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A/T light flashing

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    A/T light flashing

    Hi,

    I've noticed since flying the NGXu in v5, I seem to always get the yellow A/T push to reset button flashing whenever I set flaps and bug the speed to the selected flap setting when decelerating. It's my understanding that it should do this if the aircraft cannot decelerate at idle power to the selected speed (not sure if my understanding of that is fully correct?) but for me it happens every flight, when I select flaps for deceleration.

    Can see here in the picture as soon as I selected gear down, flap 15 and bugged the f15 speed, it immediately started flashing even though the aircraft was decelerating.

    So just wondering if it's a misunderstanding on my part maybe a new software standard, or a bug.

    Many thanks,

    Daniel
    Daniel Welsh

    #2
    That is normal Daniel. You've reduced the MCP speed below what the A/T can control and it is just letting you know it's lost that control. As the aircraft decelerates closer to the set speed it will quit blinking as A/T is able to regain control. You didn't see this in the NGX. You also didn't see how the speed bug slowly decreases from descent speeds to 240 at 10000, that slow decrease is intention by the FMS to retain A/T control.
    Dan Downs KCRP
    i7-10700K 32GB 3600MHz 1080Ti

    Comment


      #3
      Originally posted by DDowns View Post
      That is normal Daniel. You've reduced the MCP speed below what the A/T can control and it is just letting you know it's lost that control. As the aircraft decelerates closer to the set speed it will quit blinking as A/T is able to regain control. You didn't see this in the NGX. You also didn't see how the speed bug slowly decreases from descent speeds to 240 at 10000, that slow decrease is intention by the FMS to retain A/T control.
      Dan,

      Would it be better to slow down in small steps rather than slow down from, say 180 kts to 160 kts (flaps 1 to flaps 5 e.g.) in one go?"
      Kind regards,

      Hans van Wijhe

      Comment


        #4
        Originally posted by DDowns View Post
        That is normal Daniel. You've reduced the MCP speed below what the A/T can control and it is just letting you know it's lost that control. As the aircraft decelerates closer to the set speed it will quit blinking as A/T is able to regain control. You didn't see this in the NGX. You also didn't see how the speed bug slowly decreases from descent speeds to 240 at 10000, that slow decrease is intention by the FMS to retain A/T control.
        Hi thanks for your reply. That's understood, it just seems to do it even in situations where it doesn't seem to have lost that control, almost like it flashes a little prematurely. For example in the attached screenshot, when I went gear down flap 15, the speed came back to idle to slow to the flap 15 speed. Immediately as soon as I bugged the flap 15 speed, the yellow A/T light started flashing, even though I didn't have to add any more additional drag such as extra flap or speed brake lever, as soon as the gear had dropped and the flaps got to 15, that extra drag from that alone brought the speed back nicely, that is when I don't understand why it needs to flash.
        Daniel Welsh

        Comment


          #5
          Originally posted by HvW View Post

          Dan,

          Would it be better to slow down in small steps rather than slow down from, say 180 kts to 160 kts (flaps 1 to flaps 5 e.g.) in one go?"
          Hi there,

          Yes I do decelerate in increment steps, firstly I usually bug the up speed, then down to around 180 for around 10 miles out, this is with Flap 1 initially, then flap 5. I then keep flap 5 with flap 5 bug speed or 160 knots if it can do that with flap 5 configuration until 4 miles, then gear down flap 15 at 4 miles, as per RYR SOP. Then Flap 30 or flap 25 then flap 40, dependent on the landing flap required.
          Daniel Welsh

          Comment


            #6
            Originally posted by HvW View Post

            Dan,

            Would it be better to slow down in small steps rather than slow down from, say 180 kts to 160 kts (flaps 1 to flaps 5 e.g.) in one go?"
            Nah... that flashing is NOT an alarm indication, merely an advisory. There is no remedial action required. See also FCOM 4.10.22

            [Option - Airspeed deviation warning activated]
            •flashing – indicates A/T airspeed error under following conditions:
            •inflight
            •flaps not up
            •airspeed differs from commanded value by +10 or -5 knots and is not approaching commanded value.
            Dan Downs KCRP
            i7-10700K 32GB 3600MHz 1080Ti

            Comment


              #7
              Originally posted by DDowns View Post

              Nah... that flashing is NOT an alarm indication, merely an advisory. There is no remedial action required. See also FCOM 4.10.22

              [Option - Airspeed deviation warning activated]
              •flashing – indicates A/T airspeed error under following conditions:
              •inflight
              •flaps not up
              •airspeed differs from commanded value by +10 or -5 knots and is not approaching commanded value.
              Dan,

              I've found a video here of a real world approach, just for comparison as it's very similar conditions to what I encounter in the sim. I've linked the video starting from around 6 minutes in. As you can see they have flap 10, speed brake extended with the speed bugged to flap 10. The speed however does not reduce, it hovers around the 189 knots area and actually increases a little also. In the NGXu here, the A/T would be flashing at me like crazy, whereas you see in the video they don't have that happen, even though the throttles are at idle and the speed is not reducing. As per your FCOM reference above, it is also more than +10 from the selected speed of 165.

              https://youtu.be/84iR_UDA8qI?t=370

              This is what leads me to think it is just a bit too sensitive in the NGXu, as it happens to me even in situations where the speed trend is coming back to commanded value.
              Daniel Welsh

              Comment


              • DDowns
                DDowns commented
                Editing a comment
                Can you confirm that aircraft is equipped with that option?

              • mbmafra
                mbmafra commented
                Editing a comment
                In the scene that you mention, they are descending in LVL CHG and then switch to APP mode. I don't remember ever seeing the A/T light flash in the real airplane when decelerating in any pitch mode other than VNAV... I'll try to notice that next time, but it flashes quite frequently when descending in VNAV PTH.
                Last edited by mbmafra; 01Aug2020, 19:14.

              #8
              Can you confirm that aircraft is equipped with that option?
              No I sadly cannot.
              Daniel Welsh

              Comment


                #9
                Originally posted by DDowns View Post

                Nah... that flashing is NOT an alarm indication, merely an advisory. There is no remedial action required. See also FCOM 4.10.22

                [Option - Airspeed deviation warning activated]
                •flashing – indicates A/T airspeed error under following conditions:
                •inflight
                •flaps not up
                •airspeed differs from commanded value by +10 or -5 knots and is not approaching commanded value.
                Thanks, I'll keep doing then what I have been doing for years now.
                Kind regards,

                Hans van Wijhe

                Comment


                  #10
                  Something changed with the most recent update that makes the A/T warning flash more often. Whether it is more or less accurate, I have no idea.
                  Alex Pugh

                  Comment


                    #11
                    There's not a single day that the A/T light doesn't flash in the real airplane when you start lowering flaps, specially when descending in VNAV PTH. It is usually just the A/T panicking when VNAV suddenly drops the speed bug to the next flap speed and, if path and speed are adequate, the airplane will decelerate slowly towards the selected speed.
                    Last edited by mbmafra; 01Aug2020, 19:00.
                    Matheus Mafra

                    Comment


                      #12
                      Originally posted by mbmafra View Post
                      There's not a single day that the A/T light doesn't flash in the real airplane when you start lowering flaps, specially when descending in VNAV PTH. It is usually just the A/T panicking when VNAV suddenly drops the speed bug to the next flap speed and, if path and speed are adequate, the airplane will decelerate slowly towards the selected speed.
                      Okay, thanks for your reply :-)

                      I will monitor it in the NGXu over the next flights. It still seems off to me that every single flight when I go gear down and select flap 15, then bug the flap 15 speed bug, the A/T starts flashing crazy every time, that just doesn't seem right to me.
                      Daniel Welsh

                      Comment


                        #13
                        Originally posted by utd4life12 View Post

                        Okay, thanks for your reply :-)

                        I will monitor it in the NGXu over the next flights. It still seems off to me that every single flight when I go gear down and select flap 15, then bug the flap 15 speed bug, the A/T starts flashing crazy every time, that just doesn't seem right to me.
                        How does it not perform as outlined in the FCOM?
                        Dan Downs KCRP
                        i7-10700K 32GB 3600MHz 1080Ti

                        Comment


                          #14
                          Originally posted by utd4life12 View Post

                          Okay, thanks for your reply :-)

                          I will monitor it in the NGXu over the next flights. It still seems off to me that every single flight when I go gear down and select flap 15, then bug the flap 15 speed bug, the A/T starts flashing crazy every time, that just doesn't seem right to me.
                          The actual airplane definitely does not give you an A/T flash in this scenario. However, I also hardly ever see it in VNAV PTH approaches unless in strong gusty winds, and we do a lot of them, and that seems counter to the experience of Matheus, so maybe we're seeing the effects of software differences.
                          Andrew Crowley

                          Comment


                          • mbmafra
                            mbmafra commented
                            Editing a comment
                            Could be software... VNAV in my company's airplanes seem to like to enter the approach with a somewhat steeper path, and it is not uncommon in many airports we fly to to have tailwinds around 20 to 30kts past the IAF until around 2000ft AFE. That gives VNAV a hard time calculating the DECEL point properly and we constantly have to intervein with speedbrakes or early gear extension to get speed under flaps 15 placard on final, even if we constrain speed to VREF+70 at IAF.

                          #15
                          Originally posted by DDowns View Post

                          How does it not perform as outlined in the FCOM?
                          Because even when there is a speed difference of +10 knots, the yellow A/T still flashes even when it is decelrating and approaching the commanded speed, which is counter to the quote you posted from the FCOM which states it should only happen if the speed is not approaching the commanded speed set. In all the scenarios I've encountered the speed has had a negative trend moving towards the commanded speed I set, for example flap 15 bug yet it still flashes.
                          Daniel Welsh

                          Comment


                            #16
                            Originally posted by Stearmandriver View Post

                            The actual airplane definitely does not give you an A/T flash in this scenario. However, I also hardly ever see it in VNAV PTH approaches unless in strong gusty winds, and we do a lot of them, and that seems counter to the experience of Matheus, so maybe we're seeing the effects of software differences.
                            Yes could indeed be software differences.
                            Daniel Welsh

                            Comment


                              #17
                              Originally posted by utd4life12 View Post

                              Yes could indeed be software differences.
                              Curious to know what you do to stop the flashing? Do you adjust your vertical speed or some other operation? Or do you, as Dan said, treat it as an advisory only and let it flash?
                              Kind regards,

                              Hans van Wijhe

                              Comment


                                #18
                                Just click it away.... it's normal to see that light flashing when going from flap UP-1-5.
                                From Gear Down Flaps 15 it normally should not flash anymore since the airplane now has sufficient drag to decellerate.

                                The PMDG is a bit oversensitive, in that it starts to flash again if you only had a small gust, accelerating you for a second, before decelleration commences again. The real aircraft wouldn't start to flash again if you clicked the flash away. Small temporary accelerations don't cause the flashing to reactive, only major changes do.
                                Other than that the NGXu actually works quite fine and correct.

                                Comment


                                  #19
                                  Originally posted by Emi View Post
                                  Just click it away.... it's normal to see that light flashing when going from flap UP-1-5.
                                  From Gear Down Flaps 15 it normally should not flash anymore since the airplane now has sufficient drag to decellerate.

                                  The PMDG is a bit oversensitive, in that it starts to flash again if you only had a small gust, accelerating you for a second, before decelleration commences again. The real aircraft wouldn't start to flash again if you clicked the flash away. Small temporary accelerations don't cause the flashing to reactive, only major changes do.
                                  Other than that the NGXu actually works quite fine and correct.
                                  Hi thanks for your reply.

                                  So I've noticed a trend with every flight. It doesn't flash when I bug from say 250 knots to the up speed with no flap, even if it struggles to decelerate. When I select flap 1, no matter what the wind conditions even in calm wind with good deceleration, it flashes. Even if the actual speed is less than +10 than the selected speed. It always flashes every time when selecting gear down flap 15, despite the speed or conditions.

                                  So yes, I guess it is quite oversensitive.
                                  Daniel Welsh

                                  Comment


                                    #20
                                    Originally posted by HvW View Post

                                    Curious to know what you do to stop the flashing? Do you adjust your vertical speed or some other operation? Or do you, as Dan said, treat it as an advisory only and let it flash?


                                    For me in the sim I just push it and it will stop flashing, but then it starts again pretty soon after.
                                    Daniel Welsh

                                    Comment


                                      #21
                                      Originally posted by utd4life12 View Post

                                      For me in the sim I just push it and it will stop flashing, but then it starts again pretty soon after.
                                      Warning lights in an aircraft normally flash for a very good reason.

                                      Pilots need to know what brings them on in their aircraft in order to correctly identify and deal with a particular problem and that's why you should never ignore a flashing light or get into the equally bad habit of routinely pushing it to stop it from flashing. You should always try and identify what the issue is, cancel the warning to reset and arm the system and then take the appropriate steps to fix the problem. If the warning light flashes again then it is telling you the issue (whatever it might be) is still there.
                                      Michael Codd

                                      Comment


                                        #22
                                        Originally posted by Michael Codd View Post

                                        Warning lights in an aircraft normally flash for a very good reason.

                                        Pilots need to know what brings them on in their aircraft in order to correctly identify and deal with a particular problem and that's why you should never ignore a flashing light or get into the equally bad habit of routinely pushing it to stop it from flashing. You should always try and identify what the issue is, cancel the warning to reset and arm the system and then take the appropriate steps to fix the problem. If the warning light flashes again then it is telling you the issue (whatever it might be) is still there.
                                        I agree, but. This amber is more of a 'be aware' than a warning. Be aware that you are not speed protected with A/T active, keep an eye on things is the proper response. This little blinking amber light might have saved the ill fated Asiana 214 at SFO where the PF presumed he had speed protection. I'm not saying disregard the annunciation, but understand it's not an alarm one has to clear. Also, I'll concede that the feature is too sensitive in that it is triggered by deceleration rates that are not quite right. Maybe a lower rate would be a better setpoint for the blinking.
                                        Dan Downs KCRP
                                        i7-10700K 32GB 3600MHz 1080Ti

                                        Comment


                                        • Michael Codd
                                          Michael Codd commented
                                          Editing a comment
                                          I agree with you Dan. I was talking in general terms and not just about Daniel's original issue.

                                        #23
                                        Originally posted by Michael Codd View Post

                                        Warning lights in an aircraft normally flash for a very good reason.

                                        Pilots need to know what brings them on in their aircraft in order to correctly identify and deal with a particular problem and that's why you should never ignore a flashing light or get into the equally bad habit of routinely pushing it to stop it from flashing. You should always try and identify what the issue is, cancel the warning to reset and arm the system and then take the appropriate steps to fix the problem. If the warning light flashes again then it is telling you the issue (whatever it might be) is still there.
                                        I agree completely, although it seems in this situation the issue lies with how it's been implemented into the NGXu, in that it flashes in situations when it shouldn't. So I only cancel that flashing A/T in situations where I know it shouldn't be happening, such as gear down flap 15 with the speed comfortably coming back to the speed I have bugged :-)
                                        Last edited by utd4life12; 02Aug2020, 22:30.
                                        Daniel Welsh

                                        Comment


                                          #24
                                          Is there a way to make this feature optional? None of the 737s I fly do that.
                                          Herb Barrett-King

                                          Comment


                                            #25
                                            Originally posted by WN737 View Post
                                            Is there a way to make this feature optional? None of the 737s I fly do that.
                                            Feature requests can be submitted on a support ticket.... this is a user to user forum. None of us can accomplish that.
                                            Dan Downs KCRP
                                            i7-10700K 32GB 3600MHz 1080Ti

                                            Comment


                                              #26
                                              I've noticed (after installing the latest update) that the MCP speed display is flashing with the A/T light. I couldn't find any reference in the FCOM, is that a new software upgrade that was implemented in the latest ngxu?

                                              https://www.twitch.tv/videos/693166698?t=3h43m13s
                                              Almog Atar

                                              Comment


                                              • DDowns
                                                DDowns commented
                                                Editing a comment
                                                See post #6 this thread.

                                              • AlmogAtar
                                                AlmogAtar commented
                                                Editing a comment
                                                I'm familiar with the A/T indicator light and the conditions which causes it to flash, but I didn't find anything that could explain why the MCP speed display flash as well.

                                              • DDowns
                                                DDowns commented
                                                Editing a comment
                                                I've only seen the MCP SPD window flash when it is set too low (A) or high (8).

                                              #27
                                              Originally posted by AlmogAtar View Post
                                              I've noticed (after installing the latest update) that the MCP speed display is flashing with the A/T light. I couldn't find any reference in the FCOM, is that a new software upgrade that was implemented in the latest ngxu?

                                              https://www.twitch.tv/videos/693166698?t=3h43m13s
                                              I can confirm this and some of the pilots here could comment if this is realistic but my personal opinion is that is not, nevertheless let the experts talk.
                                              STEFAN ĐORĐEVIĆ

                                              Comment


                                                #28
                                                Can't relate to this scenario in real life in my personal experience for what it's worth. I don't recall seeing this behavior on our NG's but if memory serves right i've seen it once or twice on our MAX's, and obviously that was a whileeeeeeee ago :/
                                                Manuel Zarate

                                                Comment

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