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

 

[waross]

I suggested a long time ago that the problem may be much deeper than just the MCAS system.
It's looking as if the root problem has some of its origins in changes to the 737 NG series. (Larger stabilizer, smaller hand wheel)

Next issue:
A bird strike takes out BOTH AoA sensors and the internal counterweight causes both to drop to the bottom, and still agree with each other.
Random speculation?
I wonder what Capt. Sulley's thoughts are on multiple simultaneous bird strikes.



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

 

[Alistair_Heaton]

Its pretty standard in these situations.

The q400 guys that have gone over there are working a 20 day on and 10 day off roster with 2 single days off in the 20 days and are flying 4-6 sector days and 100 to 120 hours in that 20 days for 7000$ a month. That's an utterly brutal roster.

The none lawyer reply was the better one for them "We complied with the NG differences training issued by the FAA and Boeing" which I have no doubt will be considered insufficient in a court of law but only time will tell.

Its been very quiet on the CVR contents of both crashes which is unusual. There has been more than enough time to get them processed. I suspect Ethiopians joker will be the racket that was going on in the cockpit and there will be a line of phycologists willing to go pro witness saying that the pilots were enviromentally overloaded and couldn't be expected to function trained or otherwise in such a situation. There are a load of NASA study's on the subject which they can quote from. Also the possibility of a bird strike has also been quietly dropped from comment. The CVR contents are what's missing for most pilots now.

To be honest the hang bags a dawn mud slinging between Ethiopian and Boeing is just about who coughs up compensation to the relatives. If the finger is pointed at Ethiopian it will be the Warsaw or Montreal compensation which I think is limited at 250 000 $ per pax. If its Boeing you guys know the likely outcome better than I do. I will admit its not really a subject I have looked into after the basics required in Air law so if I am completely wrong so be it, I will standby to be corrected. In someways the lionair is the relatively easy one to deal with due to the low number of probomatic nationalitys onboard, I believe there was 1 European on board and no North American. The Ethiopian is a completely different mix and problems.

"I wonder what Capt. Sulley's thoughts are on multiple simultaneous bird strikes."

I think you would be surpised how hated Sully is in US airline mamngement circles. He has turned back the clock 30 years and undone billions of dollars worth of lobbying by the airlines. And he is still alive and keeps talking sense and the public consider him a hero. Nobody is stupid enough to take him on. And to note he too didn't do the procedure properly when he ditched. Turned the APU on without being told to by the checklist and failed to run the ditching checklist which resulted in the main outflow valve not being closed which allowed the aircraft to flood more quickly.


Is there any talk about having a Rodgers Commission type investigation into this whole thing?

 

[waross]

Comment noted, Alistair.
But, is it reasonable to surmise that in the case of a flock of birds taking out both AoA sensors they may both give false, but agreeing, indications?

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

 

[Alistair_Heaton]

yep but its unlikely to happen. It will need to be a pretty huge bird way over the windscreen testing size which would have to hit a AoA vane for it to come off. These things have survived TSA baboons climbing on them to check cockpit windows being closed. They survived the pitot tubes didn't. Your talking migrating geese or albatross sized birds whoe's pack density is much less than a swarm of small birds. I wouldn't like to speculate what the chances are of two of them hitting a AoA vane in just the right place to sheer it off on the same strike.


A goose will cave the radar dome in or destroy the spinnner of a turbo prop. And will utterly destroy a jet engine.

What Sully hit, a turbo prop would have eaten and spat the left overs out the back of the prop for most of it. The bullet proof ice impact panels would have taken a bit of a beating. And because the TP's engines use centrifugal compessors anything that made it to the engine intake would get thrown out the bypass door just like lumps of ice do coming off the blades. After landing the whole aircraft would stink and there would be blood and guts all over it which would have been dried to a not to be moved with a pressure washer state. Been there done that got the t-shirt.

 

[IRstuff]

That requires a long chain of events
> multiple bird strikes
> pilots not noticing
> both vanes destroyed
> both vane counterweights misaligned in the wrong direction
> assumption that the software is still stupid (this might still be a good bet, though)
> all happening during the initial climb

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

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[Alistair_Heaton]

Just for information here are the flight controls laws you get in Airbus and what you loose between them.

http://www.airbusdriver.net/airbus_fltlaws.htm

And a link that includes Boeings FBW laws.

https://www.skybrary.aero/index.php/Flight_Control_Laws

I can't find anything for the Embraer or C series.

 

[waross]

Thank you Alistair.

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

 

[LionelHutz]

Of course the issue are deeper than a single malfunctioning system.

From what I can tell;
- None of the 737's are easy to manually trim when starting from far out of trim.
- Stabilizer runaway has been dropped as a regular training requirement, likely because it never happened. At best it might still be a 1-time training thing when first moving to that type.
- Overall, pilot training isn't as focused on flying the plane as it is on operating the plane.

So, there is plenty of blame to go around. The plane was flyable, nothing was fundamentally wrong that made it impossible to keep it in the air, but the pilots didn't know how to keep it in the air.

Personally, I'm doubtful that having bigger trim wheels and/or the original stabilizer size would have made any difference.

 

[LionelHutz]

Something I didn't understand is the Ethiopian first-officer having 98 hours of flight experience outside of flying as the first-officer in 737's. That makes it appear the minimum required experience is another thing to add to to the list of blame to go around.

 

[VEBill]

"The plane was flyable..."

Agreed. Look up thread (17 May 19 17:37) where the same point was made.

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

The original post contained more explanation.

 

[Alistair_Heaton]

He did what's called a mpl which is very light on small aircraft flying and heavy on multicrew SIM training.

There are more than a few of us in the industry which are not happy with the concept.

But it really doesn't matter if the guy next to you has 100 hours or a 1000 hours in light aircraft you are pretty much on your own as a captain in none normal operations until they get 500 sectors under their belts and one recurrent SIM check.

 

[Stochastic1]

Apparently, this is a point of contention...my 2 cents...it would seem that had the air framer performed or should have performed a DFMEA for this vintage plane, including the MCAS system/software...they would have at some point had to address the very real possibility of erroneous AOA input, or a failed AOA. Sounds simple does it not...and more importantly, is not one of the cardinal rules for commercial air framer...at a minimum dual redundancy, in some cases triple redundancy? Your thoughts?

 

[IRstuff]

dual or triple redundancy is a nice concept, but there's always a limit on how much you need, or want, and how much fuel you burn to carry it around with you and how much you spend replacing everything that dies. For a given MTBF, you get better reliability at the system end, but you now have double or triple the number of components failing per unit time, AND additional testing to identify the failed units that are masked by the redundant unit taking over.

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

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[Stochastic1]

great points...especially the weight budget, and especially on a commercial workhorse like the 737...but a second AOA and associated harness...a guess 10 lbs?? Your thoughts?

 

[Alistair_Heaton]

They have two minimum, some types have three, And there is a system that does away with them and uses the pitot tubes to figure out the AOA which then gives three.

Per say adding an extra one seems like a easy job. But in reality it would cost millions and take months because it would step over the line and trigger recertification.

Everything revolved around not triggering recertification and reducing pilot training to virtually nill if you can call 45 mins CBT on an iPad training at all.

My winter ops CBT that reminds me about De icing procedure's and contaminated runways takes an hour plus a 15 min exam. And its only after 6 months since I landed with all the ice protection on. Dangerous goods takes 1.5 hours.

 

[IRstuff]

It's a mathematical trade, though, not subject to emotional arguments. The 787 Max has had 2 accidents, but both planes already had redundant AoA sensors, just not the proper processing for that feature.

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

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[waross]

With the 737 Max already having two AoA sensors it may be that the lines of code required weight heavy on the mind.

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

 

[VEBill]

Bad design can still outwit redundancy.

Airbus A330 with triple AoA sensors (etc.) and the aircraft still 'went psycho', ref QF72.

 

[Alistair_Heaton]

It wasn't a failed AoA sensor with the airbus.

It was data spikes from the databus which were spaced longer apart than the error checking algorithm was coded to deal with. And they had 3 backup computers cross checking each other

It happened to a second A330 in rufly the same place after they issued a notice to aircrew but before the software changes got through. And the spikes were the same spacing etc.

Nearby the locations there is a Military communications/other stuff base for subs. They of course won't say what they are doing or transmitting or when.

After the second event they actively looked for other aircraft getting the same data spikes. It was never to be seen again. No fault was found in the wiring looms. But they did harden the data lines against EM.

There has been another crazy ivan with an A330 which caused alot of injurys including the first officer with a broken spine. It was intially put down to the same thing, then it was discovered that the captain had a DSLR camera out in the cockpit and it had interfered with the side stick. As for his training he was a 25 year pilot officer in the UK's RAF flying the A330 Airtanker.

Its not uncommon for wierd stuff to happen to avionics near military sites. There are 3 places in the UK I won't go near in an aircraft be it light aircraft or commercial. There have been cases of dimond aircraft fadecs going crazy near them. And when we fly into St Petersburg its pretty much standard for the navigation gear to have a epiletic fit a couple of times during the approach.


So you might consider me a conspiricy theroist in realtion to the QF72 but I don't think they actually found out the full issue with that one. If it had happended a third time in the same location I would be certain but twice its just a hunch that all is not as was reported. I know its been a few years since I have done any data aquisition A/D but when I had to deal with data spikes they were pretty much constant if it was a dodgy accelerometer or strain gauge, especially if the test item was getting battered to death on the vibrator. The only time I got weird spikes it was usually down to badly screened cables and big inductors kicking in and out.

 

[VEBill]

"...wasn't a failed AoA sensor..."

Yes. That's why I intentionally included the '(etc.)', "...with triple AoA sensors (etc.)...", to acknowledge in advance that the failure wasn't with the sensors themselves. Sorry if it wasn't clear.