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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 6th Apr 2019, 09:38
  #3421 (permalink)  
 
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Originally Posted by Albino
It's an interesting point whether the stab readout is taken from what is commanded or the position of the jack. Considering the AND command is registered without stab movement I suspect it is demand, it's how the narrative reads as well.
No, the chart clearly shows the pitch trim "command" and then the line below is the actual trim position. It even says "automatic trim command with no change in pitch trim".

Originally Posted by Geroge Glass
I’ll predict that one of major findings in both of these accidents is that everybody forgot just to fly the aircraft.
And I'll predict that I and I'm sure many others will say "they were never trained to fly the aircraft". You can't forget what you didn't know.
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Old 6th Apr 2019, 09:40
  #3422 (permalink)  
 
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Originally Posted by George Glass View Post
73,
I’ll predict that one of major findings in both of these accidents is that everybody forgot just to fly the aircraft.
The B737 is a very simple aircraft with lots of bells and whistles, most of which are nice to have, not must have.
An enthusiastic Boeing instructor once took me to 35,000 ft in the simulator at the end of a training session then reached up to the overhead panel and turned everything off.
The aircraft still flew.
Dont think they do much of that stuff anymore.
I hear what you’re saying George, and I concur 100%. Except for one apparent wild card...

MCAS!
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Old 6th Apr 2019, 09:44
  #3423 (permalink)  
 
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MCAS is not needed or wanted

This constant assumption by aircraft manufacturers that the pilots don't know f*** all about flying and insist on installing complicated systems to act as a safety pilot is crazy, how often do pilots stall airliners?? very very rarely is the answer, and if they were stupid enough to stall the aircraft, recovery is relatively simple, assuming some altitude is available. A message to Boeing and Airbus, please let the pilots fly the aicraft you build and stop confusing them with unnecessary and untimately dangerous technology.
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Old 6th Apr 2019, 09:48
  #3424 (permalink)  
 
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so will the software fix, and slightly updated training, be enough to get the MAX back into revenue service?

I predict after ET not. It's apparent even with MCAS turned off, the cockpit does not return to peace and tranquility where average ability pilots can regain control and land. It's apparent from the ET interim report that a lot more was going on in the cockpit, and that was it was beyond the two pilots to get it back together, mainly due to excess speed and aerodynamic forces making proper trim next to impossible without some, as yet, untrained yoyo, manoeuvre.

I would suggest no regulator would be willing to pass the MAX back into service based on a patch and minor training update.

G
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Old 6th Apr 2019, 09:53
  #3425 (permalink)  
 
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Originally Posted by Albino
the aircraft was not controlled with pitch AND trim as per the Unscheduled Stab Trim memory items. Nobody has questioned the validity of this statement.
Nothing in the Memory items like that (as per the report, page 30). If the runaway continues after AP is switched off, is says to switch off the trim. Nothing about "counter trim with control column switches, return aircraft to pitch neutral then switch off trim" as you are alluding to. And even if they had "disengaged the autothrottle", what would that have achieved? Nothing unless you then pull off a fistful of thrust...

Then you pull out the two page AD memo from Boeing and recall what it said: at the bottom of page two "Electric stabiliser trim can be used to neutralise...".
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Old 6th Apr 2019, 09:58
  #3426 (permalink)  
 
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Originally Posted by George Glass View Post
73,
I’ll predict that one of major findings in both of these accidents is that everybody forgot just to fly the aircraft.
The B737 is a very simple aircraft with lots of bells and whistles, most of which are nice to have, not must have.
An enthusiastic Boeing instructor once took me to 35,000 ft in the simulator at the end of a training session then reached up to the overhead panel and turned everything off.
The aircraft still flew.
Dont think they do much of that stuff anymore.
mr picky points out that you mean the simulator kept on simulating. Not quite the same thing as a copilot doing that in flight.
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Old 6th Apr 2019, 10:03
  #3427 (permalink)  
 
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73qanda, ATCWhatcher,

putting the event in context and human factors

also with, onsoutherntip re interpretation of FDR trim command and tail trim movement - they may differ; see post Ethiopian Prelim Report and the back links.

Adding to some of the ‘historic’ concerns, would the slightly smaller trim wheel in latter versions of the 737 reduce the effective torque which could be applied in grabbing the wheel as part of the runaway trim drill - and applying manual trim to recover ?


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Old 6th Apr 2019, 10:12
  #3428 (permalink)  
 
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For the benefit of the “MCAS is just there to satisfy a paper regulation” mob; the aircraft control characteristics regulations require that the stick force increase with increasing attitude. This is not a “paper regulation” but a real world need for the change in attitude to be proportional to force in other words the required control inputs as applied by the pilots don’t reduce or worse reverse with changes in attitude.

To put that in automotive terms some of you might understand; oversteer is not allowed.



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Old 6th Apr 2019, 10:15
  #3429 (permalink)  
 
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I have grown slightly cross eyed following the huge volume of posts concerning the tragic events with the 737 MAX. One item that seems to have been mentioned just once (or thereabouts) is that things only started to go pear shaped immediately following flap retraction. Surely the clue should have been obvious to any adequate pilot and the previous configuration restored. As far as I understand things that would have saved the day. I have done a fair amount of 737 work but that was back in the day when they worked like normal aeroplanes (737 200& 400) so I may be wrong. This principle, however, has saved my life twice and I don't pretend to be anything other than an average operator. Am I wrong?
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Old 6th Apr 2019, 10:19
  #3430 (permalink)  
 
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Originally Posted by hans brinker View Post
They set a lower alt in the window, so not trying to climb to F320
But they stayed in ‘level change’ mode all the time. That means that the autothrottle kept the engines at climb thrust all the time.

Both altitude and speed were uncontrolled.
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Old 6th Apr 2019, 10:24
  #3431 (permalink)  
 
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Originally Posted by Capn Bloggs View Post
Nothing in the Memory items like that (as per the report, page 30). If the runaway continues after AP is switched off, is says to switch off the trim. Nothing about "counter trim with control column switches, return aircraft to pitch neutral then switch off trim" as you are alluding to. And even if they had "disengaged the autothrottle", what would that have achieved? Nothing unless you then pull off a fistful of thrust...

Then you pull out the two page AD memo from Boeing and recall what it said: at the bottom of page two "Electric stabiliser trim can be used to neutralise...".
You need to go and read step 2 again. It wasn't completed, at any point after the MCAS AND.

What would disconnecting the autothrottle have achieved? Well you could set thrust to something more sensible and fly the aircraft.

You mean page 2 of the memo that gave specific operating instructions to crew? It even included a note (obvious to most with any common sense!) to put the aircraft in trim, then cut out the stabs.
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Old 6th Apr 2019, 10:24
  #3432 (permalink)  
 
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Originally Posted by edmundronald View Post
Interesting that media have not interviewed the survivor crew. Maybe Boeing financed some scholarships for their kids?
They could provide first hand descriptions of what was going on, and how hard it was to deal with it.

Edmund

The Indonesian preliminary report, para. 1.18.1, starting on pg. 19 (pg. 28 of PDF), has a narrative of the flight prior to the Lion Air accident.

The FDR data for that flight is plotted as Fig. 7 on pg. 16 (pg. 25 of PDF). The time scale is a bit odd (about 11 minutes 10 seconds per major division), and there are no numbers on most of the vertical axes.

The plot is also for the whole flight, although dealing with MCAS occurs over about 10 minutes very early in the climb. Hence the scale makes it hard to see the details of that portion.


portion of FIg. 7 from Indonesian report

Here are vertical velocity and altitude plots of ADS-B data for that flight made using data posted on-line by FlightRadar24.





There are quite a few cycles of MCAS activation before the pilot cut out the stab trim, with one really steep descent. The bottom of that descent is about where the FO made the first PAN PAN call, per the narrative.
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Old 6th Apr 2019, 10:27
  #3433 (permalink)  
 
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Originally Posted by pontifex View Post
I have grown slightly cross eyed following the huge volume of posts concerning the tragic events with the 737 MAX. One item that seems to have been mentioned just once (or thereabouts) is that things only started to go pear shaped immediately following flap retraction. Surely the clue should have been obvious to any adequate pilot and the previous configuration restored. As far as I understand things that would have saved the day. I have done a fair amount of 737 work but that was back in the day when they worked like normal aeroplanes (737 200& 400) so I may be wrong. This principle, however, has saved my life twice and I don't pretend to be anything other than an average operator. Am I wrong?
AFAIK the captain was focused on the autopilot around the time of flaps retraction, and the co-pilot was the one who made the correct call to hit the trim cutoff switches. That should have saved them, if all the right procedures had been followed timeously. Unfortunately neither thought to reduce the airspeed, which could have unloaded the horizontal stabiliser and permitted manual trimming, until it was much too late for any further options.
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Old 6th Apr 2019, 10:39
  #3434 (permalink)  
 
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From one of the media reports:
...“If I had been flying a MAX with stickshaker activation at liftoff after the Lion Air accident, shutting off the trim would have been accomplished in a matter of seconds, not minutes,” says one U.S.-based MAX pilot. “I probably would have activated the stabilizer trim cutout switches before the gear was even up. Why that didn’t happen on the Ethiopian flight is a mystery to me.”
So, this MAX pilot’s first response to a stall warning (which could be genuine) is to deactivate the trim. This is a terrible indictment of the awful kludge which the airframe and control systems are on the MAX, that something like an incipient low-level stall comes second in priority to MCAS. The even sillier thing is that if it was a genuine stick shake, you’ve now disabled the system that was going to help you recover...
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Old 6th Apr 2019, 10:46
  #3435 (permalink)  
 
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I feel for the crew in these circumstances as they appear to have been overloaded to the extreme. Everyone is looking back with hindsight but a couple of things that I have seen in the Preliminary report:
1. It looks like a bird has hit and sheared off the AoA vane. It settles at 75 degrees Up and the aircraft is 15 nose up so the counterweight is holding it down. Then repeatedly trying to put in the Autopilot with Stick shaker going was only going to make a bad situation go even worse. Not a recommended procedure I have found anywhere in the Boeing Manuals for any aircraft. Very similar to a Ryanair event a few years ago in an 800. Crew manually flew it around and landed it.
2. I can't see where any complete checklists were done. None at all. Just the Stab Trim cut-outs thrown to cut-off by the FO when the Captain was trimming the aircraft back to neutral. If the FO had waited for the call for the checklist and actioned it with the Captain they may have been in a better position closer to neutral. Remember that MCAS in the old software form stops when you start to trim it back with the electric trim. When you stop you have 5 seconds so then is a good time to do the checklist and throw the switches. From what I can see there were two full applications of MCAS prior to them putting the Stab motors back on.
3. It appears that while in manual mode the Stab was trimmed even further nose down. I think this may have been inadvertent by the FO but made a bad situation even worse. It also made it more difficult to then manually trim back and they gave up. As someone has already mentioned you need to put a lot of force (around 50 lbs from memory) and have some coordination to wind it back at high speed. Or you pull the power back and slow down which brings us to
4. The Take off power was not at any stage pulled back and they went through VMO within about 2 minutes. From there they kept accelerating. All the way to 500 kts
5. Then to put the system back to normal then meant that MCAS was still inputting to the circuit. That was it. No chance of recovery

One of the things that Manufacturers need to realise is that a lot of their customers do not have English as their first language. (Frankly some of the Airbus manuals I have had to read with Franglish take this to another level as well). If the guys had read all the info on MCAS and understood it would things have been different? With stick shaker going on during departure in the Heavier machines you never select flaps up until you confirm what has happened and you are well clear of terrain. To take the Flaps up at 1000 ft in this situation knowing that the shaker was going was an interesting move most likely reflex to the quickly accelerating aircraft.

As someone else has said that is why Airline Crew get paid well and why training should be more about the things that will cause you large harm and how you react rather than some of the tick the box exercises.

Does the aircraft need to be redesigned. Nope. The software does need to be changed and Boeing need to be a lot more rigorous in how they approach these critical systems. I have flown the MAX and it is a nice aircraft to fly. Lets see where the media take the world with this one.
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Old 6th Apr 2019, 10:50
  #3436 (permalink)  
 
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Question

Originally Posted by FullWings View Post
From one of the media reports:

So, this MAX pilot’s first response to a stall warning (which could be genuine) is to deactivate the trim. This is a terrible indictment of the awful kludge which the airframe and control systems are on the MAX, that something like an incipient low-level stall comes second in priority to MCAS. The even sillier thing is that if it was a genuine stick shake, you’ve now disabled the system that was going to help you recover...
So true! And with the flaps extended there is no need to worry about MCAS.

But still the Most important question is:

Why did they not use electric Stab trim to get back into an in trim condition without any control column pitch forces and then Hit the cutout switches???
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Old 6th Apr 2019, 10:54
  #3437 (permalink)  
 
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Originally Posted by groundbum View Post
so will the software fix, and slightly updated training, be enough to get the MAX back into revenue service?

I predict after ET not. It's apparent even with MCAS turned off, the cockpit does not return to peace and tranquility where average ability pilots can regain control and land. It's apparent from the ET interim report that a lot more was going on in the cockpit, and that was it was beyond the two pilots to get it back together, mainly due to excess speed and aerodynamic forces making proper trim next to impossible without some, as yet, untrained yoyo, manoeuvre.

I would suggest no regulator would be willing to pass the MAX back into service based on a patch and minor training update.

G
+1

The 737 safety philosophy means that it turns into a conventional stick and rudder aircraft once you turn the AP off. And that with redundant left and right seat set of controls. The PF assumes in AP off mode that he has full authority on the flight controls and surfaces. There are automatic flap retract in over speed left but that does not reduce his controll over the aircraft.
If you brake that philosophy by introducing “features” overriding PF control inputs they need to be full FBW worth with all fail safe features needed for a FBW control.
I do not see how Boeing can implement that easily into the 737 MAX.

With the two accidents it came out, that the manual trim wheel can not be actuated manually in a high elevator deflection and high speed situation. That aerobatic manovering is the cure for that can unlikely be certified for a transport category aircraft.
With 50 years of 737 operation that was not a big problem because nobody was as stupid as the MCAS system and gave full 5 seconds of AND trim in an already peculiar nose down situation close to the ground.

In a fighter jet in such a case you might invert the aircraft and rollercoaster the stuck trim out. But that is not a solution for a transport category aircraft.
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Old 6th Apr 2019, 11:01
  #3438 (permalink)  
 
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Only The opinion of SLF, but the issue is not MCAS. The issue is the position of the engine relative to the wing. MCAS is a bandaid on an open wound to get around a rational regulatory requirement.

Boeing should not have proposed the Max, and the FAA should not have accepted it. It is a fundamentally flawed design.

i remember reading an article when the neo was announced which postulated that Boeing would not be able to match it with an upgrade of the 737 because it would require a redesign of the undercarriage to get the necessary ground clearance for the engines. So the design issue was obvious to that much maligned species, a journalist, from the start. Boeing and the FAA knew.

This goes way beyond MCAS. It is about the engineering conscience of Boeing and the independence and competence of the FAA.

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Old 6th Apr 2019, 11:05
  #3439 (permalink)  
 
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Let's not forget why MCAS was born: To make the Max feel the same as the NG at the extreme end of the envelope, thus allowing for a common type rating and 1-hour CBT conversion course. This in turn allowed Boeing to use the common rating as a marketing tool.

There are rumours afloat, that the contracted Boeing signed with SW had a clause saying Boeing would pay SW 1 million USD for every aircraft delivered, if sim training was necessary to convert from NG to Max. That's 280 million good reasons why a bean counter and lawyer driven company would come up with an idea such as MCAS.

To my mind there is 'simple' set of possible solutions to this problem:

1: Ditch MCAS
2: Restore stability and stall characteristics to an acceptable level through sound aerodynamic means
3: Forget about the common type rating; this is not your grandfathers 737 so stop pretending it is
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Old 6th Apr 2019, 11:06
  #3440 (permalink)  
 
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Originally Posted by LowObservable View Post
Woof woof, it's dark here....

So the dog that hasn't barked, as far as I know, is this:

Aside from the three-crew Lion Air flight that preceded the mishap flight, where are all the crews who might have experienced an AoA failure that triggered MCAS at flaps-up, and handled the situation safely?

For this to happen means that one of the AoA sensors has to be bad from the start, that it has to be bad enough to call a spurious stall warning, and it has to be the sensor that is driving MCAS on this flight (the last being a 50:50 chance). How often has this happened in the MAX's history? I have not seen a single such account in this long thread (I stand corrected if I missed one).

Clearly, that number would provide some valuable context to the two occurrences when the result has been fatal.
Was about to post same question. Have other incidents been reported?
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