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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 17th Mar 2019, 09:46
  #1701 (permalink)  
 
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Originally Posted by sky9
It would have been better if they had developed a B757 light rather pursue the religion of 737 commonality with the 200 series.
.
I’d say there’s more than one Boeing Exec thinking that right now.
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Old 17th Mar 2019, 09:54
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Originally Posted by FGD135
You are spending a lot of time and effort on trying to trim for nose-up, but something keeps trimming nose-down. Pretty easy to figure out.
The Ethiopian crew didn’t figure that out on a blue sky CAVOK day. The Lion air crew didn’t figure that out even with a dedicated maintenance engineer on the flight deck looking for the problem. What about in real bad weather when you need all your skill. I don’t want to have an aircraft acting on me then. If it takes a test pilot, o.k. then the Max is test pilots only...
That the other airlines got away with it might well be more luck than skill.
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Old 17th Mar 2019, 10:13
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Originally Posted by Cows getting bigger


Indeed, poorly implemented risk assessments at design level. As for the firproof box and exhaust solution, one needs to ask the FAA whty they basically accepted that an airborne fire scenario was suddenly acceptable. (There’s a REALLY long thread somewhere about that).
The 787 at Heathrow the fault was in a poorly manufactured Emergency Locator Beacon from a supplier. The two halves of the box were screwed together by the manufacturer trapping one or more wires which were shorting out and eventually while parked at LHR got hot enough to cause the Emergency Locator Beacon to catch fire fire.
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Old 17th Mar 2019, 10:21
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Originally Posted by HdwJunkieSLF
I assume Boeing is already under an internal "document preservation" -- do not delete -- order. Discovery is coming. This is going to get ugly, Trying to dodge a preservation order, or even presumption, is going to make it worse.
Or shredder working in the small hours...
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Old 17th Mar 2019, 10:38
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Originally Posted by EDLB
The Lion air crew didn’t figure that out even with a dedicated maintenance engineer on the flight deck looking for the problem.
The Lion Air crew didn't figure that out, period.

AFAIK, there is no evidence that the engineeer on board was on the flight deck, or even that their presence on the flight at all was for troubleshooting purposes, rather than just a scheduled flying spanner.

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Old 17th Mar 2019, 10:42
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Originally Posted by sky9
They could always increase the height of the main undercarriage and bring the engines down to where common sense says they should be like the A210.
I'm not sure that alone would fix it. And on top that would further lower the thrust line away from cg, i.e. increase thrust related pitch up moment.
The aerodynamic problem surely mostly stems from bigger nacelles plus installed more forward.
OK, lowering might allow you to move them back a little. but I'm not sure they are not so much in front also for cg reasons, in which case you couldn't move them back so easily.
What would have really helped are bigger tail feathers. And additionally that would have allowed you to move cg back. Which in combination with a longer gear would have allowed you to move the nacelles a bit back.
That would probably have been the correct solution. And with such an approach you could have taken the 737 into the new age. But that would have taken longer and cost more (in short term).


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Old 17th Mar 2019, 11:00
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Originally Posted by compressor stall
Extra crew training is just keeping a link in the chain.

A modern civil airliner should be designed not to rely on the flight crew having to adopt non standard (unique?) piloting techniques to counter a faulty bandaid put there to mask inherent aerodynamic flaws.
Well that is just the point. Uncommanded/runaway trim has had the same procedure since the first 737 - switch the stab trim switches off and those have also been in the same place. So this was a totally standard response to a potential error.

I have some sympathy with Reamer's responses here. The expectation is that a professional pilot will be trimming and sensing trim as second nature as a 'muscle memory' regardless of other things happening, Rather like you expect a car driver to carry on steering, It is further expected that if the trim starts annoyingly trimming against the pilot that the pilot will rapidly identify this and follow the decades old standard procedure and switch stab trim off and not wait until the nose down trim was requiring significant force. After the Lion Air crash this decades old standard procedure was put out in a directive to all Max operators. So now who of them could claim that this was an unexpected procedure? Well all those that don't bother to keep up with the directives - I would have thought that there would be some kind of sign off procedure in each airline requiring all Max pilots to sign as having read the directives which just refreshed the existing standard procedure ensuring/reminding crews that uncommanded nose down trim should be stopped by using the standard runaway trim procedure. Apparently not.


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Old 17th Mar 2019, 11:08
  #1708 (permalink)  
 
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SLF here, realise I am a guest.

May I ask the piloting community, particularly those current on 737, the number of times in which they have actioned, or considered actioning the stab trim cutout procedure in response to apparent runaway trim. How often does this happen by comparison with instances of UAS, other (potentially) unreliable instrumentation events, or stick shaker activation?

Is trim runaway a regular feature of recurrent training?
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Old 17th Mar 2019, 11:22
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How many will respond as a 'Pitch Trim Runaway?.

In all probability a 18000 hrs old grey beard would have extracted from his 'internal database' and responded accordingly.
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Old 17th Mar 2019, 11:23
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There would be huge value in having the two pilots of the Lion Air flight prior to JT610 describe what they saw and felt and how they worked through the failures and landed safely. Also to ask them what they knew of MCAS and the cutout switches at the time. I think this would inform the two accident investigations a lot in terms of human factors and how much workload they had on with cascading failures, horns etc.

G
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Old 17th Mar 2019, 11:24
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Can someone explain please. If the MCAS system is necessary for the MAX to be certified, when the system becomes faulty / has to be turned off by the pilot, why is the plane permitted to continue to fly? Shouldn’t it require an emergency diversion to the nearest safe airfield. If MCAS is a necessary safety system shouldn’t pilots have been fully trained on its use before being passed to fly the type? Suppose a pilot on a previous leg had had trouble with MCAS and turned it off, would they have been permitted to take off on the next leg with MCAS still disabled and if so is the plane still certified safe to fly?

The role of this system seems to be very vague, is it a safety critical system or an attempt to assist overworked pilots?
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Old 17th Mar 2019, 11:31
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Originally Posted by Ian W
Well that is just the point. Uncommanded/runaway trim has had the same procedure since the first 737 - switch the stab trim switches off and those have also been in the same place. So this was a totally standard response to a potential error.

I have some sympathy with Reamer's responses here. The expectation is that a professional pilot will be trimming and sensing trim as second nature as a 'muscle memory' regardless of other things happening, Rather like you expect a car driver to carry on steering, It is further expected that if the trim starts annoyingly trimming against the pilot that the pilot will rapidly identify this and follow the decades old standard procedure and switch stab trim off and not wait until the nose down trim was requiring significant force. After the Lion Air crash this decades old standard procedure was put out in a directive to all Max operators. So now who of them could claim that this was an unexpected procedure? Well all those that don't bother to keep up with the directives - I would have thought that there would be some kind of sign off procedure in each airline requiring all Max pilots to sign as having read the directives which just refreshed the existing standard procedure ensuring/reminding crews that uncommanded nose down trim should be stopped by using the standard runaway trim procedure. Apparently not.
Is the problem here the built-in 5 second pause in the system? MCAS trims nose down, PF corrects and MCAS stops. PF sees his action as "required trim applied". Maybe also notes aircraft is not fighting back and concludes "not a runaway". Five seconds later, when PF has gone on to something else, it happens again. PF again applies trim which (at least partially) works. It is going to take several iterations of this cycle before PF sees it as a runaway, unless he knows about the cyclic nature of MCAS, which the post-Lion SB doesn't seem to address.

Last edited by sooty655; 17th Mar 2019 at 11:41. Reason: for clarity.
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Old 17th Mar 2019, 11:35
  #1713 (permalink)  
 
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Originally Posted by groundbum
There would be huge value in having the two pilots of the Lion Air flight prior to JT610 describe what they saw and felt and how they worked through the failures and landed safely. Also to ask them what they knew of MCAS and the cutout switches at the time. I think this would inform the two accident investigations a lot in terms of human factors and how much workload they had on with cascading failures, horns etc.
It would also open up a huge can of worms regarding how Lion Air operates. As put, very eloquently, by a previous poster:

Originally Posted by Jo90
Having read (well skimmed) the interim report of the Lion accident particularly the part relating to the previous flight, it occurs to me that following a flight with major instrument discrepancies, continuous stick shaker and multiple uncommanded stab trim movements it might have been appropriate to add something to the tech log entries like "aircraft unfit for revenue flight pending maintenance action".

Would that have prevented the accident?


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Old 17th Mar 2019, 11:41
  #1714 (permalink)  
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Originally Posted by compressor stall
Extra crew training is just keeping a link in the chain.

A modern civil airliner should be designed not to rely on the flight crew having to adopt non standard (unique?) piloting techniques to counter a faulty bandaid put there to mask inherent aerodynamic flaws.


So, there was Qantas with an A380, where the assumed failure modes of certification didn't bear much resemblance with the real world. There was also Qantas' A330 FBW going nuts, and the B744 where the O2 bottle went cross country out the side of the plane. There was UAL 811, which didn't bear much resemblance with simulator sessions, Alaskan 261, UAL232, BA037, and the hudson ferry....


There are more things in heaven and earth, Horatio,
Than are dreamt of in your philosophy.
- Hamlet (1.5.167-8), Hamlet to Horatio

On the other hand, we have AF447... Adam Air, and a panoply of headlines of crew being outside the loop. Every day, crew deal with oddities with the aircraft, that come to light where reality meets assumptions and a gap exists. The majority of occasions do not end up in headlines, the crews just get on with the task, write up the events and go home and take crew rest. Occasionally, that doesn't work out, and we have bad days. The direction of air transport has added distance between the operator and the aircraft, through design and perceived safety benefits of reliance on automation. That is a high stakes assumption and it is routinely shown to be invalid. Consider AZ214 and similar bad days. Automation is great, but it is only great if it is working as expected, and where the monitoring is not degraded by the out of loop condition, or the degradation and or inertia that develops to the operator intervening with a system. All RPT aircraft fly like Cessnas and Pipers at the basic level, yet we have flight crew that are reticent to intervene and take control of the aircraft when wacky stuff starts. The reticence is a paradoxical response to the focus on compliance, reporting and rigid management directives to reliance on automation to reduce errors.

We can't design a reliable toaster, yet the assumption is made that an engineer 30 years ago can predict the conditions of weather, fuel state, fuel policy, system malfunctions, traffic, ATC capability, and crew training etc, such that errors cannot occur. We can't make windows or iPhones work without error, the system couldn't imagine foam bringing down a spacecraft, or cold temperatures mussing with sealing of an O ring... Passengers hop on an aircraft in country A, and fly for a day and night to country B, and land in weather that you won't drive your car in. The crews do that every day, and thousands of times, in ice storms, weather fronts, fog and sometimes sunny calm days. They do it with controlled aircraft flying in proximity to other aircraft that are not controlled, and hopefully the 15 hour student doesn't mess up, and enter the airspace that the punters are spending time in a tube complaining about the peanuts, coke and pretzels that are part and parcel of unregulated air travel. When we can build reliable toasters, then the necessity for human competency to be maintained may be mitigated, maybe.

The balance of reinforcement training is hard to get right, back in the late 90's there was a push to make crew more aware of handling of aircraft, and that led in passing to AA587. A little knowledge can be a dangerous thing. Getting the mix right is not easy, but we certainly do not have it at this time, and have not for many years. This is not generational, it is institutional. Last time I looked, the world was not flat, supported by turtles all the way down, it is a weird oblate spheroid and strange stuff happens that takes care to avoid having bad days, that care takes SA, and knowledge and skills to respond to the information that is provided to the crew. We have a problem in getting the loop right all of the time. 10^-9 reliability is fantastic, except for the poor pax that are the statistic. [yeah, -6 is the basic level, but the events we see that get into the headlines are much more remote than that]


PS: links in chains presume a simple model of the world; a chain is a linear analogue, and the world flat or oblate spheroid, is much more entertaining. When you place a band aid onto a cut, you have introduced new failure modes and vectors for badnesses, directly and indirectly. Have a fuel fright on one flight, add more, and have an aircraft roll off the end of the runway, Too many unstabilised approaches? demand AP/FD use form minimum engagement, and then wonder why the crew ding pods and tails, or ham fist AP faults. The world is stochastic, non linear, and every barrier that gets put up acts as much as a new surface to bounce issues off in new directions as it acts as a barrier. This is not a pessimistic view of the world, it is one that SMS programs (ICAO DOC 9859 etc) and audit processes need to be comprehended in their constraints and limitations. Functional resonance is a reality and that suggests the key to safe management is comprehensive awareness of the interaction of policy, procedures and practices with the real world.

Last edited by fdr; 17th Mar 2019 at 11:53.
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Old 17th Mar 2019, 11:42
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I thought we had a no-fault culture in aerospace? So put the pilots on video and lets hear from them how their flight went. And yes that should include their thought processes when they wrote the tech log at the end of the flight. If there's commercial pressure to minimise technical issues, so keeping the frame in service, then that needs to exposed as well. From my reading this hidden hand of pressure on pilots to keep the show on the road regardless is all pervasive, and it takes a brave pilot to say "no, this needs to be remedied properly" rather than just sign off and go home "not my problem".

I'd guess in the US at least the crew would have filed an ASRS.

G
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Old 17th Mar 2019, 11:43
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Don’t post often – but my observations FWIW. Firstly, I have 35 years aviation experience mostly military but my last 14 years are in flight testing and last 11 years on fairly complex unmanned systems.
Observation 1 - Having spent weeks of my life looking at Failure Modes Effects Analysis (FEMA) spread sheets/matrixes. It seem inconceivable that the Boeing engineers would allow a single point of failure (AOA vane) to result in a catastrophic failure ( lost of life). If they did and convinced the regulators of that, then this is criminal. Personally, I don’t believe that – the loss of an AOA vane and utilisation of MCAS would need to be mitigated to be a safe event. That said without seeing the analysis and the mitigation strategy if remains on the table for discussion and it could be that the mitigation was poor – but well argued to allow certification. So, the big question is how did they mitigate this event??

Observation 2 - Since the day I first strapped myself into an aircraft, I have made in my professional duty to understand the aircraft system I am flying in and have always studied and learnt from other accidents and incidents. If I was a Max 737 pilot ( I am not) I would be damn sure I knew everything about the Lion Air crash and these forums are a superb learning aid tolerating from these rare and unfortunate accidents (thank you to the many contributors who encourage learning and data gathering). I would expect I am correct in thinking that all 737 Max pilots would also be doing the same. So the next question is would the Ethiopian crew know how to handle initiation of the MCAS? The answer must surely be yes.

Obseravtion 3 - The Ethiopian aircraft landed fully serviceable (so we are told) and on an almost perfect weather day had immediate issues on take-off with systems (Airspeed/AoA)!! What are the chances of this – AOA and pitot static systems are normally very, very reliable (except in very poor weather conditions or if someone leaves the covers on or insects get into them!). However what about if sabotaged or damaged by ground handling equipment and not reported. That said most of these potential gotcha's should be picked up by people on the ground (i.e. flags in place) or on the take-off run (odd read outs) – so I don’t buy this.

Observation 4 - In my 14 years of flight testing the biggest issues are the “we didn’t expect it to do that” when testing software-based systems, normally in the rig but occasionally in flight. Software engineers are great at solving problems quickly but understanding the impact of those changes across the whole system is both very costly and timely and there is no way of knowing if you have covered all eventualities. One accident ( unmanned – total hull lost) was the classic swiss cheese of numerous low (ish) probability events leading to a piece of logic with told the aircraft it was on the ground (WOW activated) when in fact it was still flying at 30ft on approach – the WOW logic was to push the nose fully forward and doing this at 30ft was not a good outcome!! Almost immediately the logic that caused this accident was determined and the software guys admitted that they didn’t envisage the 2 other failures occurring that led to this event – how could you? This is the nature of the beast. So, are we seeing something new and unexpected with the Ethiopian crash. The FDR and CVR will almost certainly give the evidence required to gauge the set of events and actions that led to this horrible crash.
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Old 17th Mar 2019, 11:45
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As MCAS operation is a non-normal event (when it's working properly) would it not have been a good idea to make it trigger an EICAS alert message 'MCAS ACTIVE'. Properly trained crews would be able to quickly evaluate the situation and accomplish the runaway stab checklist if appropriate. Apologies if this has already been suggested.

Last edited by Discorde; 17th Mar 2019 at 15:32. Reason: amended version
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Old 17th Mar 2019, 11:50
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Originally Posted by fireflybob
Was it a certification requirement that MCAS had to be installed on the B737 Max? One presumes that if MCAS had not been installed these accidents would not have occurred. You have to be careful that when you attempt to fix one problem (potential stall) that you don't generate other issues. Are we trying to make modern aircraft too "idiot proof"?
Yes, possibly...
This was my line of attack a few pages back...
"Was there a proper debate with the AW authority about the way a neutral or diminishing control force/ AoA curve could or should be addressed ?"
Sodding about with high rate stab trim as the aircraft approaches stall and this weird repetitive re-trim logic seems to come from a generation of engineers with little if any grounding or interest in everyday aviation...
Are we producing a breed of designers not really aviation people through and through... this sort of solution would've surely been discussed to death down the pub here after work and ridiculed by the 'old hands' and thrown out early doors... as highly dubious and a heavy handed approach.
If indeed a PM ~ alpha curve like that would've been condoned at all.
The industry seems to be re-learning old lessons... don't automate your way out of bad basic design, also, simplify the flight systems, reduce training needs, not the opposite.
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Old 17th Mar 2019, 11:58
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Originally Posted by groundbum
There would be huge value in having the two pilots of the Lion Air flight prior to JT610 describe what they saw and felt and how they worked through the failures and landed safely. Also to ask them what they knew of MCAS and the cutout switches at the time. I think this would inform the two accident investigations a lot in terms of human factors and how much workload they had on with cascading failures, horns etc.
G
I am lead to believe that has been done by the KNKT and relevant issues will be part of the final Lion air report due sometimes later this year. I could imagine now that the NTSB will contact the KNKT to get those interviews ahead of the final report publication.
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Old 17th Mar 2019, 11:59
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I reckon the pilots should routinely disable it, even when Boeing say there is a new version of it working well. I wouldn't trust anything that is possibly going to trim my aircraft into a maximum dive configuration that I cannot correct with the elevators and that I need to use two hands to turn the trim wheels back to somewhere near normal. The trim is supposed to be a column force relief, not a complete override to column authority.
Incredible stuff Boeing. How did they come up with that?
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