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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Apr 2019, 09:33
  #3981 (permalink)  
 
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Originally Posted by Alchad View Post
Are you serious?? ….."continuing past 458 kts at low altitude".....that was when they were nose diving towards the ground !!!!!
Yes, the myth that they were flying straight and level at that airspeed has been perpetuated in several posts, which is rather odd given how many times the FDR traces have been posted.
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Old 14th Apr 2019, 11:09
  #3982 (permalink)  
 
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Remedial training for Boeing Designers. Airframe 101:-


Watch and learn.
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Old 14th Apr 2019, 11:10
  #3983 (permalink)  
 
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As mere SLF I'm more than disappointed by the lack of self reflection and 'wouldn't have happened to me' arrogance of some posting on this thread. This mindset makes an unnecessary hole in one of those slices of Swiss cheese.
As an engineer working with safety system reliability I'm puzzled by the arrangement of the two stab trim cutout switches on the Max. if I understand the schematic in # 3882 correctly the Main Stab Trim Cutout switch does everything and the Backup simply provides a set of series contacts for a subset of the Main switch functions.
Given that series contacts didn't appear to be necessary in previous 737 systems it might be concluded that the Backup switch is superfluous other than as a piece of window dressing to make the switch arrangement look like it always used to. This seems like a potential error trap for a pilot expecting the functionality of previous 737s.
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Old 14th Apr 2019, 11:29
  #3984 (permalink)  
 
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Originally Posted by alf5071h View Post
double-oscar, #4005,

‘… they had a stall warning on lift-off. There is guidance for this in the QRH and the Flight Crew Training Manual which wasn’t followed.‘
In addition to stall warning, the crews also had higher stick force (feel shift), airspeed and altitude disagree alerts, ambiguous speed indications; surprise.

Now where in the manual is this combination considered, and belatedly in the FAA AD, how is the description and interaction of these placed in appropriate context.
How should the possibility that the Manufacturer or the Regulator not following their procedures be framed - context, for including a procedure for a situation which was overlooked or not even conceived?

The Lion and Ethiopian crews are the most experienced in our industry in those specific conditions; unfortunately there are unable to relate their experiences for us to learn from. Thus it is everyone’s responsibility to learn from what is known of past events, but not to identify the similarities with (our) current thoughts, or fit understanding to hindsight; instead we all have identify new issue particularly those hidden or already forgotten.
Quite apart from MCAS (when it is fixed on the MAX), and with the same applying to the previous B737 NG model, the biggest story coming out of these crashes is about the effects of the faulty AOA sensor: I am still astonished that Boeing can design, and the FAA can certify, a brand spanking new aircraft model with an archaic flight system, where a single faulty AOA sensor can activate multiple warnings and cascading alerts simultaneously.
And then, to compound the insult, each of those warnings has different, and sometimes contradictory checklists. The checklists are designed to address specific flight conditions, but there seems to be no single clear checklist for sensor failure, nor any way to disable that sensor or the alarms?
What if this scenario happens under heavy workload at night under IMC? Am I missing something?
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Old 14th Apr 2019, 11:37
  #3985 (permalink)  
 
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You're missing nothing. You are asking the questions that should be appearing at BA board level. I can't see anyone subscribing to a MAX+ in 10 years time. Time for a clean sheet of paper, regardless of the MAX outcome.
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Old 14th Apr 2019, 12:03
  #3986 (permalink)  
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Cayman thinking of ditching the Max

Cayman Airways CEO and Board deliberating over their 737 MAX leases and their future.

They have just had 2 new -8 aircraft delivered in Nov and Mar, and 2 more on order for later this year/next.

They are now resorting to using a smaller 737-300 on their new longer routes which the Max was obtained for - now these 733 flights entail a tech stop.
They were also leasing an EAL 767 and the crippling $$$$ costs are the subject of CAY seeking compensation from the Lessor and/or Boeing plus looking into now cancelling all of the MAX leases outright and re-equipping.
They also think that damage limitation v/v pax with the MAX name is an issue.

Last edited by rog747; 14th Apr 2019 at 13:07.
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Old 14th Apr 2019, 12:29
  #3987 (permalink)  
 
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I’m saddened by the tragic loss of life, and the difficult situation that the crew was given. There is no excuse for the deficiencies of the MCAS design.

That being said, there is no universe in which multiple attempts to engage the autopilot at low altitude with an active stick shaker was the correct choice. There are times in this business in which the only correct choice is to turn off all the magic, grab yourself a handful of aircraft, and return to the basics of pitch, power, and performance. Not knowing the specifics of the crew or their airline, I will leave it to someone else to determine if the crew actions were deficiencies of the individuals or deficiencies of their training, but deficient they were.

Last edited by 737 Driver; 14th Apr 2019 at 14:47. Reason: Typo
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Old 14th Apr 2019, 13:04
  #3988 (permalink)  
 
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Originally Posted by Alchad View Post
Are you serious?? ….."continuing past 458 kts at low altitude".....that was when they were nose diving towards the ground !!!!!
Liftoff was at 5:38;00, 5:40:42 passing 305 kts, 5:41:20 Clacker (VMO 340), 5:42:10 still found time to talk to ATC and change heading bug, ...that's 1:33 before impact, while nobody thought about MANUALLY pulling back the thrust levers. ...Helloooo.
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Old 14th Apr 2019, 13:16
  #3989 (permalink)  
 
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Originally Posted by Fursty Ferret View Post
That’s basically what the stabiliser disconnect switches do on the 737. Pretty much all the controls are string and pulleys.

In any non-normal situation flying the aircraft manually usually comes at the expense of reduced capacity for troubleshooting and decision making. Deliberately increasing workload would be an unusual step to take.

The 737 Max accidents are (IMHO) mainly influenced by design choices that should never have passed certification and trying to slap a sticking plaster on top of those decisions is missing the bigger picture.
For the 737 up to NG one switch disables automatic trim while preserving pilot electrical trim, the second switch disables all electrical trim. On the 737 MAX either switch disables all electrical trim

Manual trim of a significantly out of trim aircraft may be difficult at best.

I have asked how well this change to the cutout was documented in the conversion slideware but have not seen a response.
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Old 14th Apr 2019, 13:25
  #3990 (permalink)  
 
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Wonkazoo reminds us of a critical point. If four conditions exist....

1 - An AoA sensor is wrong
2 - It is wrong nose-up
3 - The magnitude of the error is large enough to trigger a stall warning
4 - The AoA sensor happens to be the one driving MCAS on this segment

... then MCAS will be "armed" and it will kick in at flaps up.

Even now, we know of only three such events, two of them leading to fatal accidents. Unless there have been a lot more than three, there is no prima facie case to argue about pilot competence, and the root cause to be investigated is how MCAS was designed, tested and approved for service.
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Old 14th Apr 2019, 13:43
  #3991 (permalink)  
 
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MCAS / Fudge - 6 one half a dozen the other.

When are all you guys from the deluded "it can't happen to me", "it's pilot error", "they were incompetent", "they were not properly trained" camp going to waken up & smell the wreak here - which is so much more unpleasant than coffee! Regardless of what you may have concluded occurred in the cockpit from the available information, you simply don't know & never will know the whole story. We already know that at least some of the data available is junk / error / erroneous. Basing your opinions on the available data to hold these poor pilots responsible for the deaths of all involved is simply ridiculous, naive & morally wrong.

The time critical situation that the pilots were put in simply does not give enough time to work through & rigorously adhere to checklists & doing so may have killed them even more quickly, especially considering the complex interaction of several systems where a multitude of variables are possible & outcomes numerous. The various procedures involved is successful recovery would appear to be too complex for a normal, qualified pilot & completely inadequate at low level when time is critical - too much to p*** about with & not enough time to do it. It also appears that depending on some circumstances, normally accepted procedures may just be trap doors at low level.

Fudge 1 - Out of sight;
Shoving MCAS so far into the background so as to avoid certification & training issues (translate to cost / money). Someone / lots of someone's at Boeing surely knew that it was mistake to have MCAS quietly installed given the authority it has. "Yea guys, it's nothing, just a few tick boxes on a tablet & we are good to go" - 346 lives in less than five months suggests otherwise.

Fudge 2 - The implementation of MCAS;
Complete authority over life & death on the basis of a single sensor input (sensor, wiring, ADIRU or software).

"How will we activate this thing guys?"
"Just wire it to an AOA sensor"
"What if the AOA sensor or data is faulty?"
I mean, seriously what was after that "They don't go faulty" or "don't ask expensive questions"

"MCAS doesn't seem to work as well as we had hoped boss, should we consider an appropriate aerodynamic fix?"
"Just increase its authority by a factor of 4 or more & stop asking expensive questions"

Apart from Boeing test pilots does anyone really know how pronounced the decreasing input forces with increasing AOA really are? Is it as simple as decreasing input force or is there more to it, such as a lack of authority????

The fact that there seem to be so many differing opinions on the workings & capability of the trim & stab systems from apparent ticketed 737 drivers is concerning, as is the suggestion that that any 737 trim system may become ineffective under certain situations & that spinning the wheels will either be ineffective or impossible.

I cant help seeing MCAS as anything other than a dangerous fudge that was implemented in consideration of sales & profit. That the manufacturer would have been unaware of the potential unintended consequences is not something that I can believe.


737NG's certification was issued on the basis of improved, high accuracy production methods, yet Ducommun were using the high tech sledgehammer method. How many NG's are flying at their maximum certified altitude without the high accuracy parts required for this?

787 - the box fix....

Now 737 Max....

It seems that proper, retrospective fixes are expensive. I don't have a dog in A, B or any other camp, just saying what I see in regards to B at the moment.

Last edited by Thrust Augmentation; 14th Apr 2019 at 17:58.
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Old 14th Apr 2019, 14:28
  #3992 (permalink)  
 
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Originally Posted by GlueBall View Post
Liftoff was at 5:38;00, 5:40:42 passing 305 kts, 5:41:20 Clacker (VMO 340), 5:42:10 still found time to talk to ATC and change heading bug, ...that's 1:33 before impact, while nobody thought about MANUALLY pulling back the thrust levers. ...Helloooo.
They were trying to climb, and they had the stick shaker active. Reducing thrust when you try to climb can be a bit counterintuitive, wouldn't you say? Also, reducing thrust when you have the stick shaker active is usually not the best idea. Especially close to the ground. Also the speed, as measured on the left side, stayed at about 340 knots for about 3 minutes. It seems the pilot flying was controlling the speed using the elevator, pulling harder when it was going over 340. They only went significantly over 340 during the final dive.

So I doubt they were unware of their speed and the clacker. They probably wanted the speed, probably hoping it will allow them to climb faster and it might also make the stick shaker go away. It's like a terrain avoidance maneuver where you pitch up until the stick shaker activates. You actually want the stick shaker to activate, it tells you are doing your best to climb. And you keep it around that point, close to a stall, with the shaker intermittently activating, until you clear the terrain. Something similar may have been going on here, they may have wanted to keep the speed close to VMO.

Of course, you can then question why the pilots didn't pull even harder to climb faster, instead of allowing the speed to reach 340. The column displacement is never more than about 66% nose up in that 3 minute interval they kept the speed at VMO. But then you have to remember the stick shaker. They may have been afraid to pull harder because of the stick shaker. That may also explain why they didn't fully revert the nose down trim from MCAS when they had electric trim available. They may have been reluctant to trim and pull nose up believing they could be near a stall.

They made mistakes that are hard to explain, like attempting to enable the left side auto-pilot, and not realizing the instruments on the right side were the ones working properly. But I don't think allowing the aircraft to reach VMO is one of those mistakes.
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Old 14th Apr 2019, 14:56
  #3993 (permalink)  
 
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Regarding the changes to the pedestal cutout switches, from a procedural perspective it doesn’t matter (at least in my FCOM). Our runaway stab trim NNC requires the use of BOTH cutout switches, NG or MAX. We no longer attempt to isolate the faulty trim circuit on the NG. Thus from a differences training point of view, it doesn’t matter that they are wired differently.
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Old 14th Apr 2019, 15:34
  #3994 (permalink)  
 
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Originally Posted by Takwis View Post
...
...
That's it. NO MENTION OF ANY CHANGES TO TRIM, TRIM SWITCHES, TRIM SWITCH LABELS OR FUNCTIONS. Or MCAS.
Thank you.
That and the CYA updated runaway trim procedure that appears to have been written to support the claim that Lion Air was could have been prevented had existing procedures been followed is depressing.

For the 'just follow the procedures" crew; what would have been the likely outcome in ET if a new 'MCAS runaway' checklist had been published instead with specific instructions, I am sure Boeing engineers/test pilots could provide a much better one.

Condition:
ND trim in increment of up to 10 seconds, repeated after pilot trim inputs.

MCAS may be the cause, only when manual flying no flaps.

Action:

Fully trim the aircraft.
Note: if either trim switch is 'blipped' MCAS will be disabled for 5 seconds.
This can be used while fine tuning trim, use alternate up/down trim inputs every 3 seconds.

Once trimmed disable electrical trim.

Land and file a full tech report. (One hopes not needed but Lion Air comes to mind)
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Old 14th Apr 2019, 16:33
  #3995 (permalink)  
 
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Originally Posted by MemberBerry
They made mistakes that are hard to explain, like attempting to enable the left side auto-pilot, and not realizing the instruments on the right side were the ones working properly. But I don't think allowing the aircraft to reach VMO is one of those mistakes.
Sir. Thinking like that is cruising for a bruising.
With flight control problems, you should typically go for the center of the envelope and avoid the corners of the envelope, then explore cautiously.
Besides that, if they had managed to keep control much longer, their continued acceleration would likely have caused a structural failure! The aircraft has a Vmo limit for a reason.
What killed them was the loss of control authority that occurs in the 737 control system due to control surface forces exceeding the elevator actuator capability and loss of control movement due to cable stretch at very high control forces.
When you go really fast, that big HS can make bad stuff happen really fast before you have time to counteract with your dinky little elevator.
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Old 14th Apr 2019, 16:40
  #3996 (permalink)  
 
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Salute!

I like Thrust..I will fly his right seat any day.

Takwis could be the best expert witness in the trials. Especially if the lawyers can get more pilots that went thru the minimal training for this model. Seems to me that the suits are gonna minimize crew actions and besides, can’t get a lotta money from dead pilots.

Gums sends.......
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Old 14th Apr 2019, 16:52
  #3997 (permalink)  
 
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Endless Argument

How can this discussion become any more wearisome (albeit fascinating at the same time) than it has? To a dispassionate bystander with a decent grasp of the technical AND human factors involved and NO axe to grind (such as myself ) it has seemed obvious, pages ago, that there is plenty of blame to go around! No-one will emerge blameless from the analysis. All of the arguments from the various POVs here make sense, and only serve to show that almost everybody screwed up! 'Course if we all adopted that POV there'd be no discussion, and what fun would that be?

Last edited by Organfreak; 14th Apr 2019 at 16:53. Reason: Typoo
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Old 14th Apr 2019, 17:36
  #3998 (permalink)  
 
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STAB TRIM switches. So, the two little switches on the pedestal look the same and feel the same as those on a 738 etc. But the little white labels say something different and do something different. This isn't indicated anywhere in flight manuals, checklists, training software/documentation etc? What else has changed but isn't covered in the 'training manual'?

Hmmmm. The more I look at this the more I think the MAX has been a third-rate job. Yep, clearly the crews got it wrong.
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Old 14th Apr 2019, 17:42
  #3999 (permalink)  
 
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Originally Posted by Machinbird View Post
Sir. Thinking like that is cruising for a bruising.
With flight control problems, you should typically go for the center of the envelope and avoid the corners of the envelope, then explore cautiously.
Besides that, if they had managed to keep control much longer, their continued acceleration would likely have caused a structural failure! The aircraft has a Vmo limit for a reason.
What killed them was the loss of control authority that occurs in the 737 control system due to control surface forces exceeding the elevator actuator capability and loss of control movement due to cable stretch at very high control forces.
When you go really fast, that big HS can make bad stuff happen really fast before you have time to counteract with your dinky little elevator.
I agree they shouldn't have done that. I didn't say it wasn't a mistake. I was just saying it wasn't a mistake that is hard to explain. There are maneuvers that force you to get to the edge of the envelope to save the aircraft, like the terrain escape maneuver. So, out of everything they did, this is probably part that is the easiest to explain and excuse.

However I disagree with the statement that they kept accelerating. They accelerated for the first 2 minutes but, after getting close to VMO, their speed remained almost constant for about 3 minutes. The airspeed traces on the FDR chart were almost flat. They were not accelerating until MCAS activated again and brought the nose down.
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Old 14th Apr 2019, 17:49
  #4000 (permalink)  
 
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https://abcnews.go.com/US/american-a...ll_twopack_hed

No quick fix, it appears. AA rescheduling until August, pending resolution.
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