Ethiopian Airlines flight to Nairobi crashes with 'no survivors' of 157 people aboard

[Django x2]

Yep, they found similarities in characteristics in the flight paths between Lyon Air and Ethiopian Air. Furthermore, Canada have seen similar characteristics in planes that were still in use prior to their suspension this morning.

Boeing need to tread very carefully here. They've said that they still fully believe in the safety and air worthiness of the MAX. Clearly, from what the FAA and NTSB have discovered, that is not the case. They now need to hold their hands up before they do any more reputational damage

 

[VincentHanna]

Yep, it sounds like there is a big issue now but they don't want 1000's of sales cancelled.

When they put stock market value and sales over safety, there's a big problem.

 

[Orionaut]

Boeing need to tread very carefully here. They've said that they still fully believe in the safety and air worthiness of the MAX. Clearly, from what the FAA and NTSB have discovered, that is not the case. They now need to hold their hands up before they do any more reputational damage

Its like the Comet all over again.

Now, I dont think Boeing is going to go bust over this or anything like that, but it is deeply embarrassing.

And it is also a reminder that, even today, with all the sophisticated computerized design tools available to us. Engineering is still less of an exact science than most people believe it to be...

:/

 

[chrcoluk]

They get more credibility to holding their hands up and ensuring they will fix it rather than trying to make believe there is no issue.

 

[wesley]

Did they ever found out what caused the lion air crashed into Java sea?

 

[LOAM]

They get more credibility to holding their hands up and ensuring they will fix it rather than trying to make believe there is no issue.

This is corporate America, they'll never do that. They will release a sw patch to fix an unrelated autopilot issue.

 

[Hagar]

Its like the Comet all over again.

Now, I dont think Boeing is going to go bust over this or anything like that, but it is deeply embarrassing.

And it is also a reminder that, even today, with all the sophisticated computerized design tools available to us. Engineering is still less of an exact science than most people believe it to be...

:/

Engineering is an exact science where loads, forces, stresses can be identified and calculated appropriately. However when you place the pilot and the control surfaces on either side of a black box is when you may get unintended consequences.

 

[M1k3H]

Engineering is still less of an exact science than most people believe it to be...

:/

Engineering is exact science. The question you need to answer is: How much would you be willing to pay for things engineered to perfection?

Part of engineering is making assumptions. Those assumptions are very useful in keeping costs down, but of course have the potential to increase the margin of error when calculating safety factors.

Of course, when you do have to make assumptions, or replicate boundary conditions that are not exact (again due to cost/complexity), you err on the side that will be worse. As an example; you might be testing a component that is installed in an aircraft. However it is not cost effective to get an aircraft frame simply to install your component and test it. So you could consider what the modes of failure would be for this component. Is it purely structural? If so, if you rigidly attach it then the loads going through your component will be higher than if it was installed in the aircraft, as your rigid attachments will not "flex", thereby they won't absorb any loads. In real life, the aircraft would "flex" (even if by a tiny bit) and would absorb some of the energy.

What if you have 40 different components that are similar? Do you test all of them, or try and determine the worst one in terms of its likelihood of structural failure and test that one?

I know in a lot of the safety critical industries they do exactly that. Make assumptions, err on the side of caution, determine worst case, etc. All to save cost of course, but without adversely affecting safety.

Another example of how cost drives industries is that of automotive vs. aerospace. In the automotive world, you will crash the entire vehicle no problem. Do you think they crash entire aircraft just to test their performance in a crash? Even if Boeing/Airbus decided to do that, what about the millions of options in each aircraft? Each airline chooses their own seats, lavatories, business class, first class, sometimes engines, etc. Same stands true for automotive as well, do you expect them to test every permutation of every option? Of course not. They will usually test the heaviest option (in terms of crash testing that will tend to be worst case), or whichever option(s) yield the worst results in terms of the considered failure modes/test criteria.

All of the above introduce a statistical uncertainty because you have not physically tested everything, or because your boundary conditions will never exactly match real life scenarios , or because the scenario might be slightly different, etc, but it affords all passengers a reasonable level of safety and ensures the industry lives to both make money and serve customers.

 

[VaderDSL]

Did they ever found out what caused the lion air crashed into Java sea?

Pretty much yes, there is a preliminary report from the National Transportation Safety Committee in Indonesia.

https://reports.aviation-safety.net/2018/20181029-0_B38M_PK-LQP_PRELIMINARY.pdf

There were two? prior incidents with the aircraft which may have resulted in it crashing. The pilots reported issues with the pitots and AOA sensors which the maintenance techs seemingly resolved. When it took off again (the flight that crashed) the AOA sensors disagreed, when the flaps were raised and as autopilot was not engaged MCAS kicked in (as it was designed to prevent high AOA/low air speed stalls) which pushed nose down via trim. The pilot extended flaps and the MCAS system stopped the auto trim and they regained control temporarily. Apparently they retracted flaps shortly after and this time they lost control as MCAS started the trim nose down again.

This seems to be the basic overview of the lion air crash.

From what I've read, the larger engines on the Max and the changes to accommodate them alter the centre of gravity? and lift characteristics so it tends towards the nose rising which in high AOA low speed situations can cause the plane to stall and crash. I imagine that most planes are designed from the ground up to minimise this, but retrofitting the 737 was a fairly low cost option to extend the life of the airframe but required an automated system to prevent worst case scenario stalls. Unfortunately it seems this was seemingly tacked on with limited documentation so airlines wouldn't need to fully re certify their pilots, thus making the new planes attractive and fairly low cost to integrate into fleets.

But the above is an opinion and might not be valid.

 

[CaptainRAVE]

Sounds like the plane needs a redesign. Either way, confidence will have been lost and companies/passengers will want some serious reassurances before they use these again.

 

[sanaxe1]

When the plane is not in autopilot, the pilot used to have full control on the older generation 737s.

With the new 737 Max planes have larger more efficient engines which shifted the weight distrubition towards the rear. So, the planes had a tendency to have the nose pointing upwards. Normally, this would require a modification of the wings or fuselage.

Boeing instead installed a system which lowered the nose of the plane by itself without the knowledge of all the pilots.

In the Lion Air crash of last year, the sensors told the plane it was going nose-high when it wasn't. Therefore, the system lowered the nose down but it wasn't causing the plane to even out rather sending it towards the ground.

Had Boeing fully informed the pilots of the new system, it would've required additional training for the new system and it would have been very expensive. So they implemented the system without fully informing and training pilots. This way, they could transition easily and cheaply from the old planes to the new ones.

In the Lion Air crash, the pilot tried 28 times in 10 minutes to correct the system which was sending the Max 8 towards the ground. He was fighting against a system he didn't know existed and didn't know how to disable. Eventually the pilot was overpowered by the faulty system, leading to the crash.

The recent crash seems to share some of the characteristics of the earlier crash.

 

[wesley]

Pretty much yes, there is a preliminary report from the National Transportation Safety Committee in Indonesia.

https://reports.aviation-safety.net/2018/20181029-0_B38M_PK-LQP_PRELIMINARY.pdf

There were two? prior incidents with the aircraft which may have resulted in it crashing. The pilots reported issues with the pitots and AOA sensors which the maintenance techs seemingly resolved. When it took off again (the flight that crashed) the AOA sensors disagreed, when the flaps were raised and as autopilot was not engaged MCAS kicked in (as it was designed to prevent high AOA/low air speed stalls) which pushed nose down via trim. The pilot extended flaps and the MCAS system stopped the auto trim and they regained control temporarily. Apparently they retracted flaps shortly after and this time they lost control as MCAS started the trim nose down again.

This seems to be the basic overview of the lion air crash.

From what I've read, the larger engines on the Max and the changes to accommodate them alter the centre of gravity? and lift characteristics so it tends towards the nose rising which in high AOA low speed situations can cause the plane to stall and crash. I imagine that most planes are designed from the ground up to minimise this, but retrofitting the 737 was a fairly low cost option to extend the life of the airframe but required an automated system to prevent worst case scenario stalls. Unfortunately it seems this was seemingly tacked on with limited documentation so airlines wouldn't need to fully re certify their pilots, thus making the new planes attractive and fairly low cost to integrate into fleets.

But the above is an opinion and might not be valid.

Thanks for that. Were they not supposed to retracted flaps? Could they leave the flap extended and fly back to the airport?

 

[Hagar]

When the plane is not in autopilot, the pilot used to have full control on the older generation 737s.

With the new 737 Max planes have larger more efficient engines which shifted the weight distrubition towards the rear. So, the planes had a tendency to have the nose pointing upwards. Normally, this would require a modification of the wings or fuselage.

Sounds like someone should invent something like a trim wheel.

 

[VaderDSL]

Thanks for that. Were they not supposed to retracted flaps? Could they leave the flap extended and fly back to the airport?

I guess they could have in hindsight, but as sanaxe1 mentioned the pilots seemingly were unfamiliar with how the system was supposed to work, and it is possible that their airspeed was too high for flaps and if they have left them extended it may have cause serious damage or loss of control? (obviously looking back on the crash you can see it might have been an option). But remember there are cut out switched for the pilots to press/activate to disconnect the MCAS system, some other pilots on a previous flight had the same issue and they used the cut out switched to prevent the MCAS for issuing the runaway trim commands.

 

[VaderDSL]

Sounds like someone should invent something like a trim wheel.

It does I have no idea how it all interacts but this site seems to do a good job explaining it all https://theaircurrent.com/aviation-...aracteristics-augmentation-system-mcas-jt610/

 

[vanpeebles]

Quite a worrying design to build a commercial vehicle that is unstable and then try to mask it with it software.

 

[wesley]

I guess they could have in hindsight, but as sanaxe1 mentioned the pilots seemingly were unfamiliar with how the system was supposed to work, and it is possible that their airspeed was too high for flaps and if they have left them extended it may have cause serious damage or loss of control? (obviously looking back on the crash you can see it might have been an option). But remember there are cut out switched for the pilots to press/activate to disconnect the MCAS system, some other pilots on a previous flight had the same issue and they used the cut out switched to prevent the MCAS for issuing the runaway trim commands.

Since the lion air crash, did Boeing do anything to the software or train the pilots?

 

[Django x2]

I guess they could have in hindsight, but as sanaxe1 mentioned the pilots seemingly were unfamiliar with how the system was supposed to work, and it is possible that their airspeed was too high for flaps and if they have left them extended it may have cause serious damage or loss of control? (obviously looking back on the crash you can see it might have been an option). But remember there are cut out switched for the pilots to press/activate to disconnect the MCAS system, some other pilots on a previous flight had the same issue and they used the cut out switched to prevent the MCAS for issuing the runaway trim commands.

Most modern hydraulic flap designs can be extended into an air stream at near on 1000mph, as long as they are deployed in stages and in parallel, loss of control would not occur.

There is also no "cut off switch" as such, to disable MCAS, as required to override it is either see's AoA is efficiently low, or, and critically, the pilot uses manual trim. And it's that last part I think will stick here, because most seasoned pilots will always trim rather than yoke to correct a slight variation in pitch.

 

[VaderDSL]

Most modern hydraulic flap designs can be extended into an air stream at near on 1000mph, as long as they are deployed in stages and in parallel, loss of control would not occur.

There is also no "cut off switch" as such, to disable MCAS, as required to override it is either see's AoA is efficiently low, or, and critically, the pilot uses manual trim. And it's that last part I think will stick here, because most seasoned pilots will always trim rather than yoke to correct a slight variation in pitch.

Ah makes sense. I thought there was a cutout? I'm sure I read on some of the prior flights before Lion air which had issues, the pilots disengaged MCAS? But might have misread. The photo on

seems to suggest there is a way to set MCAS/trim to cutout?

 

[Alibaba99]

Sounds like someone should invent something like a trim wheel.

It does, however it takes something like 50 rotations of the wheel to unwind the trim applied by the MCAS system.