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  • #91
    Originally posted by 3WE View Post
    Or do you mean, "It should be quite instinctive to a qualified pilot that ineffective elevator means check the trim wheel which works just like it does on almost all aircraft including the C150 from your initial flight training?".

    ...and let's not forget: Ineffective elevator means maybe someone left the control locks in (check this forum for another active thread).

    Ineffective elevator means that maybe the engine shredded all three hydraulic lines.

    Ineffective elevator means that maybe the cargo door blew and the floor settled on the elevator cables.

    Ineffective elevator means that maybe the control cable touched the positive battery terminal and froze there.

    Ineffective elevator means that maybe the control cable came loose.

    Ineffective elevator means that maybe the elevator itself has come loose.

    Ineffective elevator means that maybe a rock kicked up from the runway and jammed the elevators.

    Ineffective elevator means that maybe they rigged the plane a little off from where it should be and this is the first flight where the CG is this far aft.

    Ineffective elevator means that maybe an inspection panel fell off.

    Ineffective elevator means that maybe your other pilot is pulling up the whole time.

    Ineffective elevator means that maybe you are going too fast and tucking over.

    Ineffective elevator means that maybe you are in a deep stall and the tail is blanked out.

    Ineffective elevator means that maybe a bunch of heavy-ass tanks have rolled to the back of the plane.

    That's a lot of maybes when your plane is stalling itself (or not pulling up) at altitudes from which you have marginal ability to recover.
    I had a feeling someone would bring up examples like these, thanks 3WE.

    In almost every case, checking pitch trim would be pretty much mandatory, and trimming might actually aid in regaining elevator effectiveness. So...none of those examples really change much. Pitch trim is intrinsically linked to how the elevator functions on an aircraft, pilots who ignore that basic fact do so at their own peril.

    Comment


    • #92
      Originally posted by Leftseat86 View Post
      What about a an aural / visual warning like "PITCH TRIM" when the trim goes to an extreme outside the usual range?
      Something like this?

      I realize it can be overlooked in a panic situation but it is right there on the PFD and, as MCM has pointed out (and I paraphrase), on the Airbus the FMA is your 'what's it doing now?" support center.

      Comment


      • #93
        Originally posted by Leftseat86 View Post
        I had a feeling someone would bring up examples like these, thanks 3WE.

        In almost every case, checking pitch trim would be pretty much mandatory, and trimming might actually aid in regaining elevator effectiveness. So...none of those examples really change much. Pitch trim is intrinsically linked to how the elevator functions on an aircraft, pilots who ignore that basic fact do so at their own peril.
        Indeed.

        Of course the point that I tend to stick on (and that maybe Gabriel is hinting at) is that when one of these bad things happen where you are seconds from dying and there's 14 possibilities, is there something to be said for having a UNIVERSAL old-fashioned wheel right out of a Cessna 150, DC-3, or 707 or is only having the "Elevator Trim Position App" from the I-tunes store on the touch screen adequate?
        Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

        Comment


        • #94
          Originally posted by 3WE View Post
          is only having the "Elevator Trim Position App" from the I-tunes store on the touch screen adequate?
          Welcome to 2015!

          Oh and make sure you have at least version 1.2 of the app... earlier versions would display incorrect information if you tried to watch a cat video at the same time the app was running.
          Be alert! America needs more lerts.

          Eric Law

          Comment


          • #95
            Originally posted by 3WE View Post
            Of course the point that I tend to stick on (and that maybe Gabriel is hinting at) is that when one of these bad things happen where you are seconds from dying and there's 14 possibilities, is there something to be said for having a UNIVERSAL old-fashioned wheel right out of a Cessna 150, DC-3, or 707 or is only having the "Elevator Trim Position App" from the I-tunes store on the touch screen adequate?
            When is this going to end with you guys, this idea that the way you fly, the actual controls you fly with, cannot evolve? It's so out of touch with the nature of technology, which has always been evolving. The first automobiles had a tiller. A steering wheel can be quite disorienting and anti-intuitive to someone who has always driven with a tiller, so we should have stuck with that I guess. I swear 3WE, every improvement made since the mid-1960's seems to be an unnecessary annoyance to you. Boeing did away with the trim wheel on new airframes back in the late 70's. Now they have done away with the trim lever as well. The only new flight deck I am aware of that is not using electrical switches for alternate pitch trim is the TU-204SM. I'm sure pilots can adapt to this change in controls if they are trained to understand the principal relationship between pitch (stab) trim and pitch control. They don't need a clacking, talking pitch wheel. They're not toddlers.

            Comment


            • #96
              Originally posted by Leftseat86 View Post
              What about a an aural / visual warning like "PITCH TRIM" when the trim goes to an extreme outside the usual range?
              Great idea!!! Nobody had thought of that!!! (except Mr Douglas).

              The MD-80 (and I suspect other Douglas planes too) have TWO warnings. A horn that sounds with even small deflections of the trim and an aural "Stabilizer in motion" when it moves more than X degrees in less than Y seconds.

              VNav? Can you shed more light on this?

              --- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
              --- Defend what you say with arguments, not by imposing your credentials ---

              Comment


              • #97
                Originally posted by Evan View Post
                When is this going to end with you guys, this idea that the way you fly, the actual controls you fly with, cannot evolve?
                They can, and have, and will.

                But sometimes in hindsight it's seen that "evolution" has unanticipated side effects. Remember New Coke? Okay that's a bad example but there are others. How about aluminum wiring in houses? It took quite a few fires before people realized that was a lousy idea... or at least poorly implemented.

                And questioning changes, especially in a very safety-sensitive area like aviation, should never end - if there are legitimate reasons to think those changes have had an adverse impact.

                If I may reveal my cynical side a little here, I think as technology advances it's also more necessary to make sure that changes actually represent improvements rather than just being for change's sake. Adding seat belts to cars that had none? Great idea - saved a lot of lives and prevented many injuries. Redesigning seat belts with weaker fabric to save weight and cost? Probably not such a great idea. But I bet it'll happen someday.

                There are a lot of forces at work promoting change for reasons that may not necessarily benefit the end user - marketing wanting to improve sales numbers by offering "something new", accountants and managers trying to improve the bottom line by cutting costs. Without opposing forces in place to balance those out, you might just hop into a new car one day and find the seatbelts are made of paper.
                Be alert! America needs more lerts.

                Eric Law

                Comment


                • #98
                  Originally posted by elaw View Post
                  And questioning changes, especially in a very safety-sensitive area like aviation, should never end - if there are legitimate reasons to think those changes have had an adverse impact.
                  You know I'm the first one to agree with that. And some changes are made for the wrong reasons, absolutely. I don't see anything to indicate that this is the case here. Every airframer has gone to electric pitch controls just as they have moved to the the 2-person glass cockpit. The reasons for that certainly include things other than safety but I don't see a significant risk opening up. Pilots, if not properly screened and trained, will crash anything. And pilots, properly screened and trained will know how to attend to pitch/stabilizer trim and will involve it in any scenario where pitch is not responsive. Even in sidestick aircraft where pitch trim in not a part of normal flying, this must be ingrained as a response into anyone meeting the definition of 'properly trained'.

                  We were talking about the A320. The position of stab trim is not felt but it is clearly indicated. The activity of the automated stab trim is also clearly indicated. In the very, very rare scenario of abnormal attitude law (or any failure-related reversion to direct law), pilots must be trained to attend to manual pitch trim. That is the caveat of having the benefits of neutral static stability without the need to ever trim in flight. Technology offers us benefits but also often requires something from us. As long as that something is not unrealistic, progress can occur.

                  It's a human problem. We have to draw a line between making everything as obvious as possible and moving ahead by expecting pilots to behave as professional airmen.

                  I would like to see improvements to everything, including the current AIrbus control laws. I would like to see them move to an active thrust lever. I would like to see them better address the dual-input issue. But because progress should always continue in the interests of safety, not because the current set-up in un-safe.

                  Comment


                  • #99
                    Originally posted by Evan View Post
                    It's a human problem. We have to draw a line between making everything as obvious as possible and moving ahead by expecting pilots to behave as professional airmen.
                    I agree, but I think sometimes people fail to recognize the limits of training and behavior. And in particular, how people will react vs. their training when placed in unexpected highly stressful situations.

                    And I think "unexpected" and "highly stressful" are the key concepts. A lot of time and effort have been put into making simulators that faithfully reproduce the behavior of aircraft and in general they've done a great job. But there are two areas lacking: first, when a pilot goes into sim training, they know things are going to "fail" and probably have some general idea of what is going to fail (engine fail at V1 during takeoff? hell yeah). So they're mentally prepared for failures... it would be interesting to put a pilot in a sim and have them sit and do almost nothing for 4 hours *then* simulate some obscure failure and see what happens.

                    And the second thing is (and I'm definitely not saying this should change) is that pilots going into sim training know that the sim is not going to kill or injure them. So how they react to any given condition may be different from how they'd react when their life is actually in danger.

                    I guess what I'm saying is that it's common sense that you can't do "just anything" to the design of an aircraft and expect pilots to deal with it. But there's a realm where you can make changes and *think* they've had no negative effect because pilots are able to deal with them properly in training and during normal operations, but when the s**t really hits the fan, pilots are apt to react incorrectly. In those cases, I think the design of the system(s) should get some or all of the blame for what happens, not the pilots who are humans doing what humans do.

                    In a very small way, I actually have personal experience with this sort of thing. When I was young, I spent many hours riding go-karts that I steered with my feet. And the steering was such that when I pressed with one foot, the kart would go the opposite direction: if I pressed with my left foot, the kart would turn right. So that action-reaction relationship was pretty well burned into my mind.

                    Years later when I took flight instruction, it drove me absolutely crazy that the rudder pedals in aircraft worked the opposite way (push with left foot and plane yaws left). I eventually got used to it, but always wondered if I were really in a bad situation that required specific use of the rudder, whether I'd push the wrong pedal. Luckily to date I haven't had a chance to find out...
                    Be alert! America needs more lerts.

                    Eric Law

                    Comment


                    • Originally posted by elaw View Post
                      I agree, but I think sometimes people fail to recognize the limits of training and behavior. And in particular, how people will react vs. their training when placed in unexpected highly stressful situations.
                      Yes, we've been all over this. Even the most experienced pilots may, in a moment of phenomenal stress, draw a blank or do something inexplicable. This is why we have two pilots and CRM. And, if there is time, a QRH full of correct procedure.

                      So, group together all of the memory items. These are the things a pilot must do correctly without time to access checklists. All of these are taught (by a competent airline with a moral conscious) to be as instinctive as possible. They are supposed to be ingrained like "there's a ball coming at my head: I will place my hand in front of it". That is within the limits of what is possible in training, but it will never be 100% reliable in any given individual (which is why we have two pilots and CRM).

                      I see NO REASON why you cannot instill the instinct to use pitch trim in a situation where elevator is unresponsive to the same degree that you can instill the instinct to get on oxygen and initiated a rapid descent upon losing cabin pressure or lowering pitch on stall warning. In fact, I think most competent pilots already have this instinct, even the ones who never have to use trim.

                      So that just leaves the incompetent pilots. And there's your problem.

                      Comment


                      • Ah, I see.

                        So when AirBoeing releases their "new improved" flight-control system that uses touchscreen PDA's, and the pilot's PDA's battery runs out unexpectedly (because it's near its end of life, not because the pilot failed to charge it), and the pilot grabs the backup PDA because competent pilots always have a backup PDA but the app's frozen, and the pilot grabs the backup backup PDA because competent pilots always have a backup for their backup but it won't work because a FA spilled coffee in it, it's still the pilot's fault that the airplane can't be controlled?
                        Be alert! America needs more lerts.

                        Eric Law

                        Comment


                        • You do know the movie "Hot shots" is not a documentary, right?
                          Be alert! America needs more lerts.

                          Eric Law

                          Comment


                          • Originally posted by Evan View Post
                            When is this going to end with you guys, this idea that the way you fly, the actual controls you fly with, cannot evolve? It's so out of touch with the nature of technology, which has always been evolving. The first automobiles had a tiller. A steering wheel can be quite disorienting and anti-intuitive to someone who has always driven with a tiller, so we should have stuck with that I guess. I swear 3WE, every improvement made since the mid-1960's seems to be an unnecessary annoyance to you. Boeing did away with the trim wheel on new airframes back in the late 70's. Now they have done away with the trim lever as well. The only new flight deck I am aware of that is not using electrical switches for alternate pitch trim is the TU-204SM. I'm sure pilots can adapt to this change in controls if they are trained to understand the principal relationship between pitch (stab) trim and pitch control. They don't need a clacking, talking pitch wheel. They're not toddlers.
                            As I read this, I do not see where you have listed ANY disadvantage to to a trim wheel nor any specific ADVANTAGE to no trim wheel.

                            You seem to be bugged that it's old and need to try a cheap shot with the 'toddlers' comment.

                            And, when I first posted my comment- it was that I saw a specific advantage to a universal trim wheel- the pilot will never be confused because he had a hundreds of hours with a trim wheel and now it's gone- sure, ADD the thumb switches (a GREAT way to help the pilot be lazy reduce his tactile attachment to the aircraft.... AND add ANOTHER thing to the flat panel display (along with Gabriel's AOA indicator), but where's the disadvantage to the wheel?

                            And, I can almost laugh at your car tiller comment...yep it's so OLD FASHIONED that it's how you guide a modern jet airplane!
                            Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                            Comment


                            • Originally posted by 3WE View Post
                              As I read this, I do not see where you have listed ANY disadvantage to to a trim wheel
                              Complexity, maintenance, inspection, weight, expense, anachronism. And in the comparison of the Airbus cockpit, the need to trim.

                              Advantage of the switches: simple, lightweight, virtually maintenance-free, elegant, easy to use, cheap, silent, simple, modern.

                              Since every aircraft that matters with the exception of the 737 has evolved to the switches or levers and no accidents that I know of can be attributed to the lack of a pitch trim wheel, I'm guessing I'm right.

                              But keep that fire burning 3WE. Progress is the devil's work.

                              Comment


                              • Terms like "modern", "elegant", and "anachronism" don't really have a place in engineering discussions but the most important thing I noticed is that the word "safety" didn't appear anywhere in your post.

                                Most of the things you mentioned in favor of ditching trim wheels come down to money: additional parts in an aircraft cost money, maintenance & inspection cost money, fuel to carry extra weight costs money.

                                And there's nothing inherently wrong with trying to save money, as long as safety isn't negatively impacted.

                                But there is some evidence that indicates that lack of trim wheels (and/or lack of clear indication the trim is changing) does have a negative impact on safety... and that's what I have a problem with.

                                There is another angle to this, and it's that with everything else equal, simplification of systems does in general improve reliability... less total parts means less parts to fail. And in aviation, reliability usually equates to safety.

                                But in this case I think that's a red herring. Is removing a rotating wheel connected to control surfaces by cables and installing an electric motor connected to those same control surfaces by gears and linkages, controlled by a microprocessor-based system containing hundreds of thousands of transistors and thousands of lines of programming code, and powered by the airplane's (very complex) electrical system really "simplification"? Not in my opinion.
                                Be alert! America needs more lerts.

                                Eric Law

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