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  • 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.
    Except a trim wheel in a current generation aircraft would be a rotating wheel thats then connected to all of those electric motors and microprocessors. The aircraft do not connect any of the flight controls directly to any of the control surfaces. So, given the way the flight controls are operated, a wheel would, by necessity, be more complex than basic switches.

    Comment


    • Good point! I guess I was seeing the argument more as a plane with entirely new tech vs. one with entirely old tech.

      But it certainly would be possible (and darn easy) to create a system whose purpose was to simulate the visual and audible cues that were provided by a mechanical trim system.

      Say a strip of LEDs on each side of the pedestal, in the same general position the trim wheels used to be. The LEDs could be lit in sequence to provide the same visual effect of "motion" that you'd get from a moving trim wheel. Then add an audio component using existing hardware that makes a noise corresponding to trim changes.

      That system would be easy and inexpensive to implement, and could hardly have a negative effect on safety as if it were to fail, you'd just be where you are now... with no "proactive" indication of changing trim.

      I realize this could be a can of worms but you could even put an item on a menu somewhere that would allow the pilots to turn the system on and off per their preference.
      Be alert! America needs more lerts.

      Eric Law

      Comment


      • Originally posted by elaw View Post
        And there's nothing inherently wrong with trying to save money, as long as safety isn't negatively impacted.
        Exactly. So now we can end this argument... oh wait...

        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.
        Evidence? What evidence?

        I'm so confused at this point. Originally the 'red flag' was that the A320 has a trim wheel that doesn't clack around. But it does give a clear indication that the trim is moving. But then, the A380, the A350 and the B787, the later B767 and 757's and a lot of lesser jets give no such 'clear' indication that the trim is moving. And as fas as I can tell, they do not experience problems because of this. I think this is due to pilot competence on a very basic aspect of flight control.

        Say a strip of LEDs on each side of the pedestal, in the same general position the trim wheels used to be. The LEDs could be lit in sequence to provide the same visual effect of "motion" that you'd get from a moving trim wheel.
        The A320 has that in the form of an active trim wheel with a trim position scale and that was deemed unsafe a few pages ago. All modern jets have a trim position indication. Like airspeed or altitude, you have to use you eyes to read it.

        Then add an audio component using existing hardware that makes a noise corresponding to trim changes.
        Great. Another confusing noise in the cockpit. Do you know how active the trim is in certain phases of flight? Should we also have one for when the airspeed is changing or the rudder trim is moving or the pitch is rising? Because there is evidence that all of those things can have a negative effect on safety as well.

        This thing is a non-issue. All you have to do is look at three facts here.

        1) Every modern airframe now uses pitch trim switches for alternate trim.

        2) Every modern airframe is designed by experts in aviation safety and certified by experts in aviation safety.

        3) There is no trend in aviation incidents to indicate a systemic problem with pitch trim awareness.

        Keeping in mind fact #4...

        4) There is a very strong trend in aviation incidents indicating a systemic problem with pilot screening and pilot training on basic airmanship.

        Comment


        • Originally posted by Evan View Post
          Evidence? What evidence?
          Indian Airlines 605, the Tarom incident Gabriel posted about earlier in this thread, and a number of others that all had the pilots not realizing the trim setting had changed as a significant causal factor.

          Originally posted by Evan View Post
          I'm so confused at this point. Originally the 'red flag' was that the A320 has a trim wheel that doesn't clack around. But it does give a clear indication that the trim is moving. But then, the A380, the A350 and the B787, the later B767 and 757's and a lot of lesser jets give no such 'clear' indication that the trim is moving. And as fas as I can tell, they do not experience problems because of this.
          Originally posted by Evan View Post
          The A320 has that in the form of an active trim wheel with a trim position scale and that was deemed unsafe a few pages ago. All modern jets have a trim position indication. Like airspeed or altitude, you have to use you eyes to read it.
          Yeah, and pilots have to use their eyes for a lot of other things too. If they were able to keep their eyes on the trim indicator 100% of the time (or even 25% of the time) there probably would not be a problem but the cases I cited above indicate there *is* a problem.

          How about an example from a different field? Nuclear reactors have gauges that can be used to tell if the core is overheating. But they also have visual and audible systems to alert operators of an overheating condition, as well as multiple automatic systems to deal with such an occurence if the operators don't do so in a timely manner. If you think all those extra systems are a useless expense, when the first reactor is built without them we'll see if we can find you a nice house next door to it.

          Originally posted by Evan View Post
          I think this is due to pilot competence on a very basic aspect of flight control.
          "Very basic aspects of flight control" are controlling a plane's pitch, roll, yaw, and speed or angle of attack in order to maintain a desired flight path. Guessing what HAL is doing from one moment to the next is not a basic aspect of flight control.

          Originally posted by Evan View Post
          Great. Another confusing noise in the cockpit. Do you know how active the trim is in certain phases of flight?
          Yep, because you can look at any youtube video taken in the cockpit of an old aircraft and hear it. Let me ask you this: are you aware of any accidents where the noise or "visual distraction" from the pitch trim system has been cited as a causal factor? I'm not.

          Originally posted by Evan View Post
          This thing is a non-issue. All you have to do is look at three facts here.

          1) Every modern airframe now uses pitch trim switches for alternate trim.

          2) Every modern airframe is designed by experts in aviation safety and certified by experts in aviation safety.

          3) There is no trend in aviation incidents to indicate a systemic problem with pitch trim awareness.

          Keeping in mind fact #4...

          4) There is a very strong trend in aviation incidents indicating a systemic problem with pilot screening and pilot training on basic airmanship.
          1) As do pretty much all airliners going back to the beginning of the jet age, and in many cases before that.

          2) Just like all airliners since about the mid-1930's.

          3) There was no trend in space shuttle explosions until the Challenger disaster. That doesn't mean that dumb things weren't done... just that prior to that date the problem didn't appear due to circumstances/luck.

          #4 I partially agree with... I think there are many ways in which training could be improved. But as others have stated (and you've never addressed), if you tighten screening to the point where every pilot that could possibly make a fatal mistake under any circumstance is prevented from flying, all aircraft would be grounded permanently. And society has deemed that approach unacceptable.
          Be alert! America needs more lerts.

          Eric Law

          Comment


          • Originally posted by elaw View Post
            Indian Airlines 605...
            What are you talking about?!! Indian AIrlines 605 was classic CFIT, FCU mismanagement, OP DES mode where it clearly isn't safe, poor energy management, failure to monitor, stable approach violations, failure on go-around procedure, man, just about everything in the book except for pitch trim issues.

            And Tarom Flt 381?! That was an A310, with good ol' trim wheels and a good ol' yoke to fly it by. That was pure pilot error. Not only did they fail to respond with basic airmanship, they failed on A310 Memory Item #7:
            7. a) Abnormal Pitch Behavior: b) Pitch Trim Runaway:

            Control Wheel – Hold Firmly
            Trim Wheel – Hold Firmly
            AP (if engaged) – Disconnect
            Pitch Trim Levers – Check Both OFF
            Pitch Trim – Manual
            Pilot's who are not proficient on memory items, why don't we talk about that issue instead?

            Comment


            • And by the way, this is the approach-to-stall procedure I have for the A310:

              Stall Recovery:
              When any stall indication (aural, stick shaker or buffet) is recognized, apply the immediate actions:

              During Any Flight Phase Except at Lift Off:
              • AP – Disconnect
              • A/THR – Disconnect
              • Nose Down Pitch Control – Apply
              Nose Down Pitch Trim – As Needed
              Note: Incase of lack of pitch down authority, reducing thrust may be necessary
              • Bank – Wings Level

              Comment


              • I think there's a bit of a logical disconnect in claiming a pilot is not proficient because they didn't do the memory items for runaway trim in a situation where they weren't aware the trim had run away!

                Although I'll agree that it's pretty basic that if you push forward on the yoke/controller and the nose doesn't drop, to check the pitch trim.
                Be alert! America needs more lerts.

                Eric Law

                Comment


                • Originally posted by Evan View Post
                  What are you talking about?!! Indian AIrlines 605 was classic CFIT, FCU mismanagement, OP DES mode where it clearly isn't safe, poor energy management, failure to monitor, stable approach violations, failure on go-around procedure, man, just about everything in the book except for pitch trim issues.
                  You're right, that was a bad example - I misread the article about it.

                  But there have been several approach accidents/incidents, although I don't remember specific airlines or flight numbers, where pilots have attempted to "push the a/c onto the runway" for lack of a better description, while the automation was trimming the nose up because it wanted the a/c to climb (either attempting to go around or hold altitude). While the root cause in those cases was the pilots' failure to understand how the automation worked and/or what mode it was in, I think a clear indication that the trim was changing would have helped the pilots realize sooner what was going on and take appropriate corrective action.
                  Be alert! America needs more lerts.

                  Eric Law

                  Comment


                  • Originally posted by elaw View Post
                    You're right, that was a bad example - I misread the article about it.

                    But there have been several approach accidents/incidents, although I don't remember specific airlines or flight numbers, where pilots have attempted to "push the a/c onto the runway" for lack of a better description, while the automation was trimming the nose up because it wanted the a/c to climb (either attempting to go around or hold altitude). While the root cause in those cases was the pilots' failure to understand how the automation worked and/or what mode it was in, I think a clear indication that the trim was changing would have helped the pilots realize sooner what was going on and take appropriate corrective action.
                    Well, let us know if you find those 'several approach accidents/incidents'. The Airbus control law is always in DIRECT law when touching down. In fact the system adds a bit of nose-down pitch to help initiate the flare. Unless you are on autopilot, the automation isn't doing anything to pitch trim. Prior to the NORMAL-DIRECT transition, the pitch wheel is actively turning in plain sight but only to achieve neutral static stability for the attitude or speed you (or the autopilot) are commanding. It doesn't have other ideas.

                    Comment


                    • What, you think I'm making this stuff up?

                      China Airlines flight 140, Airbus 300, April 1994: http://www.planecrashinfo.com/cvr940426.htm

                      The plane crashed because of an extreme out of trim configuration brought about by the fact that the tailplane setting had moved automatically and undetected to a maximum nose-up position.
                      Not a "modern" airplane, it actually has trim wheels - I couldn't find out whether there's an audible indication when they move. But the fact is the plane's automation system moved them and the pilots did not notice - if they *had* noticed, 264 people probably would not have died that day.
                      Be alert! America needs more lerts.

                      Eric Law

                      Comment


                      • Originally posted by elaw View Post
                        What, you think I'm making this stuff up?

                        China Airlines flight 140, Airbus 300, April 1994: http://www.planecrashinfo.com/cvr940426.htm

                        Not a "modern" airplane, it actually has trim wheels - I couldn't find out whether there's an audible indication when they move. But the fact is the plane's automation system moved them and the pilots did not notice - if they *had* noticed, 264 people probably would not have died that day.
                        This is one of those accidents that happened during that hazardous blend between autoflight and manual flight. Essentially it was a gross case of automation mismanagement.
                        1114:10 The CAP (PNF) cautioned the F/O (PF) by saying " You, You triggered the GO lever,", and the F/O acknowledged, saying "Yes, Yes, Yes, I touched a little."
                        A classic line if I ever heard one.

                        The F/O had accidentally triggered the TOGA mode. The Cpt repeatedly warned him of this and asked him to disengage it. He did not.

                        When the A/P was reengaged the FD was—of course—still in Go-Around and was thus commanding a climb. To stay on glide path, the F/O manually pushed against the trim force on the yoke. He then tried to retrim using the yoke switches which are—of course—inhibited in autoflight. The more the F/O pushed down on elevator, the more the THS compensated to maintain the FMGC commanded attitude.

                        But the larger issue is that the F/O was trying to override the autoflight with commands in opposition to it. This is a big no-no. It will cause the THS to do exactly what it did. If you don't like what the automation is doing, you either change the FCU settings or you disengage it. You don't fight the airplane!

                        The Cpt once again pointed out to the F/O that he was still in Go-Around mode and to disengage it. Again, the F/O did not.

                        The Cpt, rather than telling him to adjust the pitch trim manually, told him to push against it using the yoke.

                        Again the Cpt told the F/O that he was in Go-Around mode. The F/O replied "yes sir." No mode change was made.

                        The Cpt finally took over in manual flight and also pushed against the trim, pushing the trim switch only intermittently despite the out-of-trim condition. The THS responded by reducing trim proportionate to these commands. But he only commanded about 2° ND the entire time and meanwhile concerned himself with monkeying around with the thrust... honestly I can't go on reading it, this is such a hatchet job.

                        1) All they had to do was get out of TOGA and despite repeatedly warnings and commands to do so, nothing was done.

                        2) The F/O didn't seem to understand that the yoke trim switches are inhibited in autoflight. That's basic A300 pilot knowledge. And basic logic.

                        3) They had a pitch trim wheel, a pitch trim position scale and all the trim feedback they could ever want. They just never thought enough about pitch trim.

                        AIrbus had made some system mods before the crash that might have helped here but they weren't yet made on the accident aircraft because China AIrlines didn't deem them that important. Oh well...

                        What is your point? If it is that the current lack of a pitch trim wheel is a threat to safety than this example actually works against you. Can't you see that?

                        Comment


                        • elaw,

                          I'm a strong advocate (usually) for non-visual, or obvious visual, cues. Linked sidesticks, moving thrust levers, etc etc.

                          However the problem I'm having with this one is that of all the pitch-trim related accidents I've read about, all of the ones I can recall happened on aircraft with moving pitch trim wheels.

                          The situations it may help are
                          - Stab trim runaway, when you see the trim wheel just run and would notice it. However the modern aircraft don't have the trim motors connected the same way - there's computers deciding what movement to put into the trim - so the chances of an undetected (by aircraft systems) and un-notified old fashioned trim runaway are tiny.

                          - Gabriel's example of the aircraft losing speed, with the trim wheel moving providing an additional clue (additional to airspeed indicator, thrust setting, and pitch setting) that something isn't right.

                          This one is good in theory, but it didn't save Turkish. The argument is made that there's enough other clues that it is unlikely that this additional one is the point of difference.

                          Comment


                          • this may be construed as me agreeing with evan so forgive me.

                            seems to me that pitch is a basic element of aviation and must be MEMORIZED and considered to be something a pilot must check and consider in all phases of flight, as much as yaw and bank.

                            in semi-auto mode, this shouldn't change. i equate it to driving a car with the cruise control set at 65 and simply not considering that the car is gonna continue at 65 even if you are headed up a mountain.

                            Comment


                            • Originally posted by TeeVee View Post
                              ...seems to me that pitch is a basic element of aviation and must be MEMORIZED and considered to be something a pilot must check and consider in all phases of flight, as much as yaw and bank...
                              It is, and I'd say that 99.9999% of pilots agree and do exactly that.

                              Then we have those who do not and then we have numerous questions:

                              Why did they do what they did?

                              What were they thinking?

                              How were they trained?

                              Does something need to be changed?

                              Did they forget something crazy basic from their first 10 hours of flight training, or forget memory checklist item 13.2.5.236A (the answer is usually both).

                              One valid answer is that we are already doing things right and there's only so much we can do to filter out the 0.000001% folks who can screw up a ball bearing and nothing needs to be changed.

                              ...and then someone does the unthinkable, again...

                              ...wash, soak, repeat.
                              Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.

                              Comment


                              • Originally posted by 3WE View Post
                                Does something need to be changed?
                                Yes, I wouldn't trust that F/O with a lawnmower and somehow he got into a cockpit for a very long time. Hours obviously mean nothing if you don't have what it takes. What kills me is how the Old Man here just keeps saying, uh, you're still in TOGA, watches on as the F/O pushes against TOGA and does nothing until it's so far gone that even he can't dig his way out of it.

                                Something needs to be done all right. We've heard about the Asian aviation culture and cockpit gradient, but this is the opposite of that.

                                I don't think the problem with China Airlines 140 was that the pilots forgot about pitch trim. The problem was that the airline forgot about the 256 passengers and 12 flight attendants behind the door.

                                Comment

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