference.

                            • Stearmandriver
                              Stearmandriver commented
                              Editing a comment
                              Yeah like Dan said, long runways there. It might happen sometimes, I can't remember if I've personally ever done it. This isn't some sort of noteworthy abnormal procedure or anything, just a normal procedure you'll do when the takeoff data requires it. It's not super common, but there's nothing special about it.
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