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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 12th Mar 2019, 12:03
  #661 (permalink)  
 
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Originally Posted by Air Snoop View Post
Having interviewed many folk who have witnessed aircraft accidents, it is not unusual to get the sequence of events in the wrong order or to misinterpret what they are seeing. It is a very traumatic experience for them.
And that is often used in court cases to discredit witnesses. It is notable when multiple witnesses describe similar experiences though.
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Old 12th Mar 2019, 12:15
  #662 (permalink)  
 
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Originally Posted by Air Snoop View Post
Having interviewed many folk who have witnessed aircraft accidents, it is not unusual to get the sequence of events in the wrong order or to misinterpret what they are seeing. It is a very traumatic experience for them.
I agree completely, the most relevant aspect of the eyewitness accounts is the consistency in believe that the engines sounded wrong. Aural memory is much stronger and more consistently correct then visual memory. That doesn't mean in anyway that anything was actually wrong with the engines just that the sound was different. The airplane was significantly lower than normal and moving at significantly higher speed so the acoustic signature for lack of a better term would be much much different then they would expect and is what they noticed before even acquiring the aircraft visually I'd wager....
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Old 12th Mar 2019, 12:19
  #663 (permalink)  
 
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Originally Posted by Chesty Morgan View Post
Something else to ponder is that the 737 is controllable with the trim at either the forward or rear extreme. However, it's a two hands on the column job.
Surely the more pertinent question (at least for Lion Air) is: is it controllable with full forward trim and EFS activated. If it is, is it a two hands on the column job or a four hands on both columns job (and if the latter, which appendage should be used for the trim cut outs / wheels).
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Old 12th Mar 2019, 12:30
  #664 (permalink)  
 
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The difference between the QF72 incident and the Max8 accidents is that in QF72ís case, it was that its ADR AoA input data was corrupted. As a result they then sent misleading pitch orders.

It was intermittent thus causing even more confusion for the pilots and complicating their ability to identify the root cause.
They also were blessed with a great deal more altitude than the two Max accident crew. In fact one of the QF72 pilots was quoted as saying that his biggest concern during the whole event was what might happen if it occurred again while they were at low altitude.

Nor do I think that there was any trim or HST misbehavior.

Their calm, methodical and disciplined approach to the problem they faced also helped achieve a safe resolution (not that Iím in even the slightest way insinuating the contrary about either of the Max crews). Airbus subsequently issued a bulletin advising pilots how to deal with a similar event.
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Old 12th Mar 2019, 12:40
  #665 (permalink)  
 
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It is early to be making assumptions about the cause of this crash but it seems there is already good evidence of failures in the design/regulatory/certification process and that these need proper investigation.

I am not a pilot and although I design systems with safety aspects I am not in the aerospace areas. Despite this a key question is why a design change intended as a risk control measure seems to have introduced significant new risks.

On the face of it both the design/development/change control process seems to have failed but also the certification process in considering the impact of a change.

Given what MCAS does the risks of it failing to operate correctly do not need to have been properly consideer and controlled and although there is an element of hindsight it seems quite a stretch to have it vulnerable to a single point failure and with the assumptions that the pilots could control the risk of it failing under all reasonable circumstances and conditiosn without specific training.

There will be a focus on the specific cause of the accident but I would argue more worrying is what looks like a breakdown in the safety/regulatory process with respect to design modifications. Certainly for medical devices (my expertise) statistics suggest that modification of software is one of the largest causes of safety incidents and is therefore an area of focus for regulators.
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Old 12th Mar 2019, 12:45
  #666 (permalink)  
 
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Is MCAS the sort of system that would previously have been tested with flight trials on a prototype aircraft, but which is now tested using computer modelling?
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Old 12th Mar 2019, 12:49
  #667 (permalink)  
 
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If the weather was 60-65 degrees with the field elevation at 7625 then the density altitude was around 9000-9500 at take off.

If they lost an engine then it would be rather sporty.

For bonus points, was it the 200 hr TT F/O's leg?
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Old 12th Mar 2019, 12:53
  #668 (permalink)  
 
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Is it known how many times the MCAS system has activated erroneously on the MAX and been successfully dealt with?
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Old 12th Mar 2019, 12:57
  #669 (permalink)  
gmx
 
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Originally Posted by Chesty Morgan View Post
Most definitely is. I haven't seen the Lion Air data so I don't know if it ran full forward and stayed there or something else. Obviously startle factor might play a part as well but I'm not sure how startling the trim running slowly forward would be but maybe combined with the stall warning going off wouldn't encourage you to haul back as hard as you can.


I'm only saying that it is controllable at either extreme. Just.

I think its important to remember that the Lion crew kept the aircraft reasonably steady for 6 minutes after MCAS issues presented, continuously and manually counteracting the MCAS nose down events that occurred during that whole time. The crew knew they had a stabilizer runaway b/c they kept using the electric trim to correct it. They kept the aircraft basically level at 5000 feet for that 6 minute duration, until, for the last four MCAS nose down commands, the crew's manual trim responses occur but are just "blipped" (not sufficient to counteract the MCAS input), and assumedly resulted in the stabilizer being full forward.


No one knows why the crew were able to successfully counteract MCAS with manual trim operation for 6 minutes, and then fail to do so for the final 4 MCAS inputs. That is the mystery that we are hoping the CVR will explain.


Lastly, as I understand it, MCAS only dials in *ONE* nose-down increment (2 degrees or whatever it is) and then deactivates itself, until something happens to reactivate MCAS allowing it to dial in another increment. I can't recall all of the crew activities that result in MCAS being reactivated, but I believe one is operation of the manual trim. This is why the last four "blipped" manual trim inputs in the Lion flight result in four unmitigated MCAS nose-down events, because any manual trim input resets MCAS and allows it to reasses the AoA / speed picture and dial in another MCAS trim input.
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Old 12th Mar 2019, 13:05
  #670 (permalink)  
 
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Originally Posted by gmx View Post


No one knows why the crew were able to successfully counteract MCAS with manual trim operation for 6 minutes, and then fail to do so for the final 4 MCAS inputs. That is the mystery that we are hoping the CVR will explain.

Lets just hope the Stab Trim Cutout switches arenít found to disconnect all Trim (pilot electric trim included) but not MCAS Trim!
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Old 12th Mar 2019, 13:08
  #671 (permalink)  
 
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Originally Posted by PJ2 View Post
There is no information in the current B738M AOM that tells crews that the "MCAS cycles between the left AoA and the right AoA sensor". What is the source for the above statement?
my quote tells you LANCS THINKS it is in the Lion Air thread, which is why I started my post off with IF IT IS TRUE..

As the crew cannot do anything about it ie cannot select which one, why bother giving them that info, Ground crew need to know IF it switches because if there is a fault reported not being able to tell which one was in use means they HAVE to check both, personally I don't believe this to be correct info.. However if it is true my suggestion would IMHO improve the system.

Oldeberon
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Old 12th Mar 2019, 13:19
  #672 (permalink)  
 
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Originally Posted by gmx View Post
Lastly, as I understand it, MCAS only dials in *ONE* nose-down increment (2 degrees or whatever it is) and then deactivates itself, until something happens to reactivate MCAS allowing it to dial in another increment. I can't recall all of the crew activities that result in MCAS being reactivated, but I believe one is operation of the manual trim. This is why the last four "blipped" manual trim inputs in the Lion flight result in four unmitigated MCAS nose-down events, because any manual trim input resets MCAS and allows it to reasses the AoA / speed picture and dial in another MCAS trim input.
MCAS is perpetually active so as long as ONE AoA sensor relays: high angle of attack, flaps up and autopilot disengaged. Simply, it will trim the Stabilizer down for 10 seconds (2.5 degrees nose down) and pause for 5 seconds before doing it all over again if it deems conditions remain the same (which often does with faulty sensor data; in the case of MCAS it's engaged on single channel FCC). You could have an aircraft ~4 degrees nose down from level flight as early as 45 seconds.

Application of electric trim pauses MCAS (5 seconds). Selecting TRIM CUTOUT to OFF deactivates MCAS (much like Speed Trim, Mach Trim and Column switch electric trim)

So if they were manually trimming the stab wheel as you say, one would assume they'd have tried either of those two options which begs the question why wouldn't they have been able to control the aircraft in the pitch axis thereafter? Time will tell.
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Old 12th Mar 2019, 13:20
  #673 (permalink)  
 
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Originally Posted by c52 View Post
On the reliability of witnesses: I was once watching through binoculars a Starfighter display. It was flying erratically. My interest and concentration were at a peak. The pilot ejected and the aircraft exploded in the air. Or maybe it was the other way round. And since then I have not really trusted anyone's account of things they have seen.

(Frankfurt Airport/Rhein-Main AFB, about 1990)
About 5 years ago the BBC here in the UK did a very interesting TV show on the reliability of witnesses. They set up a situation (with actors) in a bar where a young woman started a fight by punching a man, and they asked people what they thought happened. Most of the older men said that a man had started the fight, not a woman. The explanation was that when they were young the idea of a woman starting a fight was so unlikely that they discounted it, even though that was what actually happened in front of their eyes. In other words, in the 1950s or 1960s it was unheard of for a woman to do something like that in public, so they just assumed that the man had started it. It just shows how unreliable eyewitnesses can be, because things like people's basic assumptions about life can get in the way of giving a true account of what happened. That's just one example, but it applies to lots of situations. People often see what they expect to see instead of what has actually taken place.

Last edited by AndyJS; 12th Mar 2019 at 13:30.
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Old 12th Mar 2019, 13:21
  #674 (permalink)  
 
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The famous eye witness accounts!

Lately I've been flying a 1948 Grumman Mallard with a good friend of mine, We landed and docked by a nice hotel and went inside for lunch, the military showed up asking if we were OK! When we asked why, they said that people have called reporting an airplane that crashed in the ocean and was on fire!
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Old 12th Mar 2019, 13:22
  #675 (permalink)  
 
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Originally Posted by gmx View Post
Lastly, as I understand it, MCAS only dials in *ONE* nose-down increment (2 degrees or whatever it is) and then deactivates itself, until something happens to reactivate MCAS allowing it to dial in another increment. .
Not my understanding. The logic of the system was posted in the extensive Indonesian thread, and if I recall correctly the MCAS system will continue operating as long as it thinks the aircraft is in a stall situation. So it gives 10 secs of trim, 5 secs waiting, and then another 10 secs of trim. That is why the Indonesian aircraft got multiple trim events (about 12 or so) in quick succession.

The system was obiously never designed to recognise that the aircraft was not stalled - it took the word of one AoA sensor as being gospel. Never mind that the airspeed and attitude were correct, the system reacted solely, and incorrectly, to the erroneous AoA sensor.

It did not even bother checking with the other AoA sensor. All you need is one line of code that says: “if AoA1 not equal to AoA2, deactivate system”. I mean, how hard was that? Ok, it would be nice to have three sensors, but even two can resolve that there is an error somewhere, so the system should not start trimming.

And while we are at it, why was there not a line of code that says: “if ASI greater than 210 kts, deactivate system”. I mean, how hard was that? Please don’t say that high speed stalls are a real problem with the Max, because I will not buy that one.

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Old 12th Mar 2019, 13:22
  #676 (permalink)  
 
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may I ask something did the pilots of the Ethiopian air engage the autopilot after the takeoff ? because if they did then the MCAS is not taking any action.
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Old 12th Mar 2019, 13:30
  #677 (permalink)  
 
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Okay, after perusing through this multi-page thread of, frankly, mostly useless and uninformed speculation and, in some cases, pure garbage, I have a few items to contribute:

Background: my first Boeing was the 737-200 and 300, left seat on the 757 and 767, currently flying the 737NG, never been closer to a Max than across the ramp. I have never operated MS Flight Sim. Multiple carriers, all overseas for the last 12 years. I spent a year flying the NG at ET a few years ago. Total flying career 32 years and counting.

First: ET pilots. I entered ET right at the introduction of the MPL program for FOs. As far as I know their new pilots are still graduating under the MPL: program. For those who don't know what that is, it's Multicrew Pilot License. It consists of 70 hours of actual airplane flight time and 130 hours of simulator. The pilot does not have a CPL. So the 200 hour copilot is plausible, though unless the Captain was an instructor the FO probably had a little more time than 200. I sometimes got a fresh FO with a grand total of 230 hours, having been signed off as meeting the standards. Here's the truth - none of them could fly an airplane. Plain and simple. No exaggeration, just the plain truth. There were multiple times I flew with an FO who, after almost a year on type still couldn't fly worth a darn. I'm not talking the finer points, I'm talking basic airmanship. Next, local captains. Most are competent but ET had (probably still has) difficulties with new upgrade captains. they move up the ranks strictly by seniority. After a year or so on the Q400 or 737 they go to junior FO on the widebody, then senior FO on the widebody, then back to the Q400 or 737 for upgrade. Big culture shock, big step backwards on technology, big change in route structure. Their upgrade line training program typically took 4 or 5 times as long as a current & qualified captain. There's a big difference between logging time droning along for 12 hours vs. short-haul. Not throwing rocks but I usually see a large quality gap between FOs who came from short-haul vs. long-haul. As was said previously, Addis is a captain only airport and almost certainly the captain was PF. Lastly on the pilot side, CRM is mostly non-existent there, it is very much a top down cockpit culture, though that probably was not a factor here.

Next, the FAA: I'm certainly glad that PPRuNe has, in three days, solved the crash! Hallelujah! The NTSB and local crash investigators need not even show up. The big uproar that the FAA has not grounded the Max is a good thing. It means they are doing their jobs, not acting rashly and on pure emotion, rather basing any decision on facts when they come. I notice that EASA has not issued a grounding order (which they certainly can). Considering that the bulk of the Max fleet is operating in the US and Europe, what on earth are they waiting for? (that's sarcasm, by the way). Maybe they are waiting for some actual data to come forth before condemning the aircraft. Maybe they know something we don't. Hmmmm....

Next, MCAS: I'm not weighing in on this as I have exactly zero more facts than anyone else. I do have a few questions though concerning the final few moments of both the ET crash and the Lion crash. Both times the aircraft was in day VMC conditions, both seemingly experienced speeds much higher than what could and should be considered normal for level flight at low altitude, so what gives? I can certainly tell my airspeed by looking out the window, regardless of how many alarms at whatever obscene volume are blaring any time. If the data is to be believed, 330+ knots at around 1000AGL to me means someone forgot the cardinal rule: fly the airplane. Pitch, power, and if possible (it was) look out the damn window!

Next, basic airmanship: If I have, simultaneously, an A/S and/or ALT disagree, stick shaker, and an increasing need for backpressure on the yoke, my first action is to fix the flight control issue and that means assuming a trim problem. I can handle the airplane all day long without an altimeter or airspeed indicator (in VMC conditions) but aircraft control is first, second and third on the to-do list. Maybe airmanship is not taught anymore (it's not but that's another story) but basic airmanship teaches us that even in an airplane without a trimmable HS, a mistrimmed airplane will be harder to control at higher speeds. So grab the thrust levers and use them. Set pitch and power. The 737 can be flown, albeit with a lot of force required, with the pitch trim at either stop, but at full nose down the control forces will be massive at high speeds. Couple that with the elevator force diminishing with higher airspeeds and it may reach a point where at speeds above barber pole you may run out of elevator. I was taught this years ago, though I know it is not taught anymore. Moral: fly the damn airplane.

I could chime in on lots more but frankly, why bother? Based on most of what I've read (and could stomach) the PP needs to be removed from PPRuNe.
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Old 12th Mar 2019, 13:34
  #678 (permalink)  
 
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The captain of this flight has been reported to have 8000 flight hours -- and was 28 years old. Does this seem anomalous to anyone. That is a lot of hours for someone so young. And has there been any information as to how many hours he had on either the MAX 8 or his previous types?
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Old 12th Mar 2019, 13:39
  #679 (permalink)  
 
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Originally Posted by CONSO View Post
Interesting details/analysis by a control guru which **may** help explanation of which sensor does what and how

https://www.satcom.guru/2018/11/737-...n-command.html

Obviously put together after LionAir . .
Thanks Conso

The link is to an article by someone worthy of the title "expert" in system design. very interesting and detailed analysis of the system, how it should function, what could go wrong, and what should be done going forward.
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Old 12th Mar 2019, 13:53
  #680 (permalink)  
 
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Has Boeing issued any Maintenance or Crew notices since the Ethiopian accident? If not, what has prompted some countries to ground the Max. Although there is speculation on this site about a similar cause to that of Lion Air crash, I have not seen anything from official sources to confirm the idea.
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