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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 19th Mar 2019, 15:59
  #2061 (permalink)  
 
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Salute!
Gotta tellya, I am disappointed by several pilots here that are apparently clones of Chuck Yeager, Neil Armstrong or Jimmy Doolittle.
Yeah! The thing flies just like an old Stearman and you don't need a single electron because you have wires and pulleys and cables and...... NOT!!!
I throw the foul flag. This latest version is not the plane your grandfather flew 30 years ago. It is not the same plane your son flew 10 years ago. The "geeks" have put in stuff to "help" the "clueless yutes" that don't have the skill you have or because the plane behaves differently. And it does!!

Good grief, you'll have everyone saying we should kiss off two accidents that might have been prevented with knowledge of a kludge system and maybe a sim ride to show what could happen.

More later,

Gums rants...

Last edited by gums; 19th Mar 2019 at 17:33. Reason: typo
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Old 19th Mar 2019, 16:01
  #2062 (permalink)  
 
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Originally Posted by MPN11
It trims the horizontal stabiliser. Endlessly, unless stopped!
No, not endlessly, and that is a very important distinction. It does it in increments, and only starts a new increment when reset, e. g. by pilot electrical trim input.

This is so important because it is the qualitative difference separating it from "runaway trim".

And you can't stop MCAS in any normal normal sense. You can only temporarily inhibit it by using manual electric trim, or you can disable electric trim altogether, and that includes disabling the speed trim system, Mach trim and pilot-commanded electric trim. Only crank-and-pulley mechanical trim remains operational.

Bernd
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Old 19th Mar 2019, 16:18
  #2063 (permalink)  
 
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Originally Posted by bsieker

No, not endlessly, and that is a very important distinction. It does it in increments, and only starts a new increment when reset, e. g. by pilot electrical trim input.

This is so important because it is the qualitative difference separating it from "runaway trim".


Bernd
Just because it is not running continuously doesn't mean it is not a runaway. How many times does it need to do something that you have not asked for to qualify?

If the lane keeping function on your car tried to pull you into the ditch 3 or 4 times would you just let it keep on doing that or would you see a pattern and turn it off?

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Old 19th Mar 2019, 16:23
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Originally Posted by flyingchanges
Just because it is not running continuously doesn't mean it is not a runaway. How many times does it need to do something that you have not asked for to qualify?

If the lane keeping function on your car tried to pull you into the ditch 3 or 4 times would you just let it keep on doing that or would you see a pattern and turn it off?
STS always asserts unwanted trim input by design.

Is there any cockpit indication of what system(STS, Mach, MCAS) is actually commanding trim movement? If not, how does one reliably tell it is from MCAS?

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Old 19th Mar 2019, 16:31
  #2065 (permalink)  
 
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Two quick notes:

- Air Canada suspends Max 8 until July 1 at least and suspends new deliveries
https://www.cbc.ca/news/canada/nova-...ly-1-1.5062354

- BBC reports fix by end of March
https://www.bbc.com/news/business-47622721

TME

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Old 19th Mar 2019, 16:33
  #2066 (permalink)  
 
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Originally Posted by flyingchanges
Just because it is not running continuously doesn't mean it is not a runaway. How many times does it need to do something that you have not asked for to qualify?

If the lane keeping function on your car tried to pull you into the ditch 3 or 4 times would you just let it keep on doing that or would you see a pattern and turn it off?
That using the cutout switches is the correct remedy both for erroneous MCAS activation and for stabiliser trim runaway does not make the two things the same. They are in fact very distinct and have very different symptoms:
erroneous MCAS activation:
  • is intermittent
  • runs for max 10s at a time
  • can be stopped temporarily by pilot trim input
  • is then inhibited for 5s
None of the above is true for a trim runaway. It
  • runs constantly
  • does not ever stop (unless it reaches the mechanical stop, is turned off by the cutout switches or is mechanically arrested by grasping and holding the trim wheel.)

The fact that at least one (and possibly two) crew did not find the remedy obvious, makes it an obvious design problem, and blaming the crew is the most useless thing to do if you want to find out how to prevent a recurrence. It is only ever the right thing to do if you want to feel smugly superior.

To reiterate: frequent automatic trim is normal on a 737 (STS, Mach Trim, ...), and is in no way comparable to a lane assist function going haywire. You comparison would be more appropriate if we were talking about the autopilot initiating a turn when none was called for.

Bernd
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Old 19th Mar 2019, 16:38
  #2067 (permalink)  
 
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Originally Posted by LDRA
STS always asserts unwanted trim input by design.

Is there any cockpit indication of what system(STS, Mach, MCAS) is actually commanding trim movement? If not, how does one reliably tell it is from MCAS?
The reliable indication is that it is always nose down trim and unless you do something about it and the AoA is still indicating a close to stall value it will wind in another nose down trim. Unsurprisingly, this will require more back stick pressure, If you trim against it then after 5 seconds it will wind in more nose down trim. If your 'driver assist' in your smart car was repeatedly trying to pull you out of your lane - how many times would it take before you switched it off? IF nose down trim repeatedly runs making the control column force difficult to handle and you also know that this is a fault that can happen in the MAX and has caused fatal crashes, would you
(a). Say it's not runaway trim as that is running continuously to the maximum position so I'll just carry on pulling harder, or,
(b) Say the trim is repeatedly doing something I think is dangerous I will set the Stab Trim cut out switches to Off as was said in that AD ..
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Old 19th Mar 2019, 16:40
  #2068 (permalink)  
 
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I’d like to get some of the macho types on here into the sim and throw a low level all Hell let loose scenario at them.
No green table, QRH open under the reading light, cigar lit and plenty of confidence - Just noise, conflicting indications, unfamiliar flight behaviour, shakers and elevator load, while the ground whizzes by.
That kind of situation requires lots of pre-knowledge, analysis and cool assessment, while you ride in a confusing mad cockpit. Even better lots of practice.
Concentrates the mind or defeats the mind.
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Old 19th Mar 2019, 16:45
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So, basically, with all said and done here and all the revelations coming out lately from Boeing, NTSB and the FAA the Lionair and ET guys just didn't have a chance.

What a Shame, it had to all come out like this, like if all this was not discussed and debated after the Lionair October crash.

THE MAX IS SAFE...…Thats what they all said.

I wonder how many of us would have made it out better if put in the exact same situation or scenario as both crashes.

Sad….
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Old 19th Mar 2019, 16:46
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Originally Posted by GlobalNav

And oversight is not as easy as it looks on paper. It gets reduced from technical examination to paper audits, turns engineers into clerks, and insulates the “overseers” from the technical details. Battles rage over the items to be retained by the FAA and can be beaten down by FAA management that is more sensitive to “customer” complaints.
Global Nav, I agree.
However these actives should not remove the need for the regulator to have sufficient understanding of the system to judge normal and non-normal operations, and then compare with crew standards and training.
Beware the assumptions in that.

Unfortunately many systems are now so complex and intertwined, only the manufacturer has the ability to understand the larger picture. Aspects of complex accident investigations may be delegated to the manufacturer, but at least their findings have to be submitted to the investigative group for peer review.

In part, this problem should be manageable with partnership, trust, and mutual understanding of design and certification processes, including safety culture. Perhaps the other overseas authorities should play a greater part in the oversight and review processes.
What happens when these aspect fail; who investigates these features?
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Old 19th Mar 2019, 16:48
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Boeing statement just issued :

A Message from Boeing CEO Dennis Muilenburg

To airlines, passengers and the aviation community:

We know lives depend on the work we do, and our teams embrace that responsibility with a deep sense of commitment every day. Our purpose at Boeing is to bring family, friends and loved ones together with our commercial airplanes—safely. The tragic losses of Ethiopian Airlines Flight 302 and Lion Air Flight 610 affect us all, uniting people and nations in shared grief for all those in mourning. Our hearts are heavy, and we continue to extend our deepest sympathies to the loved ones of the passengers and crew on board.

Safety is at the core of who we are at Boeing, and ensuring safe and reliable travel on our airplanes is an enduring value and our absolute commitment to everyone. This overarching focus on safety spans and binds together our entire global aerospace industry and communities. We're united with our airline customers, international regulators and government authorities in our efforts to support the most recent investigation, understand the facts of what happened and help prevent future tragedies. Based on facts from the Lion Air Flight 610 accident and emerging data as it becomes available from the Ethiopian Airlines Flight 302 accident, we're taking actions to fully ensure the safety of the 737 MAX. We also understand and regret the challenges for our customers and the flying public caused by the fleet's grounding.

Work is progressing thoroughly and rapidly to learn more about the Ethiopian Airlines accident and understand the information from the airplane's cockpit voice and flight data recorders. Our team is on-site with investigators to support the investigation and provide technical expertise. The Ethiopia Accident Investigation Bureau will determine when and how it's appropriate to release additional details.

Boeing has been in the business of aviation safety for more than 100 years, and we'll continue providing the best products, training and support to our global airline customers and pilots. This is an ongoing and relentless commitment to make safe airplanes even safer. Soon we'll release a software update and related pilot training for the 737 MAX that will address concerns discovered in the aftermath of the Lion Air Flight 610 accident. We've been working in full cooperation with the U.S. Federal Aviation Administration, the Department of Transportation and the National Transportation Safety Board on all issues relating to both the Lion Air and the Ethiopian Airlines accidents since the Lion Air accident occurred in October last year.

Our entire team is devoted to the quality and safety of the aircraft we design, produce and support. I've dedicated my entire career to Boeing, working shoulder to shoulder with our amazing people and customers for more than three decades, and I personally share their deep sense of commitment. Recently, I spent time with our team members at our 737 production facility in Renton, Wash., and once again saw firsthand the pride our people feel in their work and the pain we're all experiencing in light of these tragedies. The importance of our work demands the utmost integrity and excellence—that's what I see in our team, and we'll never rest in pursuit of it.

Our mission is to connect people and nations, protect freedom, explore our world and the vastness of space, and inspire the next generation of aerospace dreamers and doers—and we'll fulfill that mission only by upholding and living our values. That's what safety means to us. Together, we'll keep working to earn and keep the trust people have placed in Boeing.

Dennis Muilenburg
Chairman, President and CEO
The Boeing Company
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Old 19th Mar 2019, 16:51
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Originally Posted by Ian W
The reliable indication is that it is always nose down trim and unless you do something about it and the AoA is still indicating a close to stall value it will wind in another nose down trim. Unsurprisingly, this will require more back stick pressure, If you trim against it then after 5 seconds it will wind in more nose down trim. If your 'driver assist' in your smart car was repeatedly trying to pull you out of your lane - how many times would it take before you switched it off? IF nose down trim repeatedly runs making the control column force difficult to handle and you also know that this is a fault that can happen in the MAX and has caused fatal crashes, would you
(a). Say it's not runaway trim as that is running continuously to the maximum position so I'll just carry on pulling harder, or,
(b) Say the trim is repeatedly doing something I think is dangerous I will set the Stab Trim cut out switches to Off as was said in that AD ..
Wouldn't you also always get nose down trim from STS if you are decelerating?

It doesn't even need to be actually decelerating, just need air speed indication system to indicate deceleration, as STS trim command is primarily scheduled off air speed

Last edited by LDRA; 19th Mar 2019 at 23:35.
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Old 19th Mar 2019, 16:54
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Originally Posted by bsieker
To reiterate: frequent automatic trim is normal on a 737 (STS, Mach Trim, ...), and is in no way comparable to a lane assist function going haywire. You comparison would be more appropriate if we were talking about the autopilot initiating a turn when none was called for.

Bernd
OK, I'll bite. What do you do when the aircraft rolls (e.g. initiates a turn) when none was called for? And what about a yaw? And what about a pitch? What would any sensible airman do?
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Old 19th Mar 2019, 16:56
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Gums
Salute
I would like to address this short reply to You as it appear that You can grasp details, principals and the greater Picture.

It looks to me that the Max is certified under false pretenses , or self certified as FAA has let Boeing do most of it in house!!
The Max is unstable and not airworthy with out the MCAS!
I doubt the MCAS is fit for purpose, as I have always said the 737-800 even , has a dangerous pitch coupling.

I predict that in the not so distant future the Max will kill again if only a software fix is provided,this time due to a full stall, spin as the MCAS is inadequate.
I could be wrong, but 10 000hrs 738 plus 2000hrs sim tells me this bird is one step to fare and the Max is clearly two steps past stable and safe.
Simple as that!
Regards
Cpt B
PS
Do not take my word for it.
MOT in Canada is going to look into the FAA certification they excepted AND are doing their own certification on any fix.
Aircanada has grounded all the Maxes to 1 July
Lets hope its this July not 2020
DS
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Old 19th Mar 2019, 17:04
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Originally Posted by formulaben
OK, I'll bite. What do you do when the aircraft rolls (e.g. initiates a turn) when none was called for? And what about a yaw? And what about a pitch? What would any sensible airman do?
You got it the wrong way round. This wasn't a challenge. It was to point out that the problem of erroneous MCAS activation is not as easily identified as, say, lane-assist failing or the autopilot initiating a wrong turn.

So pilots identifying a rogue autopilot or lane-assist has nothing to do with being able to identify rogue MCAS, especially in a noisy and high-workload environment.

Moreover, you cannot assume that "any sensible airman" (if you can even define that) would do what you, in the comfort of your armchair and having perfect hindsight, have deduced was the most appropriate action, simply by our privileged knowledge of the actual outcome.


Bernd
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Old 19th Mar 2019, 17:05
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Ian W, # 2076, patplan # 2071,
Take care when attempting to compare failure reports with supposed accident scenarios; local investigation or narratives might not have the same level of expertise or understanding.
Furthermore, it would be unwise to make direct comparison with recent accidents, because without knowledge of the source of failure (where did the erroneous AoA originate), everything else is assumption.

My reading of the other events cannot identify any connection with AoA or any other parameter associated with MACS.
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Old 19th Mar 2019, 17:19
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So, hypothetically, if an intermittent short were to develop in a yoke mounted electric trim switch, and it would run nose down for a few seconds, stop run nose down again, stop. How many times would it need to do this before you called it a runaway? Or would you watch it do it again and again? Hey, look it's doing it again, too bad we don't have a checklist that would deal with this unwanted stab trim motion.
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Old 19th Mar 2019, 17:32
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Dunno about you but MY runaway stabiliser checklist says, and I quote, "Uncommanded stabilizer trim movement occurs continuously".

​​​​​​
Yes, since Lion Air, we know carrying out this checklist would have solved the problem .
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Old 19th Mar 2019, 17:41
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Apparent test flight now . . .

https://flightaware.com/live/flight/BOE302


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Old 19th Mar 2019, 18:32
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Salute!

Previous rant continued:

At least one of the Chuck Yeager wannabes here pointed out lack of previous flight writeups that likely had MCAS activation prior to the 610 crash. WRONG!!! We went thru the acatual writeups and maintenance actions right here on pPrune.
- IAS disagree - alt disagree - feel difference
The FDR traces clearly showed the same things that 610 experienced at the onset, as well as the "corrective action". It showed what they did. You know, the Luke Skywalker/Yeager procedure -turn off stuff and go "manual". It worked, but they forgot to writeup the constant stick shaker. Hmmmmmmmmmm. Would that have helped the 610 crew?
The traces show that crew had instant shaker, likely GPWS warning when they did their dive just as flaps retracted, and so forth - exactly what the 610 crew experienced.

The FAA Airworthiness Directive mentioned all of the above possible indications plus stick shaker indicating that something was awry, and recommended the "runaway trim" procedure ( basically, "O.K. R2, let's go manual!")

The recognition of inadvertant AoA-related MCAS activation upon takeoff must be pre-thought and actions rehearsed, as many things are happening. WoW and shaker starts. Flaps up and nose goes down, maybe get GPWS alert, several caution indicator lights come on and trim goes nose down again a few seconds after trimming up. and so forth. To make things worse, 610 crew put flaps down and the MCAS behaved itself. uh huh. Step 2 or 3 or "x" in the stick shaker/stall warning proedure, right? Flaps back up and MCAS starts again. Are you confused now?
So I cut the 610 crew some slack, especially since the intermittent trim was not what one would expect from the tradional runawy trim emergency.

Dunno why 302 crew didn't recognize the problem, but it may have been caused by something else and may be yet another undocumented "feature" of the MAX.

Gums sends...
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