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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 10th Mar 2019, 18:41
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NWA SLF Read the AD. Loss/malfunction of a SINGLE AOA sensor can result in nose down trim input being automatically applied. The fact that there’s an automated system producing flight control input is in contravention to the fundamental operating philosophy of Boeing aircraft, and it has consequentially and not surprisingly caught out the crews. It is also now evident that the MCAS system (implemented due to a certification requirement for pitch stability during high power applications like G/As) appears to have been written in a bit of a hurry, without taking the usual redundancy philosophy into account.

We don’t know whether that was a factor in this accident until FDR/CVR are located and analysed.

Airbus operating philosophy is very different, and has been proven in the past to not do anything stupid to the aircraft unless a) multiple sensor inputs have been disabled/crippled, and b) pilots do stupid stuff like resetting flight stability essential computers in-flight by getting out of their seat and pulling CBs on maintenance panels meant for ground and engineering use only.


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Old 10th Mar 2019, 18:46
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Originally Posted by wingview View Post
Three Boeing nose down crashes in a few month's...?!
Four. Fly Dubai also crashed nose down. Also, all last major airliners crashed were Boeings...

What if modern planes are so stretched when it comes to performance attributes that FBW is safer at this point? E.g., MCAS is a non-FBW hack to make max certifiable.
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Old 10th Mar 2019, 18:48
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Originally Posted by physicus View Post
Read the AD. Loss/malfunction of a SINGLE AOA sensor can result in nose down trim input being automatically applied.
would rather we not get into an A versus B thing, those just add noise to no good end.
The point you mention there was raised in the LionAir thread about two versus three on the AoA gages: if only two, one's vote wins, the good one or the bad one?
If the "bad one's" vote wins, what then? The AD was issued with the understanding of the system (as you note) folded in.
We don’t know whether that was a factor in this accident until FDR/CVR are located and analysed.
Yes, we agree on that. What I was thinking was that with the recency of LionAir accident, MAX crews would tend to be aware of the procedure in the AD, so perhaps looking at that failure mode first is a red herring? No idea. Not enough info. One hopes the FDR/CVR data remain intact.
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Old 10th Mar 2019, 18:55
  #144 (permalink)  
 
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Originally Posted by JamesT73J View Post
From that article:


This is highly unusual, right? Aviators have been expected and encouraged to learn such things.
IMO, the industry needs to look at this especially with the Max and the upcoming 797. I’m totally opposed to designing any inherent aerodynamic instability into a commercial airframe corrected by software. The statement from Boeing scares the hell out of me. It also scares the hell out of me that we are heading in the direction of ATP’s requiring F-35 levels of training.

MCAS was implemented due to the forward placement of the engines on the Max. Any commercial FBW aircraft should be an aerodynamically stable design. FBW should only be for control surfaces, not to allow the airframe to actually “fly.” This “improved efficiency at all cost” factor may be at a critical point.

CRM is challenging enough today.
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Old 10th Mar 2019, 18:58
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Originally Posted by derjodel View Post


Four. Fly Dubai also crashed nose down. Also, all last major airliners crashed were Boeings...

What if modern planes are so stretched when it comes to performance attributes that FBW is safer at this point? E.g., MCAS is a non-FBW hack to make max certifiable.
I didn’t realise that the Flydubai crash happened “in the last few months”,
and it was totally different circumstances (night / IMC / poor weather). And an 800,
not a MAX.
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Old 10th Mar 2019, 19:00
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Copilot had 200 hours on type ?

or 200 hrs total career . . . ?

Last edited by TylerMonkey; 10th Mar 2019 at 20:18.
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Old 10th Mar 2019, 19:01
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SLF here- I'm amazed at the stampede to MCAS blame absent any other info. The last I heard re MCAS was that it was disabled until flaps UP. It ***seems *** that from the altitude figures above terrain and time after takeoff- that flaps were**** probably **** not up. Beyond that admitted speculation, including rants about chicken.... airlines, why not wait till more facts and data as from tower, fdr and cockpit voice data/facts. ??
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Old 10th Mar 2019, 19:01
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Originally Posted by DaveReidUK View Post
I can't vouch for the accuracy of GE's terrain elevations.
GE seems to use a radar satellite survey with 30m vertical resolution on a 90m grid. Some areas are much better with a [email protected] survey. I guess this case is likely to be a radar area.

https://www.quora.com/How-accurate-a...n-Google-Earth

https://productforums.google.com/for...th/3Th8MuHzKtE

https://dds.cr.usgs.gov/srtm/version...PDF-89020B.pdf
PERFORMANCE SPECIFICATION DIGITAL TERRAIN ELEVATION DATA (DTED)
(their caps)
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Old 10th Mar 2019, 19:05
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Judging by the picture of the CEO inspecting what appears to be the largest piece of wreckage around, with the crater in the background, it must have involved considerable kinetic energy to dig that size of a crater and displace the apparent volume of surface soil banked around it, particularly given it is hard African terra firma. The extensive scorched earth around the area of impact is evidence of instant atomisation and simultanious explosion of the on board fuel. It is somewhat reminiscent of the early B737`s un-commanded rudder deployment accidents. Wing over and almost a vertical dive, 80t +, at over 400kts. Considering the height reached before the event, somehow I cannot quite envisage stab/elevator to have achieved what must have been a very aggressive control input.
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Old 10th Mar 2019, 19:08
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"This emergency AD was prompted by analysis performed by the manufacturer showing that if an erroneously high single angle of attack (AOA) sensor input is received by the flight control system, there is a potential for repeated nose-down trim commands of the horizontal stabilizer. This condition, if not addressed, could cause the flight crew to have difficulty controlling the airplane, and lead to excessive nose-down attitude, significant altitude loss, and possible impact with terrain."

That's enough to keep me off them.
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Old 10th Mar 2019, 19:10
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Very quick response from the NY Times - especially for a Sunday.

Are There Problems With the Boeing 737 Max? A Second Deadly Crash Raises New Questions

https://www.nytimes.com/2019/03/10/w...x-8-crash.html
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Old 10th Mar 2019, 19:13
  #152 (permalink)  

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Originally Posted by NAROBS View Post
Boeing's statement sounds to me like the current corporate vogue of down playing everything that's a non-smiley event, "Move along, nothing to see here".
Trouble is once you've been exposed to 600C temperature there's not much left to put "Some cream on it".

A software device that alters the trim during flight transition from one stage to another, possibly without notifying the aircrew - unbelievable. Why haven't aircrew, en masse, especially seniors, raised objections to this ?

N
It happens all the time. The software and hardware is constantly adjusting in the background. As speed increases and decreases trim and control sensitivity is being modified, all the time. All without the pilot being told, and totally unaware. It is called a well designed aeroplane.
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Old 10th Mar 2019, 19:19
  #153 (permalink)  
 
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MCAS Question

Correct me if I’m wrong, but in the case of the Lion Air accident, from what I understood, an AOA probe fault caused the MCAS to put a forward trim on the horizontal stabiliser, causing a fault that essentially looked like a runaway trim, a situation that a pilot could have recovered from by treating it like a runwaway trim.

If the above statement is correct, my question is this : did the MCAS also activate the stick shaker or any other kind of stall warning?

Because recovering from a down trimming runaway trim (pulling back on a very heavy control wheel) while at the same time having a stick shaker and some other indication telling you you are about to stall (which normally would require lowering the nose).....






Last edited by Gilles Hudicourt; 10th Mar 2019 at 19:49.
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Old 10th Mar 2019, 19:26
  #154 (permalink)  
 
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Originally Posted by excrab View Post


I didn’t realise that the Flydubai crash happened “in the last few months”,
and it was totally different circumstances (night / IMC / poor weather). And an 800,
not a MAX.
well, luckily we are are at the stage where airlinners don’t crash so often that monthly data would be relevant. So by looking at “few months” (how much is few btw?), we are cherry picking data. Admittedly the sudden spike, specially the last two, could be due to random chance alone.

That said, Fly Dubai and the Amazon 767 nosedived under similar circumstances. And as fsr as I remember some people disputed the official Fly dubai story that the pilot keptnholding the trim button.

in any case, with 3 boeing nosedives officially unexplained yet, the situation is interesting to say the least, mcas or not (and since ET probably happened before flaps up, we might have 3 boings nosediving without mcas, whic is actually even worse, isn‘t it?)
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Old 10th Mar 2019, 19:28
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Aireon's satellite constellation (Iridium Next) has actually been completed as of January of this year, and they state their systems would be operational Q1 2019. It is quite possible part or all of their hardware was collecting data today.They advertise an 'Alert' service that is free but still needs to be enrolled in by operators. I am curious if such data would be made available, either publicly or to the airline or investigators.
Their data would overlap with the ADS-B data collected by FR24, but was collected on superior receivers that are much less sensitive to terrain from their orbit, so more datapoints may well be available.
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Old 10th Mar 2019, 19:44
  #156 (permalink)  
 
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Originally Posted by Gilles Hudicourt View Post
Correct me if I’m wrong, but in the case of the Lion Air accident, from what I understood, an AOA probe fault caused the MCAS to put a forward trim on the horizontal stabilisor, causing a fault that essentially looked like a runaway trim, a situation that a pilot could have recovered from by treating it like a runwaway trim.

If the above statement is correct, my question is this : did the MCAS also activate the stick shaker or any other kind of stall warning?

Because recovering from a down trimming runaway trim (pulling back on a very heavy control wheel) while at the same time having a stick shaker and some other indication telling you you are about to stall (which normally would require lowering the nose).....
The stick shaker was indeed activated on the Lion Air flight due to the incorrect AoA sensor readings, but the stick shaker has nothing to do with MCAS, its triggering mechanism is independent from MCAS.

In fact the stick shaker has also been active for almost the entirety of the previous flight, 90 minutes, for the same reason: incorrect AoA sensor readings.

And the pilots from the previous Lion Air flight seemed to fail to mention that the logs, for some unfathomable reason. Also not sure how they could stand having a stick shaker active for 90 minutes and not return to the departure airport. They might have pulled its circuit breaker to silence it.

The previous Lion Air crew also failed to mention in the logs they had to disable the automatic trim, after fighting with it for 5 minutes, to make the plane flyable.

Having done so would have helped the next Lion Air crew to diagnose the issue faster and apply the workaround before the plane become uncontrollable and crashed.
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Old 10th Mar 2019, 19:47
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The U.S. National Transportation Safety Board will send four people to assist in the fatal Ethiopian Airlines crash, an NTSB spokesman said on Sunday.The U.S. Federal Aviation Administration is also monitoring developments concerning the crash, a statement said. “We are in contact with the State Department and plan to join the NTSB in its assistance with Ethiopian civil aviation authorities to investigate the crash,” an FAA statement said.
https://af.reuters.com/article/topNe...BN1QR0JL-OZATP

Is four the usual size of the team? I would have expected a larger team.
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Old 10th Mar 2019, 19:49
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Originally Posted by PastTense View Post
https://af.reuters.com/article/topNe...BN1QR0JL-OZATP

Is four the usual size of the team? I would have expected a larger team.
Four would be pretty normal, remember this is not a US investigation , it's an Ethiopian investigation which the NTSB is a participant in. Their main role is being the conduit between the Ethiopians and Boeing / CFM / FAA / suppliers and also providing specific requested technical expertise.
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Old 10th Mar 2019, 19:53
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There seems to be in this thread an early fixation on a previously known cause. This flies in the face of the ability of the industry to assimilate previous causes and promulgate corrective actions world wide.

I'm not about to give much credence to anybody suggesting a cause unless equal arguments include previously identified corrective actions being missing
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Old 10th Mar 2019, 20:02
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Salute!

@Gilles
Correct me if I’m wrong, but in the case of the Lion Air accident, from what I understood, an AOA probe fault caused the MCAS to put a forward trim on the horizontal stabilisor, causing a fault that essentially looked like a runaway trim, a situation that a pilot could have recovered from by treating it like a runwaway trim.
I am willing to bet that most of us think of "runaway trim" as a fairly constant uncommanded trim that we didn't expect. The MCAS trim implementation is maybe ten seconds of nose down unless you use the manual trim switch or wheel, then it "rests" for 5 seconds and tries to kill you again!!! So sympton is like "intermittent trim" or basically FUBAR trim, especially if not briefed on the MCAS implementation and realizing that the stick shaker and stall alarm was telling me to push over, but Hal was overdoing it.
The previous Lion Air crew turned off the trim and until we hear their testimpny, they may not have realized that their own plane had MCAS failure. And looking at their FDR plots, it was classic MCAS. just like flight 610 the next day.

@CONSO The flap retraction altitude/procedure for the 737MAX is not in my memory bank Seems that normal retraction requires a trim change in most planes ( Airbus, Viper, Raptor, maybe 777 excepted), but not flying that type I am not sure. In any case, it's a configuration change and that is not a great time to have uncommanded trim you are not expecting or trained for.

For the "shut up and wait" folks!! This is a "rumor" forum, but if I were flying this type I would sure as hell be reviewing everything I could get my hands on about the systems' operation ofter gear up and establishing a stabilized climb, and talking with other pilots flying the beast.

Gums opines....
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