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    brake temp

    how is the brake temperature measured? So say if its 1.6... what is that? And what is the danger zone as far as brake temps go? Normally I manage things pretty well but tonight I had to land on a short runway fully loaded..
    Jason Saucier

    #2
    From what I have been able to determine, there is no direct correlation between the brake temp values shown and actual temperature values. It generally isn't too much of a concern until you start seeing it go above about 5, or if you are going to be doing a lot of short flights that require heavy braking on landing.
    Tim Lincoln
    My YouTube Channel

    Comment


      #3
      The brake temp sensors can detect temperatures between 100F and 1200F. When the indications in the cockpit get above 5.0, the the BRAKE TEMP light will illuminate, when this happens, the brake temperatures have gotten high enough the fuse plugs installed on the tires may start to melt, deflating the tire. It’s not a guarantee that will happen, but if it happens long enough, it definitely can. Also, if the brake temp light illuminates, maintenance will most likely have to perform a High Energy Stop Inspection.

      Ryan Collier

      Comment


        #4
        Originally posted by 747Mx View Post
        The brake temp sensors can detect temperatures between 100F and 1200F. When the indications in the cockpit get above 5.0, the the BRAKE TEMP light will illuminate, when this happens, the brake temperatures have gotten high enough the fuse plugs installed on the tires may start to melt, deflating the tire. It’s not a guarantee that will happen, but if it happens long enough, it definitely can. Also, if the brake temp light illuminates, maintenance will most likely have to perform a High Energy Stop Inspection.

        Ryan Collier
        ah good info, thank you! I have never really reached the danger zone then. That clears it up, I just had never heard it discussed on any of the videos or forums.
        Jason Saucier

        Comment


          #5
          Originally posted by 747Mx View Post
          The brake temp sensors can detect temperatures between 100F and 1200F. When the indications in the cockpit get above 5.0, the the BRAKE TEMP light will illuminate, when this happens, the brake temperatures have gotten high enough the fuse plugs installed on the tires may start to melt, deflating the tire. It’s not a guarantee that will happen, but if it happens long enough, it definitely can. Also, if the brake temp light illuminates, maintenance will most likely have to perform a High Energy Stop Inspection.

          Ryan Collier
          Where is that Brake Temp light located ?
          jorge soldano

          Comment


            #6
            Yes, I’d be interested to know that too. I thought that if there were no brake temperature indications on the lower DU, there was no way of knowing in the 737 whether the brakes were hot (from the flight deck, anyway)
            Flight Sim Guides YouTube Channel

            John Price

            Comment


              #7
              Does anyone know why this is? Why is a brake temperature displayed in what seems to me to be an arbitrary scale when the perfect unit - temperature - already exists? There must be a reason, but I hope someone in the know can help me figure out why.
              - Asa Graf

              Comment


                #8
                Originally posted by Acegard View Post
                Does anyone know why this is? Why is a brake temperature displayed in what seems to me to be an arbitrary scale when the perfect unit - temperature - already exists? There must be a reason, but I hope someone in the know can help me figure out why.
                Because different brake system across all Boeing fleet (even same type with different brake component) have different temperature tolerance, but it's all set to be "need cooling" above 3.0 and "danger" when above 5.0
                Last edited by AngelofAttack; 19Sep2022, 04:15.
                ZHU Hai
                B737 Ground instructor

                Comment


                  #9
                  Originally posted by AngelofAttack View Post

                  Because different brake system across all Boeing fleet (even same type with different brake component) have different temperature tolerance, but it's all set to be "need cooling" above 3.0 and "danger" when above 5.0
                  Well that's strange because I'm getting 6.0 almost every landing and 9.0 when I screw up.

                  I just had a wheel seize with 9.0 brake temp (not sure if this 9.0 should cause wheel seize anyway) because I was forced to land faster (157 knots/15 flaps instead of my normal 142/40) due to ATC troubles. And I just don't know how to not make that happen.

                  Currently I do auto brake 3 for all landings, and my braking distance is about.... uhh, slowing to 30 knots in the other side's touchdown area on a 2000m runway?
                  Or maybe just measure RCTP 05L and say I turn out at N7, could make N5 if I brake very hard.

                  Every one I asked claim they can do stuff like "land with 15 flap in a 4000 ft runway with 4.0 brake temperature at maximum landing weight" but that just departs from my experience by such a huge margin. My experience is closer to 6.0 brake temp with 40 flap in a 6000ft runway.

                  Another strange thing is auto brake max actually gives me better brake temperature, albeit I don't do that because the plane stops like a gigantic carrier plane doing arrested landing, and I assume that's gonna be very uncomfortable.
                  Ching Charng

                  Comment


                    #10
                    Originally posted by 747Mx View Post
                    The brake temp sensors can detect temperatures between 100F and 1200F. When the indications in the cockpit get above 5.0, the the BRAKE TEMP light will illuminate, when this happens, the brake temperatures have gotten high enough the fuse plugs installed on the tires may start to melt, deflating the tire. It’s not a guarantee that will happen, but if it happens long enough, it definitely can. Also, if the brake temp light illuminates, maintenance will most likely have to perform a High Energy Stop Inspection.

                    Ryan Collier
                    Not on the 738. I killed my tires by reaching 9.0 and there's no BRAKE TEMP light.
                    In fact even by reaching 9.0 temperature it's still shown as yellow, not red in the SYS page of the lower DU.
                    Ching Charng

                    Comment


                      #11
                      i find the brake temp to bee extremly low compared to the 320.

                      in a 60t 320 at low auto brake setting with max reverse, the brake temp will be around 180-200°C whereas in the B738 with autobrake set to 3, the brake temp unit will never go above 1.5 which means that the brake temp is extremly low ? how is that possible. I think that even with max autobrake, i wouldn't need to delay take off whereas in the 320, there is a high chance to get above 300°C, therefore needing to delay potentially the TO until brake temps gets below 300°C
                      PMDG 747-400/-800
                      PMDG 737NGXu

                      Camille MOUCHEL-BLAISOT

                      Comment


                        #12
                        Originally posted by Cmbaviator View Post
                        i find the brake temp to bee extremly low compared to the 320.

                        in a 60t 320 at low auto brake setting with max reverse, the brake temp will be around 180-200°C whereas in the B738 with autobrake set to 3, the brake temp unit will never go above 1.5 which means that the brake temp is extremly low ? how is that possible. I think that even with max autobrake, i wouldn't need to delay take off whereas in the 320, there is a high chance to get above 300°C, therefore needing to delay potentially the TO until brake temps gets below 300°C
                        Then I must be getting a flawed 738.
                        I'm getting 6.0-9.0 brake temp on auto 3 every landing, and somehow auto max gives me 4.7 (of course, auto 3 would mean using a lot more manual brake than auto max)

                        Tho I think even with a 6.0 brake I probably won't need to delay takeoff because real world turnaround of 160 pax takes like... 1 hour? I think by that time the brakes would be like below 3.0.
                        Ching Charng

                        Comment


                          #13
                          Originally posted by boris.glevrk` View Post

                          Then I must be getting a flawed 738.
                          I'm getting 6.0-9.0 brake temp on auto 3 every landing, and somehow auto max gives me 4.7 (of course, auto 3 would mean using a lot more manual brake than auto max)

                          Tho I think even with a 6.0 brake I probably won't need to delay takeoff because real world turnaround of 160 pax takes like... 1 hour? I think by that time the brakes would be like below 3.0.
                          Most likely the problem is how and when you apply manual braking. I never see a brake temperature above 4.0 when using maximum autobrake, thrust reverse, spoilers and landing Flap 30 and usually the temps are closer to the high 2.0's. All it takes is a short aggressive application of manual braking to create a lot of heat, and since we don't ever feel or see an indication of g-forces it's very easy to over do the braking. A good example is when you want to take the next high speed turn off after landing and autobrake is slowing you below 60 then 50 and slowing to 40. If you take the turn off at 40 while applying gentle manual braking you're going to come to a stop by the time you exit the turn-off. On the other hand, if you start applying manual braking aggressively before the turn off and take the turn off at 20 for example you're going to have hot brakes.

                          Trust the autobrake.
                          Dan Downs KCRP
                          i7-10700K 32GB 3600MHz 3080Ti

                          Comment


                          • Cmbaviator
                            Cmbaviator commented
                            Editing a comment
                            I brake realistically not like those youtuber that didn't before plan their exit and full use full manual brake just to be able to vacate.

                            I gently apply manual brake below 60kt and at the gate, i never was above 2.0

                          #14
                          i was curious and tested this tonight in the 738, i generally had not been looking at my brake temps (i have failures off so i suppose i never would have noticed anyway haha).. but my temps were definitely way lower also. similar to cmbaviator's numbers...landing at LKPR flaps 30, 153 knots speed, autobrakes 3, i was a little late with hitting the reverse thrust, my temps ended up 2.1 and were 1.8 or so by the time i got to the gate.
                          cheers,-andy crosby

                          Comment


                            #15
                            Originally posted by DDowns View Post

                            Most likely the problem is how and when you apply manual braking. I never see a brake temperature above 4.0 when using maximum autobrake, thrust reverse, spoilers and landing Flap 30 and usually the temps are closer to the high 2.0's. All it takes is a short aggressive application of manual braking to create a lot of heat, and since we don't ever feel or see an indication of g-forces it's very easy to over do the braking. A good example is when you want to take the next high speed turn off after landing and autobrake is slowing you below 60 then 50 and slowing to 40. If you take the turn off at 40 while applying gentle manual braking you're going to come to a stop by the time you exit the turn-off. On the other hand, if you start applying manual braking aggressively before the turn off and take the turn off at 20 for example you're going to have hot brakes.

                            Trust the autobrake.
                            When using max autobrake I indeed don't use much manual brake. I think I was doing the "real life way", where manual brake is only used at 60 knots briefly (and the main purpose of that was actually to disengage autobrake).

                            I still get 4.7 brake temp for that, so the problem isn't really solved with me not using manual. I'm still getting significantly higher temperature than others (albeit now the temperatures are a lot more manageable)

                            Last night I went to the longest runway I can get and decided to do 3 autobrake with little to no manual, got 2.2, but instead of making the first exit, I got the second, which is 1.5 km from where I touch down and just shy of 2km from runway threshold. (isn't that closer to a 747 landing run than a 737?)

                            But then just 30 minutes ago, I managed to land in a 2000m runway with plenty of space to go while being 500kg overweight with just 3 autobrake and no manual braking. There are two advantageous factors tho, one is the runway being visibly uphill, and the other is the 10-15 knot headwind. (in my previous flights with 738, it's usually calm wind or largely crosswind). Including the brakes needed for turning pad and other taxiing action, I got 2.5 brake temp at gate.

                            I wonder if the PMDG 738 reflects the characteristics of carbon brakes? I think when I was using 3 autobrake before, I touch down, see the poor deceleration, and just decided to intervene with manual. Maybe carbon brakes are just like ceramic brakes who need to be pre-heated for maximum efficiency?

                            Still, it doesn't make much sense to me that stopping in the same distance, autobrake creates less heat than manual. According to conservation of energy, stopping the same plane in the same distance should create the same amount of heat in the same period of time.
                            Ching Charng

                            Comment


                              #16
                              Originally posted by spesimen View Post
                              i was curious and tested this tonight in the 738, i generally had not been looking at my brake temps (i have failures off so i suppose i never would have noticed anyway haha)
                              Having failures off wouldn't stop you from toasting your brakes.​
                              Originally posted by boris.glevrk` View Post
                              Still, it doesn't make much sense to me that stopping in the same distance, autobrake creates less heat than manual. According to conservation of energy, stopping the same plane in the same distance should create the same amount of heat in the same period of time.
                              But are you sure that you're manually applying the same brake pressure as you would be when using autobrakes. Keep in mind that autobrakes only provides a set deceleration rate, so if you're using more reverse thrust to slow the plane down, you won't be using nearly as much braking power to achieve the same deceleration rate. So if you're using idle reverse and autobrakes 3, you're using more braking power to slow the plane down versus if you're using full reverse and autobrakes 3.
                              Captain Kevin

                              Kevin Yang

                              Comment


                                #17
                                Originally posted by Captain Kevin View Post
                                Having failures off wouldn't stop you from toasting your brakes.​

                                But are you sure that you're manually applying the same brake pressure as you would be when using autobrakes. Keep in mind that autobrakes only provides a set deceleration rate, so if you're using more reverse thrust to slow the plane down, you won't be using nearly as much braking power to achieve the same deceleration rate. So if you're using idle reverse and autobrakes 3, you're using more braking power to slow the plane down versus if you're using full reverse and autobrakes 3.
                                I said: Stopped at same distance, with same reverse thrust and stuff.
                                if I stopped at the same distance and all other factors are the same I'd say the brake power is the same.

                                I think I have more or less figured out how to keep brake temp in "okay" levels. just refrain from applying manual too early. use manual as late as you can, perhaps only when you already see the taxiway you want to use. I did that and got a 4.7 brake temp (which is about the same as max autobrake tho). Still better than the previous 7.0-9.0 depending on landing speed.
                                Ching Charng

                                Comment


                                  #18
                                  Coming back to the BRAKE TEMP indicator light, from what I can tell, if the aircraft is equipped with a brake temperature monitoring system, there should be a light on the Right Forward Panel (the FO’s panel) just below and outboard of the brake pressure indicator. I verified this morning that it’s missing. I want to verify it’s location and possibly put in a ticket. Maybe I’ll be extra productive and gather all the info I can for the main cargo door on the freighter variants being hydraulically actuated, as opposed to electrically so, as well.

                                  Ryan Collier

                                  Comment


                                    #19
                                    yesterday, i was at 61tons, AB2 and very little manual breaking with full reverse until 60kt, the brake temp was 0.0 unit after shutdown.
                                    PMDG 747-400/-800
                                    PMDG 737NGXu

                                    Camille MOUCHEL-BLAISOT

                                    Comment


                                      #20
                                      Originally posted by boris.glevrk` View Post
                                      I said: Stopped at same distance, with same reverse thrust and stuff.
                                      if I stopped at the same distance and all other factors are the same I'd say the brake power is the same.
                                      You said you stopped in the same distance. You made no mention of the thrust reversers until just now, which is why I brought that up.
                                      Captain Kevin

                                      Kevin Yang

                                      Comment


                                        #21
                                        Originally posted by Captain Kevin View Post
                                        You said you stopped in the same distance. You made no mention of the thrust reversers until just now, which is why I brought that up.
                                        Either I used reverser in both cases or I don't in both cases. When people don't mention something they mean they are the same in the different situations being compared.

                                        Literally the only difference was 3 autobrake + more manual brake versus max autobrake + less manual brake. Everything else are control factors and were the same (ok except the wind because I use live weather)

                                        Max brake + less manual always gives better stopping distance AND better temperature, which doesn't make a lot of sense. Since the thrust reverser is on, the longer you take to stop, the more energy is killed by reverse thrust (constant backward force), and should thus result in less brake temp.

                                        Similar stuff still persists even after I get a hold on 3 autobrake.
                                        Now I'm making N7 taxiway with 3 autobrake + delayed manual brake (circa 80 knots) while I can make N5 with max autobrake + almost no manual brake, both resulting in about 4.5-4.7 brake temp. (I land from N1 side of that runway so N7 means further than N5. N6 is a taxiway of the opposite direction and intersects with N5 so I stopped one exit further, not two)

                                        IDK, unless autobrake has some extra cooling measure, otherwise "stopping at same distance, autobrake gives better temp" or "same temperature, autobrake stops earlier" both don't make much sense considering conservation of energy.
                                        Ching Charng

                                        Comment


                                          #22
                                          Originally posted by boris.glevrk` View Post
                                          Either I used reverser in both cases or I don't in both cases. When people don't mention something they mean they are the same in the different situations being compared.
                                          Okay, but I can't assume that. Having been around here for a very long time now, I've seen people have the misconception that the autobrakes give a set brake pressure rather than a set deceleration rate, so unless you specifically tell me that, I have no way of knowing what you know as far as how the system is supposed to work, nor do I have any way of knowing what you actually did.
                                          Captain Kevin

                                          Kevin Yang

                                          Comment


                                            #23
                                            Originally posted by Captain Kevin View Post
                                            Okay, but I can't assume that. Having been around here for a very long time now, I've seen people have the misconception that the autobrakes give a set brake pressure rather than a set deceleration rate, so unless you specifically tell me that, I have no way of knowing what you know as far as how the system is supposed to work, nor do I have any way of knowing what you actually did.
                                            I don't know how are autobrake X defined, but I know autobrake max is stronger than autobrake 3.

                                            Basically we're looking at identical landings with only the portion of auto/manual brakes different. Given the conservation of energy, if they stop at the same distance, the brakes should generate same amount of deceleration (and exchange same amount of kinetic energy into heat).

                                            So unless somehow manual brake has a different braking-to-heat ratio (such as, IDK, maybe autobrake has an extra cooling mechanism?), it would sound very off.

                                            I've also thought about ventilation effect at higher speeds (i.e. "the longer you stay at high speed the less heat you accumulate"), but that won't explain "max autobrake makes N5 at 4.7 brake temp, 3 autobrake makes N7 at 4.7 brake temp", because max autobrake stays at high speed shorter.
                                            Ching Charng

                                            Comment


                                              #24
                                              Originally posted by 747Mx View Post
                                              Coming back to the BRAKE TEMP indicator light, from what I can tell, if the aircraft is equipped with a brake temperature monitoring system, there should be a light on the Right Forward Panel (the FO’s panel) just below and outboard of the brake pressure indicator. I verified this morning that it’s missing. I want to verify it’s location and possibly put in a ticket. Maybe I’ll be extra productive and gather all the info I can for the main cargo door on the freighter variants being hydraulically actuated, as opposed to electrically so, as well.

                                              Ryan Collier
                                              Ryan, you should write up the ticket as a feature request. The FCOM clearly marks the brake temp indicator as an option, which I suspect very few operators paid the extra bucks for; in other words, a missing indicator is not a bug.

                                              As for the BCF cargo door, my readings indicate that it is a 28VDC independent door hydraulic system. So it is electro-hydraulic and not related to aircraft HYD systems.
                                              Dan Downs KCRP
                                              i7-10700K 32GB 3600MHz 3080Ti

                                              Comment


                                                #25
                                                Originally posted by boris.glevrk` View Post

                                                I don't know how are autobrake X defined, but I know autobrake max is stronger than autobrake 3.

                                                Basically we're looking at identical landings with only the portion of auto/manual brakes different. Given the conservation of energy, if they stop at the same distance, the brakes should generate same amount of deceleration (and exchange same amount of kinetic energy into heat).

                                                So unless somehow manual brake has a different braking-to-heat ratio (such as, IDK, maybe autobrake has an extra cooling mechanism?), it would sound very off.

                                                I've also thought about ventilation effect at higher speeds (i.e. "the longer you stay at high speed the less heat you accumulate"), but that won't explain "max autobrake makes N5 at 4.7 brake temp, 3 autobrake makes N7 at 4.7 brake temp", because max autobrake stays at high speed shorter.
                                                I'm trying to understand this.... but I'm old and slow. I don't know what N7 and N5 are so I assume you are saying AB Max compared to AB 3 rolls to a stop or a taxi speed (I can't guess that one) in a further distance than AB Max but both create the same brake temperature?

                                                Given a fair testing scenario, AB Max will decelerate at a higher rate than AB 3 (this is something that we often test in beta using Boeing engineering data); however, both trials resulting in the same brake temperature is unexpected. Since dV/dT is acceleration/deceleration and the dV is the same but the dT is greater for AB 3 and I'd expect slightly less heating. Interesting.

                                                Maybe there is something about your test technique that decreases the fairness of the test? We we test in beta we also have to use a special log created by debugging code that provides us exact distances from touchdown, to application of braking, to complete stop with times and average deceleration rates. Nope, never looked at brake temperatures unless they were cooking.
                                                Dan Downs KCRP
                                                i7-10700K 32GB 3600MHz 3080Ti

                                                Comment


                                                  #26
                                                  Originally posted by DDowns View Post
                                                  I don't know what N7 and N5 are
                                                  Looking at the start of the thread, it would appear as though N7 and N5 are taxiway exits at RCTP.
                                                  Captain Kevin

                                                  Kevin Yang

                                                  Comment


                                                    #27
                                                    Originally posted by DDowns View Post

                                                    I'm trying to understand this.... but I'm old and slow. I don't know what N7 and N5 are so I assume you are saying AB Max compared to AB 3 rolls to a stop or a taxi speed (I can't guess that one) in a further distance than AB Max but both create the same brake temperature?

                                                    Given a fair testing scenario, AB Max will decelerate at a higher rate than AB 3 (this is something that we often test in beta using Boeing engineering data); however, both trials resulting in the same brake temperature is unexpected. Since dV/dT is acceleration/deceleration and the dV is the same but the dT is greater for AB 3 and I'd expect slightly less heating. Interesting.

                                                    Maybe there is something about your test technique that decreases the fairness of the test? We we test in beta we also have to use a special log created by debugging code that provides us exact distances from touchdown, to application of braking, to complete stop with times and average deceleration rates. Nope, never looked at brake temperatures unless they were cooking.
                                                    As I mentioned in a slightly earlier post, I landed on a runway from the N1 taxiway side (therefore exiting at N7 means further brake distance than exit at N5).

                                                    First group:
                                                    Max autobrake+ very few manual: stop at N7, brake 4.7
                                                    3 autobrake + more manual: stop at N7, brake 7.0 (hence my claim of "stopping at same distance, auto 3 gives more brake temp, breaking the law of energy conservation")

                                                    second group:
                                                    max autobrake + fewer manual: stop at N5 brake 4.7
                                                    3 autobrake + delayed but still more manual: stop at N7, brake 4.7

                                                    basically:
                                                    group one has max and 3 autobrake stop at same distance with different brake temps
                                                    group two has max and 3 autobrake stop at different distance with same brake temps
                                                    both groups have identical other factors (MLW, full reverser, spoilers)

                                                    So that seemingly suggest that autobrake and manual brake have different temp factor despite when they are producing approximately same amount of brake force (which would break energy conservation).

                                                    Unless somehow autobrake has an extra brake cooling feature not available to manual brakes, it doesn't seem to quite make sense to me.


                                                    After some practice I can now stop the plane with 3 autobrake, with desired distance (N7 in this runway's case) while still getting *more or less* reasonable brake temp (if I brake just a little later I can get sub 3.0 temperatures but that would miss N7 just by a very small margin). I wonder what makes the brake temp act like that: it seems that even stopping at the same distance, heavy braking early is much hotter than heavy braking later.
                                                    Ching Charng

                                                    Comment


                                                    • DDowns
                                                      DDowns commented
                                                      Editing a comment
                                                      The only way to fairly test autobraking is to always touchdown at the same exact place at the same weight and speed and wind and let autobrake bring it to a full stop. Any application of manual braking interferes with the test. Then use some kind of tool to measure the distance from touchdown to stopping, which is why PMDG gives beta testers test software that does the measurements for us.

                                                    #28
                                                    Dumb question but do you have your brakes assigned to an axis in the controls? I discovered yesterday that my pedals were assigned to Left Brake and Right Brake instead of axis, so they were working like a button…all or nothing lol.
                                                    Matt Smith

                                                    Comment


                                                      #29
                                                      Originally posted by DDowns View Post

                                                      Ryan, you should write up the ticket as a feature request. The FCOM clearly marks the brake temp indicator as an option, which I suspect very few operators paid the extra bucks for; in other words, a missing indicator is not a bug.

                                                      As for the BCF cargo door, my readings indicate that it is a 28VDC independent door hydraulic system. So it is electro-hydraulic and not related to aircraft HYD systems.
                                                      I understand the brake temp indication is an option. In the fleet I work with, less than half of the planes have that option installed. Of the ones with the brake temp indication system, all of them have the brake temp annunciator light though. I am curious if there are 737’s in the world that has a brake temp indication on the SYS page but do not have the amber annunciator light on the right forward panel.

                                                      As for the cargo door, the 28VDC is the power input for the MD door and the selector valve. The door actuator gets its hydraulic power from the System A hydraulic system. In normal operation, the Sys A Elec Pump is selected to on and the door is either opened or closed. There is a hand pump located in the right hand wheel well for when the Sys A hydraulics are not available. However, the procedure calls out for the associated circuit breakers to be pulled, the door to be manually unlocked/locked, and the selector valve must be manually positioned to the open or closed position. This is how the door operates on the BCF’s. I haven’t been able to locate it, but I swear I saw something on IAI’s website that indicated the door used the A system as well. All I could find recently was that the door is hydraulic.

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