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.
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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
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Originally posted by elaw View PostAnd 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.
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.
Then add an audio component using existing hardware that makes a noise corresponding to trim changes.
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.
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Originally posted by Evan View PostEvidence? What evidence?
Originally posted by Evan View PostI'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 PostThe 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.
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 PostI think this is due to pilot competence on a very basic aspect of flight control.
Originally posted by Evan View PostGreat. Another confusing noise in the cockpit. Do you know how active the trim is in certain phases of flight?
Originally posted by Evan View PostThis 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.
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
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Originally posted by elaw View PostIndian Airlines 605...
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
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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
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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
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Originally posted by Evan View PostWhat 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.
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
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Originally posted by elaw View PostYou'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.
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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.Be alert! America needs more lerts.
Eric Law
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Originally posted by elaw View PostWhat, 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.
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."
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?
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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.
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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.
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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...
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.
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Originally posted by 3WE View PostDoes something need to be changed?
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.
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