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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 14th Mar 2019, 11:08
  #1301 (permalink)  
 
Join Date: Nov 2013
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Originally Posted by Non-Driver View Post
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, 11:09
  #1302 (permalink)  
 
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Originally Posted by poldek77 View Post
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, 11:12
  #1303 (permalink)  
 
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Originally Posted by mickjoebill View Post
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, 11:15
  #1304 (permalink)  
 
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Originally Posted by Less Hair View Post
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, 11:23
  #1305 (permalink)  
 
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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, 11:27
  #1306 (permalink)  
 
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Originally Posted by DaveReidUK View Post
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, 11:28
  #1307 (permalink)  
 
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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, 11:45
  #1308 (permalink)  
 
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Originally Posted by bill fly View Post
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, 11:52
  #1309 (permalink)  
 
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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, 11:59
  #1310 (permalink)  
 
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Originally Posted by Redbeard View Post

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, 12:48
  #1311 (permalink)  
 
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Originally Posted by positiverate20 View Post
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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Old 14th Mar 2019, 12:49
  #1312 (permalink)  
 
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Originally Posted by SRMman View Post
Anyone like to hazard a guess, assuming the MCAS is indeed the problem, what Boeing's technical solution will be (not to mention how long it will take!)?
Input from minimum 2 AOA vanes, disabling (with warning) if disagreement
Automatic disabling of MCAS if pilot counters with manual trim

Assuming everyone well motivated, which fleet grounding should do nicely, here's a guess on timescales:
Redesign and recode: 2 weeks
Safety case, prototype, testing, certification: 6 months
Fleet fitment: 3 months
My consultancy fees: $2.4m
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Old 14th Mar 2019, 13:03
  #1313 (permalink)  
 
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Another SLFie who may be stating the obvious, but surely the goal of any airframer is to produce an aircraft that even the minimum standard of pilot can fly and have a decent chance of successfully troubleshooting in the event of something going awry? Not prejudging anything BTW
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Old 14th Mar 2019, 13:03
  #1314 (permalink)  
 
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Originally Posted by boxmover View Post
Adding a spring system would involve incorporating new hardware on the Max. That new hardware would come at an on cost. The attraction of the Boeing solution is that it uses the existing hardware plus some new software.
Boeing got the cheaper solution certified so what is there motivation to go to a more expensive solution.
The question is is should it have been certified.

Why adding a spring ?
There is already an Elevator Feel System (EFS) which is controlled by a calculator, the Elevator Feel Computer module, thus it is controlled by software.


The elevator feel computer receives pitot pressure, hydraulic pressure, and mechanical inputs. The elevator feel computer sends metered hydraulic pressure output to the dual feel actuator on the elevator feel and centering unit. Feel hydraulic pressure in the elevator feel computer varies between 180 psi (base feel) and 1400 psi (maximum). The actual feel pressure to the dual feel actuator is determined by the hydraulic pressure from system A and system B, pitot pressure, and stabilizer mechanic
(from www.satcom.guru)







So, if the issue at stake was just about restoring the linearity of the control pitch force versus AoA angle, this could have been done just by enhancing the EFS system algorithms.
Just one little issue: the FCC doesn't feed the Elevator Feel computer with the AoA information.

It bet that Boeing engineers have balanced this against creating a new software function called MCAS whose implementation only affects the FCC module.
Now that the implementation costs of MCAS appear to be vastly different from the initial estimates, Boeing might reconsider enhancing the EFS.

I mean, that route might be preferable to adding even more complexity to a MCAS module whose existence and purpose is debatable.

Last edited by Luc Lion; 14th Mar 2019 at 13:16.
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Old 14th Mar 2019, 13:07
  #1315 (permalink)  
 
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Originally Posted by mfeldt
So there was a captain unable to quickly grasp what was happening because it was only his/her second flight on the type, and an FO with less than month of experience who couldn't grasp what was wrong??? I'm never going to fly again!
It is quite unavoidable with a new model joining a fleet
Perfectly possible. Train the training captains first, let them have some real, non-sim experience of it on test flights, all to a plan, start revenue flights with two captains, then progressively have them train the FO's, starting with the experienced ones. It's not hard to come up with that. Isn't devising this sort of transition what the role of Chief Pilot is all about ?
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Old 14th Mar 2019, 13:15
  #1316 (permalink)  
 
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Originally Posted by PerPurumTonantes View Post
Input from minimum 2 AOA vanes, disabling (with warning) if disagreement
Automatic disabling of MCAS if pilot counters with manual trim
Ding ding ding.

You may want to add "figured out how the aircraft was certified in the first place with input from a sole sensor".

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Old 14th Mar 2019, 13:21
  #1317 (permalink)  
 
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Originally Posted by EternalNY1 View Post
Ding ding ding.

You may want to add "figured out how the aircraft was certified in the first place with input from a sole sensor".
And add training module for crew type rating
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Old 14th Mar 2019, 13:27
  #1318 (permalink)  
 
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LL,

Thanks. That would work, while requiring differing software and inputs for Max and rest of the family, however.
Could be that a dedicated separate system would be simpler to calibrate and quicker to certify.
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Old 14th Mar 2019, 13:36
  #1319 (permalink)  
 
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Originally Posted by dead_pan View Post
Another SLFie who may be stating the obvious, but surely the goal of any airframer is to produce an aircraft that even the minimum standard of pilot can fly and have a decent chance of successfully troubleshooting in the event of something going awry? Not prejudging anything BTW
The FAA language is "a pilot of average skill".

However the first time such a pilot now gets behind the yoke is after the aircraft has been certificated, sold to an airline, built, delivered... Maybe they should involve FO Joe Average a bit earlier in the lifecycle.

Gone are the days when airline chief pilots would schlepp off to Seattle and throw the thing around the sky for a while before telling the executives whether it was suitable to buy. Now if it promises a 1% operational cost saving it is bought straight off the CAD screen.

Back in the 1960s there was even a BOAC inspection and flight-test team at Everett!

Last edited by El Bunto; 14th Mar 2019 at 13:46.
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Old 14th Mar 2019, 13:44
  #1320 (permalink)  
 
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Originally Posted by ManaAdaSystem View Post
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.
ManaAdaSystem,
look at the diagram below ; the "control column stab trim cutout switches" only operate on the electric path of the electric trim buttons.
The STS is on the other electric path, the path of the autopilot system.


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