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Engine spool dynamics for the NGX

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    Engine spool dynamics for the NGX

    I've linked a thread from when the NGXu came out regarding a comparison between the sim and real world behavior of jet engines, namely the cfm56. Im just curious if any improvement has been made to this with the NG3 for msfs? judging by the streams of the beta (yes I know its a beta) it looks like this particular area has not improved from the ngxu p3d version. Since this old thread, pmdg had released the 777-200ER for P3D which does a much better job of simulating the type of behavior showcased in the video, so its obviously possible.

    The thread:
    https://forum.pmdg.com/forum/main-fo...spool-dynamics
    Last edited by Pilot53; 14Aug2022, 15:56.
    -Mike Iacovetta

    #2
    I assume you're asking about the NG3 rather than the NGX since the NGX isn't even P3D V5 compatible, let alone MSFS compatible.
    Captain Kevin

    Kevin Yang

    Comment


      #3
      Originally posted by Captain Kevin View Post
      I assume you're asking about the NG3 rather than the NGX since the NGX isn't even P3D V5 compatible, let alone MSFS compatible.
      Yeah NG3 my bad whoops lol
      -Mike Iacovetta

      Comment


        #4
        While I am not 100% whether Mike is talking about the same thing as me but I do find the NGXu’s CFM56’s to be spooling up a lot faster than the real thing. That is especially noticeable when doing a config check. In the real thing moving the thrust lever quickly forward and backward barely spools up the engines while in the sim the engines react very quickly.

        And also during engine start the N1 usually only starts to rotate a lot later than in the sim. In real life the N1 is taking quite a bit to start rotating, around 15-18 % N2 when the N1 would reach around 1%

        I wish this was ever corrected as they both been never corrected
        Balint

        Comment


          #5
          Agreed, spool time from ground idle to roughly 40% was always too fast in the previous sims. It was like the acceleration time was linear across the whole power band, which isn't the case in reality.

          Kind of a minor point for most of the operating range though as spool time is pretty good once above 40%. But yep would be nice to see an improvement there.
          Andrew Crowley

          Comment


            #6
            Honestly it doesn't seem to be fixed and yet PMDG still says it does listen to people and make great products. This was reported over 3 years ago and not a single response regarding the issue from the dev/support team. Kinda outlines their agenda to be honest...
            Alp Deniz Senyurt

            Comment


            • teddinator
              teddinator commented
              Editing a comment
              Not to mention the poor guy who reported it got mocked by Robert. That was a cringe worthy moment.

            #7
            Good job posting this. You've got guts, OP. I thought about posting about it but couldn't.

            Doesn't look like there's any improvement in this area in NG3.

            Also missing from the simulation is the fact that EGT drops when the engine stabilises.
            Having seen a recent incident involving Chris demanding a Latino folk to see his government issued ID to verify his real name, I've changed my mind about using my real name on a public forum due to privacy concerns. I hope one day PMDG will learn to respect customer's privacy and allow anonymous posting. Until then, take down my posts if you must, as I do not wish to participate in this forum any longer. Farewell my friends.

            Comment


              #8
              Gents,

              Thank you for your input. The engineering data against which the spool models are built comes directly from the engineering specification of the certified simulator for the engine type. Off the top of my head I don't know which specific EEC module or engine core was used as the basis for the certification data as it isn't something you retain in memory for no reason.

              I have asked Dr. EV to take another look at our engineering data here. Given current workloads it unlikely to happen before late summer.


              Robert S. Randazzo
              PMDG Simulations
              http://www.pmdg.com


              Comment


              • teddinator
                teddinator commented
                Editing a comment
                Thanks Robert. That's understandable. The sim is more than good enough at it is, but you know how us armchair pilots are like

                If any doubt, the following post on avsim has a couple YouTube videos showing engine spooling behaviour and EGT behaviour at 40% N1. There are other videos on YouTube showing exactly that, of course.

                Hello, I was wondering something, Before we give TOGA we usually give 40% N1 to see if stable and as far as I recall once N1 has reached stable 40% the EGT decreases which makes it stable then we give TOGA. Can anyone confirm this? I looked at many videos online and I see the EGT decreasing befor...

              • Stearmandriver
                Stearmandriver commented
                Editing a comment
                Crabby, the spool time from ground idle to 40% WAS much too fast in the NGx. I'm pretty sure I read the NGXu was the same, but I've never used P3d. But this isn't a make-believe issue, if the same spool time made it into the NG3.

                It IS, however, an incredibly minor issue that doesn't really operationally affect anything in a significant way. I don't personally care about it; just throwing out data.

              • Pilot53
                Pilot53 commented
                Editing a comment
                Crabby, maybe if you actually took the time to read the post that I linked you would realize this behavior has been verified by at least two real world current NG pilots, but no, dont do that, just keep on making bad jokes that contribute nothing instead.

              #9
              Originally posted by rsrandazzo View Post
              Gents,

              Thank you for your input. The engineering data against which the spool models are built comes directly from the engineering specification of the certified simulator for the engine type. Off the top of my head I don't know which specific EEC module or engine core was used as the basis for the certification data as it isn't something you retain in memory for no reason.

              I have asked Dr. EV to take another look at our engineering data here. Given current workloads it unlikely to happen before late summer.

              Just curious, I know the team has their hands full with the -800 and the EFB, but has this been looked into at all?
              -Mike Iacovetta

              Comment


                #10
                Mike

                Spool times were actually changed in one of the more recent updates to more accurately reflect the lag to 40% so it is much closer to how the real thing behaves.
                Paul Gollnick
                PMDG Technical Support
                Support.PMDG.com

                Comment


                  #11
                  Originally posted by Jet Tech View Post
                  Mike

                  Spool times were actually changed in one of the more recent updates to more accurately reflect the lag to 40% so it is much closer to how the real thing behaves.
                  If you follow the procedure and bring the engines to 40% before applying takeoff power it works almost like the real thing, but if you skip that step and firewall the throttles the engine spool up to full power in just a second or two which is exactly opposite of how they should behave. In the real aircraft if you advance the throttles to full power without letting them stabilize at 40% they actually take longer to spool. There should also be an egt overshoot when the engines stabilize that is not there currently. When advancing the throttles for a just a second to test the config warning the engines will spool up to 35% right away, they should take much longer to respond.
                  -Mike Iacovetta

                  Comment


                    #12
                    I submitted a ticket on this, hopefully it can get looked into further.
                    -Mike Iacovetta

                    Comment


                      #13
                      I found this thread interestingly enough because I notice that in the PMDG aircraft, it is a bit difficult to do the pre-takeoff check of exercising the throttles in order to see if you get the config horn- the PMDG aircraft's thrust will increase. In the real aircraft you can easily go idle-firewall-idle quickly with no real result in thrust. Not sure if that observation makes sense, Emi probably understands what I mean! However, it is not a very big deal - probably a sim limitation. And maybe the sim is based off a different EEC software than what I fly out in the world.
                      Brendan R

                      Comment


                        #14
                        Originally posted by bjratchf View Post
                        I found this thread interestingly enough because I notice that in the PMDG aircraft, it is a bit difficult to do the pre-takeoff check of exercising the throttles in order to see if you get the config horn- the PMDG aircraft's thrust will increase. In the real aircraft you can easily go idle-firewall-idle quickly with no real result in thrust. Not sure if that observation makes sense, Emi probably understands what I mean! However, it is not a very big deal - probably a sim limitation. And maybe the sim is based off a different EEC software than what I fly out in the world.
                        Indeed a sim limitation, I pushed the devs really hard on this but it was just not possible.

                        Comment


                        • meurkel
                          meurkel commented
                          Editing a comment
                          But how exactly does the sim limit you in that regard? FBW created their own engine model from scratch and they never mentioned any sim limitations.

                        #15
                        Originally posted by Emi View Post

                        Indeed a sim limitation, I pushed the devs really hard on this but it was just not possible.
                        I wonder how fenix and fbw got around this in their a320s because the behavior is correct in this scenario. I know its a different airplane and engine in the case of the neo but the behavior is very similar in this regard between models.
                        -Mike Iacovetta

                        Comment


                          #16
                          Originally posted by Pilot53 View Post

                          I wonder how fenix and fbw got around this in their a320s because the behavior is correct in this scenario. I know its a different airplane and engine in the case of the neo but the behavior is very similar in this regard between models.
                          I wonder too...
                          Thomas Allensworth,
                          KCRQ
                          Carlsbad
                          Cessna 310R and PMDG enjoyer

                          Comment


                            #17
                            Originally posted by Pilot53 View Post

                            I wonder how fenix and fbw got around this in their a320s because the behavior is correct in this scenario. I know its a different airplane and engine in the case of the neo but the behavior is very similar in this regard between models.
                            I assume it‘s one of the technical reason why neither Fenix nor FBW will be available for xbox.
                            Ryzen 9 5900X, RX 6900XT, 32GB DDR4 RAM @3600MHz, 4k
                            Marc Eland
                            GFO Beta

                            Comment


                            • DDowns
                              DDowns commented
                              Editing a comment
                              Are they not running their simulations outside of MSFS completely except for visuals and control interfaces?

                            • Ephedrin
                              Ephedrin commented
                              Editing a comment
                              I think so. But that would probably give them unlimited freedom of how they model their engines while I think PMDG has to tweak within the cfg files of MSFS. But, of course, that's all nothing but an assumption.

                            #18
                            Originally posted by Ephedrin View Post

                            I assume it‘s one of the technical reason why neither Fenix nor FBW will be available for xbox.
                            I would be a bit surprised if this was the reason, Robert has said many times that making the aircraft compatible with xbox would not be allowed to compromise the fidelity of the simulation.
                            -Mike Iacovetta

                            Comment

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