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Old 16th July 2019, 20:05   #181
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Let me say right at the beginning that not for one moment do I think that Boeing expected the aircraft to crash for a (known) fault of their making - it is not a Ford Pinto case, where decisions were based on probability calculations. And I do not think Boeing is technically incompetent. Given these let me put it the way I, admittedly a layman, see it.

Right at the beginning of the Max development, one technical flying characteristic was foreseen, and one (commercially motivated) ironclad rule was set out.

The first was Boeings realization that a 'normal' 737 pilot would have a high chance of putting the Max in a stall because its native flying characteristics were quite different from that of the other 737s.

The second was the requirement that ANY 737 pilot, with minimum retraining (30 mins on an iPad, as it turns out) should be able to fly the Max. The retraining was to be so minimal that a pilot certified for a 'normal' 737 was also certified for a Max, and I suppose vice versa.

Boeing's solution to this dilemma was the MCAS.

Boeing was so certain that in normal course of routine operations the aircraft would encounter a stall that it 'gave' the MCAS 'great authority'. In terms of the amount it could trim, and the persistence with which it refused to disengage.
(My view is that by itself it was not a big deal. What made it a big deal was how it interplayed with the second part).

The second part was that it could not be revealed how intrinsic and important the MCAS was to the operation of the Max. (Otherwise right now one of the easiest courses of action would be to remove/ disable MCAS permanently). Revealing that would likely have meant that for pilot certification the Max would be considered sufficiently different from the rest of the family to require recertification.

This started the series of unfortunate events - the importance of the MCAS being downplayed (essentially kept hidden from pilots with just enough done to cover Boeings backside), DESIGNATED as a secondary assisting feature, and most importantly, logically connected to only one AoA sensor, though there were two physically present and wired up. (Apparently to take the output of more than one sensor would have automatically meant bumping the MCAS from secondary to primary/ important status, with all its commercial problems).

And the die was cast.

Please read this post along with my thoughts on this matter, spread over three different threads.

@Jeroen - pls. tell me where I'm wildly off the mark.


Quote:
Originally Posted by A350XWB View Post
Not B787 MAX, it's B737 MAX.

Quote:
The additional layers of protection include:
Flight control system will now compare inputs from both AOA sensors.
Boeing Statement on AOA Disagree Alert.
This is where I feel we will have the greatest disagreement. With Boeing + FAA + entities with commercial interest on one side and EASA + possibly other regulators on the other side. Because the source of the disagreement will be philosophical, not technical.
By now nobody disputes the importance of the MCAS. Which automatically means that it has to (should? We are afterall in todays world!) follow the accepted norms of such safety critical subsystems for commercial aircraft - triple redundancy. Which also means three AoA sensors. Now that is really going to be a problem!

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Sutripta
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Old 17th July 2019, 12:13   #182
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

It was not so much about the chances of pilots putting the 737 MAX into a stall as more about meeting the formal Stall Characteristics Requirements, the infamous 14CFR $25.203 (a). The pitch up tendency due to the new location and larger size of the engine nacelle cause additional lift during high AoA. This reduces yoke force.

This pitch up tendency is not allowed under the aforementioned regulation. That’s why Boeing had to come up with a solution. They did try several aerodynamic solutions apparently (e.g. Leading edge stall strip) but none of these were sufficient to pass this particular part of the certification.

The net result of of the yoke force reducing could be the pilot pulling harder and thus bringing the aircraft closer to a stall condition.

MCAS was introduced to give automatic nose down stabiliser input during elevated AoA, when flaps are up. During a normal flight MCAS should not intervene at all, because pilots are not supposed to fly the plane anywhere near these high AoA. But of course, it might happen and is known to happen, pilots are not perfect, there might be a big wind shear etc.

Jeroen

Last edited by Jeroen : 17th July 2019 at 12:15.
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Old 17th July 2019, 15:46   #183
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

So 14CFR $25.203 (a) makes it a statuary requirement as well.
My contention - that the problems come from the need to fulfil/ reconcile two two separate requirements, one technical, one commercial. And the murkiness which followed trying to meet these.

In the general narrative where am I wrong?

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Old 17th July 2019, 18:10   #184
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

As I pointed out it was not about Boeing certainty in pilots stalling the aircraft, neither does the Max have what I would call native different flying characteristics from the other 737s.

Only at low speed, high AoA, flaps up, no auto-pilot does it behave differently. One very special corner in the total flight envelop; Again, normally pilots would not put themselves here intentionally, but it does/might happen during this very specific, normally not encountered, flight regime.

In all other aspects a 737MAX flies identical to any other 737.

I think your ploy about how it had to be kept under wrap is perhaps a bit too dramatic. But that is just personal.

I have seen or heard very little whether MCAS was mentioned anywhere in the maintenance procedures and routines. The pilots might have no need to know about MCAS, it still needs maintenance, so the technicians and engineers on the ground should know I would imagine. Have not really seen or heard anything from that point of view.
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Old 17th July 2019, 19:45   #185
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

^^^
So you are saying that had it not been for regulations, MCAS would not have been included?

Sure everyone has personal views. Like using terms like 'blipped'.

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Old 17th July 2019, 21:50   #186
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

I really can not say what would have happened if there had not been such a regulation. Who knows what Boeing would have or would not have done?

I have often mentioned, on other threads, that I do not consider simply complying with rules & regulations sufficient. Companies/individuals need to have their own thoughts, vision, on top of rules & regulations. Those are just the default/minimum basics. It is what you would expect without looking.

A good criteria on how important safety is to a company? Check how far they push the envelop on safety beyond to what they simply have to comply with due to rules and regulation. How much is their own thinking over and above?

I do agree with your overal assessment that the real problem stems from having two reconcile technical with commercial requirements. As such, nothing new under the sun. Every commercial enterprise, big and small, does this every day. On this occasion Boeing did a very poor job.

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Old 17th July 2019, 23:41   #187
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Quote:
Originally Posted by A350XWB View Post
Not B787 MAX, it's B737 MAX.
That was a typo. I actually meant the 737 MAX.

Quote:
Originally Posted by A350XWB View Post
Wrong. In most of the error situations, the specific system where the error ...

...
Boeing Statement on AOA Disagree Alert.
I admit I was not able to pen down my thoughts clearly.
But Jeroen Sir has done so beautifully along with an example in this post (Lion Air Boeing 737 MAX crashes in Jakarta) and those are exactly my thoughts.

Also, in no way am I implying that Boeing was not at fault here. They goofed-up, big time. Conceptually MCAS was right but its implementation was flawed.
All I was saying is that it is understandable where Boeing was coming from about not categorizing MCAS as a separate system.
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Old 18th July 2019, 16:30   #188
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

slightly off topic, but for all the aviation enthusiast, interested in "Handling the big Jets", the book by author Davies is a must have. Explains a lot of details pertaining to flying and handling jets in relatively simple terms.

I have read this book multiple times and still refer to it on many occasions.

I recently came across this interview with Davies. You will hear him talk about what I really feels stalling a jet. Some interesting insights into how certification worked in those days!

Enjoy

https://www.aerosociety.com/news/aud...he-boeing-727/

Jeroen
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Old 18th July 2019, 22:07   #189
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Quote:
Originally Posted by Jeroen View Post

I have often mentioned, on other threads, that I do not consider simply complying with rules & regulations sufficient. Companies/individuals need to have their own thoughts, vision, on top of rules & regulations. Those are just the default/minimum basics. It is what you would expect without looking.
Strange. I think one of the defences for Boeing was that they had done nothing wrong because whatever they had done was legal.

Quote:
I do agree with your overal assessment that the real problem stems from having two reconcile technical with commercial requirements. As such, nothing new under the sun. Every commercial enterprise, big and small, does this every day. On this occasion Boeing did a very poor job.
Not comparable. The 'everyone does it does not fly (bad pun) in this case'.
In most of those cases lives are not lost/ put at risk because of those decisions.
When lives are at risk the standards should be, and were different. It is these far more exacting standards which made commercial flying one of the safest modes of transportation.

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Old 18th July 2019, 22:42   #190
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Quote:
Originally Posted by Sutripta View Post
Strange. I think one of the defences for Boeing was that they had done nothing wrong because whatever they had done was legal.
Exactly to my point. Just because its legal does not necessarily mean more could have been done. It’s a lame excuse, however, it works well in courtrooms for obvious reasons.

If you take safety serious, you need to go further than just by what is required by law. An analogy in my line of work. We will comply with all OH&S rules and regulations in any country in the world. We believe OH&S is of paramount importance. So we have developped our own framework, that surpasses on many aspect local rules and regulations.

If Boeing had taken the same approach, they would have said; not only does MCAS complies with all formal rules en regulations, but based on our own safety design framework, this is what has been added over and above.

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Old 19th July 2019, 16:09   #191
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

Boeing takes $5bn hit over grounding of 737 Max

Quote:
Boeing is taking a $4.9bn hit to cover costs related to the worldwide grounding of its 737 Max aircraft.
The charge is set to wipe out profits when the world's biggest planemaker posts quarterly results next week.

In a statement, Boeing also said its "best estimate at this time" is that the aircraft will return to service in the last three months of this year.

A 737 Max crash in Indonesia in October, and another in Ethiopia in March, killed 346 people in total.
Boeing is facing one of the worst crises in its history after its best-selling aircraft was grounded worldwide after the disasters.

Crash investigators have concentrated their efforts on the aircraft's control system and Boeing has been working with regulators to roll out a software upgrade.
The manufacturer, facing intense scrutiny over the regulatory clearance for the aircraft to fly, has cut the monthly production rate from 52 to 42 as airlines hold off purchases.

Most of the $4.9bn charge will be used to compensate Boeing's customers for schedule disruptions and delays in aircraft deliveries.
Source

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Old 19th July 2019, 19:24   #192
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Default Re: Lion Air Boeing 737 MAX crashes in Jakarta

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Originally Posted by Joxster View Post
Boeing takes $5bn hit over grounding of 737 Max
This is a $100bn a year company, running at around 10% nett margin. I am not quite sure how the deal with the $5bn from an accounting point of view, but it will show up of course in their 2019 financials. If their estimate turns out to be pretty ok, it will be a one time 2019 hit to the bottom line and then business as usual again.

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