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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Mar 2019, 09:01
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Originally Posted by N600JJ
Has anyone criticized the work that was done by French BEA re. the analysis of data from AF447 involving both the French national carrier and an aircraft manufactured by European Airbus whose ties with France are well known to all? From a pure France's perspective AF447 was presumably much more critical to France than ET302 may ever be. And I doubt that anyone (sensible) in France feels happy that this is happening to Boeing today....
Certainement pas, nous sommes tous connectés!

Perhaps the CVR/FDR being sent to France may be a tacit recognition underneath pragmatism, that there needs to be other eyes looking at this?
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Old 14th Mar 2019, 09:03
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Originally Posted by ManaAdaSystem


How large? I have tried to let it trim without counter trimming just to see how far out of trim the aircraft gets. I get more and more back pressure on the yoke but STS keeps trimming.
On top of that, STS trims on all departures, not only in the light aircraft, high thrust aft CG situation.
It’s a weird system that I could do without.
The switch involved is the same one that interrupts pilot electric pitch trim if opposite the column displacement direction. I believe this interrupt is also active on the ground. When positioning the stabilizer for takeoff using wheel mounted thumb switch try moving the column in the opposite direction at the same time to see how far it has to be out of detent before stabilizer motion stops even though thumb switch remains activated. A note of caution that thumb switch input in opposition to column such that the column cutout activates if held for very long may trip a monitor designed to detect persistent contradictory column and trim commands. That might take some explaining. I apologize that I don't know the details on such monitoring (in particular how long the condition must persist before said monitor trips). I'm sure there must be some 737 savvy PPRUNErs out there who know and by the amount of traffic on this thread they are probably monitoring.
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Old 14th Mar 2019, 09:28
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Originally Posted by DaveReidUK
OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.
Absolute guess here, but Lufthansa have managed and supervised ET's tech and mech support for many years, so it's possible the default response to a problem in Addis is 'send it to Germany', or 'ask the Germans'.
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Old 14th Mar 2019, 09:28
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Originally Posted by DaveReidUK
OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.
I don't think the ECAA is driving this decision to have the black boxes analyzed in Europe, and I didn't see them announcing anything in this regard.

Rather, I think this maneuvering is coming from Ethiopian Airlines -- more specifically, the airline's CEO, who has a lot of influence in the country's aviation sector.
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Old 14th Mar 2019, 09:35
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Paris/Addis Ababa - Two black boxes from the Boeing 737 MAX aeroplane that crashed in Ethiopia arrived on Thursday in Paris for expert analysis, officials said, as regulators around the world awaited word on whether it was safe to resume flying the jets.

A spokesman for France's BEA air accident investigation agency said the flight data and cockpit voice recorders would be handed over to the agency later in the day.

https://www.iol.co.za/news/africa/et...lysis-19877943
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Old 14th Mar 2019, 09:37
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To quote a 737 Max pilot:

"..what else don’t I know?"


From https://leehamnews.com/2019/03/13/co...-transparency/

"Herein lies an essential lesson for Boeing: When your reputation depends on safety, it does not matter what has been proven or who is at fault. What matters is that you are seen taking the lead to protect the safety of the publicat all costs."
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Old 14th Mar 2019, 10:00
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Originally Posted by FCeng84
The switch involved is the same one that interrupts pilot electric pitch trim if opposite the column displacement direction. I believe this interrupt is also active on the ground. When positioning the stabilizer for takeoff using wheel mounted thumb switch try moving the column in the opposite direction at the same time to see how far it has to be out of detent before stabilizer motion stops even though thumb switch remains activated. A note of caution that thumb switch input in opposition to column such that the column cutout activates if held for very long may trip a monitor designed to detect persistent contradictory column and trim commands. That might take some explaining. I apologize that I don't know the details on such monitoring (in particular how long the condition must persist before said monitor trips). I'm sure there must be some 737 savvy PPRUNErs out there who know and by the amount of traffic on this thread they are probably monitoring.
It works on ground. I have seen this when the wind push the yoke forward and I want to set takeoff trim. I need to pull the yoke back before I can engage the trim.
With STS it will continue to trim up even if I need to apply quite a lot of forward pressure to keep the nose from rising. I thing the parameters for the trim cut out to function are very high. Or possibly it doesn’t stop STS from operating.

Last edited by ManaAdaSystem; 14th Mar 2019 at 10:44.
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Old 14th Mar 2019, 10:01
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France is one of the MAX engine Co-manufacturers. This is why they likely have all the software needed from the very beginning.
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Old 14th Mar 2019, 10:07
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Originally Posted by Cows getting bigger
To quote a 737 Max pilot:

"..what else don’t I know?"


From https://leehamnews.com/2019/03/13/co...-transparency/

"Herein lies an essential lesson for Boeing: When your reputation depends on safety, it does not matter what has been proven or who is at fault. What matters is that you are seen taking the lead to protect the safety of the publicat all costs."
Precisely, the old Boeing would not need reminding.
Nor would they have lobbied the President to intervene if they were certain the data supported their public rehearsed statements of safety.

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Old 14th Mar 2019, 10:08
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Originally Posted by Non-Driver
And exactly how many F-reg MAX's are there I wonder .......
Not so much a question of D-reg or F-reg aircrafts here but more on Honeywell software (and potentially associated hardware), expertise, timescales and bandwidth I guess
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Old 14th Mar 2019, 10:09
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Originally Posted by poldek77
It is quite unavoidable with a new model joining a fleet
i partially agree with you on that, yes the captain possible first/ second flight as one day you just have to start. But the decision to add a totally fresh out of school,FO, no experience in aviation is just bad planning and judgement of the airline.
wondering how much extra sim emergency training (if at all possible) crew’s got after the Lion crash and info given by Boeing
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Old 14th Mar 2019, 10:12
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Originally Posted by mickjoebill
Have we passed the point in modern aviation where it is not possible to (quickly) switch off all these pilot and performance aids and fly “manually”?

At very least, the last resort if flying in VFR conditions?


Mjb


With a aircraft with powered flying controls let alone fly by wire signaled power controls define what manual control is.

Without any force feedback and at higher speeds it would be easy to badly over stress an aircraft.

plus

If you want pilots trained and current to fly without the “aids to flight” under stressful conditions you will need significant training both initial and recurrent. That won’t come cheap.
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Old 14th Mar 2019, 10:15
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Originally Posted by Less Hair
France is one of the MAX engine Co-manufacturers. This is why they likely have all the software needed from the very beginning.
More that they are the home of Airbus and Dassault and electronics manufacturers such as Thales.
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Old 14th Mar 2019, 10:23
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“Boeing has determined — out of an abundance of caution and in order to reassure the flying public of the aircraft’s safety — to recommend to the FAA the temporary suspension of operations of the entire global fleet of 371 737 MAX aircraft,”
Does anybody find it odd, that Boeing's public statement is attempting to suggest they the company 'ordered' the grounding?
Isn't that Cart before the Horse?
Or is it evidence of regulatory capture??
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Old 14th Mar 2019, 10:27
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Originally Posted by DaveReidUK
OK, thanks. I wonder why the ECAA didn't ascertain the BFU's capability before announcing that they were sending the recorders to Germany.
<cynic mode> First announcement for political reasons (i.e. not France) then unavoidably changed to France for technical reasons?
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Old 14th Mar 2019, 10:28
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MCAS Raison d'etre

So MCAS was born from meeting certification requirements re: stick force per alpha (or maybe stick force per G) in the 》1G range.

Can anyone tell.ne authoritatively whether this requirement stems from stall or maneouvre overload prevention ?

Oh! Or both!

thanks
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Old 14th Mar 2019, 10:45
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Originally Posted by bill fly
As has been very well explained, the reason for MCAS was to cause ANU stick force to increase or at least not to decrease when AoA approaches stall angle. That was a certification requirement.
However, by repeating the trim input at remaining high AoA, something more than just desired stick force increase is achieved.
What is needed is a one time increment in stick force to bring the Max into line with the other 737 models - if that was the aim.
This can be achieved by adding feel spring force to the control run, cut in point determined by AoA.
If there were then a fault in the AoA signal, the increment would be applied - once - which would be trimmable and controllable.
The whole sorry idea of playing with the stab trim to achieve what is really a desired primary control feel correction is unnecessary and as we see, unsatisfactory and potentially dangerous.
A feel spring solution should satisfy the certification authorities and the desire by the manufacturer to keep the Max in the 737 family, rating wise.
But your proposed solution wouldn’t be free to produce. The Boeing solution used existing hardware and a bit of new software.
Its not difficult to see why Boeing went the way it did. To me the question is what level of scrutiny did the plan receive.
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Old 14th Mar 2019, 10:52
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Your summation of the situation 'bill fly' is much appreciated. There seems to me to be something "off" about the concept of MCAS as it currently exists, and seems to be causing problems for flight crews. The repetitive, insidious nature of the correction is what baffles me. I do not understand why this mismatch of "real life application" of MCAS in its intended role was not thoroughly wrung out during the test pilot phase.
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Old 14th Mar 2019, 10:59
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Originally Posted by Redbeard

i partially agree with you on that, yes the captain possible first/ second flight as one day you just have to start. But the decision to add a totally fresh out of school,FO, no experience in aviation is just bad planning and judgement of the airline.
wondering how much extra sim emergency training (if at all possible) crew’s got after the Lion crash and info given by Boeing
At lots of airlines crews get 4 days per year in the sim, either 4 individual days or 2 blocks of 2 days. Few if any airlines will have added extra sim trips. Adding sim trips is not straight forward, you need both sim capacity and the ability to take crews off flying. These days most airlines have very little slack in their system.
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Old 14th Mar 2019, 11:48
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Originally Posted by positiverate20
I agree with you on the sensor problem, but entirely disagree with the perception that a failure of the system would have minimal risk to the aircraft.

In the scenario given, hundreds of feet above ground, stick shaker, the captain is in a pretty tough situation and is trouble shooting- does stab memory item, switches stab cut-out. Alarms off, and thanks to yoke and increased thrust returns to some form of climb. At this stage, despite your argument that the pilot should be able to return trim to normal, he has just followed the procedures that Boeing themselves have instructed. Checklist complete, some stability back and now focus on safely trying to get back to ground.

Now, throughout this next phase, with the stab having X° nose down, it may not present itself as a problem due to the additional engine power, because, at increased thrust, as you've explained, the Max set-up has a tendency toward a higher AoA, which is why MCAS is required in the first place! So, in a sense, the characteristics of the MAX set-up will be masking the trim. MCAS is required for certification to counteract the increasing rotation around the CG caused by the both the thrust moment and aerodynamic behaviour of the engine cowling of the Max engine. So, in this precise stage of the hypothetical flight the PIC may not actually notice the plane being out of trim, and if he does, will surely not realise just how much out of trim he actually is. Any other time in normal MAX operation the autotrim or the MCAS trim would be operating anyway. MCAS, as you've said, is a certification requirement for MAX aircraft because of it's specific aerodynamic characteristics. What I'm portraying in this scenario is that if the pilot functioned perfectly during the emergency at 190, but in doing so cut-off the trim at X° nose down. That trim hasn't changed and the checklists didnt require the crew to make any manual trim wheel changes. By the time he actually realises how out of trim he is, he's doing 350, and despite the stab still being at the same X° nose down since cut-out, the forces have multiplied. Now if there is any nose down attitude or reduction in power then there's absolutely no chance to recover.

Obviously all hypothetical, an airspeed disagree on takeoff could lead to circumstances similarly, or a multitude of other possible reasons, however, in the situation that I've hypothesized, it would almost certainly always end in a similar steep nose down attitude.
I am going to assume you don’t fly for a living. There is no way you would not recognize a stab out of trim condition while hand flying the aircraft. In addition the aircraft would only accelerate like you portray if the pilot failed to adjust power to maintain the desired airspeed. A professional pilot who lets his airspeed get 100 knots fast perhaps should be doing something else.
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