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Auto Throttle arm procedure question.

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    Auto Throttle arm procedure question.

    The FS2Crew tutorial says to arm the auto throttle 5 minutes before engine start.I prefer to wait until just before entering the runway to preclude any chance of an accidental TOGA activation on the ramp or during taxi. I wonder what most airlines prescribe for this procedure. I assume it is company specific or is it Captains perogative?
    Last edited by Lanica; 30Jul2021, 16:33.
    Victor Green

    #2
    Hi,
    I, according to the SOP of the big european airline that I got and I try to follow every time I fly (both at home and in the "big sim" the "full motion" (not certified) B738 sim where I go to train every now and then) the A/T is armed before entering the takeoff rwy.
    The sequence (Emi can explain better than me) is:
    1) the crew will confirm that rwy and approach are clear;
    2) Seat the cabin crew by announcing on the PA "cabin crew seats for departure";
    3) select strobes ON, A/T arm, LNAV arm (if required) and transponder to TA/RA...
    ETC.
    Anyway according to me selecting the A/T arm too early is not good and could be dangerous ie for ground crew because if you, i.e. for a mistake, push with your finger a A/T engage button on the throttle during taxi or, after the push back, turning towards the taxiway you could cause an hurricane behind you....(i.e. 300kg of air ejected at an average speed of 450 m/sec) and a lot of damages...
    Best Regards
    Andrea Buono
    Andrea Buono - Como - I

    Comment


    • Lanica
      Lanica commented
      Editing a comment
      Thanks for the input Andrea.

    • Emi
      Emi commented
      Editing a comment
      Nicely summarized, nothing to add.

    #3
    There are plenty of deviations of procedures like this one. One airline tells their pilots to do things a certain way while another will tell their pilots to do the opposite. For example, if we're talking real world airline SOPs, another leading 737 operator's FCOM goes the other way - turning it on during the preflight setup after an OAT entry in the FMC has been made (or uplinked). It's also in their preflight checklist.

    In short, it's airline specific.
    Last edited by threegreen; 30Jul2021, 21:22.
    Niklas Graefe
    Prepar3D v5.2 | 737/777 | i9 9900K 5 GHz | Corsair 32 GB | RTX 3090 24 GB | W10 | HP Reverb G2

    Comment


      #4
      I wonder what the reasoning is for arming so early. Just doesn't seem to be the safest to my unlearned eye.
      Victor Green

      Comment


        #5
        Originally posted by Lanica View Post
        I wonder what the reasoning is for arming so early. Just doesn't seem to be the safest to my unlearned eye.
        I agree, I'm interested also but their FCOM doesn't give a reason or at least I can't find any. I suspect it may have been simply adopted from the Boeing SOPs which have the same instruction.
        Niklas Graefe
        Prepar3D v5.2 | 737/777 | i9 9900K 5 GHz | Corsair 32 GB | RTX 3090 24 GB | W10 | HP Reverb G2

        Comment


          #6
          All PMDG option have air-aspirate TAT tube, so FMC would load OAT automatically, that means A/T can be armed as soon as AC power was applied.
          IRL some airline not have this option, so for commonality, on SOP, it's after the OAT was manually inputted in FMC, so practically, it's "as soon as possible".
          For all other Boeing from 757 onward, the AT ARM switch will stay at ARM for flight crew unless these is a QRH call for disarm it. so I don't see there is any safety concern about it.
          ZHU Hai
          B737 Ground instructor

          Comment


            #7
            Originally posted by Andrea1 View Post
            Anyway according to me selecting the A/T arm too early is not good and could be dangerous ie for ground crew because if you, i.e. for a mistake, push with your finger a A/T engage button on the throttle during taxi or, after the push back, turning towards the taxiway you could cause an hurricane behind you....(i.e. 300kg of air ejected at an average speed of 450 m/sec) and a lot of damages...
            I would consider that more of a theoretical risk, for several reasons. First, the autothrottles don't move at warp speed when pushing the TO/GA button. Then, the engines themselves don't spool up that quickly (you can see this when setting the 40% N1 on the runway before setting the takeoff thrust). And lastly, hitting the TO/GA inadvertently implies that one's hand is on the throttle in the first place, so the pilot can disconnect A/T and retard the levers more or less instinctively. Embarassing maybe, but not really dangerous.

            Personally, I like airline SOPs that require arming A/T before pushback. Doing this while setting up the MCP (SPD, HDG and ALT) for departure seems like a good point in time. This way it doesn't get forgotten in the busy phase before takeoff, which is not unlikely if it's not in your muscle memory… or on your checklist (Delta actually has this item on their 737 before takeoff CL).

            Comment


              #8
              Originally posted by StachM View Post

              I would consider that more of a theoretical risk, for several reasons. First, the autothrottles don't move at warp speed when pushing the TO/GA button. Then, the engines themselves don't spool up that quickly (you can see this when setting the 40% N1 on the runway before setting the takeoff thrust). And lastly, hitting the TO/GA inadvertently implies that one's hand is on the throttle in the first place, so the pilot can disconnect A/T and retard the levers more or less instinctively. Embarassing maybe, but not really dangerous.

              Personally, I like airline SOPs that require arming A/T before pushback. Doing this while setting up the MCP (SPD, HDG and ALT) for departure seems like a good point in time. This way it doesn't get forgotten in the busy phase before takeoff, which is not unlikely if it's not in your muscle memory… or on your checklist (Delta actually has this item on their 737 before takeoff CL).
              too many if's and could's compared to the danger of TOGA thrust set on the ramp and absolutely no benefit. Imagine you forget to arm it while entering the runway... what will happen? Your engines will remain at 50% where you pushed the levers and that's it.. Compared to a couple of potential deads that's a risk I can rather go with. And imagine what happens if the TOGA button was hit with the hand NOT remaining on the throttle, nobody would deliberately press these buttons on the ramp.
              i7-6700k, GTX 1080TI, 32GB DDR4 RAM @2666MHz, 4k
              Marc Ehnle

              Comment


                #9
                Originally posted by Ephedrin View Post

                too many if's and could's compared to the danger of TOGA thrust set on the ramp and absolutely no benefit. Imagine you forget to arm it while entering the runway... what will happen? Your engines will remain at 50% where you pushed the levers and that's it.. Compared to a couple of potential deads that's a risk I can rather go with. And imagine what happens if the TOGA button was hit with the hand NOT remaining on the throttle, nobody would deliberately press these buttons on the ramp.
                Given its position the 737 TOGA switch is unlikely to be pushed accidentally, and the levers would be easy to manually hold back if it was. Consider the much more powerful 777 where the A/T switches are always in ARM. Is that a risk?

                Comment


                  #10
                  Originally posted by Ephedrin View Post

                  too many if's and could's compared to the danger of TOGA thrust set on the ramp and absolutely no benefit. Imagine you forget to arm it while entering the runway... what will happen? Your engines will remain at 50% where you pushed the levers and that's it.. Compared to a couple of potential deads that's a risk I can rather go with. And imagine what happens if the TOGA button was hit with the hand NOT remaining on the throttle, nobody would deliberately press these buttons on the ramp.
                  Like I said. A risk. But I contend it's a theoretical one, since I am not aware of any incidents or accidents. Are you?

                  Comment


                    #11
                    The reality is that some airlines have huge departments dedicated to constantly improving SOPs and some stick to old procedures (on paper) but let their pilots deviate more using common sense. In big "rich" airlines, if they find an improvement, they never hesitate to change the company SOPs, update all the manuals and notify and train their crew. Some other airlines are not like this and they simply copy paste old procedures from other airlines and don't update them regularly. I flew for a small airline before. Their manuals were simply a modified version of Iberia's manuals when they operated the 757 (the previous owner of their airplanes). They still uses the "landing" call out after minimums. That's what their manuals tells them to do and that's the callout you would use on a line check. In reality, most pilots in that airline say "continue" like most airlines with more modern SOPs.

                    In airlines that don't update their SOPs so frequently you'll find that each pilot has his own SOPs. Some use V/S for the last 3, 2, 1 to go, some don't. Some arm the A/T on the stand, some do it when entering the runway. Some do low drag approaches and some don't. So this is one of those things.

                    Changing a procedure costs money. You need to update manuals and references in every company document. In cases, the manual has to be submitted to the authorities for approval. It's a whole process.
                    Omar Josef
                    737 FO
                    757/767 rated
                    Spain

                    Comment


                      #12
                      Originally posted by Kevin Hall View Post

                      Given its position the 737 TOGA switch is unlikely to be pushed accidentally, and the levers would be easy to manually hold back if it was. Consider the much more powerful 777 where the A/T switches are always in ARM. Is that a risk?
                      yup it is... those engines push hundreds of tons to 150 knots within 1 mile.. nothing you want to "accidentally" spool up when pilots constantly tell you don't want to spool them to more than 30%N1 break away thrust for this very reason. Why take a risk when you can avoid it with a flip of a swich that has NO other disadvantage? No systems depend on the AT arm switch to boot, nothing can't be executed because of this switch. And if you forget it on the runway you can still flip it and press TOGA again. But if you (for ANY reason) "move" the toga button with your sleeve or whatever else (I don't know how strong they are) it can be too late until you realise what you've done and hold the engines back. It's one of these switches that are totally pointless to flip on the ramp. There's a line up procedure anyway.

                      And jup, the switches in the 777 are a risk that COULD be avoided too, the AT Arm switches don't do anything here on the ground either. They are left on because they have a different logic behind them. If it was up to me I would turn them off on the ground too. I think none of the Boeings won't spool their engines up after landing automatically anymore but pre-takeoff it's an avoidable danger. Nothing would be lost if the AT was to be armed during the pre-takeoff flow.


                      Like I said. A risk. But I contend it's a theoretical one, since I am not aware of any incidents or accidents. Are you?
                      A theoretical risk is worth to be taken into consideration. In aviation changes are done always after an accident or incident so things don't happen twice. Of course we can say "it hasn't happened yet" here too.


                      To end it with a sarcastic tone: In SXM people deliberately stand behind the engines of a 747 after all... One stone...
                      i7-6700k, GTX 1080TI, 32GB DDR4 RAM @2666MHz, 4k
                      Marc Ehnle

                      Comment


                      • Kevin Hall
                        Kevin Hall commented
                        Editing a comment
                        If someone pressed TOGA, watched the thrust levers to advance to TOGA thrust and did nothing then yes, it would be something to guard against (mainly by preventing anyone like that getting into the flightdeck at all). Realistically there is no risk of injury involved as it's so easy to stop the levers moving. Also, you can't deliberately move the 737 TOGA button with your sleeve unless you try very hard, so doing it accidentally is unlikely.

                        The only reason the switch needs to be put in ARM in the 737 is that disengaging the A/T causes it to drop down to OFF.
                        Last edited by Kevin Hall; 31Jul2021, 16:22.

                      #13
                      Originally posted by Ephedrin View Post
                      To end it with a sarcastic tone: In SXM people deliberately stand behind the engines of a 747 after all... One stone...
                      Interesting you mention that. If I remember, somebody got hit by one, let go of the fence, tripped over the curb, and got hurt. There was another incident where somebody let go of the fence, tripped over the curb, landed on her head, and died.
                      Captain Kevin

                      Kevin Yang

                      Comment


                      • DDowns
                        DDowns commented
                        Editing a comment
                        Many decades ago when I was a young Captain in the AF, I was out on the Offutt AFB Localizer trestle (a wooden platform at runway end where the ground dropped away and the platform was there to support the antenna) when the E-4B (B742) took to the active. I took my cap off and watched and was washed with a warm sweet smell of JP-4 as she spooled up and left me standing there. It was one of those moments that stay with you, no drama or Hollywood stunts but just a strong warm breeze from a big beautiful (very beautiful) aircraft.

                      • Captain Kevin
                        Captain Kevin commented
                        Editing a comment
                        I wouldn't dispute that. In fact, the only reason I even knew about the one girl who got hurt was there was a video of it. As for the girl who died....I suppose that one's kind of hard to hide.

                      • threegreen
                        threegreen commented
                        Editing a comment
                        Been there, done that. Mind you, I positioned myself well to the left behind a Corsair 747 spooling up precisely to avoid going flying myself and that was enough. There were several people directly behind it that went flying that day, one managed to go all the way into the sea.

                      #14
                      Or a spot on “Jackass”.
                      Victor Green

                      Comment


                        #15
                        Originally posted by Lanica View Post
                        Or a spot on “Jackass”.
                        Johnny Knoxville would probably sit into a shopping cart behind a 747
                        i7-6700k, GTX 1080TI, 32GB DDR4 RAM @2666MHz, 4k
                        Marc Ehnle

                        Comment


                          #16
                          Our procedure is to arm the A/T during the preflight setup at the gate.
                          Joe Diamond

                          Comment


                            #17
                            Originally posted by JoeDiamond View Post
                            Our procedure is to arm the A/T during the preflight setup at the gate.
                            Do you know any specific reason?
                            Niklas Graefe
                            Prepar3D v5.2 | 737/777 | i9 9900K 5 GHz | Corsair 32 GB | RTX 3090 24 GB | W10 | HP Reverb G2

                            Comment


                            • DDowns
                              DDowns commented
                              Editing a comment
                              I've always considered arming the A/T part of the MCP preflight. There really isn't a downside, just one of several ways to do it.

                            • JoeDiamond
                              JoeDiamond commented
                              Editing a comment
                              Just my personal speculation but probably because there isn't any compelling reason not to arm it at the gate during the preflight. One less thing to worry about once the airplane is moving. You already have enough things to worry about while you taxi, why add another item that could be accomplished beforehand?

                            • threegreen
                              threegreen commented
                              Editing a comment
                              Thank you.

                            #18
                            We arm it once performance calculations are done and V2 is set in the MCP. Previously it was upon entering the runway. Not sure of the logic behind the change, but probably to be in line more with Boeing's guidance and to be similar across all 737 types.
                            ATPL - Class I Instructor - Seaplane - B737 - BE1900D

                            Comment


                              #19
                              For my company, it's armed as part of our lineup procedure. It's actually on our Before Takeoff checklist, below the line too. Not sure why we decided to arm it there in our procedures but it could be something to do with subtle system differences between the classics and NGs. We only have -300s and -400s. About 7 years ago (and before my time here) we used to have -200s. Don't know what the autothrottles were like on those. Perhaps companies just left their arming later in their procedures for familiarity when they upgraded from -200s or classics to NGs?

                              I've heard about the 'prevent accidentally activating TOGA' thing before but the buttons are sort of buried on the throttle lever and it's sort of tricky to get my index finger far enough to hit it. I saw a captain just use his thumb from under the throttle and I've started doing that and it's actually easier. It also takes enough force to trip that it can really only be done on purpose. Like others suggested above, even if you somehow managed to unintentially activate TOGA it's not very hard to just disconnect and pull the throttles back to idle.
                              Ryan Gamurot

                              Comment


                                #20
                                Originally posted by rgamurot View Post
                                For my company, it's armed as part of our lineup procedure. It's actually on our Before Takeoff checklist, below the line too.
                                Ah, I remenber those old days before Boeing's SOP full overhaul (Not quite, I wasn't in actual aviation industry in those old days, but just knows that in sims)...

                                As the "official" SOP from boeing nowadays, all 737's SOP have been updated after I think is early 2000s to almost same standard (and also very simulair across all Boeing model except 707-727 and 742).
                                It's actually amazing to know there are still company use the old SOP, The new Boeing's SOP is the main trigger for me to get intersted in aviation human factor and get the track on aviation career.
                                ZHU Hai
                                B737 Ground instructor

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