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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 15th Mar 2019, 09:03
  #1441 (permalink)  
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I'm wondering why the engines seem to have been at high thrust in both accidents, this one and the Lion Air.

I'd imagine it to be a bit difficult to get to 383 knots at impact from 1000 feet agl, starting at 230kts say clean, at idle, because I imagine one of the first things one would do when the nose tipped over is reduce to idle.
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Old 15th Mar 2019, 09:08
  #1442 (permalink)  
 
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Good call Hunbet - looks like you were right !


Originally Posted by hunbet View Post
“Evidence we found on the ground made it even more likely that the flight path was very close to Lion Air’s,”

I suspect they located the stab trim jackscrew and could tell it's position.

Also :“The FAA is ordering the temporary grounding of Boeing 737 MAX aircraft operated by U.S. airlines or in U.S. territory. The agency made this decision as a result of the data gathering process and new evidence collected at the site and analyzed today. This evidence, together with newly refined satellite data available to FAA this morning, led to this decision," the FAA said.

https://www.bloomberg.com/news/articles/2019-03-15/piece-found-in-crash-wreckage-said-to-show-jet-was-set-to-dive

A screw-like device found in the wreckage of the Boeing Co. 737 Max that crashed last Sunday in Ethiopia indicates the plane was configured to dive, a piece of evidence that helped convince U.S. regulators to ground the model, a person familiar with the investigation said late Thursday night.

Federal Aviation Administration chief Daniel Elwell on Wednesday cited unspecified evidence found at the crash scene as part of the justification for the agency to reverse course and temporarily halt flights of Boeing’s largest selling aircraft. Up until then, American regulators had held off as nation after nation had grounded the plane, Boeing’s best-selling jet model.

The piece of evidence was a so-called jackscrew, used to set the trim that raises and lowers the plane’s nose, according to the person, who requested anonymity to discuss the inquiry.
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Old 15th Mar 2019, 09:36
  #1443 (permalink)  
 
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737 MAX Software Enhancement Boeing’s Public Statement

The Boeing Company is deeply saddened by the loss of Lion Air Flight 610, which has have weighed heavily on the entire Boeing team, and we extend our heartfelt condolences and sympathies to the families and loved ones of those onboard.
Safety is a core value for everyone at Boeing and the safety of our airplanes, our customers’ passengers and their crews is always our top priority. The 737 MAX is a safe airplane that was designed, built and supported by our skilled employees who approach their work with the utmost integrity.

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.

Boeing has been working closely with the Federal Aviation Administration (FAA) on development, planning and certification of the software enhancement, and it will be deployed across the 737 MAX fleet in the coming weeks. The update also incorporates feedback received from our customers.

The FAA says it anticipates mandating this software enhancement with an Airworthiness Directive (AD) no later than April. We have worked with the FAA in development of this software enhancement.

It is important to note that the FAA is not mandating any further action at this time, and the required actions in AD2018-23.5 continue to be appropriate.

A pitch augmentation control law (MCAS) was implemented on the 737 MAX to improve aircraft handling characteristics and decrease pitch-up tendency at elevated angles of attack. It was put through flight testing as part of the certification process prior to the airplane entering service. MCAS does not control the airplane in normal flight; it improves the behavior of the airplane in a non-normal part of the operating envelope.

Boeing’s 737 MAX Flight Crew Operations Manual (FCOM) already outlines an existing procedure to safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor. The pilot will always be able to override the flight control law using electric trim or manual trim. In addition, it can be controlled through the use of the existing runaway stabilizer procedure as reinforced in the Operations Manual Bulletin (OMB) issued on Nov. 6, 2018.

Additionally, we would like to express our deepest condolences to those who lost loved ones on Ethiopian Airlines Flight 302. A Boeing technical team is at the crash site to provide technical assistance under the direction of the Ethiopia Accident Investigation Bureau and U.S. National Transportation Safety Board. It is still early in the investigation, as we seek to understand the cause of the accident.

Last edited by Cloudee; 15th Mar 2019 at 10:04.
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Old 15th Mar 2019, 09:37
  #1444 (permalink)  
 
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MCAS (Maneuvering Characteristics Augmentation System) is implemented on the 737 MAX to enhance pitch characteristics with flaps UP and at elevated angles of attack. The MCAS function commands nose down stabilizer to enhance pitch characteristics during steep turns with elevated load factors and during flaps up flight at airspeeds approaching stall.
(my emphasis) I'm reading this to mean that the intention is to "assist"(TM) during steep turns and not that a steep turn is a condition of MCAS operation.

That said, if the ATC is correct, there were issues including unusual speed/acceleration for most of the flight which would possibly have been with autopilot engaged when MCAS isn't active. The pilot requests turnback and then disappears off radar.

So, accepting it contradicts Occam's Razor and needs another cheesy hole, perhaps something else non-MCAS-related was seriously wrong, but then on turning back, MCAS nose down trim becomes the final nail in the coffin as evidenced by trim jack screw position on ground.
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Old 15th Mar 2019, 09:55
  #1445 (permalink)  
 
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Originally Posted by FlightCosting View Post
One thing is clear amongst all the scuttlebutt, the 737 MAX is a new type not an ng with a few tweaks and a slightly different cockpit layout.
Buying a new aircraft type is a big undertaking for any airline and expensive getting their existing pilots certified on the type while still operational on the existing 737 fleet. This makes it more difficult for Boeing to sign up customers for big orders so they tricked customers into buying the MAX by certifying the aircraft as a variant so that current ng type rating applied with only new cockpit familiarity checks.
Precisely.
As year after year business schools pump out MBA graduates the only thing they conceive is cost and lowering it.
Labour unit cost is the single most controllable cost an airline has.

Manufacturers heard the drum beat a long time ago.
Regulators heard it too.

In the never ending battle of short term expense versus long term safety, the latter finishes a long way behind.

Consumers hear it too.

Our hubris as a species is incredible. We convince ourselves time and again absence of evidence is evidence of absence until again the 'unforeseen' appears again just to be re-learned as it was since long forgotten.
The normalisation of deviance.
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Old 15th Mar 2019, 09:58
  #1446 (permalink)  
 
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Originally Posted by WHBM View Post
If that is the case then there is likely only one version of the code (eases management of it), but a flag set Yes or No if the fee has been paid or not.

If so, and the right code to avoid the issue was actually installed in the aircraft but deliberately switched off, lawyers for the pax, especially those from the second accident, will have a field day.
Ineed, after Lion Air I though Boeing should have made this feature available for free in all MAX airplanes. Could the ET be prevented if they had this display? Interestingly, Boeing only lost 15% at NYSE. For comparison, Volkswagen lost over 60% due to their emission scandal. But this could be, and should be big if it's due to MCAS.
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Old 15th Mar 2019, 09:59
  #1447 (permalink)  
 
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Originally Posted by Cloudee View Post
For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer.
If "safer" means avoiding a crash every six months, I would say that "safe" for Boeing means "dangerous". If not, why would a safe aircraft be grounded ?
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Old 15th Mar 2019, 10:03
  #1448 (permalink)  
 
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And this time EASA may well not rely on the FAA for lifting ban or even worse re-certification if required...
D.P. Davies required modifications to the B707 before it was allowed on the British register so the above scenario is very possible, especially if the French want to give Airbus a leg up.

I'm surprised we haven't seen the ambulance chasing lawyers descending on the victims families en mass yet. Those of us who remember the Bhopal disaster involving Union Carbide in 1984 will remember the spectacle.
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Old 15th Mar 2019, 10:06
  #1449 (permalink)  

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Red face Options

Options on a new aircraft have long been offered, just as in a motor car. Some enhance safety, some convenience, some comfort. They all cost. To incorporate all options as standard would render the product unsaleable.

If the airline decides not to take-up certain safety-related options, on their own head be it. Not the manufacturer's.
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Old 15th Mar 2019, 10:09
  #1450 (permalink)  
 
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In summary then:

The newer engines required to optimise the MAX have a larger diameter than that allowed by the wing/ fuselage geometry. In order to fit those engines Boeing had to move them forward which changed the aerodynamic characteristics of the aircraft. That change consisted on insufficient pitch down moment when close to the stall in clean configuration. In order to meet certification criteria Boeing introduced a system that automatically moved the stabiliser to artificially induce the pitch down moment . In order to introduce this system with minimal costs existing equipment was used including a data input from a single source - the AOA probe. In order to reduce qualification costs this system was not mentioned in the MAX operation manuals.

In the Lion Air case the AOA probe was not calibrated properly, meaning the direction and magnitude where correct but the value was 20 degrees out. When the flaps where retracted the MCAS started to work as intended -based on the erroneous aoa data- by introducing bursts of down trim, those bursts got interrupted every time the pilot trimmed manually via the electric trim. At a certain point the crew started to pull hard at the yoke and the automatic stab trim cutout switch operated, with the effect that electric manual trim no longer worked, MCA trim in the other hand did continue to operate but it no longer got interrupted by manual pilot trim eventually trimming all the way nose down, a position that exceeds the authority of the elevator. At that point they only had two options left
1. Offload control column pressure to release the automatic stab trim cut-out then trim back to neutral.
2. Manually disconnect the electric stab trim via the override switches at the base of the throttle quadrant then use manual trim for the remainder of the flight.

Three crews managed the above but the fourth got overwhelmed in the Lion Air case. The Ethiopian on the face of it looks quite similar but there isn't enough data yet to even have a guess. A bit of a mess but where I tend to agree with Boeing is in which way is this any different from a classic runaway stabiliser? Ok there is more distractions going on but bottom line is if the stabiliser starts to run and you dont get on those disconnect switches soon enough you will end up in the same place.
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Old 15th Mar 2019, 10:16
  #1451 (permalink)  
 
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Originally Posted by RoyHudd View Post
If the airline decides not to take-up certain safety-related options, on their own head be it. Not the manufacturer's.
Except the aircraft is required to achieve certain standards of safety and, it appears, does not achieve that standard without the option activated. Ergo the default design should have additional features and it is back with the manufacturer and their regulator to take action.
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Old 15th Mar 2019, 10:21
  #1452 (permalink)  
 
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Rated De said "As year after year business schools pump out MBA graduates the only thing they conceive is cost and lowering it"

Stop and think whether this is not utter nonsense.
You imagine Airbus gave the A320 a seven inches wider fuselage than the 737 to save operating cost?
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Old 15th Mar 2019, 10:26
  #1453 (permalink)  
 
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Originally Posted by Capt Kremin View Post
The data shows a 63 second ground roll followed by a rotation at 207 knots. At this point the MCAS may have simply been doing its job.
The FR24 data do NOT show that.

After about 45" roll (05:38:45.798) and for 5 seconds the ground speed is stable at 182/183 kts while the vertical speed is positive, reaching 2368 ft/mn. Though the pressure altitude is not consistent with the speed and vspeed evolution, speed and vspeed indicates the aircraft is already airborne and climbing at 182 kts (about 170 kts IAS). And one minute later it has gained 1000 ft and speed (250 kts). Then only the problems begin, may be after retracting the flaps.
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Old 15th Mar 2019, 10:32
  #1454 (permalink)  
 
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Originally Posted by oldchina View Post
Rated De said "As year after year business schools pump out MBA graduates the only thing they conceive is cost and lowering it"

Stop and think whether this is not utter nonsense.
You imagine Airbus gave the A320 a seven inches wider fuselage than the 737 to save operating cost?
Did they build the MCAS?
MCAS saved re-certification cost. It appears increasingly likely that a system considered necessary for safety wasn't explained and trained to the pilot. Why do you think that would be?

Post graduate courses are indeed pumping out the said graduates.
When did Airbus actually design the A320?

Go and listen to the opinions of the Boeing engineers who actually used to build the product.
Listen to what they say changed. Then have a look at any Ivy league business school, read the curriculum, look at the individual modules and see what the graduate is focused upon.

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Old 15th Mar 2019, 10:39
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Originally Posted by calypso View Post
Three crews managed the above but the fourth got overwhelmed in the Lion Air case. The Ethiopian on the face of it looks quite similar but there isn't enough data yet to even have a guess. A bit of a mess but where I tend to agree with Boeing is in which way is this any different from a classic runaway stabiliser? Ok there is more distractions going on but bottom line is if the stabiliser starts to run and you dont get on those disconnect switches soon enough you will end up in the same place.
Two crashes and 3 near crashes, that means that only above average (or more lucky) pilots can avoid a crash after a single AOA sensor failure...

It would be interesting to know whether the MCAS ever was activated and avoided a stall in nominal conditions

Last edited by deltafox44; 15th Mar 2019 at 10:39. Reason: typo
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Old 15th Mar 2019, 10:40
  #1456 (permalink)  
 
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Originally Posted by Kolossi View Post
So, accepting it contradicts Occam's Razor and needs another cheesy hole, perhaps something else non-MCAS-related was seriously wrong, but then on turning back, MCAS nose down trim becomes the final nail in the coffin as evidenced by trim jack screw position on ground.
For me it's difficult to see how this doesn't potentially finish off the "Max" IMO.

Increasingly the perception is that It isn't really a software problem, it's a aerodynamics design problem. Apparently those engines don't work with that body, at least not comfortably. Sure it can be sellotaped over with some software fixes/more sensor redundancy, whatever. But it doesn't solve the design issue and nowadays it isn't only regulator certification that has to be overcome, it's "public opinion certification" as well. We're not in the DC-10 era where controversy takes years to eek out into the open but in the age of instant global knowledge - even if that knowledge is incomplete or based on un-authoratitive sources. 1 hull loss can maybe be got away with by saying "we fixed it". But with 2 it's difficult to see how any ongoing controversy doesn't just mean that people won't refuse to get on the thing.
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Old 15th Mar 2019, 10:49
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"The normailization of deviance." This. Exactly this. Shown to be a factor in many disasters, including Challenger. Sober thinking, smart people advised against certain actions and designs, and were shut down by others worried more about short term costs or schedule pressure.
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Old 15th Mar 2019, 10:52
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Originally Posted by CONSO View Post
Bird strike or ramp rash or software error are three most obvious- the point is to alllow a SINGLE sensor to directly override pilot input and not be documented that it even exists is as close to criminal as one can imagine.
There is no such thing as 100% reliable sensor. You can vote in software, but in case of two sensors you dont know, which value is OK and which is bad, you need at least three to have confident voting system. There are much better options sw engineer can use, if he knows something about the subject and phisical reality it deals with. I'm just plain earth based industry programmer, but can imagine some verification methods that works even with one sensor. The basic method is to observe sensor behavior in time, just as you watching if it works by your own eyes, in many phases of flight.
- during the takeoff run just before plane goes airborne, you can assume that values AoA should be close to zero. If not, sensor is stuck or misaligned.
- after that should the values change to positive normal range, if not, the sensor is stuck. This is also the case of normal in/flight behavior, values in acceptable range, that change slowly and possibly with small difference between two sensors according to actual flight conditions. So you can tell its still living and not stuck somewhere.
And the most significant, dont check for value constantly over the set threshold. You should check if value rises from accepted range dynamically and in one moment oversets it, then act.
Programmers working for Boeing or component manufactors should have known this. I'm somewhat surprised they obviously dont. Or maybe the flight computer is totally out of resources after mods.

Last edited by Prag; 15th Mar 2019 at 12:19.
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Old 15th Mar 2019, 10:58
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Originally Posted by deltafox44 View Post
The FR24 data do NOT show that.

After about 45" roll (05:38:45.798) and for 5 seconds the ground speed is stable at 182/183 kts while the vertical speed is positive, reaching 2368 ft/mn. Though the pressure altitude is not consistent with the speed and vspeed evolution, speed and vspeed indicates the aircraft is already airborne and climbing at 182 kts (about 170 kts IAS). And one minute later it has gained 1000 ft and speed (250 kts). Then only the problems begin, may be after retracting the flaps.
The first thing I would normally do with FR24 data, after correcting for QNH, is to throw away transmitted VS values.

The aircraft climbed fairly steadily before levelling off at approximately 1050' AAL just over 60 seconds after rotation, so 2000+ fpm at any point seems a tad unlikely.
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Old 15th Mar 2019, 11:11
  #1460 (permalink)  
 
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Originally Posted by deltafox44 View Post
The FR24 data do NOT show that.

After about 45" roll (05:38:45.798) and for 5 seconds the ground speed is stable at 182/183 kts while the vertical speed is positive, reaching 2368 ft/mn. Though the pressure altitude is not consistent with the speed and vspeed evolution, speed and vspeed indicates the aircraft is already airborne and climbing at 182 kts (about 170 kts IAS). And one minute later it has gained 1000 ft and speed (250 kts). Then only the problems begin, may be after retracting the flaps.
You must be looking at different data then.
The vertical speed is positive but nothing happens to the altitude till 207 knots is reached. The other possible scenario, which is probably more likely, may be that the aircraft was carrying out a Flaps 1 takeoff, which would be consistent with the speeds reached on the runway at rotate and the gear up call, (the 182 knots). The brand new FO, who at 200 hours may have been doing his first line sector, then inadvertently selected flap up instead of gear up. The aircraft settled back on to the runway and the captain rotated again at 207 knots, which would be a normal recovery, but now the MCAS is activated in a hot and high, extremely low altitude situation.

We will know soon anyway. The flight recorders are being looked at now in Germany.
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