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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Apr 2019, 23:56
  #4021 (permalink)  
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Takwis:

Close, RBF. In the NG, the left one is labeled "MAIN ELECT" and the right one is "AUTO PILOT". MAIN ELECT "deactivates stabilizer trim switch operation" and AUTO PILOT "deactivates autopilot stabilizer trim operation". A few pages later, "The STAB TRIM MAIN ELECT cutout switch and the STAB TRIM AUTOPILOT cutout switch, located on the control stand, are provided to allow the autopilot or [my emphasis] main electric trim inputs to be disconnected from the stabilizer trim motor." They are wired in parallel.
I know what you mean, but electrically, they are independent circuits up to the NG. If parallel, either would force an on state.

Coming from the NG, the First Officer may well have tried cuting out just the autopilot trim, but there is no way for us to confirm it, because, in the MAX, the two switches are now wired in series. If one is off, all the electric trim is off. PRI stands for PRIMARY and B/U for "Backup". Both have the notation "deactivates main electric and autopilot trim operation".
And presumably, with the main circuit, MCAS.

The Control Column switches are overridden by MCAS, but the MAX Flight Reference Manual does not mention that.
Are you sure?
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Old 15th Apr 2019, 00:20
  #4022 (permalink)  
 
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Originally Posted by L39 Guy
The overriding issue with both Lion Air and Ethiopean is why they could not manage the aircraft whereas, as it has been reported earlier in this thread (about 4,000 posts ago) that this same event happened at least five times with US carriers and they all managed to safely gain control of the aircraft and land safely.
No they didn't. The reports of dodgy Max behaviour were from the ASRS about the autopilot diving after it was were engaged.

If there had been any other MCAS events that had been handled well by Americans, Boeing would have been screaming about them from the rooftops.
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Old 15th Apr 2019, 02:46
  #4023 (permalink)  
 
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Originally Posted by meleagertoo View Post
OF COURSE IT IS! THAT'S THE WHOLE POINT!
Had they done this and followed up CORRECTLY with the blindingly obviously necessary UNRELIABLE AIRSPEED checklist this whole disaster would almost certainly not have happened.
Here's a tip: get off your high horse and into the FCOM. Especially the system description of the stall warning. You’ll find this information which you would know anyway if you ever performed a 737 preflight:

“The SMYD Computers provide outputs for all stall warning to include stick shaker and signals to the pitch limit indicator and airspeed displays and the GPWS windshear detection and alert.

Two test switches are installed in the aft overhead panel. Pushing either of these initiates a self-test of the respective stall warning channel. The No1 activates the Captain stick shaker and the No.2 activates the F/O stick shaker. Either stick shaker vibrates both columns though column interconnects. “




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Old 15th Apr 2019, 03:11
  #4024 (permalink)  
 
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We know Boeing introduced MCAS because the new MAX engines, being more powerful and lower slung, together with the effect of a larger cowling, would have a larger coupling moment. So without MCAS cutting in, a significantly larger Pitch Rate than on a 737NG is fairly easy to achieve.
No we don't. MCAS is designed to increase stick forces at greater AoA as the cowlings for the engines generate nose up forces at large AoA leading to reduced stick force. Further, the engines are actually mounted higher and more forward to allow ground clearance vs the NG and generate a lower thrust couple as they are actually closer to the aircraft c.g. and so generate less torque.
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Old 15th Apr 2019, 03:25
  #4025 (permalink)  
 
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Lots of people getting upset at experienced B737 drivers being “ judgmental” and assuming they would have done better.
Well, back to basics.
- Stick shaker on rotation. Do NOT engage the autopilot.
- Commence Airspeed Unreliable Checklist.
Yes you DO reduce thrust to 80% and maintain 10 degrees nose up.
The procedure is specifically designed to keep you flying at a safe speed and rate of climb. Just do it.
Disconnect the auto throttle as per the checklist.
-Fly the aircraft
-DO NOT maintain straight and level with autopilot and autothrottle engaged and allow aircraft to continue to accelerate to VNE while failing to ensure terrain clearance.
-Uncommanded Trim? Complete Runaway Stabilizer checklist as per training and specific Boeing recommendation in AD briefing we have all read ,and presumably understood ,as a result of previous accident.
-DO NOT allow airspeed and trim status to runaway to the extent that recovery becomes difficult or impossible.
Anything so far beyond the wit of a well trained Pilot?
Am I a Boeing troll? No, just an experienced B737 Pilot who still cant understand how you can get an aircraft so out of shape.
What do you think we get paid for?
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Old 15th Apr 2019, 04:01
  #4026 (permalink)  
 
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Originally Posted by George Glass View Post
Lots of people getting upset at experienced B737 drivers being “ judgmental” and assuming they would have done better.
Well, back to basics.
- Stick shaker on rotation. Do NOT engage the autopilot.
- Commence Airspeed Unreliable Checklist.
Yes you DO reduce thrust to 80% and maintain 10 degrees nose up.
The procedure is specifically designed to keep you flying at a safe speed and rate of climb. Just do it.
Disconnect the auto throttle as per the checklist.
-Fly the aircraft
-DO NOT maintain straight and level with autopilot and autothrottle engaged and allow aircraft to continue to accelerate to VNE while failing to ensure terrain clearance.
-Uncommanded Trim? Complete Runaway Stabilizer checklist as per training and specific Boeing recommendation in AD briefing we have all read ,and presumably understood ,as a result of previous accident.
-DO NOT allow airspeed and trim status to runaway to the extent that recovery becomes difficult or impossible.
Anything so far beyond the wit of a well trained Pilot?
Am I a Boeing troll? No, just an experienced B737 Pilot who still cant understand how you can get an aircraft so out of shape.
What do you think we get paid for?
Amen👍 And well said
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Old 15th Apr 2019, 04:41
  #4027 (permalink)  
 
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Originally Posted by George Glass View Post
Lots of people getting upset at experienced B737 drivers being “ judgmental” and assuming they would have done better.
Well, back to basics.
- Stick shaker on rotation. Do NOT engage the autopilot.
- Commence Airspeed Unreliable Checklist.
Yes you DO reduce thrust to 80% and maintain 10 degrees nose up.
The procedure is specifically designed to keep you flying at a safe speed and rate of climb. Just do it.
Disconnect the auto throttle as per the checklist.
-Fly the aircraft
-DO NOT maintain straight and level with autopilot and autothrottle engaged and allow aircraft to continue to accelerate to VNE while failing to ensure terrain clearance.
-Uncommanded Trim? Complete Runaway Stabilizer checklist as per training and specific Boeing recommendation in AD briefing we have all read ,and presumably understood ,as a result of previous accident.
-DO NOT allow airspeed and trim status to runaway to the extent that recovery becomes difficult or impossible.
Anything so far beyond the wit of a well trained Pilot?
Am I a Boeing troll? No, just an experienced B737 Pilot who still cant understand how you can get an aircraft so out of shape.
What do you think we get paid for?
Give that the pilots recently have read the new AD in relation to MCAS.

The stick shaker was an item of possible occurrences of MCAS but not limited to.

The pilot reported having control issues to the tower, not an unreliable airspeed. So they may not be interested in the Unreliable Airspeed Checklist and more trying to recall the AD.

MCAS apparently does not work with AP engaged - and in the obvious confusion with clearly not enough training on the difference on type to the MAX, the attempt to get control was to put on the AP.

I do not think that there is any possible reason that can claim that this MAX, does not require far more and far better training than what was/has been given.

After the first MAX crash I expect there was a large amount of "the pilots stuffed up" and this AD is just a band aid to keep PR looking good. After the second crash, I will bet that a very large number of MAX pilots had a second and very detailed look at both the AD and MCAS - and many were concerned.

The reason that both these aircraft crashed is because MCAS moved the stabiliser (had it not - no crashes) - there was no training given about MCAS and MCAS was not even mentioned when these aircraft were delivered. That is the basic error, anything after that is a domino.
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Old 15th Apr 2019, 05:09
  #4028 (permalink)  
 
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The event did not start as an MCAS event. It started as an AoA failure. Maybe a birdstrike.
I am not trying to be smart after the fact. I’ve had a similar event and survived by doing what I was trained to do.
At some point the travelling public has to be reassured that not every technical failure ends up in a smoking hole.
I’ll fly a Max anytime.anywhere.
And no, I don’t work for Boeing.
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Old 15th Apr 2019, 05:25
  #4029 (permalink)  
 
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Originally Posted by George Glass View Post
Lots of people getting upset at experienced B737 drivers being “ judgmental” and assuming they would have done better.
Well, back to basics.
- Stick shaker on rotation. Do NOT engage the autopilot.
- Commence Airspeed Unreliable Checklist.
Yes you DO reduce thrust to 80% and maintain 10 degrees nose up.
The procedure is specifically designed to keep you flying at a safe speed and rate of climb. Just do it.
Disconnect the auto throttle as per the checklist.
-Fly the aircraft
-DO NOT maintain straight and level with autopilot and autothrottle engaged and allow aircraft to continue to accelerate to VNE while failing to ensure terrain clearance.
-Uncommanded Trim? Complete Runaway Stabilizer checklist as per training and specific Boeing recommendation in AD briefing we have all read ,and presumably understood ,as a result of previous accident.
-DO NOT allow airspeed and trim status to runaway to the extent that recovery becomes difficult or impossible.
Anything so far beyond the wit of a well trained Pilot?
Am I a Boeing troll? No, just an experienced B737 Pilot who still cant understand how you can get an aircraft so out of shape.
What do you think we get paid for?
All good George and seems sensible and expressed by numerous other 737 drivers in this long thread. Especially the 80 percent and 10 degrees. I mean that's just physics isn't it. On a dark night (terrain allowing) you can keep the blessed thing flying while the rest is sorted out. But one thing I wonder about. Is that power and pitch based on any given percent MAC being inside the authorised Cof G envelope? I mean, if you are unknowingly heavier than MAXTOW and with a C of G outside the envelope, in a hot and high airfield with V2 calculated to occur a little closer to the end than you would normally like, is that checklist going to help you stay airborne while you establish why your airspeed has gone to crap and the stick is shaking? Not saying that was the case in this event (especially with in daylight and CAVOK) but seriously just wondering how quick you need to decide that UAS checklist may not be your first and best port of call when the stick is shaking and your decaying airspeed is actually reliable! I suppose a wing drop like Cubana de Aviación Flight 972 might be the teller but I imagine it's all a bit late by then. An agressive pitch up immediatley after take off might also be a clue. Serious question, not trying to be smart a*** . (Ex Mil Loadmaster C130/B727).
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Old 15th Apr 2019, 06:25
  #4030 (permalink)  
 
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Originally Posted by Lord Farringdon View Post
I mean, if you are unknowingly heavier than MAXTOW and with a C of G outside the envelope
Neither of those was the case for ET302, according to the Preliminary Report.
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Old 15th Apr 2019, 07:50
  #4031 (permalink)  
 
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Originally Posted by svhar View Post
Stall warning and overspeed warning. Why are they there? It is 2019. You have at least 3 ASI's. You don't need a sledgehammer or a siren to tell you when something is wrong. You can see in silence from various displays where the problem is. A master caution light that you can reset should be enough.
Hi Svhar -the warnings are there for the very reason that if they go off, you clearly are a bad pilot who has not been minding the basics. To stall for example you have to ignore 6 separate aural, visual and sensory clues/warnings prior to actual stick shake. So it’s the system saying “ which part of ‘you are stalling and about to die’ , don’t you understand “”
So you are right- they shouldn’t be needed, but they are.
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Old 15th Apr 2019, 08:02
  #4032 (permalink)  
 
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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.
These indications were all in the post Lion Air AD.
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Old 15th Apr 2019, 08:08
  #4033 (permalink)  
 
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Originally Posted by neila83 View Post
Thank you for providing the proof that pilots were not provided with a way of knowing they have an AoA disagree. Unless they happened to work for American Airines who had the optional extra. And yeh the pilots used electric trim up and then hit the cutout switches. There is a question that may be around the additional problem Boeing is investigating about why they didn't trim up further with the electric trim. It's a question because it happens at the start and the end, and there's no logical reason for the pilots to do that, which suggests there may have been an additional system problem. We shall see.
Isnt a single stick shake indication that you have AOA disagree? Esp if One ASI and SBY ASI are reading what you would expect ? And pitch power are correct. 15 NU and 90%N1? Ground speed around 150 kts ( you need to be below 100 go get stick shake) ?
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Old 15th Apr 2019, 08:14
  #4034 (permalink)  
 
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When the Stick Shaker kicked in he could have thought it was due to his over-enthusiastic take-off (perhaps because of shortish runway and heavy load)

Sorry but what is an enthusiastic takeoff ? There is only one correct technique irrespective of all the myriad factors at play. The aircraft is loaded up to the max permitted weight for the r/w length, temperature, altitude etc and no more. Takeoff is then normal and the same margin as at sea level.

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Old 15th Apr 2019, 08:46
  #4035 (permalink)  
 
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The reason that both these aircraft crashed is because MCAS moved the stabiliser (had it not - no crashes) - there was no training given about MCAS and MCAS was not even mentioned when these aircraft were delivered. That is the basic error, anything after that is a domino.[/QUOTE]

Nobody denies I think that MCAS needs a redesign. That’s how we make aviation safer. Eliminate all causes of future events. The. MCAS is one. It is being done. It will be certified .Now to the much bigger potential problem. What if the are pilots- and I’m ignoring these two crashes- who can’t handle things when it’s not a simple failure but a compound failure. ? Thousands , maybe of a generation of pilots who only know what they can read in a manual or have been taught? Compare with good surgeon. I wouldn’t want one going near me who wasn’t able to handle complications beyond what he normally sees. Who has in depth knowledge of his complex world as a result of constantly keeping ahead of the curve. Not barely able to manage the basics, never mind the unexpected.
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Old 15th Apr 2019, 09:07
  #4036 (permalink)  
 
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Originally Posted by RatherBeFlying View Post
We do not yet know how effective electric trim is when the stick shaker is operating. Possibly the usual light touch on the switch may not be enough to sustain electric contact with stick shaker on. Have to wait for the report on that unless somebody finds time to research it on a sim..
The ET302 preliminary report shows the electric trim working normally with the stick shaker activated.
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Old 15th Apr 2019, 09:24
  #4037 (permalink)  
 
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Originally Posted by oggers View Post
The ET302 preliminary report shows the electric trim working normally with the stick shaker activated.
It shows it has been working on several instances. It does NOT show whether it has failed on other instances, due to stick shaker or anything else, which could explain why they did not use it to trim back to normal...
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Old 15th Apr 2019, 10:11
  #4038 (permalink)  
 
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Originally Posted by deltafox44 View Post
It shows it has been working on several instances. It does NOT show whether it has failed on other instances, due to stick shaker or anything else, which could explain why they did not use it to trim back to normal...
It is a possibility. However on the last occasion before selecting cutout the trim switch was operating for 10 seconds continuously whilst the stick shaker was activated so I don't think it likely that the stick shaker can actually break the contact. We also have the Lion Air data and it doesn't speak to me of an issue with the stick shaker interfering with the operation of the electric trim switch.
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Old 15th Apr 2019, 10:34
  #4039 (permalink)  
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As the starter of this evocative thread of the first early morning report of a 737 accident in Africa, I have of course followed it all closely - The shock that morning that it was a 2nd new 737 MAX that actually had crashed in astonishingly similar circumstances to Lion Air has rocked the aviation world, and the public.

I do think most of you now need to go have have a nice cup pf tea and try to stop pontificating on weird and wonderful graphs, text and charts, (I do not of course mean the revealed readouts we know of so far) and to really now stop putting blame on the crews that simply were trying to save their aircraft due to unknown phenomena seemingly trying to kill them, which has seen 2 brand new jets of a design from the early 1960's dive into the ground at high speed minutes from take off.

This is unprecedented in our industry in many years - Last seen when the DC-10 was in service 40 years ago - Also long before social and digital media, and the likes of PPRuNe and YouTube and the freedoms of getting information quickly.

Many of the posts on here have shown much sense and empathy even at such an early stage in the investigations, and of course many pilots and crews are worried, however, we have descended somewhat that some here will brush it off as if the crews should have done this, and done that, or ''I could have saved the plane''...

No one knows as yet as to why these 2 new jets dived into the ground and lost over 300 lives.

The 3 Comet 1 structural failure crashes claimed 99 lives - those investigations were undertaken at a time when FDR or CVR data was not available -
How we have evolved from 65 years ago.

Can we calm down a wee bit over the MAX theories - except we do know that MCAS was implicated and functioned each time -

As I see it 2 have been lost (another 1 was an almost lost) and in all 3 the flight crews were faced with, and then all were startled with rapidly unfolding, and unknown dilemmas as to why their aircraft was trying to kill them just after lift off trying in vain to save it.

At this stage none of us know for sure why.

edited 11.43

Last edited by rog747; 15th Apr 2019 at 10:57.
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Old 15th Apr 2019, 10:53
  #4040 (permalink)  
 
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I previously posted this on the related software thread - it might provide some additional context to the discussions that are going on here:

I stumbled upon an interesting case study on the use of memory items and (subsequent) checklists using 15 volunteer current 737 line pilots that were present at a crew base of a major US airline. Half captains, half FO’s. Half of all pilots had (varied) military experience. Pilots reported being trained in both 737 Classic and 737 NG. The 737 Classic flight deck was used.

I summarize ...

Each scenario began by describing a normal flight situation, and then interjecting cues that suggest a particular failure. Subjects were asked to react to the cues as they would inflight, performing any procedures they felt were necessary. The participants were provided with their airline QRH, and were allowed to select the checklist they felt was most appropriate for the situation.

Five non-alerted abnormal procedures that contain memory items were used.
1. aborted engine start ----- correct checklist by 10 of 15, ..
2. engine limit/surge/stall - correct checklist by 2 of 15, ..
3. rapid depressurization -- correct checklist by 14 of 15, two pilots added memory item steps,
4. runaway stabilizer trim - correct checklist by 14 of 15, four pilots added memory item steps,
5. dual engine failure ------ correct checklist by [12] of 15, this scenario had most errors in memory item steps of all 5 scenarios, multiple item steps were added by pilots.

The pilots in this study demonstrated a tendency to fixate on the most prominent cue, and perform the checklist appropriate to that cue. However, a thorough analysis of the situation can reveal that the single most prominent cue does not always lead the pilot to the correct checklist. There were 23 checklist selection errors. With three exceptions, the errors appear to be caused by the pilots’ fixation on a single cue.

There appear to be consistent patterns in the observed checklist step errors. Many of the ‘adding item steps’ errors appear to result from the pilots’ creativity (read: (experience based) troubleshooting) in dealing with an abnormal situation. It was observed that many pilots perform steps in addition to what was required based on their understanding of how the airplane systems functioned, even though their understanding of the systems may be incorrect.

... End of summary.

You might think on reading the study that: A single study aimed at being as realistic and objective as possible does not present a ‘truth’. But, that not everybody is perfect, might be a reasonable conclusion.

Last edited by A0283; 15th Apr 2019 at 11:18. Reason: Insert - ... End of summary.
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