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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 22nd Apr 2019, 02:34
  #4201 (permalink)  
 
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NG / New differences
Flight Control Systems
Only the F/Os column cutout switch module is affected because it is the only module that interfaces with the FCC..

Help... think I must've missed something earlier.on that rin-down of changes.. Anyone else wondering where that jumped out of...

Last edited by HarryMann; 22nd Apr 2019 at 02:52.
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Old 22nd Apr 2019, 06:44
  #4202 (permalink)  
 
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FAA has an express statutory power to reinspect, re-examine, suspend, or revoke any certificate, including a type certificate, where "safety ... and the public interest require that action”. Read about Special Certification Reviews and examples such as MD-11 at https://scholar.smu.edu/cgi/viewcont...3&context=jalc.

Hopefully FAA led Joint Authorities Technical Review of MCAS will amount to a multi-national SCR. See https://www.faa.gov/news/updates/?newsId=93206.

Bad news for Boeing is that MAX grounding is not likely to be lifted before JATR reports in 90 days.
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Old 22nd Apr 2019, 07:14
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Originally Posted by ozaub View Post

Bad news for Boeing is that MAX grounding is not likely to be lifted before JATR reports in 90 days.
I do not think the family and friends of the 346 fatalities consider it bad news at all.
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Old 22nd Apr 2019, 07:25
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Re: Joint Authorities Technical Review. This is a very unusual move by the FAA.
Political positioning, need for world consensus to protect FAAs standing?
Or a much needed safety initiative to look at issues arising?

The team will evaluate aspects of the 737 MAX automated flight control system, including its design and pilots’ interaction with the system, to determine its compliance with all applicable regulations and to identify future enhancements that might be needed.’

Is this just an ‘evaluation’. Or if aspects are not compliant with regulations (whose regulations), will change be mandated or only treated as ‘enhancements’, or aspects which should be incorporated in future (non-grandfather rights) regulations?

Previous regulatory overview Ethiopian airliner down in Africa

and technical / training areas requiring review Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed

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Old 22nd Apr 2019, 11:47
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Originally Posted by safetypee View Post
Re: Joint Authorities Technical Review.
The team will evaluate aspects of the 737 MAX automated flight control system, including its design and pilots’ interaction with the system, to determine its compliance with all applicable regulations and to identify future enhancements that might be needed.’
Boeing had better have every single expert to hand with every schematic and line of code ready to be looked at. If the inspecting Engineers ask for clarification on X,Y and Z it could take Boeing another month to go get the information and come back. This could be a simple exercise or could be months depending on what depth it goes to..And the final answer may not be positive. I was worried when I heard since MCAS was fingered that a cross FCC bus was added to handle it better. That's major tinkering with major components. Not the sort of thing to be done in a few months as an add-on!

Hopefully none of the regulators will take any notice of the commercial imperatives to getting the MAX back in the air. Trump's White House might browbeat the FAA but none of the foreign regulators..

G
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Old 22nd Apr 2019, 17:30
  #4206 (permalink)  
 
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Originally Posted by groundbum View Post
I was worried when I heard since MCAS was fingered that a cross FCC bus was added to handle it better. That's major tinkering with major components.
Pretty sure cross FCC bus is already there, not absolutely sure AOA is on it, but if not, adding it would be a lot different to creating entirely new bus.

MCAS could have been done with two AOA sources in the first place, it wasn't (allegedly - see whistleblower quotes further up thread) because that would require an MCAS-fail warning light and sim-training. This now appears to be being done in a half-arsed way by using AOA-disagree as a de-facto MCAS-fail warning, which means operators who don't currently have AOA-disagree option will presumably need to implement extra training (or get blamed for future MCAS prangs) but the US operators with the no-sim-training penalty clauses will not because they already have the AOA disagree option. Funny that...
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Old 22nd Apr 2019, 17:42
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Originally Posted by infrequentflyer789 View Post
Pretty sure cross FCC bus is already there, not absolutely sure AOA is on it, but if not, adding it would be a lot different to creating entirely new bus.

MCAS could have been done with two AOA sources in the first place, it wasn't (allegedly - see whistleblower quotes further up thread) because that would require an MCAS-fail warning light and sim-training. This now appears to be being done in a half-arsed way by using AOA-disagree as a de-facto MCAS-fail warning, which means operators who don't currently have AOA-disagree option will presumably need to implement extra training (or get blamed for future MCAS prangs) but the US operators with the no-sim-training penalty clauses will not because they already have the AOA disagree option. Funny that...
I thought I'd read that AoA-Disagree was going to be added by default as part of the fix(?).
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Old 22nd Apr 2019, 17:43
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Originally Posted by groundbum View Post
I was worried when I heard since MCAS was fingered that a cross FCC bus was added to handle it better. That's major tinkering with major components. Not the sort of thing to be done in a few months as an add-on!

G
They say that it is a software only fix which raises the uncomfortable question of why it was not implemented to read both sensors in the first place. I am still not onboard with the idea that any engineer would make such a decision simply to hide the feature from the regulatory process but it makes one wonder. If so then manslaughter charges are appropriate and I am not kidding, that would be like designing a commercial kitchen without fire suppression because you did not want to involve the fire department in the permit. (And then blaming the cook for starting a fire!)
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Old 22nd Apr 2019, 18:29
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Originally Posted by Water pilot View Post
They say that it is a software only fix which raises the uncomfortable question of why it was not implemented to read both sensors in the first place. I am still not onboard with the idea that any engineer would make such a decision simply to hide the feature from the regulatory process but it makes one wonder. If so then manslaughter charges are appropriate and I am not kidding,
Safety culture and a certain independence within the organisation between the responsible safety managers and commercial decisions, is, at least within automotive & machine, part of the ISO26262/IEC61508 and therefore state of the art.
They may have a few things to explain...

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Old 22nd Apr 2019, 20:11
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Originally Posted by Bend alot View Post
If you need to buy new simulators to train for the MAX fleet, then the aircraft is different to other 737's.

So Boeing and FAA claims, of they are basically the same and do not require simulator training gets hard to swallow.

Now I can live with larger TV screens and more powerful engines as a reasonable change not requiring simulation, just look at the Toyota Hilux range - different engines and gauges but they drive similar.
But changes like that made on the MAX, to the spoilers and introduction of MCAS (flight controls) should have appropriate training. My personal opinion is a short read and sign on a iPad is not good enough.

Here is a link to the changes.

Boeing 737 MAX - Differences
So what simulator exercises would you incorporate to reflect the differences in the MAX, specifically the MCAS? How about an uncommanded nose down trimming? That is already incorporated in a conventional stab trim runaway, a basic requirement of getting a type rating on any B737. Or how about an unreliable airspeed including stick shaker? An unreliable airspeed exercise is also part of a type rating on any B737. In other words, there is nothing so uniquely different with the MAX that justifies a new simulator let alone MAX (MCAS) specific training. And even if you were to provide this (redundant) training, there is no guarantee that the crews would do the drill anyways as we have tragically witnessed with these accidents.

Not having the exact simulator for training has loads and loads of precedents - I can guarantee that the simulator configurations at a non-airline specific training facility (Flight Safety, CAE, Boeing, Airbus) would be different than what one would find on the aircraft of a particular airline. And even airline specific training facilities often don't have simulators that match their fleet as the fleet may have many configurations. As an example, where I work we have B767-300's with GE and Pratt engines, those engines start and behave completely differently (GE uses N1 as the reference power, Pratt uses EPR). Or an A340 simulator that is used for both the -300 and -500 which have entirely different fuel systems, different engines (CFM vs Rolls Royce), B787 simulators where the -800 and -900 are different (the -900 has more flaps settings for example).

The point is is that is both impractical and unrealistic to have "perfect" simulators; instead one has relied upon professional and experienced pilots to deal with differences between the simulator and the aircraft and also deal with different aircraft within a fleet.
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Old 22nd Apr 2019, 21:34
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Originally Posted by L39 Guy View Post
So what simulator exercises would you incorporate to reflect the differences in the MAX, specifically the MCAS? How about an uncommanded nose down trimming? That is already incorporated in a conventional stab trim runaway, a basic requirement of getting a type rating on any B737. Or how about an unreliable airspeed including stick shaker? An unreliable airspeed exercise is also part of a type rating on any B737. In other words, there is nothing so uniquely different with the MAX that justifies a new simulator let alone MAX (MCAS) specific training. And even if you were to provide this (redundant) training, there is no guarantee that the crews would do the drill anyways as we have tragically witnessed with these accidents.

Not having the exact simulator for training has loads and loads of precedents - I can guarantee that the simulator configurations at a non-airline specific training facility (Flight Safety, CAE, Boeing, Airbus) would be different than what one would find on the aircraft of a particular airline. And even airline specific training facilities often don't have simulators that match their fleet as the fleet may have many configurations. As an example, where I work we have B767-300's with GE and Pratt engines, those engines start and behave completely differently (GE uses N1 as the reference power, Pratt uses EPR). Or an A340 simulator that is used for both the -300 and -500 which have entirely different fuel systems, different engines (CFM vs Rolls Royce), B787 simulators where the -800 and -900 are different (the -900 has more flaps settings for example).

The point is is that is both impractical and unrealistic to have "perfect" simulators; instead one has relied upon professional and experienced pilots to deal with differences between the simulator and the aircraft and also deal with different aircraft within a fleet.
I'm sorry but this is genuinely disengenous.

You can't argue what about this, or that.

They didn't have this, or that.

They had all of it.

What you are arguing is that because individual elements of the failure were trained independently, that there was no combination of trained failures that could be expected to overcome the flight crew.

That no matter what the automation did and no matter how many failure modes were presented concurrently, that the flight crew should be expected to compensate regardless.

This just doesn't make sense.

The problem here is precisely that the combination of so many individually trained and for that matter untrained failures was too numerous to encourage and support successful and timely diagnosis by a typical crew.

Last edited by Turbine70; 23rd Apr 2019 at 00:41.
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Old 22nd Apr 2019, 21:48
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Originally Posted by Turbine70 View Post

The problem here is precisely that the combination of so many individually trained failures was too numerous to encourage and support successful timely diagnosis.

I don’t see a “combination of individual failures”. The failure of the Angle of Attack was only ONE failure. The crew did not correctly deal with that failure and made things worse for themselves.
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Old 22nd Apr 2019, 21:50
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Originally Posted by Lost in Saigon View Post



I don’t see a “combination of individual failures”. The failure of the Angle of Attack was only ONE failure. The crew did not correctly deal with that failure and made things worse for themselves.
Angle of Attack failures weren't even on the list of problems presented to the crew.

Last edited by Turbine70; 23rd Apr 2019 at 00:34.
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Old 22nd Apr 2019, 23:03
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So what simulator exercises would you incorporate to reflect the differences in the MAX, specifically the MCAS? How about an uncommanded nose down trimming? That is already incorporated in a conventional stab trim runaway, a basic requirement of getting a type rating on any B737.
Scenario 1: In the simulator, doing a “runaway trim exercise”. There you are at 6,000’ straight and level, 220kts, nothing happening. Oh look, the trim has started moving on its own, can’t stop it, I wonder if this is right? No? OK, do the runaway checklist. Sim passed! Easy, this trim runaway.

Scenario 2: In the aeroplane, cleaning up. Trim starts moving forward, then stops. Is that MCAS gone wrong (or even possibly functioning correctly), is it STS doing its job or is it the other guy who’s flying it trimming the aircraft? Hmmm. There goes the trim again...

Scenario 3: All the above plus continuous stick shaker, aural warnings and UAS symptoms.

Honestly, I’m not quite sure how you would train an MCAS runaway in the sim, if disconnecting the trim when there wasn’t an actual runaway = fail. It’s easy to say “they should have done the trim runaway checklist” but how do you tell NORMAL operation of MCAS/STS from ABNORMAL in a very limited timeframe? If you disconnect the trim every time it moves, you’re going to be doing lots of very short flights...
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Old 23rd Apr 2019, 00:23
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That last paragraph has been said before, but seems to be forgotten time and time again. IMHO, it is the crux of the matter.

Getting into the mind of an average pilot, whatever that might be these days. One thing's for sure, it's not one that's had his senses sharpened by months of focussed discussion on this specific crisis, and not necessarily comparable to some of the pilots on here that have a wealth of experience on a wide range of Boeing products.
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Old 23rd Apr 2019, 01:43
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Originally Posted by L39 Guy View Post
So what simulator exercises would you incorporate to reflect the differences in the MAX, specifically the MCAS? In other words, there is nothing so uniquely different with the MAX that justifies a new simulator let alone MAX (MCAS) specific training.
The only uniquely different thing is that the MAX could not meet certification requirements without MCAS (or other major changes)- that is a basic fact and not been disputed. No other 737 has MCAS that is a unique feature.

MCAS version 1 had different training requirements as it had a lot of authority and travel (far great was required than design plans) - but it did meet certification requirements with this authority.

MCAS version 2 has a large number of cut out features and is limited to a once of small movement. This puts the question as to have now can it still meet the certification requirements? My guess is it technically can depending on how grey you wish to read the data.

So my opinion is that it is not only possible, but very likely that the MAX will operate in the zone that fails certification limits. Reason is it either will not engage when "required", not input enough travel or be accidentally shut down prematurely.

I would expect that it be appropriate to have simulator training that included the actual stick forces encountered when MCAS did not active or only partially activated - my reasons for this is that this lack of feel is not evident in the previous aircraft and given MCAS involvement will be reduced, there is a greater possibility pilots will be exposed to this insufficient feel that does not meet certification levels.

Most people would find it reasonable to expect a pilot to have experienced flight conditions in the area outside the certification limits, if it is reasonably probable that the aircraft will be in this condition. With the proposed changes to MCAS there are now many conditions that will stop it from operating or only give partial operation, so a far greater possibility of flight outside the certified limit.

One would also assume it very handy to experience the MCAS experience just after takeoff operating normally, then again when it fails to disengage and turns into a runaway.

Might help to get the high AOA on a flapless landing.

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Old 23rd Apr 2019, 03:57
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Some decades ago I spent several sessions in a Viscount simulator (with a variety of abilities in the other seat) run by a serial killer who diligently added failures until a simulated smoking hole was commonly produced. You learned prioritization or got snuffed.

These days it seems simulator time is too expensive for crews to really get to know the airplane.

And now we see Boeing trying to put out a model that earlier model crew can step into without any simulator time.

I am reminded of the time as a 12 year old on my bike racing another kid downhill on a suburban street. Kids were playing jump rope on the other side. Half the street was clear. No problem. Then a kid began running across our side of the street. He'd be across the street by the time we got there. No problem. Then the kid stopped when he saw us. Lots of room between him and the curb. No problem.

Then the kid started running again when I was maybe ten feet away

It turned out he had a history of getting hit by bikes and the odd car.

The start / stop cycles of MCAS remind me of this kid. The crews got painted into a corner. Stick shaker and airspeed disagree distracted them from the real problem until it was too late. It definitely didn't help that the underfloor trim cutout switch no longer blocked automatic trim.

There's still an open question on the ergonomics of the control wheel trim switches when the stick shaker is operating. I suspect that the electrical contact has to be maintained for a minimum period (perhaps sub-second) for the relay to begin driving the trim motor. How much pressure is required to sustain the electric contact when stick shaker is operating?
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Old 23rd Apr 2019, 08:28
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FullWings,

Never a 737 pilot and now long out of date. But I believe your post sums up the problem pretty accurately. How many of us would have diagnosed the problem correctly in the time available?
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Old 23rd Apr 2019, 11:33
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RatherBeFlying #2447

There's still an open question on the ergonomics of the control wheel trim switches when the stick shaker is operating. I suspect that the electrical contact has to be maintained for a minimum period (perhaps sub-second) for the relay to begin driving the trim motor. How much pressure is required to sustain the electric contact when stick shaker is operating?
Quite. Could I be boring and again point to the switch 'noise' just on the centreline of the graph. I've always felt it might say far more than is being allotted to it in our discussions but have no knowledge of this graph's validity.
Lionair Upper: manual trim middle: automatic trim
is a tad confusing but blue surely must be thumb switch inputs. If so, where did this microscopic data come from?

It's from spornrad # 4076


Ethiopian airliner down in Africa
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Old 23rd Apr 2019, 12:34
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Trim Wheel

came across this thread, relevant quote from it below. Obviously no way of knowing if genuine or not, but given what else has been posted on the difficulty of operating the manual trim wheel, it does sound plausible.


Shutdown caused Boeing crash. - Page 4 - International Skeptics Forum

Quote...

"I agree it's a flawed design. And I used to work there. I'm glad I don't now.

Regarding the trim wheels: When the NG was being introduced, I happened to be the Lead Engineer in charge of them and a whole lot of other stuff. There were some issues. The new display system created a pinch point between the dash and the wheel. We had to make the wheel smaller. And the new trim motor resulted in the wheel, which is directly connected to the stabilizer by a long cable, springing back when electric trim was used. It was an undamped mass on the end of a spring. We had to add a damper.
Result: Depending on the flight conditions, the force to manually trim can be extremely high. We set up a test rig and a very fit female pilot could barely move it.
As I said, I'm glad I'm no longer there."

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