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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 03:53
  #901 (permalink)  
 
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Originally Posted by Tryingharder View Post
Sorry to intrude here, just a passenger, but I'm baffled what risk assessment in a safety critical industry means that an aircraft that is already airborne needs to find a destination other than the one it was planning to go to in the UK?

I appreciate the fact that the type is effectively prohibited from UK/European airspace but surely asking the crew to go hawking around the world looking for a diversion is introducing additional risk to the baseline risk now associated with this aircraft rather than reducing it. It's got to land somewhere right? And even if it's going to go wrong it's better it goes wrong with every potential advantage in the crew's favour even if that's only ATC in English and familiar with the terrain at a familiar airport. As opposed to an unfamiliar airport with altitude / temperature that might even predispose to the failure condition being encountered after wandering round introducing additional constraints such as fuel.

I apologise if that risk assessment was done today on the basis of the weather in the UK being a risk - but I can't see it.

I work in a safety critical business; medical devices. If I know there's a safety advisory on a piece of kit then I'll risk assess the likelihood/impact of keeping it in service vs the benefit to the patient. That's a very different conversation when the operation's not started (on the ground) vs patient "on the table" (aircraft airborne). And sometimes we might be "brave" when the patient really needs it.

Just askin'
You are correct. Itís called @ss covering bureaucracy where common sense and rational thinking unfortunately often has no place.

CP
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Old 13th Mar 2019, 04:06
  #902 (permalink)  
 
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Originally Posted by retiredmecheng View Post
First time poster here, and not a pilot, but... I just noticed this in an article on the Guardian. Doesn't sound like MCAS, but perhaps another example of "un-wanted" automation trying to bring a plane down. Apologies if this has been posted before, but I haven't seen it yet on this (fascinating) thread...

"Two US airline pilots filed voluntary safety reports last year to a database compiled by Nasa, saying an automated system seemed to cause their 737 Max planes to tilt down suddenly.

The pilots said that soon after engaging the autopilot on Max 8 planes, the nose tilted down sharply. In both cases, they recovered quickly after disconnecting the autopilot.

The problem did not appear related to the automated anti-stall system that is suspected of contributing to a deadly October crash in Indonesia."
I saw that on Rachel Maddow tonight. I agree that this doesn't seem to be MCAS related, given that MCAS doesn't activate when the AP is on. Depending on how out of trim the aircraft is when the autopilot is turned on, it might well command nose down.
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Old 13th Mar 2019, 04:17
  #903 (permalink)  
 
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Originally Posted by positiverate20 View Post
No idea how to retrieve a 20 minute post I'd written- where does the "Auto-save" go??

Anyway, quickly, and quite ironically, I was explaining that I've little to no "software coding" literacy nor any in-depth knowledge as to how it works.

My point was basically (acknowledging this is off-topic at this stage for flight in question, but in same tangent as previous MCAS discussion):

We know, with Lion Air anyway, MCAS caused problems.
We know MCAS failed- in that it wasn't designed to have the effects that it had.
With this in mind, how can we be so confident that MCAS adhered to:
- the pitch limitations
- the 10 seconds of operation
- the 5 seconds 'wait and see' period
- not functioning if flaps extended
etc. etc.

My point was- if the system failed- how, at this stage anyway, can anyone be certain that one component of the system failed entirely and that every other single component performed perfectly? Despite whatever failure mode it's in, does it still adhere to the pitch input rates, same operating window etc.?

I'm more comfortable with hardware, because I understand it, and know how it can fail- which is why it shocks me that the MCAS system is dependent on one single AoA vane's data- ludicrous. However, we can't at this stage determine the hardware was the only fault for Lion Air, are there other flaws or weaknesses hidden in the software, circuitry, functioning, logic of the MCAS elsewhere? Maybe MCAS was never an issue? Maybe errant data from a faulty ASI corrupted the MCAS or made it behave erratically?

I'm uncomfortable with the encroachment and infringement of automation by way of control inputs during what was considered to be manual flight. It frightens me that even with all AP functions off, computer software can still manipulate controls in this way.
Actually MCAS functioned as it was supposed to in the Lion Air crash, it received a high AOA signal and kept trimmed accordingly. The broken part was the AOA sensor. There's no need to be afraid of computers adding control inputs with the auto pilot off, the 320 does it all the time and has half the hill loss rate of the 737.

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Old 13th Mar 2019, 04:21
  #904 (permalink)  
 
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Eyewitnesses say they saw a trail of smoke, sparks and debris as the plane nosedived. https://www.bbc.com/news/world-asia-47536502

Does that really sound like an MCAS event?
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Old 13th Mar 2019, 04:24
  #905 (permalink)  
 
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Originally Posted by cncpc View Post
I saw that on Rachel Maddow tonight. I agree that this doesn't seem to be MCAS related, given that MCAS doesn't activate when the AP is on. Depending on how out of trim the aircraft is when the autopilot is turned on, it might well command nose down.
By "it" do you mean the MCAS or the autopilot (as an entity that has a bunch of sub-elements). Your point on possible out-of-trim taken on board.
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Old 13th Mar 2019, 04:24
  #906 (permalink)  
 
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Originally Posted by hans brinker View Post
Actually MCAS functioned as it was supposed to in the Lion Air crash, it received a high AOA signal and kept trimmed accordingly. The broken part was the AOA sensor. There's no need to be afraid of computers adding control inputs with the auto pilot off, the 320 does it all the time and has half the hill loss rate of the 737.
True. But the Airbus planes are stable throughout their flying envelope. The Max alas is not. The FAA should have never allowed a software fix as a remedy for a basic design flaw. And there must have been engineers at Boeing who were very upset of having been overruled by bean counters and MBA types. Admittedly the MCAS as it is today is a remedy (to the symptoms) worse than the disease. But there should never have been an MCAS in the first place, the right thing to do was to redesign the horizontal stabilizer.

Only airliner I can think of that turned out to have a stability issue was the BAC-111. But that was found late in the game, not by design, and the remedy apparently worked.

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Old 13th Mar 2019, 04:29
  #907 (permalink)  
 
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If ever you wanted a good example of regulatory capture, the continuum with China sitting at one side champing at the bit to throw at stone at a US company at the first hint of smoke, and the FAA sitting right at the other holding fast while everyone else sees a fire is a pretty great illustration of the effect.
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Old 13th Mar 2019, 04:36
  #908 (permalink)  
 
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Originally Posted by threemiles View Post
FAA says when then new MCAS software is certified and out it shall be implemented by an AD Note. I am not sure this is the right sequence if FAA feels something is very critical. Because the interim AD had nothing in it but hot air it reads like the MCAS problem is minor. Now they say it deserves implementation of the fix by AD note not by Service Bulletin. Again, this smells and the FAA does not seem to act logical and independantly but rather as the long arm of Boeing and US commercial interests. A logical step would be a grounding order by FAA until the fix can be implemented.
A Service Bulletin (SB) is the means by which the manufacturer embodies the necessary instructions for implementing the modification or for continued airworthiness. It identifies all the technical and engineering data necessary for implementation.

An Airworthiness Directive (AD) is an instrument issued by a national airworthiness authority (like the FAA) which usually identifies the applicable SB to be enacted, and a time by which it must be incorporated and/or any exceptions. It is a legal document in the context of a nation's airworthiness system and typically carries a responsibility for an aircraft operator/owner to comply with. A manufacturer's SB is not.
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Old 13th Mar 2019, 04:45
  #909 (permalink)  
 
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So its a stick pusher that pushes the stick. Plain English please.
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Old 13th Mar 2019, 04:47
  #910 (permalink)  
 
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Originally Posted by A0283 View Post
@FCeng84 - I really appreciate your effort to help clarify a number of issues. Hope Boeing will elaborate on this in the end ;-)

For me there is a difference between an "AoA increase" and a "positive AoA rate". Hope you can clarify that during your further explanations.

I was wondering if you were talking about "positional feedback" with MCAS or "force feedback" or both. In another explanation you exclude the "positional".

If you use the cutout and remove the power you disable MCAS ... which would put you outside the 'normal' certified envelope... do I read that correctly? ... With MCAS aimed at the NNC part of things, using the cutout appears to push you in yet again an other area, and outside certification?... Or is that a wrong interpretation?
Please excuse that I don't recall the context for "AoA increase" and "positive AoA rate". Can you point me in the right direction for that?

MCAS acts only to move the stabilizer an increment in the airplane nose down direction and then (if AOA decreases below the MCAS activation AOA threshold and the pilot has not provided an electric trim command) to take that increment of stabilizer out (i.e., run the stab airplane nose up the same amount). I don't see how this translates to "positional feedback" or "force feedback".

I think your last paragraph above gets at the issue of hazard levels, hazard mitigations, and availability of those mitigations. MCAS is implemented to address a handling qualities deficiency. The hazard level of not having MCAS drives the requirement for MCAS availability. Any failure that renders MCAS inoperative or leads to MCAS behavior for which the crew is expected to deactivate MCAS must have a probability that is low enough to permit loss of MCAS.
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Old 13th Mar 2019, 04:54
  #911 (permalink)  
 
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Originally Posted by bunk exceeder View Post
So its a stick pusher that pushes the stick. Plain English please.
You mean MCAS?

A stick pusher doesn't move the stab does it?
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Old 13th Mar 2019, 04:57
  #912 (permalink)  
 
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I watched Sean Hannity tonight, he was magnificent as usual.
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Old 13th Mar 2019, 04:58
  #913 (permalink)  
 
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Originally Posted by acad_l View Post
Only airliner I can think of that turned out to have a stability issue was the BAC-111. But that was found late in the game, not by design, and the remedy apparently worked.
I am not a pilot nor an engineer, just a geek so correct me if I am wrong but there have been systems similar to MCAS to keep planes stable during hand flying. The ones I know of are the LSAS system on the MD11 and the pilon flaps on the MD90. The difference is that they where not relying on a single sensor.
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Old 13th Mar 2019, 05:12
  #914 (permalink)  
 
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Originally Posted by Lonewolf_50 View Post
By "it" do you mean the MCAS or the autopilot (as an entity that has a bunch of sub-elements). Your point on possible out-of-trim taken on board.
The autopilot.

You'd think a professional crew would have the aircraft trimmed right before turning on the autopilot.

I don't think these two reports, which I take it are from the two crew on one incident, are relative to this accident, but...?

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Old 13th Mar 2019, 05:15
  #915 (permalink)  
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Originally Posted by Bonzo777 View Post
Why did it take so long and 300+ pax and crew deaths for the industry to acknowledge that a 50 years old original design cannot be modified/updated/re-engineered endlessly?
Tell that to Porsche with their 911
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Old 13th Mar 2019, 05:24
  #916 (permalink)  
 
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Originally Posted by 12A View Post
Tell that to Porsche with their 911
And I bet there are more than a few 911 owners here.
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Old 13th Mar 2019, 05:26
  #917 (permalink)  
 
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Originally Posted by hans brinker View Post
Actually MCAS functioned as it was supposed to in the Lion Air crash, it received a high AOA signal and kept trimmed accordingly. The broken part was the AOA sensor. There's no need to be afraid of computers adding control inputs with the auto pilot off, the 320 does it all the time and has half the hill loss rate of the 737.
The broken part was a MCAS system that reacted to a single faulty input - instead of comparing that input with its partner; deciding there was a discrepancy; and switching itself off.

On second thoughts, the real broken parts were the designers and engineers who thought that MCAS was a good idea. It looks to me like a case of group confirmation bias, were a small cabal decide upon an action, and they have sufficient authority that nobody else will question their wisdom. As someone said above, flight crews have to do CRM every year, so do Boeing engineers do DRM or ERM every year? (design or engineering resource management)

Silver

Last edited by silverstrata; 13th Mar 2019 at 05:52.
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Old 13th Mar 2019, 05:30
  #918 (permalink)  
 
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Applying airspace bans to in-flight aircraft nonsensical

By the time a MAX 8 or 9 has made it to cruise, the phase of flight that claimed Lion and ET is long past. And the pax have to land somewhere, preferably within reasonable reach of destination

There is an argument to made for changing the destination to an airport where a positioning flight will present a minimum hazard to people on the ground.
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Old 13th Mar 2019, 05:30
  #919 (permalink)  
 
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MCAS is operational with flaps up. Most (if not all) airlines do not start retracting flaps till 3000’ AFE. According to reports, Ethiopian never achieved anything higher than about a 1,000’ (not even close to 3k).

Most opinions on here are probably from media types baiting for info so they can self profess themselves for the cameras. Give it a rest till something concrete comes out from the FDR/CVR etc investigations.
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Old 13th Mar 2019, 05:32
  #920 (permalink)  
 
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MCAS- Massachusetts Comprehensive Assessment System.
Or
Mast Cell Activation System if you prefer.
What does it do? Push the stick? Does the poor 200 hr co pilot know what a stick pusher is? Let alone an MCAS that isn’t mentioned anywhere? Perhaps not a true pusher but call it something that isn’t gibberish please. With Colgan, these things might be issues of understanding.



Last edited by bunk exceeder; 13th Mar 2019 at 05:50.
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