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U.S grounds ALL 737 Max

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U.S grounds ALL 737 Max

Old 17th Mar 2019, 16:18
  #61 (permalink)  
 
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I see a second AoA sensor and AoA disagree WAS an option for the 737 MAX, the two accident aircraft did not have that option.
My solution
> Install second AoA/Mis-compare option.
>MCAS dis-connect on control wheel.
> SIM training for all pilots before return to service.
Here's a good synopisis of whats going on.
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Old 17th Mar 2019, 16:23
  #62 (permalink)  
 
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Originally Posted by DaveReidUK View Post
I don't believe that in this day and age you can run a commercial aircraft programme while simultaneously incorporating "secret stuff" than only a handful of people in the company know about. Many, many people inside (and outside) Boeing will have been involved in the design, implementation and flight testing of MCAS.
The pollution cheat device scandals would seem to suggest otherwise. Auto industry is also highly regulated, and employs a far larger number of people than aircraft manufacturing. Yet they got away with it for a very long time, and the eventual discovery came from outside the companys involved.

Boeing have seen more than their fair share of production, design and supplier scandals - most of which have successfully been kept out of the mainstream media. The same can be said for a large number of other companies in a wide range of industries.

On balance, I'll hazard the proposition that, in general, large corporations are pretty apt at keeping their dirty laundry away from public view.
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Old 17th Mar 2019, 19:53
  #63 (permalink)  
 
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Summarizing from the latest surviving posts today

my comments are;
Lack of faith in the industry will ultimately doom it.

What is needed is understanding followed by trust that flows to all users.

I can assure you from the safety aspects and lessons learned that we search out every new lesson world wide and act on it. There is no industry hidden rooms of secrets when it comes to safety. The engineers that rub elbows on crash sites will not allow it. They will act together as one voice when needed regardless of who pays their salary.. As an example I can assure you that Airbus is just as concerned as the posters here.
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Old 17th Mar 2019, 20:55
  #64 (permalink)  
 
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> SIM training for all pilots before return to service.
According to the New York Times, article titled, After 2 Crashes of New Boeing Jet, Pilot Training Now a Focus, March 16, 2019, there is currently ONE 737 Max simulator in the United States and apparently American and United Airlines pilots currently do not have access to it.

From the article:

When United was set to take delivery of the 737 Max in 2017, a group of pilots put together training materials without ever flying the aircraft or a full simulator. James LaRosa, a 737 captain and union official who helped lead the training group, said he flew to a Boeing training center in Seattle to learn about the new plane on a mock cockpit that didn’t move like typical simulators.

In addition to a two-hour iPad training course from Boeing, he and colleagues used their experience in the cockpit to create a 13-page handbook on the differences between the Max and its predecessor, including changes to displays and the engines. The training materials did not mention the new software that later became a focus of the Lion Air crash investigation.
...

But Boeing isn’t planning to overhaul its training procedures. And neither the F.A.A., nor the European Union Aviation Safety Agency, are proposing additional simulator training for pilots, according to a person familiar with the deliberations. Instead, the regulators and Boeing agree that the best way to inform pilots about the new software is through additional computer-based training, which can be done on their personal computers.

...

And airlines are getting flight simulators, even if they aren’t required by regulators. One flight simulator maker has received 40 orders.

It will be months before pilots in the United States can use them.

Hours after the Ethiopian Airlines crash, Mr. Tajer, the American Airlines union spokesman, spoke with the carrier and asked for an update on the simulator request. The reply: One had been ordered, and pilots would be able to train on it by the end of this year.

United Airlines, the world’s third-largest carrier, was told that it has to wait until 2020 for one. Today, there is only one simulator specifically designed for the Max in the United States.


https://www.nytimes.com/2019/03/16/business/boeing-max-flight-simulator-ethiopia-lion-air.html?emc=edit_nn_20190317&nl=morning-briefing&nlid=4764506920190317&te=1

A version of this article appears in print on March 17, 2019, on Page A1 of the New York edition with the headline: Left Little Time for Pilot Training.
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Old 17th Mar 2019, 21:11
  #65 (permalink)  
 
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Agreed! Didn't Airbus do the same thing with the Phugoid damping? Even Sully didn't know about it.

Originally Posted by DaveReidUK View Post
I don't believe that in this day and age you can run a commercial aircraft programme while simultaneously incorporating "secret stuff" than only a handful of people in the company know about. Many, many people inside (and outside) Boeing will have been involved in the design, implementation and flight testing of MCAS.

It may well be true, however, that only a few knew (even before Lion Air, if the rumours of internal Boeing memos turn out to be true) that MCAS could, under certain circumstances, come back and bite you. If there's a smoking gun to be found, that's where it is.
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Old 17th Mar 2019, 21:20
  #66 (permalink)  
 
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Someone check my sanity here. From the Seattle Times article:

According to a detailed FAA briefing to legislators, Boeing will change the MCAS software to give the system input from both angle-of-attack sensors.
Good, good.

It will also limit how much MCAS can move the horizontal tail in response to an erroneous signal. And when activated, the system will kick in only for one cycle, rather than multiple times.​​​​​​​
First, that sentence doesn't make sense; if a signal is known to be "erroneous", surely MCAS shouldn't act at all?! More significantly, my understanding is that MCAS was given the greater control authority because, when the system with the original intended control authority was tested, it was found to be inadequate and still produced handling characteristics that were not certifiable; Boeing had to significantly increase MCAS authority (without properly informing the FAA of the design change!) in order to get the high AoA handling certifiable. So how can they now reduce MCAS authority and retain certification?

I'm starting to wonder if Boeing are going to have to change the airframe, not the software, to produce an acceptable solution.
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Old 17th Mar 2019, 21:41
  #67 (permalink)  
 
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Originally Posted by Ranger One View Post
Someone check my sanity here. From the Seattle Times article:



Good, good.



First, that sentence doesn't make sense; if a signal is known to be "erroneous", surely MCAS shouldn't act at all?! More significantly, my understanding is that MCAS was given the greater control authority because, when the system with the original intended control authority was tested, it was found to be inadequate and still produced handling characteristics that were not certifiable; Boeing had to significantly increase MCAS authority (without properly informing the FAA of the design change!) in order to get the high AoA handling certifiable. So how can they now reduce MCAS authority and retain certification?

I'm starting to wonder if Boeing are going to have to change the airframe, not the software, to produce an acceptable solution.
Might this mean that the airframe is too unsafe in high AoA situations without MCAS, so MCAS cant be allowed to disable itself if input goes unreliable? If the interpretetion is correct that MCAS only decrease its authority and not disable itself in case of erroneous AoA signals?

Last edited by SteinarN; 17th Mar 2019 at 22:25.
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Old 17th Mar 2019, 22:24
  #68 (permalink)  
 
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Originally Posted by Ranger One View Post
First, that sentence doesn't make sense; if a signal is known to be "erroneous", surely MCAS shouldn't act at all?!
The thinking behind that is presumably that it is safer to assume that the higher of two differing AoA signals is the correct one and initiate a single-shot application of MCAS if the criteria are satisfied.

More significantly, my understanding is that MCAS was given the greater control authority because, when the system with the original intended control authority was tested, it was found to be inadequate and still produced handling characteristics that were not certifiable; Boeing had to significantly increase MCAS authority (without properly informing the FAA of the design change!) in order to get the high AoA handling certifiable. So how can they now reduce MCAS authority and retain certification?
It was the initial 0.6° nose-down trim application that wasn't certifiable. There's no indication in the Seattle Times article that Boeing are planning to revert to that.
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Old 18th Mar 2019, 00:06
  #69 (permalink)  
 
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Originally Posted by DaveReidUK View Post
The thinking behind that is presumably that it is safer to assume that the higher of two differing AoA signals is the correct one and initiate a single-shot application of MCAS if the criteria are satisfied.


It was the initial 0.6° nose-down trim application that wasn't certifiable. There's no indication in the Seattle Times article that Boeing are planning to revert to that.
On the first point about AOA signal selection, picking the higher of two would get you into the same situation that was seen with Lion Air. A comparison monitor that disables MCAS would be much more robust and seems to be what rumors are suggesting. It may be that Boeing is also considering how the system would response to two sensors that track, but are both erroneously high. That may be where the suggestion of limiting the response to a single MCAS increment comes in.

On the second point, MCAS was originally thought to be needed only at high Mach number where 0.6 degrees is sufficient. The need for MCAS at lower Mach numbers was discovered later. The 2.5 degree MCAS authority is only at low Mach numbers with a schedule that ramps MCAS authority down to about the original design value of 0.6 degrees at high Mach numbers. From what we have heard I about the need for MCAS I doubt it will be sufficient to limit it to 0.6 degrees at all Mach numbers.
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Old 18th Mar 2019, 07:48
  #70 (permalink)  
 
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Originally Posted by FCeng84 View Post
On the first point about AOA signal selection, picking the higher of two would get you into the same situation that was seen with Lion Air.
Not if, as implied in the article, MCAS deployment is limited to a single application.

"According to a detailed FAA briefing to legislators, Boeing will change the MCAS software to give the system input from both angle-of-attack sensors.

It will also limit how much MCAS can move the horizontal tail in response to an erroneous signal. And when activated, the system will kick in only for one cycle, rather than multiple times."
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Old 18th Mar 2019, 08:10
  #71 (permalink)  
 
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Originally Posted by calypso View Post
Absolutely. Even with the current safety record, before any mods, a 737 MAX is 100 times safer than the taxi that takes you to the airport which in turn is way safer than cycling or walking which in turn are way way safer than motorcycles. What I would not do is fly Lion Air.
Do you have any stats to back this up?

Uber has 5.5 million rides per day. How many are deadly?

Flying is not all that safe when you compare it in # of journeys taken.
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Old 18th Mar 2019, 08:31
  #72 (permalink)  
 
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Originally Posted by DaveReidUK View Post
The thinking behind that is presumably that it is safer to assume that the higher of two differing AoA signals is the correct one
Not entirely sure they aren't doing that already - on a quick check back through the published info I can't find anything that says it only uses one side AOA, only that one bad AOA can trigger it.

Reason I was checking - I compared the MMELs. On NG you can MEL "1 aoa sensor", on MAX you cannot, and no mention of MCAS either.

Availability requirement for MCAS seems to be higher than STS (which can be MELed), and possibly higher than a single AOA would give?

It was the initial 0.6° nose-down trim application that wasn't certifiable. There's no indication in the Seattle Times article that Boeing are planning to revert to that.
It's been stated that FAA thought 0.6 was the total authority - maybe as well as that being increased to 2.5 the reset/repeat was added at that point too, possibly because it couldn't pass one of the cert tests without it. Or maybe the reset wasn't documented to, or understood by, the FAA.
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Old 18th Mar 2019, 08:33
  #73 (permalink)  
 
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Not a software problem?

Interesting tweets from a pilot. Also interesting, as he claims Boeing does offer dual AoA sensors as an option on the MAX, but neither of these crashed planes had it.


Boeing sells an option package that includes an extra AoA vane, and an AoA disagree light, which lets pilots know that this problem was happening. Both 737MAXes that crashed were delivered without this option. No 737MAX with this option has ever crashed.
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Old 18th Mar 2019, 08:34
  #74 (permalink)  
 
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Originally Posted by infrequentflyer789 View Post
Not entirely sure they aren't doing that already - on a quick check back through the published info I can't find anything that says it only uses one side AOA, only that one bad AOA can trigger it.
My understanding is that MCAS uses Captain's and F/O's AoA sources on alternate flights.

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Old 18th Mar 2019, 10:04
  #75 (permalink)  
 
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All current Boeing commercial models have 2 AOA vanes. None are offered with 3.
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Old 18th Mar 2019, 10:34
  #76 (permalink)  
 
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One reads/hears the mantra “Safety is our no. 1 concern”. from airlines and aircraft manufacturers so it is with some head scratching as to why why the AoA disagree light is just an option.
I treat this mantra with a touch of disbelief.
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Old 18th Mar 2019, 10:41
  #77 (permalink)  
 
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Originally Posted by Gove N.T. View Post
One reads/hears the mantra “Safety is our no. 1 concern”. from airlines and aircraft manufacturers so it is with some head scratching as to why why the AoA disagree light is just an option.
I treat this mantra with a touch of disbelief.
This gets into the whole topic of presenting the crew with data they need to do their job but no more that might be distracting. I’m in the camp that AOA is a key to flight and should be displayed. There are other opinions.
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Old 18th Mar 2019, 12:24
  #78 (permalink)  
 
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Originally Posted by Speedywheels View Post
I don’t know how true this is but I heard Boeing are compensating the operators to the tune of $50k per aircraft per day. If true, that’s a cool $18 million for every day. I also heard Boeing expect the aircraft to be grounded until the end of May at the earliest. That’s knocking on the door of $1.5 billion
I don't know where you heard that - but the "at the earliest" part sounds very reasonable. That still a very aggressive time frame.
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Old 18th Mar 2019, 12:32
  #79 (permalink)  
 
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Originally Posted by Ranger One View Post
More significantly, my understanding is that MCAS was given the greater control authority because, when the system with the original intended control authority was tested, it was found to be inadequate and still produced handling characteristics that were not certifiable; Boeing had to significantly increase MCAS authority (without properly informing the FAA of the design change!) in order to get the high AoA handling certifiable. So how can they now reduce MCAS authority and retain certification?

I'm starting to wonder if Boeing are going to have to change the airframe, not the software, to produce an acceptable solution.
From what I have read, the amount of control authority was determined by what it would take to make the MAX operate as previous models did - to reduce cross-over pilot training (boy, did that not ever fail).
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Old 18th Mar 2019, 14:16
  #80 (permalink)  
 
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Originally Posted by DaveReidUK View Post
My understanding is that MCAS uses Captain's and F/O's AoA sources on alternate flights.
That is my understanding too, I am just starting to think that I have reached that understanding by just assuming MCAS works the way the rest of the 737 FCC stuff does and not from actual released information.

MCAS clearly used same AOA source on consecutive LionAir flights, the reason for that has not yet been confirmed.
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