Go Back  PPRuNe Forums > Flight Deck Forums > Rumours & News
Reload this Page >

Ethiopian airliner down in Africa

Rumours & News Reporting Points that may affect our jobs or lives as professional pilots. Also, items that may be of interest to professional pilots.

Ethiopian airliner down in Africa

Old 3rd May 2019, 09:23
  #4781 (permalink)  
 
Join Date: Nov 1999
Location: UK
Posts: 1,217
I am not disagreeing with you but if it was a trim fight, then why could they not keep the aircraft flying (albeit very untidily), and keep on feeding opposing trim inputs to return to land?

Why were the pilots in fear and panicked? Why did they not run their memory drills?

I would like to think that faced with this problem, I would think right bugger this : “pitch - power - speed”, now what the hell is going on? But would I ?

I think SIM training needs to be seriously looked at. UAS (and trim runaway) drills are pre-briefed, and the actions explained. Then into the SIM and a UAS event occurs. Unsurprisingly, the pilots do the drill and recover the aircraft. Tick. Next item.

But UAS is not done every SIM visit every 6 months. It might only be done once every 2 or 3 years, as the training cycle rotates. Even then, it will be one of several training elements the pilots will do in that SIM session, and each pilot will typically fly just one of each exercise each, then move on to the next training item.

Just as we always have to do an engine failure at take-off, a single engine ILS to a go-around, then a single engine NPA, I think that we should always practice situations where we have to revert to basic pitch - power - speed. No autopilots, no flight directors, no auto-thrust, no speed reading/UAS. And it should be sprung on us with no prior warning. Recovery from UAS or unusual aircraft behaviour needs to be an instinctive reflex.

(For Single engine, read OEI.)
Uplinker is offline  
Old 3rd May 2019, 09:43
  #4782 (permalink)  
 
Join Date: Jul 2014
Location: Harbour Master Place
Posts: 606
Originally Posted by Uplinker View Post
I am not disagreeing with you but if it was a trim fight, then why could they not keep the aircraft flying (albeit very untidily), and keep on feeding opposing trim inputs to return to land?

Why were the pilots in fear and panicked? Why did they not run their memory drills?

I would like to think that faced with this problem, I would think right bugger this : “pitch - power - speed”, now what the hell is going on? But would I ?

I think SIM training needs to be seriously looked at. UAS (and trim runaway) drills are pre-briefed, and the actions explained. Then into the SIM and a UAS event occurs. Unsurprisingly, the pilots do the drill and recover the aircraft. Tick. Next item.

But UAS is not done every SIM visit every 6 months. It might only be done once every 2 or 3 years, as the training cycle rotates. Even then, it will be one of several training elements the pilots will do in that SIM session, and each pilot will typically fly just one of each exercise each, then move on to the next training item.

Just as we always have to do an engine failure at take-off, a single engine ILS to a go-around, then a single engine NPA, I think that we should always practice situations where we have to revert to basic pitch - power - speed. No autopilots, no flight directors, no auto-thrust, no speed reading/UAS. And it should be sprung on us with no prior warning. Recovery from UAS needs to be an instinctive reflex.

(For Single engine, read OEI.)
The enormous elephant in the room is training. Luckily I was from the old school where we had to hand fly a lot, it was trained and encouraged, I still practice. Our organisation recently decided to do away with circling approaches because the GNSS will always be available... until it isn't because of traffic, ATC requiring a visual approach or circuit etc. Circuits are now back on the menu in sims, after an absence of 5 or 6 years as line crews are actually having to do them instead of having a runway aligned VNAV path to 500' or less. We had been deskilled, and it was recognised we needed to bring these skills back.

Unfortunately executive level management across the industry have seen automation as their nirvana, it reduces training costs if you get a pilot to stick in an autopilot at 500' and disconnect at the minima. It can be a measured skill, and therefore converted into a KPI for automated compliance monitoring, which equates to a the safest possible operation in the executives mind. The issue is the industry has deskilled it's pilots in the quest for the minimum training footprint. It works until those rusty or non-existent skills are required on a dark and stormy night. Loss of control is the major source of fatalities in the industry. Until there is a genuine commitment to keeping up the basic flying skills, these type of accidents will occur. Boeing didn't help with the MAX.
CurtainTwitcher is online now  
Old 3rd May 2019, 10:12
  #4783 (permalink)  
 
Join Date: Mar 2019
Location: UK
Posts: 4
Originally Posted by L39 Guy View Post

That’s a fair point. My response and likely that of my “cohorts” is this: what was presented to the three crews upon lift-off was a classic Unreliable Airspeed (UAS) scenario which is a an emergency that any B737 type rated pilot ought to have seen in a simulator complete with all the bells, whistles and other distractions. The fidelity of simulators is really quite amazing.

So how is it that 1/3 crews did the drill and saved the aircraft (by controlling and flying the aircraft including a managing its speed thanks to doing the UAS drill) while the other 2 crews did not do the drill which ultimately lead to an uncontrollable aircraft as speed was so high that no human could manually trim the aircraft?

Once we have addressed that issue then the next one is how is it that the successful Lion Air crew needed a jumpseat pilot to point out that they had a runaway stab trim and the fatal Lion Air crew was thumbing through the checklist looking for a memory item when they lost control of the aircraft.

To me, this points to a serious training issue at both of these airlines.


"How is it that...?" is exactly the right question IMO, but the answer may be "they were physiologically incapable under the circumstances" rather than "they didn't know how".

Like, the first step in response is probably to ensure that pilots' rational minds do indeed know how to recover the aircraft in a classroom setting. If that's missing then yeah, incompetence, basic training issue, needs fixing immediately. It's possible that this was missing in all three of these cases. It's also possible, based on available evidence, that it wasn't; in this scenario, we proceed to the next step.

If the pilots' rational minds have the solution but they're not applying it, then my understanding of human factors suggests that the likely problem is that their reacting minds - Mark Levy's "chimpanzee brain" from the video linked earlier - is siezing control, in keeping with a few billion years of evolutionary training, and letting the aircraft fly itself into the ground, because chimpanzees can't fly jet aircraft.

There's a couple of obvious approaches to deal with this scenario. The first is to figure out what stimuli are causing the chimpanzee to take over, and removing those stimuli. This is classic human factors work. For example, the stick shaker is AIUI a nice bit of human factors design that is intended to reliably break the pilot's concentration and draw attention to the fact that the aircraft is approaching a stall. Probably there is an amount of time it needs to run before 99.9% of humans have consciously noted it, and that's probably single-digit seconds. Having it drop down to an insistent throb after that point might maintain the information while allowing the pilot to concentrate again. (Maybe this is the wrong fix; the point is that this is the *class* of solution you'd be looking for.)

The second one is to actively train the chimpanzee to sit down and shut up, which probably requires replicating the systems' conditions more faithfully in training. Yes, a simulator captures the aircraft system's condition very accurately, I'm not disputing that, but it's not obvious that it's capturing the human system's condition. Specifically, I would imagine that the chimpanzee learns very quickly that the simulator is essentially safe and it has nothing to worry about, so it doesn't flip out if it suspects the simulator is about to crash. In a real in-flight emergency, that's not going to be the case, so pilots probably should be explicitly trained to manage their own minds and bodies in emergency situations to prevent the chimp from taking over.

One possible solution (on which there is probably a bunch of research that may show it to be a very poor idea) would be to hook crews up to an IV line in sim training, and give them a massive slug of adrenaline when they first realise something is wrong. Their body is then going to want to drop into a classic fight-or-flight response; given that a stall can neither be run away from nor punched to death, this is unproductive, so you'd want to train pilots to manage this physiological process so they can get back to applying their rational-mind training as quickly as possible, and fly the damn plane. If they don't have this training, it's not surprising that they're failing at this in real life, and if that's the case then all the sim time and process-knowledge in the world isn't going to save them.
SystemsNerd is offline  
Old 3rd May 2019, 10:21
  #4784 (permalink)  
 
Join Date: Jul 2000
Location: Thailand
Posts: 940
I confess I have not read ALL the previous posts. I trust I am not treading on anyone's toes here. Pitch-power-speed is the go-to mantra for most of us who learned to fly with an AVGAS engine, a fixed pitch propeller in front of us and an instructor to our right. However, when the aircraft misbehaves in an unexpected fashion not mentioned in any QRH or training manual then the sense of disorientation, surprise, incredulity, inadequacy, anger, and frustration will swamp the brain and preclude all rational thought. Disengaging the auto-pilot, leveling the wings, looking for the horizon, and applying 75% of available power will still appear to the observer as a failed exercise and lead to further confusion etc, intensifying the cycle until utter hopelessness swamps the poor pilot. Imho, these two MAX 8 crashes were design faults and Boeing is squarely to blame for the failure to engage with owners regarding the subtle changes to the anti-stall system. I am glad I was not on board because even though we can all sit here and imagine that we would have done it differently, many of us might not.
rubik101 is offline  
Old 3rd May 2019, 10:48
  #4785 (permalink)  
 
Join Date: Jan 2013
Location: Seattle Area
Posts: 127
Originally Posted by derjodel View Post
An undocumented system of which the pilots have no clue it even exists can interrupt airplane trim. If the pilot doesn't want to end in a coffin corner, they need to figure out on the spot that:
- this is not STS
- because it's not STS it must be either a bug or an undocumented system
- to save their lives they need to return the trim manually to a low/zero column force each time the undocumented command is triggered.

Despite facing those conditions, the Lion Air crew managed to react appropriately about 2 dozen cycles. Fighting the unknown system raised pilot's adrenaline and fear and induced panic. Thus, incapacitated by stress put on them, they no longer managed to manually correct the erroneous system input that was trying to - and succeeded to - kill them.
I want to be clear I was simply answering a previous poster's question about how MCAS worked, and not attempting to defend the system design.

Regarding your last paragraph, one theory is that for some reason the pilot who had been successfully countering MCAS for 24 cycles transferred control to the other pilot, who did not put in sufficiently large opposite trim inputs and lost it in three cycles.
Dave Therhino is offline  
Old 3rd May 2019, 11:47
  #4786 (permalink)  
 
Join Date: Jul 2011
Location: Canada
Posts: 55
Originally Posted by ottorot8 View Post


Sorry, but your wrong. I’ve been flying 737’s for the last 28+ years. That covers the 200, 300, 500, 700, 800 and I have about a dozen flights in the Max8. You could take about 70-80% of just the -200 cockpit and use it for spare parts on a Max8. Same switches, gauges, lights, etc. The list goes on.
Yes, the overhead panel is 1960’s but the cockpit displays, FMS, engines, wings, and other major components sure aren’t. The point is not a part by part count but the major components of the MAX are completely different than the -100 even to the extent that one could legitimately not call it a B737.
L39 Guy is offline  
Old 3rd May 2019, 11:55
  #4787 (permalink)  
 
Join Date: Jul 2011
Location: Canada
Posts: 55
Originally Posted by derjodel View Post
Was it? By this definition, isn't any STS operation a trim runaway?
Runaway Stabilizer: Uncommanded stabilizer trim movement occurs continuously. (Source B737 NNC)
L39 Guy is offline  
Old 3rd May 2019, 11:56
  #4788 (permalink)  
 
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 58
Posts: 414
@SystemsNerd
One possible solution (on which there is probably a bunch of research that may show it to be a very poor idea) would be to hook crews up to an IV line in sim training, and give them a massive slug of adrenaline when they first realise something is wrong. Their body is then going to want to drop into a classic fight-or-flight response; given that a stall can neither be run away from nor punched to death, this is unproductive, so you'd want to train pilots to manage this physiological process so they can get back to applying their rational-mind training as quickly as possible, and fly the damn plane. If they don't have this training, it's not surprising that they're failing at this in real life, and if that's the case then all the sim time and process-knowledge in the world isn't going to save them.
That kind of intensive training was used for early astronauts (The Right Stuff), since the risks were very high, but the dropout rate was very high. Some of today's veteran pilots with military fast-jet experience, might also have gone through that process. In the current era of widespread passenger jet transportation, I don't think that kind of training is viable.
GordonR_Cape is offline  
Old 3rd May 2019, 12:55
  #4789 (permalink)  
 
Join Date: Jul 2004
Location: Found in Toronto
Posts: 609
Originally Posted by CurtainTwitcher View Post
In the isolation of a simulator session where the sim instructor selects a runaway trim malfunction, fully agree with you.

Press play below before reading on...

https://youtu.be/TrjTUvhpBlE

This was not a classic runaway trim. No trim issues were encountered until the flaps were retracted. Retract flaps, now some forward trim starts, trim back with the electric trim and everything is good for 5 seconds, just enough time to start thinking about else, there goes the trim again, fix it with electric trim, all good for 5 seconds, repeat until end of sequence. You are also dealing with an airspeed unreliable. Not easy with that racket going on the background.

To the pilots in all three event flights, this was a trim fight, not a continuous runaway in the QRH condition statement for a Runaway Stabilizer. Judge for yourself from a current in-service document:

Condition: Uncommanded stabilizer trim occurs continuously
The trim worked as they expected, sort of. If English was not your first language, it would be even more difficult.

The Lion Air crews were in the worst position, they had no prior knowledge of the subtle system changes and faults that had led them to trim fight, not a runaway.

Originally Posted by L39 Guy View Post


Runaway Stabilizer: Uncommanded stabilizer trim movement occurs continuously. (Source B737 NNC)



In November 2018, after Lion Air, some (or all) operators, changed the checklist list and removed the word “continuous”.
























Last edited by Lost in Saigon; 3rd May 2019 at 13:40.
Lost in Saigon is offline  
Old 3rd May 2019, 13:05
  #4790 (permalink)  
 
Join Date: Dec 2014
Location: Schiphol
Posts: 335
Hard to keep up ...

But this comes from the Wall Street Journal:

Boeing test pilots lacked key details of 737 MAX flight-control system

Boeing limited the role of its own pilots in the final stages of developing the 737 MAX flight-control system implicated in two fatal crashes, departing from a longstanding practice of seeking their detailed input, people familiar with the matter said.


As a result, Boeing test pilots and senior pilots involved in the MAX’s development didn’t receive detailed briefings about how fast or steeply the automated system known as MCAS could push down a plane’s nose, these people said.
A0283 is offline  
Old 3rd May 2019, 13:25
  #4791 (permalink)  
 
Join Date: Dec 2015
Location: Cape Town, ZA
Age: 58
Posts: 414
Originally Posted by A0283 View Post
Hard to keep up ...

But this comes from the Wall Street Journal:

Boeing test pilots lacked key details of 737 MAX flight-control system Boeing limited the role of its own pilots in the final stages of developing the 737 MAX flight-control system implicated in two fatal crashes, departing from a longstanding practice of seeking their detailed input, people familiar with the matter said.

As a result, Boeing test pilots and senior pilots involved in the MAX’s development didn’t receive detailed briefings about how fast or steeply the automated system known as MCAS could push down a plane’s nose, these people said.
I already posted this article link in one of the parallel threads, and since the overall story is quite profound. Even though most of the information is not new, it is worth skimming, to be reminded of some of the details: https://www.theverge.com/2019/5/2/18...error-mcas-faa

Summary:
- Mistakes began nearly a decade ago when Boeing was caught flat-footed after its archrival Airbus announced a new fuel-efficient plane that threatened the company’s core business. It rushed the competing 737 Max to market as quickly as possible.
- In developing the Max, Boeing not only cut corners, but it touted them as selling points for airlines. Since the 737 Max was the same plane type as its predecessors, pilots would only need a 2.5-hour iPad training to fly its newest iteration.
- MCAS is the new software system blamed for the deadly Lion Air and Ethiopian Airlines crashes. But its failure in both crashes was the result of Boeing and the Federal Aviation Administration’s reluctance to properly inform pilots of its existence or to regulate it for safety.
- The FAA has admitted to being incompetent when regulating software, and, as a policy, it allows plane manufacturers to police themselves for safety. Nowhere in its amended type certification of the 737 Max is MCAS mentioned.
- Even still, Boeing only recommends a 30-minute self-study course for pilots on MCAS, rather than additional simulator or classroom instruction.
- Despite the two crashes, neither Boeing nor the FAA believes they’ve done anything wrong. A Boeing spokesperson said the company believes the system is still “a robust and effective way for the FAA to execute its oversight of safety.”
Nothing specific to test pilots, but these comments are telling:
And many pilots felt that, for the first new 737 in over 20 years, Boeing seemed to be oddly reluctant to prep them for it.

Captain Laura Einsetler, who’s flown for over 30 years, including on 737s, considers an all-computer-based course to be completely inadequate as an introduction to a new airplane.

“I don’t have the schematics. I don’t have the cockpit panels. I don’t have an instructor that I can ask questions to,” she says. “You’re hoping that the first time you see the Max is on a nice clear day. But sometimes it’s not, and you’re showing up at night or in bad weather into an airplane that has all these changes.”
The subtext: pilots were on a need-to-know basis about MCAS, and until the Lion Air crash, Boeing felt that they hadn’t needed to know.

Einsetler strongly disagrees. “We need to have the understanding and knowledge of how everything works on the jet, so that we can command the jet to do what we need it to do, not just be along for the ride,” she says.

“Not a lot of information got out there in a timely fashion,” concurs Juan Browne, a 777 pilot with over 40 years of flying experience. “It almost makes me wonder, did Boeing engineers themselves really understand how much power and authority they built into this system?”
GordonR_Cape is offline  
Old 3rd May 2019, 13:40
  #4792 (permalink)  
 
Join Date: Dec 2006
Location: Florida and wherever my laptop is
Posts: 1,314
Originally Posted by robocoder View Post

Quote:
Originally Posted by SystemsNerd Thus, when asking "why didn't they just fly the plane?", one possible answer is undoubtedly some variant on "they were incompetent". But another possible answer is "they were put into a scenario in which any human being would consistently fail to solve the problem, regardless of competence". Probably the truth is somewhere between those two points.
​​​​​​Thank you so much for this This is why I cannot accept the analysis of those that pile with unwavering assertiveness on the pilots' performance. We have only a partial view of what they experienced. We simply cannot know what the average crew would do in their shoes, vs what some hypothetical post-hoc average response should be, as evident as it may seem. Even so, are they at fault for the training they received? That's why when someone can't come back to tell their version, I prefer unanswered questions to "sure" answers.
As stated by SystemsNerd, the human cognition has limitations and foibles that many people are unaware of. One of these is the limited number of 'cognitive channels' also known as multiple resource theory. (see papers by Christopher Wickens and Erik Hollnagel) Simply you cannot read this posting and recite a something you have learned like NNC memory items at the same time - both use verbal cognition - if you are reading and someone says something you may hear them but you will not understand what they said and you will stop reading and ask them to repeat what they said. If you have to read, talk and listen at the same time you can only really do one at a time (we have all had to read a paragraph again as we stopped understanding what we were reading and listened instead).
So if you are running through memory items of an NNC - and you read the EICAS you may miss NNC items or not understand the EICAS - if the PM is shouting at you it may just be noise - if there is sufficient noise that channel stops completely and you do not even hear/comprehend the PM or that cavalry charge.

Mixed into this is the effect of the level of stress/alertness. This is normally referred to as an 'inverted U'.


from MindTools.com

So when you are bored with low stress your performance is actually poor, A little pressure / stress and your performance is ideal, but too much high stress and your performance will drop off rapidly.

Putting all that into an aviation perspective, A well trained pilot with experience of things going pear shaped and operating under pressure will not feel so much stress and concentrate on one item at a time and a lot of what will be done will be (what is called here ) muscle memory - innate training like stamping on a brake or steering a bike to stay balanced - or trimming an aircraft - it requires no thought as it is second nature. This is the importance of training - with not so much training it is easy to get into the overstressed very low performance state and 'get behind the aircraft'. The more inputs you are given the higher the stress and the less you are able to process and the normal human reaction to that is what is known as attentional or cognitive tunneling - a concentration on one aspect of what is happening that you _do_ think you can control and a total disregard of anything else. Everyone is different in this regard and the only way to avoid getting into the wrong side of the U is training, repeated training to get that muscle memory. Unfortunately, there is always a beancounter standing in the way of that.
Ian W is offline  
Old 3rd May 2019, 13:54
  #4793 (permalink)  
 
Join Date: Mar 2006
Location: England
Posts: 848
Yo gums,
Further to my comments on your additional request for ‘aero’ explanation ( Ethiopian airliner down in Africa) see the following:-

During design of the MAX, Boeing added two more leading-edge vortilons [generating vortices over the top of the wing at high AOA] in 2018, for a total of six per side and also lengthened and raised the inboard leading-edge stall strips to assure stall behavior would be as docile as that of the NG.
(https://www.twu557.org/index.php/new...x-new-software)

This suggests that Boeing had identified issues earlier than I suggested; also because of the nature of the changes the aero effects were more significant than currently being discussed for MCAS.
The use of vortilons might be a simple alternative to adding many more vortex generators, but stall strips to reinforce the inner-wing stall before outboard sections, opposing pitch up, is more like ‘a new aircraft’ fix.
A very crude comparison of the effects of nacelle lift might be made with military blended wing / fuselage, or leading edge extensions; what ever these provide for the fighter world then its not helpful in commercial aviation - or at least a same type rating for the 737 MAX.

Also, Boeing ‘Commenting on criticism of the single string failure potential of the AOA input to MCAS, a Boeing official said the original design was based on a standard industry process of hazard classification which defined the potential failure as one that could be mitigated “very quickly performed by a trained pilot using established procedures”.

Add to that, a remarkable comment from the FAA; “Pilots of large aircraft are trained from Day 1. When the pitch of the aircraft is doing something you’re not telling it to do, you do a runaway pitch trim checklist,” Acting FAA Administrator Dan Elwell, a former airline pilot …
This does not add confidence that the FAA have a good understanding of training, nor the much wider safety aspects of loss of control (for wind-shear / turbulence pitch up - do we always inhibit trim ! )
https://www.twu557.org/index.php/new...-human-factors

Then re the training discussion:-
Pilots for three U.S. air carriers tell … that during their sim training they had never been exposed to extreme and continuous AOA indication errors, they’ve not experienced AOA induced airspeed and altitude deviations on PFDs and have not had to deal with continuous stall-warning stickshaker distractions. They also note that they have never been required to fly the aircraft from the point at which a runaway stab trim incident occurred all the way to landing using only the manual trim wheels. “We’re just checking boxes for the FAA,” says one Seattle-based pilot’.

P.S. some web links may be transposed, or changed by the host site - search news items (I’m working on it).

Last edited by PEI_3721; 3rd May 2019 at 14:01. Reason: P.S.
PEI_3721 is offline  
Old 3rd May 2019, 14:02
  #4794 (permalink)  
 
Join Date: Apr 2009
Location: Hotel Gypsy
Posts: 2,830
Originally Posted by 737 Driver


I have no doubt that this is true, but it is also largely irrelevant from a procedural viewpoint. The pilots don’t need to be able to read a wiring diagram and tell you all the things that happens when they throw the cutout switches. They just need to know when they need to throw the cutout switches - as in the case of the runaway stab trim procedure.


737 driver, I have an itch and please take this comment with the best of intent.

When I was taught to fly, PPL through CPL etc, it was instilled in me to understand what every switch/knob did before I played with it (initial thanks to Norman Buddin, ex Hunter pilot and CFI). We were not in the business of altering things without understanding the impact.

So, please correct me if I am wrong, but earlier versions of the 737 had two distinct outcomes associated with the two stab trim switches whilst the Max basically has two switches in series? Somewhere along the line a change operating procedures seem to have pre-dated the wiring change. I’m trying to understand why pre-Max pilots didn’t know, or weren’t told about, the difference between the switches. Isn’t it better airmanship to understand why, what and how when managing aircraft systems, or are we witness to the pre-cursor of ‘Children of the Magenta’ in pilots who never questioned why they threw two switches and what each did?





Cows getting bigger is offline  
Old 3rd May 2019, 14:17
  #4795 (permalink)  
 
Join Date: Mar 2019
Location: On the Ground
Posts: 114
"In November 2018, after Lion Air, some (or all) operators, changed the checklist list and removed the word “continuous”."

"
By this definition, isn't any STS operation a trim runaway? "

Pilots of large aircraft are trained from Day 1. When the pitch of the aircraft is doing something you’re not telling it to do, you do a runaway pitch trim checklist,” Acting FAA Administrator Dan Elwell, a former airline pilot …"

Cool. Looks like we're finally going to get my F/Os some experience in using the manual trim wheel.

Originally Posted by Cows getting bigger View Post

When I was taught to fly, PPL through CPL etc, it was instilled in me to understand what every switch/knob did before I played with it (initial thanks to Norman Buddin, ex Hunter pilot and CFI). We were not in the business of altering things without understanding the impact.

Cows Getting Bigger (best username ever!), I agree with you 100%...and would add my thanks to Swede Gamble ("Know Gamble in Aviation").
Takwis is offline  
Old 3rd May 2019, 14:19
  #4796 (permalink)  
 
Join Date: Feb 2011
Location: Grand Turk
Age: 56
Posts: 64
Originally Posted by Dave Therhino View Post
MCAS can be interrupted with the electric trim switches on the yoke each time it activates, and trim can be returned to a low/zero column force state each time if the pilot puts in adequate opposite trim inputs. That is what the Lion Air crew did for approximately 2 dozen cycles of MCAS before the final few cycles, where the pilot flying at that point failed to put in an adequate amount of opposite trim in those final cycles, allowing the out of trim condition to increase to the point where they couldn't recover in the altitude available.
That is the assumption that is at question (my emphasis). If your suggestion is correct then the crew did not apply sufficient opposite trim inputs. It remains in doubt as to whether it is possible to apply sufficient opposite trim inputs. If Boeing is to be believed the Lion Air pilots casually flew the aircraft into the sea and did not attempt to apply sufficient opposite trim inputs. I do not buy into this theory. I suspect that the only solution is to use the cutout switches at an early stage. There may be multiple reasons that sufficient opposite trim is not possible. What is raising doubt is that the Lion Air pilots were trying to do just what you suggest and did not succeed. Granted, that they should have taken a different path, but it remains they were trying to trim nose-up and apparently were unable. There is a lot more to this story, I suspect that many assumptions being made are not entirely correct. People are trying to reverse engineer from Boeing publications that may not be entirely accurate and are too brief to give a full explanation of the systems. So far it does not seem to make sense. I could be wrong, but my bullshit meter is quivering.
wheelsright is offline  
Old 3rd May 2019, 14:26
  #4797 (permalink)  
 
Join Date: Dec 2014
Location: Schiphol
Posts: 335
@PEI_3721 - I was looking at a MAX video and noticed, next to the usual big strake at about 10 o'clock on the center of the cowling, a set of 2 smaller longitudinal white painted vanes/strakes on the inside of the engine on the sliding part of the thrustreversers. When the reversers slid back after TD, the vanes/strakes did not hit the leading edge of the wing, because a kind of small 'trapdoor' opened upward to let them pass through. On sliding forward the vanes/strakes became visible again and the 'trapdoor' closed behind them. Would be interesting to hear from you what their purpose is in the aerodynamic context that you were just posting about ;-)
A0283 is offline  
Old 3rd May 2019, 14:27
  #4798 (permalink)  
 
Join Date: Sep 2017
Location: Uk
Posts: 62
Originally Posted by L39 Guy View Post

Yes, the overhead panel is 1960’s but the cockpit displays, FMS, engines, wings, and other major components sure aren’t. The point is not a part by part count but the major components of the MAX are completely different than the -100 even to the extent that one could legitimately not call it a B737.
Yes but it's still an old generation design with old generation aircraft failings.
No EICAS , no FBW (with resultant large pitch /power couple, defo not good news on manual go arounds), only two hydraulic systems, no effective autopilot go around (Cat3 excepted) etc etc, not even auto generator switching!
Most of the design changes apart from maybe the nice big screens seem to be all about economic improvements, not safety improvements, ie thinner more efficient but less speed stable wing, longer fuselage with resultant higher approach speed to prevent tail strikes on landing.
I could list more, it's a real shame they didn't build a new modern aircraft from the ground up (like the 777/787) but that would have really hit profits in the short term, I'm sure Boeing wish they had now.
Sucram is offline  
Old 3rd May 2019, 14:31
  #4799 (permalink)  
 
Join Date: Apr 2019
Location: USA
Posts: 217
Originally Posted by SystemsNerd View Post
With respect, I think there may be a breakdown in communication here that may be in large part responsible for the ongoing disagreement. When people say "human factors", they don't mean "the human element", they mean Human Factors*, i.e., the study of how the human mind and body interacts with designed systems.

The human mind does not, ironically, work in the ways most people think it does - it has well-documented limitations and sources of error plumbed into its design. A human factors expert can I believe pretty trivially design a scenario where most (if not all) humans will consistently fail to correctly solve even relatively trivial problems, regardless of their competence under normal conditions.

Thus, when asking "why didn't they just fly the plane?", one possible answer is undoubtedly some variant on "they were incompetent". But another possible answer is "they were put into a scenario in which any human being would consistently fail to solve the problem, regardless of competence". Probably the truth is somewhere between those two points.
I pretty much agree with everything you say except for the "any human" reference in the second to last sentence. I think that there is broad, though not unanimous, agreement that the accident crews made some serious errors that led to the final loss of aircraft control. Where I and some other participants here differ is that I strongly believe that much of the human factors element you refer to is amenable to training. One only has to look at the performance of the crew on the Lion Air 610 flight the day prior to the original accident. Despite being presented with a novel malfunction, one of the pilots kept flying the aircraft. IMHO, that crew took a bit too long to get to the trim cutout switches, but the takeaway is that every time MCAS made an input, the flying pilot took it right out again. At no time was there evidence that they were losing that fight.

It has been suggested that this crew would have ultimately crashed if not for the jumpseater suggesting that they try the cutout switches, but frankly that is an unwarranted assumption. Having been both in the flying seat and the jumpseat on many occasions, it is absolutely true that the jumpseater may catch something quicker, but that does not mean the flying crew will not catch it at all. There definitely appears to been a limited understanding of the stab trim system by both the Lion Air and Ethiopian crews (very much amenable to training), but it did not prevent the crew above from maintaining aircraft control.

I will agree that any human pilot at some stage in their training will be easily overwhelmed by even the most basic aircraft emergency scenarios. That is why we train so extensively for them. I had previously posted that in the Ethiopian accident, the Captain did fly the aircraft after a certain fashion, and that he had defaulted to his training. The problem was that he defaulted to the wrong training. Just about all of the ET302 Captain's initial actions can be understood in the context of a normal takeoff profile. Unfortunately, a normal takeoff profile left him in a highly unstable position from which dealing with the ultimate stab trim problem became a bridge too far.

When I and other posters keep saying that the pilots should have kept FLYING THE AIRCRAFT, we do not say this from a perspective that operating a malfunctioning aircraft is some inborn capability that every person has. Heck, walking isn't even an inborn capability. However, it is a skill that is amenable to training. That is, as long as you get the right kind of training. As has been already discussed extensively, training in modern commercial airliners has largely devolved into a process of following scripts. Pilots are presented with known problems with known solutions. Even at my airline, there is much less of the relatively unscripted training that really drove home the need to set aside any distractions and focus on the basics of flying the aircraft without the benefit of any automation until the situation was stabilized.

There are multiple links in the chain of causation leading to these accidents. I don't think anyone is questioning that MCAS needs to be fixed, or the FAA needs to step up its oversight, or that airlines need to review their internal training and operations policies. The professional pilot corps, however, needs to look at what we can do to correct the airmanship deficiencies that were exposed by these accidents.

Last edited by 737 Driver; 3rd May 2019 at 18:40.
737 Driver is offline  
Old 3rd May 2019, 14:38
  #4800 (permalink)  
 
Join Date: Mar 2019
Location: On the Ground
Posts: 114
Originally Posted by A0283 View Post
I was looking at a MAX video and noticed, next to the usual big strake at about 10 o'clock on the center of the cowling, a set of 2 smaller longitudinal white painted vanes/strakes on the inside of the engine on the sliding part of the thrustreversers. When the reversers slid back after TD, the vanes/strakes did not hit the leading edge of the wing, because a kind of small 'trapdoor' opened upward to let them pass through. On sliding forward the vanes/strakes became visible again and the 'trapdoor' closed behind them. Would be interesting to hear from you what their purpose is in the aerodynamic context that you were just posting about ;-)
It's not aerodynamics, its just a physical way to keep the reverser sliding cowl from hitting the leading edge devices...been there since the Classics.
Takwis is offline  

Thread Tools
Search this Thread

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.