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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 3rd Jul 2019, 20:44
  #981 (permalink)  
 
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Originally Posted by wonkazoo View Post
Can anyone please tell me why heads didn't explode with the headline last Thursday??
If someone's head is exploding, then that person doesn't really understand what was reported. Frankly, I'm a little surprised that you are bringing this up again. You quoted a post of mine a few days back which explained exactly why this is not the smoking gun that everyone wants it to be, but you have apparently chosen to ignore that response and slap this red herring back on the table.

Let's go through it again, with a little more detail. First of all, this is not a smoking gun because it is not even the same gun. The problem was discovered when the new, yet to be flight-certified FCC software was being stress-tested in a Boeing engineering simulator. This simulator can be used to plug in different components of flight control hardware and software during both development and test phases and is part of the certification process of any new aircraft or related subsystems. The tests that were being conducted intentionally introduced faults into the FCC in order to see how it would respond. Normally, a fault on a single FCC should attempt to hand off the process to a different processor on the same FCC, or failing that, to a different FCC (there are two on the 737). The test did not involve the MCAS subroutines of the new FCC software.

This news was reported through several outlets, but Leeham New's seems to have the best detail:

Bjorn’s Corner: New pitch trim issue forces further changes to 737 MAX software

Quoting the article:
.
The flaw is not related to MCAS but to how the revised software affects the aircraft’s processors in the Flight Control computers when these have simulated fault conditions.

During a check on how different faults (in this case a fault in one of the microprocessors in the Flight Control computer) can cause Trim Runaway conditions the FAA found the 737 MAX Flight Control computer got overwhelmed by the data flows the simulated fault caused and it delayed the actions the FAA pilot could take to stop the trim runaway.
and:

The discovery is not done in the part of the code which handles MCAS. It’s found as a wider verification the software changes haven’t produced any secondary hazards in the 737 MAX flight control system.

Software changes in a flight control system are always verified with an exhaustive FMEA analysis (Failure Mode and Effects Analysis) and it’s during such verifications the new condition was discovered.
As currently understood, the MCAS software on the accident aircraft did not input nose down trim because of a fault, but simply because it performed a task exactly how it was programmed to do so. Yes, it was ill-conceived program, but there is no indication that it created a fault condition.

All the test above tells us is that the new software has either a coding issue (which may involve just reprogramming work) or it is demanding more than the processor can handle (which may involve a change in processors). There was extensive discussion previously in this thread by individuals with background in this kind of work who explained all the ways in which errors could have been introduced into the new software.

Also important to understand is that this type of testing was performed on the original Flight Control components (hardware/firmware/software) that were part of the originally certified aircraft. Certainly one might suggest that this testing missed something. Possible, but this is where the accident investigation process steps in.

In order to determine the cause(s) of an accident, to include an attempt to replicate all the physical and electronic evidence left behind, the accident investigators will run every suspect component through a battery of tests. Since the actual components were destroyed, it is almost certain that the investigation teams pulled similar components from the field and then used the same (or similar) Boeing engineering simulator to test these components for all manner of possible failures, including the exact tests run by the FAA as described above. Ideally, these components would have been produced in the same lots as the those in the accident aircraft. Since there hasn't been much reticence in reporting all the other existing flaws with the MCAS and related software, it doesn't seem likely that an issue that caused a fault like the one reported for the new software would be selectively concealed from the public. Another item for the "Dog that did not bark" file.

Back to the Leeham article which first quotes from a so-called 8-K public filing:

The Federal Aviation Administration has asked The Boeing Company to address, through the software changes to the 737 MAX that the company has been developing for the past eight months, a specific condition of flight, which the planned software changes do not presently address.”

Here is what Wiki says about an 8K filing: Form 8-K is a very broad form used to notify investors in United States public companies of specified events that may be important to shareholders or the United States Securities and Exchange Commission.

The filing means FAA has found a flaw in the software Boeing has developed to fix to the MCAS problem. The find and its consequences are significant enough so Boeing’s shareholders should be informed about it. It can affect the value of Boeing on the stock market.
That last point is very important. If Boeing was aware of an issue that might further delay the re-certification of the MAX, then it must provide some kind of disclosure since it is material information that would effect the stock price. Any issues with components of the Main Electric Trim system would likely require significant rework (redesign and/or replacement of switches, wires, relays, motors, controller, etc.) and add to the already known delay. By SEC rules, this type of delay would require a similar 8-K report by Boeing. One more dog that isn't barking.

Lots and lots of dogs not barking, and there is a very good reason for it.

Last edited by yoko1; 3rd Jul 2019 at 21:19.
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Old 3rd Jul 2019, 21:12
  #982 (permalink)  
 
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Cutout Switches

Originally Posted by MemberBerry View Post



Yeah, the fact that the cutout switches are not wired identically in series is a bit strange. It's almost like somebody told the person responsible for the design "you have 5 minute to finish the damn thing, stop messing around with it and let's make it final, we have a deadline.". Anyway, about what the connections through the cutout switches seem to do:

1. connections 2 - 3 are wired in series between the two cutout switches, and are connected to the rest of the circuit in such a way that either of the cutout switches would do two things when used:
- interrupt the power between the circuit breakers and the thumb switches, making the thumb switches inoperable;
- de-energize the relay that connects the 3 phase 115V AC power to the trim motor, basically disconnecting the motor from AC power.

This means just cutting connection 2 - 3 on any of the two switches is enough to disable both manual and automatic electric trim.

2. connections 5 - 6 are wired in series as well between the two switches, and it seems that, if any of the two cutout switches are used, it would interrupt a 28V signal to the FCC, probably indicating to the FCC that the cutout switches have been used. No idea what the FCC will do based on that information.

3. connections 8 - 9 are wired only on the primary cutout switch, and as you said they seem to connect the FCC to the trim motor in some way. No idea why they don't go through the backup cutout switch as well, and exactly what signal they carry between the FCC and the motor. It almost looks like somebody forgot to route that connection through the second cutout switch. I don't see any reason for that.
Thanks for the succinct description of the cutout switch circuit functions. The design is strange isn't it? Given that previous 737s had two switches with different functions it is a real departure to have two switches in series when system reliability claims for stab runaway wouldn't have demanded it. Clearly the overall function has to be the way it is in order to give MCAS authority over the pilots. A cynic might argue that one switch could achieve that but that Boeing added the Backup switch to make it look like it always used to. If you hadn't been told about this new functionality and your point of reference was the previous design, the Lion Air & Ethiopian cockpits would not have been good places to work it out.
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Old 3rd Jul 2019, 21:13
  #983 (permalink)  
 
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Originally Posted by MurphyWasRight View Post

I do disagree though that had step6 (re-enable manual electric trim only) been available it would not have helped ET:
Once they realized that manual mechanical trim was not available, due lack of training on use of flip out handles and/or aero loads alone, step 6 would have allowed them to re-trim the aircraft, even though they had not followed the memory items perfectly.
Possibly, but let me throw out one more thought that relates to both why the procedure was changed and why the crew might not have made the decision you think they would.

The Boeing trim system found on the 707, 727, and 737 has evolved over time. Initially, there was a fast motor for the pilots use, and a slower motor for the autopilot (back when the autopilot was the only other source of electric stab trim). That logic continued even as systems were added and more things could move the stabilizer (Mach Trim, Speed Trim). The thumb switch moved the trim quickly, the automatics moved it slowly. I don't know about the 737 classics, but on the 737NG the logic also included flap position. Flaps down trim was always faster than flaps up trim, and pilot trim was always faster than automatic trim. However, this logic now created four distinct trim speeds (0.4/0.2/0.27/0.09 deg/sec)

Part of the old procedure in isolating the malfunctioning trim system was a subjective evaluation of whether it was moving fast or slow. If if was moving fast, then the Main Electric Trim was suspect. If it was moving slow, then one of the automatic systems. However, with the existence of four distinct speeds and the fact that the "fast" automatic was now faster than the "slow" Main Electric, there was some concern that pilots might misidentify the malfunctioning system, use the wrong cutout, and aggravate the problem. Keep in mind that a runaway stab is not anything you want to dally with - prompt and correct action are critical. This was one of the drivers for simplifying the procedure in the first place.

One of the issues that has been highlighted with the original MCAS design is that it operated at a higher speed than the Main Electric Trim in the flaps up configuration. Thus, it is entirely possible that this faster movement could have been interpreted as a problem with the Main Electric Trim, and not one of the automatic sources. Logically, then the crew would attempt to restore the automatic trim thus 1) reintroducing the runaway while 2) taking away the most effective tool to stop it - namely the Main Electric Trim.

In fact, this is effectively what happened with ET302. They did not properly run the Runaway Stab procedure, they cutout the trim in a significant out-of-trim conditions, and in an act of desperation they restored the malfunctioning system which promptly drove the stab to the stop. It should be noted this crew also had the opportunity to reactivate the cutout switch, but did not, probably because the MCAS movement at the excessive speed they were flying created such a strong negative g force that they were startled or thrown off balance.

Last edited by yoko1; 3rd Jul 2019 at 21:59.
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Old 3rd Jul 2019, 21:41
  #984 (permalink)  
 
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Originally Posted by yoko1 View Post
They did not properly run the Runaway Stab procedure, they cutout the trim in a significant out-of-trim conditions, and in an act of desperation they restored the malfunctioning system which promptly drove the stab to the stop.
Because they were running the airspeed unreliable checklist with the stick shaker going off! Any reasonably foreseeable single failure that requires the pilots to two concurrent memory checklists close to the ground is not pilot error. Also remember, that it was not until after the fateful ET flight that information about the inability to use the manual trim above ~230 knots without the historical "roller coaster" procedure. None of the three crews had sufficient information provided by the manufacturer about the operation of the MCAS system or manual trim limitations to effectively manage the situation.

I have posted this ad nauseam and will continue to do so. All three crews were faced with this for the entire duration of their flights causing a significant reduction in cognitive capacity and ability to communicate.

I believe a significant number of crews globally, regardless of background, training or experience would have found themselves in very similar circumstances to these two fatal flights because of the interaction between the airspeed unreliable checklist & the inability to manual trim once the MCAS had fired and continued to maintained the stab grossly out of trim. We cannot look at just one of the problems in isolation, what were the crews facing "on the day".

Last edited by CurtainTwitcher; 3rd Jul 2019 at 21:53.
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Old 3rd Jul 2019, 21:41
  #985 (permalink)  
 
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Originally Posted by yoko1 View Post
However, with the existence of four distinct speeds and the fact that the "fast" automatic was now faster than the "slow" Main Electric, there was some concern that pilots might misidentify the malfunctioning system, use the wrong cutout, and aggravate the problem.
I agree, they could misidentify the malfunctioning system, but if the F/O kept his hand on the cutout switch after reenabling the wrong system, they could immediately disable trim again at the first sign of a runaway. On the other hand, MCAS running intermittently, and apparently randomly for somebody not knowing how it works, and being reset by the thumb switches, adds even more confusion to the scenario. The pilots might assume the runaway is caused by the thumb switches, not by the automatic systems, since the runaway starts 5 seconds after using the thumb switches. Horrible system. I know it wasn't Boeing's intention, but it's like it was designed to create as much confusion as possible.

Now, about those blips towards the end of the Ethiopian flight, now that we know that using either of the cutout switches disables recording the thumb switch trim commands on the FDR, that could be one possible explanation for the blips. It could be that, while trimming with the thumb switches at the end, they were also playing with the cutout switches and intermittently disabling trim as a result. For example they could have been experimenting with the backup cutout switch, thinking it might be analogous to the autopilot cutout switch on the NG.
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Old 3rd Jul 2019, 21:49
  #986 (permalink)  
 
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Originally Posted by yoko1 View Post
You are falling into the cognitive trap of believing that this must be an either/or proposition. Problems with design and problems with training are not mutually exclusive. In fact, I'm willing to bet that the final reports are going to have a long list of primary and contributory causes. It would be quite a shame to fix just one of them.
I think with a bit of good will we can agree this just about sums up several months of discussion here.

So according to this proposition Boeing needs to fix BOTH the design failure(s) , and the training failure(s).

And on the one side there seems to be an insistence that the hardware be fixed by software only with one AoA sensor input to MCAS, and on the other side that the training not require Max sim time. Somehow BOTH of these "economic requirements" seem problematic.

So it might be useful -as this is not forbidden by the rules- for people who sit in the front seats to make their desire for BOTH a solid fix for MCAS, AS WELL as for the provision of simulator training for runaway stab trim on the MAX, noisily known to Boeing, the FAA, their unions and their employers, and dare I say it, to the press.

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Old 3rd Jul 2019, 21:53
  #987 (permalink)  
 
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Originally Posted by yoko1 View Post
Possibly, but let me throw out one more thought that relates to both why the procedure was changed and why the crew might not have made the decision you think they would.
...
...
One of the issues that has been highlighted with the original MCAS design is that it operated at a higher speed than the Main Electric Trim in the flaps up configuration. Thus, it is entirely possible that this faster movement could have been interpreted as a problem with the Main Electric Trim, and not one of the automatic sources. Logically, then the crew would attempt to restore the automatic trim thus 1) reintroducing the runaway while 2) taking away the most effective tool to stop it - namely the Main Electric Trim. In fact, this is effectively what happened with ET302. They did not properly run the Runaway Stab procedure, they cutout the trim in a significant out-of-trim conditions, and in an act of desperation they restored the malfunctioning system which promptly drove the stab to the stop.
Note that my proposed 'step 6' (NG or reconfigured MAX switches) is not a memory item, only taken after all electric trim shut down and allows possible restoration of manual electric trim only:

To restore manual electric trim set the [corect switch name] to enabled, be prepared to immediately disable if runaway trim re-occurs. Do not re-enable should this happen.

Could add a "in event mechanical trim is difficult/impossible " prolog to it.
It does not require crew to determine probable fault cause while performing the memory items, since they remain unchanged.

All of this would be a moot point if mechanical trim as a backup was reliable over the certified range, which it strongly appears not to be.
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Old 3rd Jul 2019, 21:55
  #988 (permalink)  
 
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Speed Typing

Originally Posted by yoko1 View Post
If someone's head is exploding, then that person doesn't really understand what was reported. Frankly, I'm a little surprised that you are bringing this up again. You quoted a post of mine a few days back which explained exactly why this is not the smoking gun that everyone wants it to be, but you have apparently chosen to ignore that response and slap this red herring back on the table.

Let's go through it again, with a little more detail. First of all, this is not a smoking gun because it is not even the same gun. The problem was discovered when the new, yet to be flight-certified FCC software was being stress-tested in a Boeing engineering simulator. This simulator can be used to plug in different components of flight control hardware and software during both development and test phases and is part of the certification process of any new aircraft or related subsystems. The tests that were being conducted intentionally introduced faults into the FCC in order to see how it would respond. Normally, a fault on a single FCC should attempt to hand off the process to a different processor on the same FCC, or failing that, to a different FCC (there are two on the 737). The test did not involve the MCAS subroutines of the new FCC software.

This news was reported through several outlets, but Leeham New's seems to have the best detail:

Bjorn’s Corner: New pitch trim issue forces further changes to 737 MAX software

Quoting the article:
.


and:



As currently understood, the MCAS software on the accident aircraft did not input nose down trim because of a fault, but simply because it performed a task exactly how it was programmed to do so. Yes, it was ill-conceived program, but there is no indication that it created a fault condition.

All the test above tells us is that the new software has either a coding issue (which may involve just reprogramming work) or it is demanding more than the processor can handle (which may involve a change in processors). There was extensive discussion previously in this thread by individuals with background in this kind of work who explained all the ways in which errors could have been introduced into the new software.

Also important to understand is that this type of testing was performed on the original Flight Control components (hardware/firmware/software) that were part of the originally certified aircraft. Certainly one might suggest that this testing missed something. Possible, but this is where the accident investigation process steps in.

In order to determine the cause(s) of an accident, to include an attempt to replicate all the physical and electronic evidence left behind, the accident investigators will run every suspect component through a battery of tests. Since the actual components were destroyed, it is almost certain that the investigation teams pulled similar components from the field and then used the same (or similar) Boeing engineering simulator to test these components for all manner of possible failures, including the exact tests run by the FAA as described above. Ideally, these components would have been produced in the same lots as the those in the accident aircraft. Since there hasn't been much reticence in reporting all the other existing flaws with the MCAS and related software, it doesn't seem likely that an issue that caused a fault like the one reported for the new software would be selectively concealed from the public. Another item for the "Dog that did not bark" file.

Back to the Leeham article which first quotes from a so-called 8-K public filing:



That last point is very important. If Boeing was aware of an issue that might further delay the re-certification of the MAX, then it must provide some kind of disclosure since it is material information that would effect the stock price. Any issues with components of the Main Electric Trim system would likely require significant rework (redesign and/or replacement of switches, wires, relays, motors, controller, etc.) and add to the already known delay. By SEC rules, this type of delay would require a similar 8-K report by Boeing. One more dog that isn't barking.

Lots and lots of dogs not barking, and there is a very good reason for it.
Yoko1

Have to give you credit for one thing, your speed of typing and ability to compose an arguement has me very impressed. A mere 8 minutes after replying to my post, your respond to Wonkazoos post in a very well drafted piece including a number of quotes from other articles. For a self confessed 737 pilot you missed an alternative career in journalism.

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Old 3rd Jul 2019, 22:15
  #989 (permalink)  
 
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My personal view and this applies to both B and A is that they are remiss in allowing ANY alarms, flight director, stickpusher, or any other flight display other than Gyro , heading, thrust in any case of "does not compute", "input out of range" or any other case where the software self check sanity check throws an error. If the computer is not 100% SURE then turn it all off

what this comes down to is that there needs to be a CLEARLY DEFINED REVERSION STATE that is REGULARLY TRAINED AND FLOWN and that in all case of unreliable input the aircraft should revert to this defined and trained for state (without spurious alarms!)
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Old 3rd Jul 2019, 22:30
  #990 (permalink)  
 
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Point taken - I was trying to point out that a description that is essentially Eaton advertising blurb may be overplaying the 'microprocessor' aspect of something that isn't quite so spangly. My guess (and that's all it is) is that you are correct and that the IGBTs are processor driven. I'd just suggest that the software is probably embedded and not particularly complex given the nature of that task so it may be doing digitally what was previously done by analogue means.
One of the reasons that seem to me to point away from the stab motor is that as far as I understand it the stab 'motor' did as we think it was told by MCAS (happy to be challenged on that)
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Old 3rd Jul 2019, 23:29
  #992 (permalink)  
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re the chip overload.

and it delayed the actions the FAA pilot could take to stop the trim runaway.
I hope that doesn't include the basic use of the thumb switches.

Again I feel my old bones needing there to be reversion to an aircraft with nothing but the electric trim thumb switches. And then, nothing but a crank and cables which won't fight back.

There has to be the potential for this aircraft to become a basic flying machine.

Member Berry #988
For example they could have been experimenting with the backup cutout switch, thinking it might be analogous to the autopilot cutout switch on the NG.
What a good point. A last ditch try of that B/U switch by itself?
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Old 3rd Jul 2019, 23:43
  #993 (permalink)  
 
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Microprocessor overload

Proposed fix
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Old 3rd Jul 2019, 23:43
  #994 (permalink)  
 
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Originally Posted by phylosocopter View Post
My personal view and this applies to both B and A is that they are remiss in allowing ANY alarms, flight director, stickpusher, or any other flight display other than Gyro , heading, thrust in any case of "does not compute", "input out of range" or any other case where the software self check sanity check throws an error. If the computer is not 100% SURE then turn it all off

what this comes down to is that there needs to be a CLEARLY DEFINED REVERSION STATE that is REGULARLY TRAINED AND FLOWN and that in all case of unreliable input the aircraft should revert to this defined and trained for state (without spurious alarms!)
This is one of my biggest pet peeves about the 737 (can't speak for other aircraft, but maybe other operators can chime in). There are quite a few noise-makers that activate when certain parameters are exceeded. Some of them can be silenced, but many cannot. Unfortunately, erroneous alarms can be also triggered by underlying malfunctions (as demonstrated by the stick shaker in the MAX accidents), and pilots are expected to just deal with them.

And yes, these alarms are very, very annoying and very, very much a source of distraction. If someone were to make me King of Boeing, one of my first commands would be to install a master button in the cockpit of every airliner that enabled me to silence any alarm, even if only temporarily, and effectively tell the plane to shut the flock up and let me do my job. I seriously hope that one of the recommendations out of these accidents is to provide some relief and/or mechanisms that will allow pilots to silence these kind of alarms when it is obvious that they are erroneous.

What is particularly troubling is that some alarms can be silenced by the simple act of pulling an associated circuit breaker that is within easy reach (the left stick shaker CB is behind the Captain's left shoulder), but we are procedurally not allowed to do so. Once upon a time, it was allowed at the Captain's discretion, but no longer. A Captain can always take a chance and play the "Captain's Emergency Authority" card and do what he/she thinks is needed to save the ship, but he/she would then be counting on a sympathetic Fed/Supervisor/Chief Pilot to agree with his reasoning at the subsequent hearing. I'm pretty sure the penultimate Lion Air 610 crew flew the aircraft the rest of the way to landing with the stick shaker going off, and I am aware of other similar events in which the crew did not feel justified in pulling the CB because the lack of any procedure or policy authorizing such an action. This is the environment we operate in. This is the job we signed up for.

Back to my wheelhouse - are we looking adequately at the training, certification, and operating environment that these crews were immersed in? If the airlines/regulators/manufacturers expect pilots to aviate, navigate, communicate and work an active malfunction while there is an ongoing, distracting alarm that cannot be silenced, then they can damn well train pilots to that standard. I can assure you that is not how we currently train.

Last edited by yoko1; 4th Jul 2019 at 02:32.
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Old 3rd Jul 2019, 23:49
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Originally Posted by Alchad View Post

Have to give you credit for one thing, your speed of typing and ability to compose an arguement has me very impressed. A mere 8 minutes after replying to my post, your respond to Wonkazoos post in a very well drafted piece including a number of quotes from other articles. For a self confessed 737 pilot you missed an alternative career in journalism.
Thanks. In a previous life, I was kind of an all-purpose staff writer/researcher (technical, P.R., editorial, whatever). Some parts of the job were very interesting, but I don't miss the windowless office and continuous (and sometimes unrealistic) deadlines.
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Old 3rd Jul 2019, 23:56
  #996 (permalink)  
 
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Great find! Thanks for posting.
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Old 4th Jul 2019, 00:04
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Right...mimic Microsoft Windows

Originally Posted by FrequentSLF View Post
Proposed fix
Sorry, I don’t do Windows.
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Old 4th Jul 2019, 00:13
  #998 (permalink)  
 
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Lifting a comment from the thread Loss of Control In-Flight-Flight Crew Training because it so germane:

Originally Posted by old,not bold View Post
.
UK CAA Safety Notice 2019/005 landed in my inbox just now.

It is a devastating indictment of regulators and operators who have allowed a situation to develop where this SN is necessary.

Stripped of the dreadful jargon-ridden, ungrammatical verbiage it is telling everyone to get back to teaching and practising basic flying skills.
Could not have said it better myself.
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Old 4th Jul 2019, 00:24
  #999 (permalink)  
 
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Originally Posted by MemberBerry View Post
I agree, they could misidentify the malfunctioning system, but if the F/O kept his hand on the cutout switch after reenabling the wrong system, they could immediately disable trim again at the first sign of a runaway.
I just need to point out that the ET302 FO could have done this when they restored power to the trim system, but he did not. That particular piece is a training issue, not a design issue.
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Old 4th Jul 2019, 00:26
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Originally Posted by yoko1 View Post
This is one of my biggest pet peeves about the 737 (can't speak for other aircraft, but maybe other operators can chime in). There are quite a few noise-makers that activate when certain parameters are exceeded. Some of them can be silenced, but many cannot. Unfortunately, erroneous alarms can be also triggered by underlying malfunctions (as demonstrated by the stick shaker in the MAX accidents), and pilots are expected to just deal with them.

And yes, these alarms are very, very annoying and very, very much a source of distraction. If someone were to make me King of Boeing, one of my first commands would be to install a master button in the cockpit of every airliner that enabled me to silence any alarm, even if only temporarily, and effectively tell the plane to shut the flock up and let me do my job. I seriously hope that one of the recommendations out of these accidents is to provide some relief and/or mechanisms that will allow pilots to silence these kind of alarms when it is obvious that they are erroneous.

What is particularly troubling is that some alarms can be silenced by the simple act of pulling an associated circuit breaker that is within easy reach (the left stick shaker CB is behind the Captain's left shoulder), but we are procedurally not allowed to do so. Once upon a time, it was allowed at the Captain's discretion, but no longer. A Captain can always take a chance and play the "Captain's Emergency Authority" card and do what he/she thinks is needed to save the ship, but he/she would then be counting on a sympathetic Fed/Supervisor/Chief Pilot to agree with his reasoning at the subsequent hearing. I'm pretty sure the penultimate Lion Air 610 crew flew the aircraft the rest of the way to landing with the stick shaker going off, and I am aware of other similar events in which the crew did not feel justified in pulling the CB because the lack of any procedure or policy authorizing such an action. This is the environment we operate in. This is the job we signed up for.

Back to my wheelhouse - are we looking adequately at the training, certification, and operating environment that these crews were immersed in? If the airlines/regulators/manufacturers expect pilots to aviate, navigate, communicate and work an active malfunction while there is an ongoing, distracting alarm that cannot be silenced, then they can damn well train pilots to that standard. I can tell you now that they do not.
flew the Fokker 50 a long time ago, had a dedicated panel with 5(?) guarded switches to silence most if not all aural warnings. Can't believe A&B don't have that. There are several crashes were it is obvious that the disorientation from all the conflicting alerts were a big contribution.
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