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weird fan sound -- intentional?

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    weird fan sound -- intentional?

    just finally got around to installing the new versions of everything..


    I just noticed i get a weird rhythmic clicking sound (brrrrrrrrrrrr), sounds like a blower fan or soemthing.. reminds me of putting cards in spokes of biccyle wheels as a kid.. its pretty subtle but noticable at quiet times

    if i'm not mistaken the 747's do it also
    Mike Teague - p3dv4.5 - B736 B737 B738 B739 B77L B77W B744 B748

    #2
    The fan switch is upper right of pressurization panel, depending on 737 variant and 747. The recirculation fan on the 747 is upper right of A/C panel and is quite loud when used. Only needs to be used when there is smoke or high temps.


    Dan Downs KCRP
    i7-10700K 32GB 3600MHz 1080Ti

    Comment


      #3
      its not the recirc fan making the sound i'll try to narrow it down
      Mike Teague - p3dv4.5 - B736 B737 B738 B739 B77L B77W B744 B748

      Comment


        #4
        Mike,

        Maybe it's the analog standby altimeter? Go to equipment options and see if you have the analog standby instruments installed. If so, switch to ISFD and see if the noise stops.
        Mike Roth

        Comment


        • DDowns
          DDowns commented
          Editing a comment
          I overlooked his description of clicking sound. I bet you nailed it Mike.

        #5
        ok if i start cold & dark, its something on the battery bus
        Mike Teague - p3dv4.5 - B736 B737 B738 B739 B77L B77W B744 B748

        Comment


        • DDowns
          DDowns commented
          Editing a comment
          See Mike's post one minute before yours.

        #6
        Originally posted by Chaos81 View Post
        Mike,

        Maybe it's the analog standby altimeter? Go to equipment options and see if you have the analog standby instruments installed. If so, switch to ISFD and see if the noise stops.
        wow. yep that is it

        isfd is silent
        Mike Teague - p3dv4.5 - B736 B737 B738 B739 B77L B77W B744 B748

        Comment


          #7
          heres what i was talkin about anyway

          https://imgur.com/pad1X5F
          Mike Teague - p3dv4.5 - B736 B737 B738 B739 B77L B77W B744 B748

          Comment


            #8
            It's the gyros in the stby attitude indicator. Yes, it's really that loud ..
            Regards,
            Eric Hill

            Comment


              #9
              Originally posted by MCAchief View Post
              It's the gyros in the stby attitude indicator. Yes, it's really that loud ..
              I always thought it was a vibrator that made a square wave out of DC for the gyro motor. Gyros do not make a clicking sound, they spin.
              Dan Downs KCRP
              i7-10700K 32GB 3600MHz 1080Ti

              Comment


                #10
                Originally posted by MCAchief View Post
                It's the gyros in the stby attitude indicator. Yes, it's really that loud ..

                It's actually as Dan says above my post. The gyros don't make the sound, it's the vibrator in the altimeter.
                Some captains in the old planes tended to pull the CB of that vibrator..... (no comment on that, if you're reading this: Never pull a CB unless instructed by a checklist or by maintenance!) you could see the difference instantly on the standby altimeter when climbing or descending. The needle would constantly get stuck somewhere and then jump a couple hundret feet up/down before getting stuck again, so that thing definitely has its sense.
                Nowadays we luckily only have ISFD equipped planes anymore so that thing is not an issue for me anylonger.
                It was darn annoying I can tell you though...

                Comment


                  #11
                  Originally posted by Emi View Post


                  It's actually as Dan says above my post. The gyros don't make the sound, it's the vibrator in the altimeter.
                  Some captains in the old planes tended to pull the CB of that vibrator..... (no comment on that, if you're reading this: Never pull a CB unless instructed by a checklist or by maintenance!) you could see the difference instantly on the standby altimeter when climbing or descending. The needle would constantly get stuck somewhere and then jump a couple hundret feet up/down before getting stuck again, so that thing definitely has its sense.
                  Nowadays we luckily only have ISFD equipped planes anymore so that thing is not an issue for me anylonger.
                  It was darn annoying I can tell you though...
                  This is interesting.. The other day I saw this video from a 744 and was wondering why the stby alt would do this...Do you think the Captain pulled the CB here or is this normal instrument behaviour ?

                  watch for example from 10:00 on:
                  https://www.youtube.com/watch?v=P6mvYyyMHV0
                  Manolo Ruiz Carrió

                  Comment


                    #12
                    Originally posted by Sekkha View Post

                    This is interesting.. The other day I saw this video from a 744 and was wondering why the stby alt would do this...Do you think the Captain pulled the CB here or is this normal instrument behaviour ?

                    watch for example from 10:00 on:
                    https://www.youtube.com/watch?v=P6mvYyyMHV0
                    I can't comment on the 747 (would love to be able to though!), but that looks pretty much like a 737 with a popped CB.
                    Maybe it's by design in the 747 as I recall never hearing that sound in it, I don't know. That'd be a question for a 747 driver.

                    Comment


                      #13
                      Originally posted by Sekkha View Post

                      This is interesting.. The other day I saw this video from a 744 and was wondering why the stby alt would do this...Do you think the Captain pulled the CB here or is this normal instrument behaviour ?

                      watch for example from 10:00 on:
                      https://www.youtube.com/watch?v=P6mvYyyMHV0
                      If the vibrator is on (as it should be), the needle is indeed sticking excessively. This is an inherent problem with all mechanical altimeters. As they age, the internal gears can bind slightly - mainly due to the lubricants drying out. There is a specific test for this as part of the recertification tests required for all altimeters very 24 months. Below 10,000 feet, the maximum “jump” allowed (if the needle sticks and then releases) is 70 feet. The allowable change increases at higher altitudes.

                      Unless a flight crew specifically writes up
                      a standby altimeter for excessive friction, it probably won’t be caught until the next scheduled recertification test. On the other hand, if they pulled the vibrator circuit breaker all bets are off, but that is not something pilots should be doing.
                      Jim Barrett - KELM

                      Comment


                        #14
                        Vibrator makes sense. I believe I was misled some time ago by an "instructor". They probably, like me, associated it with the grinding in an old electric turn coordinator.
                        Regards,
                        Eric Hill

                        Comment


                          #15
                          Originally posted by Chaos81 View Post
                          Mike,

                          Maybe it's the analog standby altimeter? Go to equipment options and see if you have the analog standby instruments installed. If so, switch to ISFD and see if the noise stops.
                          Thanks that fixed it for me as well...

                          So next question, is this a bug in the latest build? I didn't have the problem until I did the latest update. I've always used the analog backup instruments.

                          Dave Weese

                          Comment


                            #16
                            Originally posted by CXA007 View Post

                            Thanks that fixed it for me as well...

                            So next question, is this a bug in the latest build? I didn't have the problem until I did the latest update. I've always used the analog backup instruments.
                            This isn't a bug. The analog instrument is really loud. I am guessing that that the sound was updated during the last round.
                            Michael Sill

                            Comment


                              #17
                              Indeed the sound was much too quiet previously. It sounds about right now I'd say.

                              Comment

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