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

Soldato
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Just to discuss some points you raised -

The 'additional AOA/MCAS software and extra "sensor reliability" checking software' does not yet exist on current fleets

Yes it does, the "sensor reliability" software is an output cross-check which is installed when they added the extra AOA display to the PFD and shows "AOA DISAGREE" on the PFD if both AOA's show a different result. This already available software is installed as part of an AOA upgrade being added by US firms like Southwestern (link here) and NOT the new patch stuff which is due later and works in a different, less effective way.

it will form the basis of the software patch yet to be implemented

Not right, see above. The patch looks like it changes limits within the Control Laws to make the MCAS pitch down demand less forceful but over a longer duration (demand vs time) and it looks to have no additional "sensor reliability" addition over what it already has, which is - if the sensor is broke then MCAS doesn't work - and therefore not the same as being cross-checked between two sensors in the available software mentioned above.

Most of the US fleet of Max's do have an addition AoA readout however - this is a standard option for Boeing aircraft, but you have to pay for it.

The biggest 737 MAX US carrier is Southwestern with 34 which is only just adding it now after complaints post the Lion crash, the other two US carriers have less aircraft (9 United and 24 AA) and only AA have said they already have the extra AOA displays, United haven't said anything.

And it's debatable whether or not this readout would have prevented the crashes.

True but I'd say it would have shown the crew immediately after take-off that there was an AOA discrepancy via the "AOA DISAGREE" on the PFD. The crew would then know immediately that the left AOA probe was bad as they could cross-check between Pilot and F/O displays, helping the crew diagnose the MCAS problem much quicker, especially after the post Lion crash brief regarding MCAS/AOA. However, even with all that extra info, the extra brief about AOA/MCAS post the Lion Crash etc I honestly don't know if it would have changed anything but I'd like to think it would.
 
Associate
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I'm afraid to a degree I disagree.

The AoA indication on the PFD and in the event of a AoA vane failure, the amber 'AoA DISAGREE' annunciation have been availiable as a standard option on Boeing aircraft for decades. It is purely an indication and has nothing to do with the MCAS system other than MCAS uses output data from the AoA sensor, it does not change the MCAS software in anyway.

In any event, an output cross check of the two AoA vanes does not make them more reliable. The only way to do that is to add an additional sensor and poll data from all three to decide if one is giving erronous readings. Most operators do not elect to have it, probably as it of limited use as far as I can see - although if somebody can convince me otherwise I'm open to change my mind.

I thought Southwest already had the additional AoA reading installed but it looks like I was wrong there.

It's relatively easy to tell what your AoA is anyway, it's indicated approximately as the distance between the flight path vector (FPV) and nose of the aircraft as displayed on the PFD.

I must confess I have no idea what the software patch that is coming to the Max fleet will do, since our fleet is grounded I daresay I will find out in good time. As a small point, the B737 is not a fly by wire aircraft and does not have control laws, at least as I understand what they mean. That is to say, pilot inputs are modified by software before being sent to the control surfaces. Airbus's have control laws. Also, it's by no means certain that a software change will be an acceptable means of fixing the problem - I think this has quite a long way to run.

Regarding your last point, I'm afraid I have to disagree the most. As someone who flies this type of aircraft, I'm of the opinion that an additional failure flag on the PFD amongst the myriad of other failure flags, stick shaker and aural warnings would not have made any difference. I believe, most probably, that the crews of both aircraft became oversaturated with information and where unable to ascertain what was happening.
 
Caporegime
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@esmozz interesting that you mention oversaturation. I used to design control systems in the past, albeit for a very different industry, and this was always of concern.
 
Soldato
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Norfolk.
Hi esmozz, I would again disagree on the first two and last paragraphs however I don't don't think the thread would appreciate our back and forth. I would suppose the main difference in opinions comes down to yourself being an end user on this type vs mine as an avionics engineer so I would like to give the crew as much additional redundancy/help as possible whereas you've suggested it wouldn't make any difference.
 
Soldato
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Location
Norfolk.
Absolutely this.

Seconded - An FAA design philosophy still enforce today is that "a power change must not cause a large pitch change" yet that is exactly the "problem" with the 737 MAX new engine design/placement and why it needs a software"bodge" called MCAS to correct the hardware design flaw.

They needed taller undercarriage legs to fit the new engines correctly but that would be a lengthy and expensive re-build/re-design so instead they did the cheaper option, and now nearly 400 people are dead.
 
Soldato
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This sounds absolutely damning:

https://www.bbc.co.uk/news/business-47812225

A preliminary report into the crash of an Ethiopian Airlines plane last month says the aircraft nosedived several times before it crashed.

"The crew performed all the procedures repeatedly [that were] provided by the manufacturer but were not able to control the aircraft," Ms Dagmawit said in a news conference in Addis Ababa.

In a statement, the chief executive of Ethiopian Airlines, Tewolde GebreMariam, said he was "very proud" of the pilots' "high level of professional performance".

"It was very unfortunate they could not recover the airplane from the persistence of nosediving," the airline said in a statement.
 
Associate
Joined
24 Oct 2013
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210
Its quite likely I'll be proved wrong but I'm really struggling to believe that despite toggling the main electric trim and autopilot trim switches to render both systems inoperative (according to the emergency procedure), the MCAS system continued to trim forward and push the nose down.
 
Soldato
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7,810
I remember reading his book, Airframe in the 90's, which was about Air safety.

I remembered that too, it is what came to mind.

That is what made me think of Creighton.

As I recall,
it wasn't the plane that was the problem. The crash occurred because the pilot let his kid fly the plane and who ended up fighting the safety systems that would otherwise have corrected the situation had he just let go of everything and let the plane fly itself.

I will have to see if I can rummage it out and re read it. (I am, to the consternation of my GF, one of those people who never gets rid of books, so I know I have it somewhere :p )
 
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