Boeing 737 Max8 Aircraft Crashes and Investigations [Part 3] 36

[Sparweb]

This is the continuation from:

thread815-445840
thread815-450258

This topic is broken into multiple threads due to the long length to be scrolled, and many images to load, creating long load times for some users and devices. If you are NEW to this discussion, please read the above threads prior to posting, to avoid rehashing old discussions.


Some key references:

Ethiopian CAA preliminary report

Indonesian National Transportation Safety Committee preliminary report

The Boeing 737 Technical Site

No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
STF

 

[3DDave]

The actions were effective when tried. The data traces showed a match between trim switch use and both stab trim change and MCAS action suppression on both accident flights. One suspicion on the Ethiopian flight is that because of the excessive speed that the trim inputs caused large shocks to the cockpit and the pilots were afraid of the shake it produced. What isn't explained is why they did not immediately return the trim motor switches back to the off position.

It's also important to note that even though there are cutout switches specifically identified to counter trim runaway, actual trim runaway is not trained in all phases of flight, including when exceeding Vmo.

 

[waross]

As I understand it, 50 years of 737 flying had no need of MCAS.
However the 737 Max series had issues with characteristics.
"MCAS does exist because of unacceptable flight characteristics- in one very specific area of the flight envelope."
Actually the area of the flight envelope is either steep nose up or tight banked turns.
MCAS is NOT the problem. MCAS as deployed is one solution. There are other possible solutions.
There are hardware solutions, and soft ware solutions.
Why was MCAS chosen?
I surmise that in order to get part of the orders for new planes that would otherwise go to Airbus, Boeing promised delivery dates that may have been challenging.
MCAS could be implemented in software and looked to be cheap, quick and light.
With costs to Boeing and the airlines at over 2 Billion dollars and possibly ending up several Billions more, cheap isn't working very well for Boeing.
With the Max fleet grounded worldwide and possibly a slowdown in production, quick didn't pan out either.
The first crash was a regrettable tragedy that never should have happened.
I can't find the words to express Boeing's subsequent actions in regards to MCAS up to the second crash.
It may be time to reevaluate the order of priorities.
The present priorities seem to be.
1. Beat the competition.
a/ do it cheaply.
b/ Do it quickly.
2. No new certifications.
3. No new training other than an hour on an I-Pad.
a/ Don't mention MCAS as then it may require more training.
4. Definitely no simulator training.
a/ Again, don't mention MCAS as then it may require more training.
5. Safety. Not an issue if it will impede a higher priority.

I accept that to be competitive more efficient engines must be used.
I accept that the engine of choice is the Leap engine.

Some of the factors involved in using the newer, larger engines:
The cost in dollars.
The cost in time to market.
Fly-ability of a new design.
The cost in weight.
The cost in safety.
The cost in training.
The cost in company reputation.
The cost in certifications.

Going back to priority number 1, which isn't working that well anyway;
How would the market have responded to a kit to install leap engines on existing 737s?
It is probably doable. The landing gear on the Max 10 is probably not usable as is, but it demonstrates that longer landing gear may be developed to allow the engines to be mounted under the wings.
Make it fast.
Make it Cheap.
Make it safe.
Pick two.







Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[LionelHutz]

Bill, you can keep posting long indignant rants about how Boeing did it cheap and they should fix the plane without MCAS but the simple facts are that the plane won't be changing any further and Boeing won't stop production and give up almost 5000 orders so a new version of MCAS will remain in use on the MAX.

The likely reason MCAS was not mentioned was not to make the plane cheap and fast to market but rather because it was determined that MCAS was part of the motorized stabilizer control and there already was pilot training and troubleshooting documentation in the manuals on runaway stabilizer. So be it MCAS or another system causing runaway stabilizer movement, the procedures to handle the failure already existed.

Excuses or not, when you examine many plane crashes you will find that the pilots were distracted by the issues and made it their main focus instead of having flying the plane as their main focus. The second crash story might be different if the Ethiopian pilots had either electrically trimmed the plane properly first before throwing the switches or pulled back the throttles and kept the plane at a reasonable speed before attempting to manually trim the plane.

 

[waross]

The point that I am trying to make is that MCAS is not the problem.
MCAS is one of many possible solutions to a problem.
I am trying to suggest that it may be prudent to consider other solutions to the base problem.
I see that you are playing the "Blame the pilots" card.
Shades of Captain Sullenberger. 35 seconds in a cockpit panic made the difference between a goat and a hero.
Boeing has shown a willingness and the ability to remove engineers who management does not agree with on safety issues.
This is an interesting statement:
"The likely reason MCAS was not mentioned was not to make the plane cheap and fast to market but rather because it was determined that MCAS was part of the motorized stabilizer control and there already was pilot training and troubleshooting documentation in the manuals on runaway stabilizer. on runaway stabilizer."
The other point of view is that:
The likely reason that it was determined that MCAS was part of the motorized stabilizer control and there already was pilot training and troubleshooting documentation in the manuals on runaway stabilizer and that MCAS was not mentioned was to make the plane cheap and fast to market."
Another interesting statement:
"So be it MCAS or another system causing runaway stabilizer movement, the procedures to handle the failure already existed."
Yes, for 50 years pilots have been handling runaway stabilizer events in the &#& with no problems. What changed?
No training.
No pilot awareness of a new system.
Trim runaway may now be caused by bird strikes.

One extreme view is that MCAS is a perfect system. It just needs tweaking a little.

The other extreme view is that the plane should be scrapped entirely.
Interestingly, that is the track that Boeing was on until Airbus beat them to market with a new model.

I am not advocating scrapping the Max. I am suggesting that we should be taking a broader look than just the MCAS system.

Can we agree to disagree that fixing MCAS may not satisfy a Five Whys investigation?
There is more than one way to view this whole situation.
Forgive me for playing devils advocate.



Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[HamburgerHelper]

I have watched a lot of episodes of "Air Disasters" on the Discovery Channel. There seems to be a running trend of planes crashing because someone didn't understand the auto-pilot or some other automation or the automating system was disabled unknowingly. In a lot of these cases where this happens, the pilot is put into a bad situation while not having full control of the plane and too much is going on to figure out in a timely matter what the problem is. Are there that many situations where the control systems need to operate automatically? Are automatic controls adding to safety?

------------------------------------------------------------------------------------------
If you can't explain it to a six year old, you don't understand it yourself.

 

[waross]

Hi HH. One example of "situations where the control systems need to operate automatically" was given by Alistair and relates directly to stabilizer trim.
As the flaps and slats are deployed the aircraft trim changes significantly.
The stabilizer trim automatically adjusts to maintain the trim as the flaps and slats extend and retract.
This has been working on the 737 for 50 years.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Alistair_Heaton]

Seems the FAA is going to release the max to fly next week in US airspace. No news yet about training requirements.

There is a meeting in 3 weeks time with the other major world caa's to discuss getting the bans from thier airspace.

I have no reference for this I am currently in the SIM center and some Ng pilots that flew the max are in doing their checks on the Ng SIM and were chatting in the coffee bar.

 

[VEBill]

There seems to be a running trend of planes crashing... ...automation...

The distinction of this trend can (if you like) be viewed as follows:

These newer style incidents are where the aircraft is in very nearly in perfect condition, right up to the moment of impact.

They're quite distinct from the old style incidents which typically started with something going bang; where the aircraft had a million dollars damage at the very outset of the incident.

With the new style of incident, perhaps it's just a sensor that is defective or clogged. Perhaps some software is acting in a strange manner. Perhaps the pilots are confused by a flood of error messages. Perhaps the training is inadequate for the subtle complexity of the new systems.

If these incident aircraft could be gently caught in a hypothetical net, then they could be dusted off, sensors fixed or cleaned, pilots training improved, system design re-considered, and software re-coded.

Viewed in this manner, these two separated trend lines seem to be moving in opposite directions. The old style incidents are generally on a downward trend since forever. But these new style incidents are (partially) backfilling the gap over the past 30 years or so.

 

[Alistair_Heaton]

The AOA sensors are the same as on the classic and Ng types there has been no change to the AoA system sensing since the 60's. The what takes the data changed but the actual sensor is the same. And they are not lifed so in theory there will be ones out there that are 50 years old.

 

[VEBill]

Good summary on BBC

 

[IRstuff]

Satcomguru ruled out the possibility of the vane coming loose, since the counterweight would cause a different data output, and IIRC, he felt that no mechanical problem, per se, could cause a constant AoA error that showed up in the FDR data.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[moon161]

Some of what I read connected the AOA sensor failures to QA problems at the north carolina assembly plant. [edit that doesn't make sense b/c the NG's are made in seattle]

 

[VEBill]

Flaws in flight simulator.

 

[Alistair_Heaton]

"The failures that these sensors DO experience is, by an overwhelming percentage, due to bird strikes of the sensor blade. That failure has nothing to do with the shaft coupling inside. "

The other failure mode is that they have a heavy duty heater in them that stops ice forming on them in clouds like the pitot tubes have. I don't have a clue how that system is wired on the 737 but there are situations when the power to the tube either gets shut down or the heater its self burns out. For my type its when the associated AC bus comes off line. Which would require the AC bus tie to not be able to remain in so wouldn't just be a generator failure.

As ice builds up on them the reading goes out and may trigger the Stick shaker. Its covered in our QRH though when the caution light for that system/side comes on.

 

[LittleInch]

The bit I can't understand from the various issues associated with bad data is the there doesn't appear to be any conditioning of the data. I.e. inputs which are physically impossible to achieve ( e.g. 5 degree AoA going to 70 in less than a second), random bad data ( I think the airbus which violently dipped in Australia they pinpointed to a single data point which changed by some huge amount in a millisecond).

Other complex process control systems which control process plants, nuclear power stations etc can manage this and alarm/alert operators and ignore that data in the safety systems. Why don't aircraft control systems do this?

Ultimately Boeing made an airplane with different flying characteristics in certain modes, but then attempted to solve the physical issue by software. Then somehow ignored their own rules about the level of redundancy required for critical systems and equally somehow didn't analyse the impact of bad data. And let the system repeat itself time after time with no easy kill switch which didn't disable the whole trim system. That was the real killer. IMHO.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[waross]

I understand that the pilot's indignation is because they were not told that MCAS existed.
If they didn't know about it they didn't have to be trained on it.

Just when you think that it's over, it gets worse.
Drilling down in the link posted by VE1BLL:
New York Times.

Every day, there is new news about something not being disclosed or something was done in error or was not complete,” said Dennis Tajer, a spokesman for the American Airlines pilots union and a 737 pilot.---
Boeing recently discovered that the simulators could not accurately replicate the difficult conditions created by a malfunctioning anti-stall system, which played a role in both disasters. The simulators did not reflect the immense force that it would take for pilots to regain control of the aircraft once the system activated on a plane traveling at a high speed.---
"On the Ethiopian flight, the pilots struggled to turn the wheel while the plane was moving at a high speed, when there is immense pressure on the tail. The simulators did not properly match those conditions, and Boeing pilots found that the wheel was far easier to turn than it should have been.---
But it's likely that pilots will be briefed on it via additional personal computer training, since there is just one 737 MAX simulator available for training use in the U.S.---

(And one in Canada)
Now it looks as if there are NO valid flight simulators available for Max 8 training.
Just another minor software glitch from Boeing.
It looks like even if the pilots had successfully completed simulator training, they may have still crashed.
How could Boeing provide adequate training when their own simulator was flawed?
Given that the pressures exerted on the tail were much greater than programmed into the simulator, is it reasonable to consider a re-certification of the tail assembly?

What's next.
I wonder if smoking gun memos will surface.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[3DDave]

Is it necessary to correctly simulate a condition that the pilots should never allow the plane to get to and, if they have, why would there be the assumption they could ever recover from it? By the time the Ethiopians got to that point they'd already blown past a half dozen "don't do this" actions.

What Boeing could have done is a trim wheel force study over IAS vs elevator, which would have told the pilots of the accident aircraft nothing they could use. They are already trained not to exceed Vmo, what would some other "Don't do this" would make a difference?

 

[VEBill]

So a reminder memo could be issued, and the fleet immediately released for flight?

Perhaps I'm not reading what you meant.

 

[3DDave]

What I meant is that leaping onto the simulator for not simulating a condition the pilots should never allow to develop is a waste of time. It's just gathering more firewood to burn someone at the stake and cannot make anyone any safer.

Tragically, releasing a memo doesn't help because the Ethiopian airline apparently chucked it into the trash.

 

[itsmoked]

Bill; Would you please start using the QUOTE FUNCTION. Your posts are so hard to read I'm starting to give up on them.

People quote in their posts then you come along and quote them with your quotes which is mindfuddling. Quoting them with quote marks makes readers struggle to understand what's your writing and what's other's. Use the quote function:

.

Always put other people's writings in a quote box, it's easy. You don't need to identify the other poster if you're quoting a post that's only 2 or 3 posts back. If it gets farther back than that it helps to add their name when the Quote Function asks for it.

Keith Cress
kcress -

http://www.flaminsystems.com