Boeing 737 Max8 Aircraft Crashes and Investigations [Part 5] 19

[Sparweb]

This is the continuation from:

thread815-445840
thread815-450258
thread815-452000
thread815-454283

This topic is broken into multiple threads due to the length to be scrolled, and 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.

Thank you everyone for your interest! I have learned a lot from the discussion, too.

Some key references:
Ethiopian CAA preliminary report

Indonesian National Transportation Safety Committee preliminary report

A Boeing 737 Technical Site

Washington Post: When Will Boeing 737 Max Fly Again and More Questions

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

 

[thebard3]

Price of Scotch is going up, time to start hoarding.

I switched to tequila years ago anyway.

Brad Waybright

It's all okay as long as it's okay.

 

[Alistair_Heaton]

just had a beer with someone that has flown the MCAs version xray software version...


All he will say about it due to extensive gagging orders is... no comment

 

[Alistair_Heaton]

Hardly surprising but bad sad all the same.

Doesn't really change the design issues though.

https://www.seattletimes.com/busine...rlines-went-into-records-after-737-max-crash/

 

[thebard3]

Unless there's some order in place ordering that these records to be impounded, I would think that any airline would immediately begin to review maintenance records (and anything else they think might be salient) following an incident. There are no specific allegations of wrongdoing other than to say there might be some wrongdoing, and also that 3 years ago some folks weren't qualified for their jobs. It just sounds like spectacular journalism to me.

Brad Waybright

It's all okay as long as it's okay.

 

[LittleInch]

what's the "xray software version"?

some sort of code?

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

 

[Alistair_Heaton]

There have been that many iterations going through. It could though be a form of humour as a 8 digit software version is quiet hard to remember.

Looks like they have released the EASA verdict on the process though. Arguments over what level of DAL testing is required I suspect is the crux of it.

Maint and training records are sealed pending the investigation tuning up and collecting them. All airlines would love to go in and make sure that no bit of paperwork is incorrect but they can't, in EASA the SMS is meant to check everything within the airline. You then have external audits by the regulators to further confirm it. Every ICAO country has a law in its Aviation act which makes it a legal requirement after a fatal accident.

 

[Alistair_Heaton]

on the pickle forks subject it seems that it might have something to do with a mod to fit winglets to reduce fuel burn altering the loading profile.

Currently they are getting 5% failure rate with inspections. But most aircraft with the winglet mod are long route machines so are under 22000 cycle inspection trigger point.


To fix it will take a heavy maint hanger plus 3-4 weeks. Unfortunately there are only 25 spare sets in existence and the NG production has shut down.


They are meant to be lifed for 90 000 cycles the same as the hull but aircraft with 25 000 cycles are failing.

This will cause even more issues to MAX customers who were upgrading their NG fleet.

 

[thebard3]

https://abcnews.go.com/Politics/ame...6149278&cid=clicksource_4380645_null_hero_hed

So things are all hunky-dory now, I guess.

Brad Waybright

It's all okay as long as it's okay.

 

[RVAmeche]

That seems optimistic.

 

[KvdW]

It's a matter of how you bring the message. I understood that American Airlines previously extended the flight cancellations until December 3rd, 2019 and now decided to further extend the cancellations until January 15th, 2020.

 

[RVAmeche]

True, but it's not up to American Airlines it's up to the FAA. I assume AA has some new information from the FAA that leads them to believe that, but it seems optimistic given the scope of the software and hardware issues involved.

 

[waross]

Probably a revision of their Dec.3, 2019 deadline.
The new information was probably;
"Forget the December 3 return to flight."
I suspect that this announcement has more to do with full disclosure to the securities regulators than with the Max 8 schedule.
I won't be surprised if a month from now there is a similar announcement pushing the date back another month.

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

 

[VEBill]

"...what level of DAL..."

It would seem to be DAL = 'A', as evidenced by two Catastrophic incidents.

Simplest approach to reduce the appropriate DAL involves rewiring the switches. But they'd then open the Training can of worms.

That's a nice corner that they've painted themselves into.

 

[Alistair_Heaton]

Not only training the pilot response time to certain events has been blown out the water. Which will have other knock on system requirements.

Plus also there are issues with the cockpit alerting systems and sensory overload.


If its DAL A then I believe your looking at another 9 months min before it fly's again but more likely 12 months.


And the media releases are I think are more to do with required financial updates than anything to do with the process of recertification.

Oh and the pickle forks are not the same as the max or classic pickle forks so they are having to restart production of them as they only have 25 of them in stock and the failed aircraft have already used them up.

https://gizmodo.com/how-these-simple-scimitar-winglets-make-the-737-a-whole-837341873

is one form of winglet

The other is called blended

https://www.boeing.com/commercial/aeromagazine/articles/qtr_03_09/article_03_1.html

United got the scimitar winglet fitted but I think Air southwest has the blended. Ryanair in Europe has the blended as well. There doesn't seem to be any meat out there yet what's causing the cracking.

https://leehamnews.com/2019/10/08/boeings-737-in-another-pickle-part-2/#more-31313

How long that will take to restart production you guys will know better than me. But this is going to have huge effects on regional fleets around the world if it stays at even 5% failure rate. All the excess capacity has been soaked up covering the MAX.


You might think that this doesn't have anything to do with the max but a major issue like this in the fleets that the MAX was meant to be replacing is a huge issue there is just nothing to replace the aircraft with without completely retraining cockpit and technicians. And even then unless your going to start pulling coal burners out the desert there is no modern hardware available that can take a 737 load. It will be the final nail in the coffin for quiet a few Boeing operator airlines.

 

[Alistair_Heaton]

JATR report out

https://www.faa.gov/news/media/attachments/Final_JATR_Submittal_to_FAA_Oct_2019.pdf

 

[moon161]

There doesn't seem to be any meat out there yet what's causing the cracking.

From articles I've read, including the leaham news one, it's because the winglets change the lift distribution so that the spanwise center of lift is further out toward the tips and thus the moment at the root is higher even though the total lift is about the same. [edit- you think they would have accounted for that after developing the idea for about 30 years].

 

[Alistair_Heaton]

There is a difference between a post production mod fitted using a third party and a OEM fitted winglet. The level of analysis is far less.

The OEM doesn't care because they carry no risk. If its fitted as standard as they are in the MAX then it is their problem similar to the MCAS.

As I said I haven't seen any meat on the subject only sensible speculation on the cause. If it does turn out to be post production winglets fitting then its not just a problem for the NG there are quite a few other types across the whole lot of OEM's which could have problems.


Failing at 22k cycles though instead of 90k is a huge reduction in life span.

 

[moon161]

Its been forever since I looked at an S-N diagram. Can anyone fresh estimate the change in peak stress that life reduction corresponds to?

 

[GregLocock]

That's about 20% increase in stress

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Alistair_Heaton]

Its machine Al alloy and it will be at the dirty end of the SN curve due to weight saving. They will have inserts in the holes as well and if the vector on them changes it throws their effect out the window.


That said the safety factor would have to have been used up as well.