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kgwilson

Ethiopian 737-800 Max crash - No survivors

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Once a stab is way out of trim for the speed and configuration the "roller coaster recovery" manually is pretty drastic (Slow and high physical force comes back) This is pretty hard to avoid as we are dealing with very large forces . The screw jack would sometimes freeze up (i've had it happen) if the wrong grease is applied and it's really cold soaked at high cruise levels.. It's still in trim for a high speed so you have to warm it up at lower levels to allow your plane to be retrimmed. Much less of a problem than here but similar recovery expected to be available or assumed to work

With this auto trim commanded to pitch down so much, the amount of out of trim is too much to expect to be able to recover the plane in time especially manually which is slow to change but the basic problem has been there for a long time in most Commercial jets.. where the trim range is very large of necessity. The emphasis/ priority was to be able to nose down to avoid the high rate of descent "deep stall" that sometimes happened . Over the years this was seen as the principal problem to be addressed. The AF 447? Airbus was in that state when it crashed at a high ROD in a flat attitude stalled from cruise level. The opposite of the problem we have here. Nev

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Once a stab is way out of trim for the speed and configuration the "roller coaster recovery" manually is pretty drastic (Slow and high physical force comes back) This is pretty hard to avoid as we are dealing with very large forces . The screw jack would sometimes freeze up (i've had it happen) if the wrong grease is applied and it's really cold soaked at high cruise levels.. It's still in trim for a high speed so you have to warm it up at lower levels to allow your plane to be retrimmed. Much less of a problem than here but similar recovery expected to be available or assumed to work

With this auto trim commanded to pitch down so much, the amount of out of trim is too much to expect to be able to recover the plane in time especially manually which is slow to change but the basic problem has been there for a long time in most Commercial jets.. where the trim range is very large of necessity. The emphasis/ priority was to be able to nose down to avoid the high rate of descent "deep stall" that sometimes happened . Over the years this was seen as the principal problem to be addressed. The AF 447? Airbus was in that state when it crashed at a high ROD in a flat attitude stalled from cruise level. The opposite of the problem we have here. Nev

Thank you Facthunter.

There is another piece of the jigsaw: I had wondered why the trim had such exaggerated nose down capability.

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The problem with the 2 Max crashes is that the trim got so far nose down that the roller coaster manual recovery method was virtually impossible due to the low altitude of both aircraft. Those trim wheels rotate at a pretty fast rate when the system is doing it. I don't know how many revolutions are required for a 1 degree change but I think it is quite a lot. At only 6000 feet & heading towards the ground at over 400 knots there is not much time to do anything.

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.....................The 737 Max disasters have ignited tensions between regulators on either side of the Atlantic, amid concerns over the FAA’s relationship with Boeing, including the degree of self-certification.

 

Ethiopia chose to send the data recorders from the crash to safety investigators in Paris, and the European Union Aviation Safety Agency has indicated it would carry out its own assessment of the 737 fix, rather than rely on the FAA................

 

https://www.theguardian.com/business/2019/may/29/boeing-737-max-will-be-grounded-until-august-says-airline-trade-body

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I see today that all 737s will have to have the tracks for the leading edge slats checked for cracking. That includes the grounded Max part of the fleet.

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Still a WIP, then:

Two people briefed on the matter told Reuters that an FAA test pilot during a simulator test last week was running scenarios seeking to intentionally activate the MCAS stall-prevention system. During one activation it took an extended period to recover the stabilizer trim system that is used to control the aircraft, the people said.

 

https://www.theguardian.com/business/2019/jun/26/united-extends-ban-on-boeing-737-max-after-regulator-finds-new-problem

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MAX Fixes Will Take Until At Least September, Boeing Says

 

Jun 27, 2019 Sean Broderick

 

 

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Boeing

 

 

WASHINGTON—Boeing will need at least until September to address a new flight control computer (FCC) issue and wrap up changes needed to get the fleet flying again, Aviation Week has learned.

 

The issue came to light during engineering simulator tests with FAA test pilots during the week of June 17. During a runaway horizontal stabilizer troubleshooting procedure, FAA determined that line pilots would need more time to correctly diagnose the failure and execute the appropriate checklist. The tests also showed that a computer chip malfunction could lead to uncommanded stabilizer movement during the emergency procedure. FAA told Boeing to address the issues, and the manufacturer is complying.

 

“We are working through the software update and the potential implications for the timeline for the safe return to service of the 737 MAX fleet and resuming MAX deliveries,” a Boeing executive told Aviation Week. “Our current assessment is we will submit our final certification package to the FAA in the September timeframe.”

 

Boeing is confident that the latest issues can be addressed with software changes. The alternative—replacing computer chips on more than 500 MAXs—could prolong a worldwide grounding that started in mid-March.

 

Boeing is modifying specific FCC software linked to two 737 MAX accident sequences within five months. The second accident, the Mar. 10 crash of Ethiopian Airlines Flight 302, triggered the global grounding.

 

The software changes focus on the MAX’s maneuvering characteristics augmentation system (MCAS), which helps the MAX mimic the flight characteristic of its 737 Next Generation predecessor in certain scenarios. The latest FCC issue is not believed to be linked to the proposed MCAS changes.

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The problems began more than 10 years ago when Boeings management in an ever increasing costs savings drive began to outsource the manufacture of parts by providing only high-level specifications and then asking suppliers to design more parts themselves. Hundreds of costly engineers were laid off in 2015 and software was out sourced to Indian company HCL formerly Hindustan Computers. This caused confusion as often the lack of aviation knowledge from the code cutters meant that there was to and froing due to communications issues and mistakes. There were kickback benefits for Boeing though as Air India placed a 16 $billion order in return for Boeings promise of 2.5 $billion of work for Indian companies in 2005. Boeing also got a 32 $billion order from Spiceject in 2017 for 737 Max aircraft further cementing the Indian relationship and a significant coup in a market previously dominated by Airbus.

 

Boeing's 737 Max software outsourced to $13-an-hour engineers

 

The problems relating to the outsourcing caused delays and is a major reason the Dreamliner was several years behind its original rollout schedule.

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Quality control issues that could have easily been predicted. Harsh treatment of whistle blowers and not allowing experienced employees from say Seattle to observe supervise /check/ operations by overnight created companies. New progressive profit driven practices produce a Chrysler like result. A race to the bottom on quality and a reputation hard won over many years destroyed. . Been burned by a few model failures, gets a near monopoly in the US and freaks out over the Airbus "competition" goes to cost saving and lack of new model research and it's bitten them badly.. Building BIG aeroplanes is not a very easy way to make money in an industry with big cash flows and low profit expectations at best and a lot of Unknowns in the operating circumstances of buyers who also skate on thin ice economically or/and operate with subsidies and have to have a "good deal" done to permit purchase.. ALL very shaky.. Nev

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To add to the problems Boeing are refusing to allow any non company pilots to use their simulator. I think they are afraid that they would cop more flack if the pilots could see what the position really is. I certainly don't appreciate the thought of flying in an airliner with the same sort of reliability as a Windows computer. Boeing seem to think all they need is is to upgrade a computer chip. Much the same approach as Qld government to computer programs. IE go for the cheapest solution and hope it works.

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Travelling by train is starting to look safer :-)

 

Cheers,

 

Jack.

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Is there any doubt that responsible Boeing staff should be prosecuted for criminal negligence? Which involves jail time. Surely aviation is one of those industries where the duty of care is high and any decisions made that do not prioritise safety should be seriously questioned. Other US businesses have got away in the past with making risky decisions that eventually required Government financial assistance but adopting that 'business model' here raises different issues.

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"Surely aviation is one of those industries where the duty of care is high "

History paints a different story. In the 50's one or two lost airliners WAS acceptable.

Just look at the Comet.

spacesailor

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No it was never acceptable. The Comet was the first ever Jet airliner and the company paid the price. Boeing rose from those ashes with the 707 and through its own failings is now paying the price which it may never fully recover from.

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The Comets had quite a few hours up before the fatigue failures at the windows showed up. Pressurisation was a complexity they hadn't fully covered with cycles and resultant fatigue stresses. They made all their findings freely available to the rest of the world. Nev

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That company bosses said at the first grounding (could have been sabotage.terrorism) that one or two incidences was acceptable.

On the old BBC TV, Callous bugger !.

Never forgotten.

spacesailor

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Boeing are now re jigging the computer programs so that both computers will compare notes. It sounds as if Boeing is being taken over by Windows. It certainly doesn't impress me. It was ridiculous to have the computers look at one AOA indicator when there were two on board. Even the most ignorant programmer could have seen the problem..

Now they are raising the question of chips being hit by cosmic rays and changing computer ones to zeroes. Maybe they should take up fishing as that looks like a red herring to me.

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While they have the attitude they do, I doubt it. I hope you are right. Don't forget only a few short years ago we had NO DEATHS for a whole year. We have sure made up for it proving perhaps, it was just a fluke.  Nev

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I cannot see how this debacle can make air travel safer.

The current push is to reduce the requirement for pilot input. As we have seen Boeing made pilot input un necessary to control nose up attitudes and that resulted in non pilot commanded nose down attitudes. We have seen a lowering of airline pilot ability requirements, then a computer driven answer to that problem. Now I don't know what they will do, but I do like to have a competent pilot up front although the experts don't like that idea.

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