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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Mar 2019, 00:21
  #1241 (permalink)  
 
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Have we passed the point in modern aviation where it is not possible to (quickly) switch off all these pilot and performance aids and fly “manually”?

At very least, the last resort if flying in VFR conditions?


Mjb


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Old 14th Mar 2019, 00:32
  #1242 (permalink)  
 
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Originally Posted by Speed of Sound

Given all of the above along with the fact that this isn't simply a batch of dodgy AoA sensors, but a possible design fault that could affect every aircraft in the fleet, it would be an act of sheer folly not to ground the entire fleet.
I can't disagree. There is a perception that the two incidents being dealt with happened "elsewhere", and the importance of protecting the credibility of the FAA and Boeing is paramount
.
May be its time for the NTSB to assess what has led to this shambles.
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Old 14th Mar 2019, 00:39
  #1243 (permalink)  
 
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Originally Posted by FCeng84
The requirement compliance that MCAS was introduced to address can involve the column being further aft than the position of the column cutout switch. Were MCAS subject to being interrupted by that switch, it would not be able to do the job for which it was designed.
Just trying glean what flight regime MCAS needs to protect. So, they didn't want the column cutout switch to work because they envisioned pulling hard and not trimming. Trimming would normally return the column to neutral. Two things come to mind. Windshear escape in the clean config and steep turns with guys that don't trim. I (having the T-38 training mantra embedded, "trim trim trim") would trim during steep turns so that would not be a problem for me or MCAS. Of course steep turns are a simulator exercise so not really relevant. Again I ask why put out the original AD and not caution about being careful when pulling with the loss of MCAS.
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Old 14th Mar 2019, 00:48
  #1244 (permalink)  
 
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I think the satellite data *could* refer to any ACARS maintenance information transmitted to Boeing and/or GE and/or Ethiopian. Just like the AF accident, there were ample maintenance fault messages received well before the FDR was recovered that might have given the precipitation of events

Regarding the larger picture here, an average crew, newly aware of the newly-revised MCAS ‘warnings’ could still be easily saturated by stick-shaker, air data miscomps, and ever-increasing stick forces in that scenario.

Disconect stab trim trim, pitch and power for a safe climb-away...may have been too much for a crew of certain caliber. Simulator training may have mitigated an accident of an afflicted crew, but time will tell what went wrong, and how.

Last edited by FIRESYSOK; 14th Mar 2019 at 01:04.
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Old 14th Mar 2019, 00:50
  #1245 (permalink)  
 
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Originally Posted by Recidivist
I understand - what I was thinking of was not the complexities of flight as the pilot sees them, but purely focussing on the automation aspect - why allow an automatic system to operate the airplane when AoA and pitch gyro are indicating different things? Sure, it's possible both are correct, but the pilots are there to make those decisions. Why allow the automation to continue to pitch down when the altimeter is showing accelerating loss of height? A pilot may indeed do this to recover from a stall, but surely it would be rare to rely on autopilot to get you out of a stall?
I gather there are situations where the pilots are presented with a message that indications disagree, and the automatics effectively hand the matter over to the pilot - I'm just exploring why that isn't the case when to continue with the automatics could result in catastrophe.

Edit: Replying to predictorM9
For the AoA sensor and the pitch angle, these are not the same and so they disagree in general (the difference between the two is the angle of climb or descent, which is not always zero).
Even if you have an accelerating loss of height, you can not know if you are out of the stall or not, so the automation relies only on the measurement of the angle of attack to determine that. They don't reconciliate the data from all sensors to check what sensor is ok and what sensor is faulty, the logic to do that would be a bit complex and probably not certifiable.


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Old 14th Mar 2019, 00:51
  #1246 (permalink)  
 
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Originally Posted by tartare
I think Boeing's ballsed this up - and the FAA have a lot of reflecting to do on the overwhelming power of public sentiment versus the facts.
There comes a point in crisis management where you must address the perceptions, arguing the facts is useless.
Few if any will likely share this sentiment, but I feel for Boeing's PR team at the moment.
As a former corporate spin doctor these crises are horrific to manage.
The public baying for your blood.
Investors trashing your stock.
Politicians jumping on the bandwagon.
And nearly always - panicked and agitated senior managers, and others right up to Board level, jumping in, trying to do your job for you, ignoring advice and only making a bad situation worse.
Seen it and lived it so, so many times - and it's always the same.
Well said. The grounding was inevitable and the delay just added to the reputation damage.
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Old 14th Mar 2019, 00:56
  #1247 (permalink)  
 
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Originally Posted by FCeng84
What happened to one of your first priorities on an airplane that requires the pilot to manage pitch trim? If steady column forces are present, pitch trim should be used to drive the stabilizer so that those column forces are relieved. I concur with the criticism that with MCAS as currently implemented we can get headed down this path as a result of one errant sensor, but I don't see that the eventual result should put the airplane so far out of trim that pitch control power via the column is exhausted. MCAS moves the stabilizer, but does not interfere with the pilots ability to override and move the stabilizer back to the proper trim position.
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place! So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is. Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes. By the time he actually realises how out of trim he is, he's doing 350, and despite the stab still being at the same X° nose down since cut-out, the forces have multiplied. Now if there is any nose down attitude or reduction in power then there's absolutely no chance to recover.

Obviously all hypothetical, an airspeed disagree on takeoff could lead to circumstances similarly, or a multitude of other possible reasons, however, in the situation that I've hypothesized, it would almost certainly always end in a similar steep nose down attitude.
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Old 14th Mar 2019, 01:01
  #1248 (permalink)  
 
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Salute MJB !!

On most airliners it is possible to fly "manually" with good training and practice/experience. Landings and takeoffs by the carbon-based life forms are good examples. Even then, many planes have pitch and yaw dampers to keep the planes really stable and predictable when not using the autopilot.
The Airbus that went down years ago over the Atlantic was a very stable and predictable aerodynamic machine. It handled so well that the crew flew it into a stall and did not realize that they had done so. Most pilots could prolly fly that type in the backup control laws with just a bit of practice.
The basic 737 used to be that way, but the basic design was modified time and again until it no longer exhibited the same aerodynamics as the one certified 40 or 50 years ago. Just look at a classic version and then the MAX. Who would think that the two shared the same original designation? Boeing added this and that to avoid an expensive "start over" cetrtification process, plus, the FAA allowed Boeing to "build upon" the existing certification. A new process/designation for the MAX would have not been allowed to add another kludge to preserve longitudibnal stability and handling requirements. The plane would have been required to demonstrate traditional control force and pitch moments at high AoA without the MCAS kludge.

A pure FBW control system has all the "protections" and limits/warnings and such as part of the basic design. But no FBW commercial airliner has failed to meet the basic aerodynamic requirements for stability and control if they all had ropes, levers, pulleys, cables, torque tubes, etc to move the ailerons, rudder and elevator. They are not the military or utility platforms and do not haul 200 folks about to visit aunt Clara.
So Boeing adds another thingie besides the STS speed stability doofer to meet Part 25 requirements and it gets signed off. Most of we pilots would handle the new thingie if and a BIG IF we knew it was added AND we were told what possibel failure indications existed AND we practiced a bit. GASP!! None of that was done.
My experience was in military planes and before each flight we had to sign off every little notice, directive and change and such before flying. On some mods we had to fly with an instructor before being cleared "solo". The MCAS mod required none of those things, and I have problems with not having seen a revolt by a thousand 737 pilots that only discovered MCAS after Lion 610 pranged.

'nuff bitching, and I close for now

Gums

Last edited by gums; 14th Mar 2019 at 02:18. Reason: typos, mainly
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Old 14th Mar 2019, 01:06
  #1249 (permalink)  
 
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Interesting article:
https://www.theatlantic.com/notes/20...37-max/584791/
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Old 14th Mar 2019, 01:26
  #1250 (permalink)  
 
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Now that this is a huge international news story, it's interesting to see the developing outside media opinion/current consensus.

One very commonly expressed thread is that the probable JT610, possible ET302 accident cause is new overcomplicated automation confusing pilots (this is similar to Trump's Tweet also).

But interestingly this is actually the opposite of the MCAS issue. The MCAS algorithm appears much too simple for it's power, primarily taking a single AoA vane input without consistency checks, and applying them to the stabilizer periodically with no limit except when maximum downtrim is reached. Automation simplicity is one approach to reducing failure modes, but within reason as demonstrated in this case.
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Old 14th Mar 2019, 01:33
  #1251 (permalink)  
 
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I think it is common for those who don’t fly Airliners, and also for those with only one or two years experience on them, to underestimate the effect of contradictory information being presented on the Primary Flight Displays.
For me, just when I thought I was a gun at flying appropriate thrust settings and attitudes during simulated Airspeed Unreliable scenarios, just as my confidence was peaking ( about six years on the NG after ten years on turbo-props), I was presented with a pitot-static issue on departure ( in the sim) that really had me struggling to know what was right. With the machine blaring WINDSHEAR WINDSHEAR WINDSHEAR while the stick shaker rattled away and the IAS was a moderately believable number......what to do? Is the WINDSHEAR real and I need to pitch to 15 etc etc or is the stickshaker real and I need to reduce pitch etc? Here come the Pitch Limit Indicators, gotta respect them right? They’re now down at 6 degrees nose up......
I managed to sneak away with it because of good support from my First Officer but it has given me a reality check with regard to the effects of contradictory information being presented when in IMC. I am now quicker to check my First Officers screen and I am also more aware of when Winshear is simply not going to be possible.
My point though, is that the machine (NG sim) applied no nose down trim, even without the machine applying nose down trim it can be very very challenging to apply sensible attitudes and thrust settings in real time as an event of this nature unfolds.
With unexpected and potentially unknown flight control inputs taking place in conjunction with contradictory information being presented one would hope to be in VMC with an excellent horizon.
Just my thoughts for those who think it is as simple as setting 10/80 and calling for the stab trim cutout switches to be operated.
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Old 14th Mar 2019, 02:07
  #1252 (permalink)  
 
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Originally Posted by wrench1
“These knobs don't seem to work in flight. The First Officer offered to hit the SEL function in flight, to test it out, but I thought something irreversible or undesirable might happen (not knowing what we were actually selecting), so we did not try it out in flight.”

SERIOUSLY????????
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Old 14th Mar 2019, 02:28
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At some point somebody is going to have to check in the sim how effective the Boeing procedures are in practice, and how many AoA sensor failures out of a hundred would end up underground.

Edmund
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Old 14th Mar 2019, 02:33
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At some point somebody is going to have to check in the sim how effective the Boeing procedures are in practice, and how many AoA sensor failures out of a hundred would end up underground.
Easier said than done. To get a realistic idea you would have to choose pre rostered Capt/FO combinations from all sorts of different training backgrounds and they would have to have no idea what was about to happen.
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Old 14th Mar 2019, 02:35
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Thumbs up

Originally Posted by gums
Salute MJB !!

..... snip

A pure FBW control system has all the "protections" and limits/warnings and such as part of the basic design. But no FBW commercial airliner has failed to meet the basic aerodynamic requirements for stability and control if they all had ropes, levers, pulleys, cables, torque tubes, etc to move the ailerons, rudder and elevator. They are not the military or utility platforms and do not haul 200 folks about to visit aunt Clara.
So Boeing adds another thingie besides the STS speed stability doofer to meet Part 25 requirements and it gets signed off. Most of we pilots would handle the new thingie if and a BIG IF we knew it was added AND we were told what possibel failure indications existed AND we practiced a bit. GASP!! None of that was done.
My experience was in military planes and before each flight we had to sign off every little notice, directive and change and such before flying. On some mods we had to fly with an instructor before being cleared "solo". The MCAS mod required none of those things, and I have problems with not having seen a revolt by a thousand 737 pilots that only discovered MCAS after Lion 610 pranged.

'nuff bitching, and I close for now

Gums
A salute back to you

You point to a problem which i whole heartedly agree.

Now can you also point to a solution in commercial service among the various nations flying these aircraft?
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Old 14th Mar 2019, 02:55
  #1256 (permalink)  
 
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Originally Posted by 73qanda

Easier said than done. To get a realistic idea you would have to choose pre rostered Capt/FO combinations from all sorts of different training backgrounds and they would have to have no idea what was about to happen.
Not only that, but you have to be sure the sim accurately represents what happens with such failures in the real aircraft - for a "behind the scenes" system such as MCAS, this is NOT guaranteed - yet.
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Old 14th Mar 2019, 03:15
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BFU, Bundesstelle für Flugunfalluntersuchung, repeat afer me !

It seems that the German bureau of accident analysis refuses to receive the CVR/FDR from request of Etiopia... (BFU, Bundesstelle für Flugunfalluntersuchung, repeat afer me !)
So, the french BEA (= AAIB or NTSB or ATSB) will take care of this...

I'm not authorized to post a link/url, but search for :

francetvinfo.fr crash-aerien-en-ethiopie-les-boites-noires-seront-analysees-en-france on Google...
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Old 14th Mar 2019, 03:20
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Originally Posted by positiverate20
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place! So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is. Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes. By the time he actually realises how out of trim he is, he's doing 350, and despite the stab still being at the same X° nose down since cut-out, the forces have multiplied. Now if there is any nose down attitude or reduction in power then there's absolutely no chance to recover.

Obviously all hypothetical, an airspeed disagree on takeoff could lead to circumstances similarly, or a multitude of other possible reasons, however, in the situation that I've hypothesized, it would almost certainly always end in a similar steep nose down attitude.
737 is not a FBW system with augmented elevator control. The elevator follows only the column. The pilot will know at all times when flying manually just how out of trim the airplane is by how much column force/displacement is needed to maintain the target pitch attitude. Having shut off electric stabilizer control, the workload associated with maintaining pitch trim is increased as it requires manual, mechanical rotation of the trim wheel, but the cues as to when trim is needed, in which direction, and how much are the same as what the pilot has seen for every hour of flying that airplane manually that he or she has done. As with every day flight with a completely healthy airplane, the amount of pitch trim required to recenter the column after having used that column to compensate for the pitching moment changes associated with thrust and configuration changes will be no different and thus the cue to provide pitch trim will be no different. The task of inserting that trim is higher workload, but nothing any 737 pilot (MAX or otherwise) should find particularly difficult to keep up with.

From your mention of "autotrim" I get the sense that you may not realize that when flying the 737 manually the automatic stabilizer control functions that are active (STS and MCAS) tend to drive the stabilizer away from trim thus making the pilot trim workload higher than it would be without them. The automatic stabilizer control is not there to "automatically trim the stabilizer". It is in fact there to "automatically untrim the stabilizer" such that the pilot has to provide column in the opposite direction yielding handling qualities and awareness that are dictated by the FARs.
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Old 14th Mar 2019, 03:21
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Originally Posted by positiverate20
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.
Trimming the plane for neutral stick force is part of safely trying to get back to the ground. This is a fundamental airplane flying concept since the 172 presolo days. Literally lesson one. At what point does this get lost? Are you seriously proposing that someone cease trimming since the emergency checklist does not say to trim? What about the fact that the emergency checklist doesn't say to use the ailerons to turn back toward the airport, what do you do then? Say well we're stuffed now, we're out of options, we have to take whatever is straight ahead?

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place!
NO! As multiple people including FCEng have explained multiple times, this is not why MCAS is required!

So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is.
I'm not following. If there's a neutral stick force given all the current pitch moments (including the thrust couple) then it is, by definition, in trim. If thrust is reduced then it well get out of trim toward nose down (stick force to hold steady pitch will become a pull)

Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes.
You're joking, right? This has to be a joke.
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Old 14th Mar 2019, 03:37
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Before the damages trials for Indonesian and Ethiopian take place, someone is going to have to run through a bunch of these scenarios in the sim, and see in what percentage of a few hundred trials of AoA sensor faults the pilots manage to survive even if they apply all recommended Boeing procedures.


Edmund
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