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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 13th Mar 2019, 00:12
  #861 (permalink)  
 
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EASA became crazy

Originally Posted by LookingForAJob
I openly admit that I am no fan of the way in which EASA works - being overly reliant on rules and law with sometimes peculiar interpretations of that law - but it's strange to see, following rather than leading, its member States' CAAs, that it chooses to issue an AD which appears to fail to meet the legal requirements set out in Commission Regulation No 748/2012 for such documents.

Of course, if evidence shows that the safety level of this aircraft may be compromised I would hope that this would be declared, even if the details of that evidence are not provided. Overall, as others have suggested, this is a situation which is being driven by public opinion (which may include a good many pilots). Those who claim that it's driven by safety I fear may be deluding themselves. I'm not suggesting that it is wrong that these aircraft are being grounded, but actions are hardly being led by the agencies that are established to protect the travelling and innocent ground-dwelling public.
I agree. A grounding is certainly justified but using an AD for this is ridicolous. Moreover a number of B38M returning flights, that were airborne and at cruising levels, had to divert because of a stupid AD deadline at 19 UTC, leaving hundreds of European citizens somewhere abroad. EASA is a political nonsense tool as much as FAA became a commercial tool.
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Old 13th Mar 2019, 00:13
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Originally Posted by Charley
The FZ8xxx callsigns are empty (non-revenue) positioning flights. Both FlightStats and each airports websites confirmed the flights they should have been making were cancelled.

The flight out of Kiev though does have pax aboard. Wonder if it will be held short of the Bucharest or Sofia FIR/UIRs in the same was as the earlier QS flight was.
Bucuresti FIR to FZ730: Thou shall not pass.
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Old 13th Mar 2019, 00:15
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Originally Posted by FCeng84
Hans - your patience is amazing. You are correct about the relationship between 737MAX engines and need for MCAS. It has nothing to do with the thrust pitching moment!!!

There is a cert requirement that as AOA increases, the nose up pilot command required must not decrease. This is demonstrated at fixed thrust levels so there is no change in thrust pitching moment. The 737MAX issue here that gives rise to the need for MCAS is that as AOA increases the lift provided by the engine cowling that is so large and mounted so far forward of the wing causes a nose up pitching moment that results is a decrease in the column pull needed to maintain a steady positive AOA rate. That characteristic is not compliant with the requirements. MCAS comes active during this maneuver putting in nose down stabilizer that must be countered by the column. The net effect of engine cowling lift and MCAS nose down stabilizer as AOA increases is that the column needed to complete the maneuver does not decrease part way through the range of AOA for which characteristics must be demonstrated. 737MAX without MCAS fails the cert demo. 737MAX with MCAS passes the cert demo.
That is a very clear explanation - the most clear of anything I've read. Well done FCeng84.

What is interesting, then, is that MCAS activates without column input. If the purpose of MCAS is to essentially negate the lift of the engine cowling - which causes lift when AOA increases - then one would think the system would only activate as a result of column pull. In other words - the system is to create a consistent feel on the column - so why have it activate absent deliberate pull on the column? Why doesn't the system require both an increase in AOA and a pull on the column before it trims AND?
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Old 13th Mar 2019, 00:21
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The new Boeing is NOT the same as “old” Boeing. Old Boeing was an engineering company that built solid, reliable aircraft. Everything was done in house by American. New Boeing are bean counters and exporters of the cheapest widget to put between parts A and B. Think of old Boeing as Toyota. Engineering tells accounting what they need. Accounting figures how to make it work. New Boeing is accounting telling engineering what they need. They’re really not even the same company. The only similarities are that they both make airplanes. A perfect example. Boeing has representatives that accompany new aircraft orders. This people used to be liaisons that would smooth things over between mx, finance, safety, training and even sales. They had a company credit card and a lot of freedom and leeway. These same individuals now have their dinner receipts audited by an accountant to make sure that they didn’t order steak or lobster. Boeing has become a good barometer of Merika. No leadership, petty micromanaging and mediocrity.
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Old 13th Mar 2019, 00:24
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It seems the issue is not so much with MCAS as with the engine location relative to the wing.

MCAS reads like a half baked solution to a problem that should not be there in the first place.

If so, this is not the kind of design philosophy I associate with Boeing.

Diverting aircraft in the cruise because they have a problem taking off doesn’t sound like a terribly rational response either.
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Old 13th Mar 2019, 00:30
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737 Pitch Trim Related Switches

There seems to be some confusion with regard to 737 switches associated with pitch trim. That is very understandable as there are quite a few and it is easy to get them mixed up. Let me take a run at an overview:

Wheel mounted pilot electric pitch trim switches - two pairs of side-by-side switches with one pair mounted on each of the two control wheels for thumb activation
- Spring centered with contacts in both the fwd/push and aft/pull directions.
- Fwd/push commands airplane nose down stabilizer motion via electric stab trim motor
- Aft/pull commands airplane nose up stabilizer motion via electric stab trim motor
- Stabilizer motion requires activation of both switches found on the same wheel in the same direction. This design avoids unintended stabilizer motion for a failure of one switch or a short in one of the two associated wiring circuits.

Column cutout switches - one each in push and pull directions
- Not visible to the crew, hidden within the column mechanism
- One is activated for column push beyond a certain threshold, the other for column pull beyond a certain threshold
- These prevent pilot electric pitch trim in the direction opposite the column (nose up trim inhibited when column is pushed for example)
- These also serve to stop STS stabilizer commands in the direction opposite the column
- These do not stop MCAS stabilizer commands in either direction

Column cutout override switch (not sure of the location(s) or how many there are)
- When in the override position, this causes the column cutout switches to be bypassed allowing electric stabilizer trim in either direction regardless of column position
- These do not have any role with respect to normal operation
- These have no function with respect to MCAS as MCAS stabilizer commands are not subject to the column cutout functionality that is overridden here

Stabilizer cutout switches - on pair of guarded switches located on the lower, aft end of the aislestand
- These are the switches that when activated remove electric power to the stabilizer trim motor and thus disable all electric trim (pilot wheel switches, STS, MCAS, autopilot offload)
- These are the switches that have been most discussed in this thread
- These are the switches that the runaway stabilizer procedure calls for toggling to stop errant stab motion

I hope this helps.

Last edited by FCeng84; 13th Mar 2019 at 04:49. Reason: formatting for easier reading
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Old 13th Mar 2019, 00:37
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Originally Posted by 4runner
The new Boeing is NOT the same as “old” Boeing. Old Boeing was an engineering company that built solid, reliable aircraft. Everything was done in house by American. New Boeing are bean counters and exporters of the cheapest widget to put between parts A and B. Think of old Boeing as Toyota. Engineering tells accounting what they need. Accounting figures how to make it work. New Boeing is accounting telling engineering what they need. They’re really not even the same company. The only similarities are that they both make airplanes. A perfect example. Boeing has representatives that accompany new aircraft orders. This people used to be liaisons that would smooth things over between mx, finance, safety, training and even sales. They had a company credit card and a lot of freedom and leeway. These same individuals now have their dinner receipts audited by an accountant to make sure that they didn’t order steak or lobster. Boeing has become a good barometer of Merika. No leadership, petty micromanaging and mediocrity.
Yes, and this happened when they acquired McDonnell-Douglas and brought-in most of MD's executives to run things.
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Old 13th Mar 2019, 00:38
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Originally Posted by WillFlyForCheese
That is a very clear explanation - the most clear of anything I've read. Well done FCeng84.

What is interesting, then, is that MCAS activates without column input. If the purpose of MCAS is to essentially negate the lift of the engine cowling - which causes lift when AOA increases - then one would think the system would only activate as a result of column pull. In other words - the system is to create a consistent feel on the column - so why have it activate absent deliberate pull on the column? Why doesn't the system require both an increase in AOA and a pull on the column before it trims AND?
I'm glad to be able to provide some clarity. MCAS operates as a function of AOA with no regard to column position. As you state, "MCAS is to essentially negate lift (more specifically pitching moment) of the engine cowling". By cancelling out the nose up pitching moment from the cowling with increased AOA, MCAS smooths out the overall Cm-alpha (pitching moment vs. AOA) characteristic of the airplane so that column required to command a maneuver to high AOA does not decrease along the way.
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Old 13th Mar 2019, 00:43
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Originally Posted by Luc Lion
That's also my understanding : "control column actuated trim cutout switches" have no effect on MCAS while the "stabilizer trim cutout switches" on the control stand do stop MCAS.
(I understand that it's the AUTOPILOT Cutout switch that does the job).
But I am not a B737 pilot, so I am happy to stand corrected.
There is no control column cutout switches, but the trim control on the control column will stop and override MCAS for 5 sec. There are trim cutout switches on the pedestal that stop MCAS permanently.
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Old 13th Mar 2019, 00:45
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Originally Posted by FCeng84
I'm glad to be able to provide some clarity. MCAS operates as a function of AOA with no regard to column position. As you state, "MCAS is to essentially negate lift (more specifically pitching moment) of the engine cowling". By cancelling out the nose up pitching moment from the cowling with increased AOA, MCAS smooths out the overall Cm-alpha (pitching moment vs. AOA) characteristic of the airplane so that column required to command a maneuver to high AOA does not decrease along the way.
Understood. But if the (sole?) purpose is to "smooth out of the overall Cm-alpha characteristic of the airplane so that column required to command a maneuver to high AOA does not decrease along the way", then why does it trim AND with no column input at all? It appears to be a design to have the primary (or only?) effect of mimicking a condition on the column. if so - why have it operate in the absence of a pull on the column?

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Old 13th Mar 2019, 00:47
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Kiwis become the latest to suspend the Max - affecting a small number of Fiji Airways flights.
Interesting to observe the rest of the world effectively ignoring the FAA - perception versus known facts.
What a monumental debacle for Boeing.
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Old 13th Mar 2019, 00:50
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Originally Posted by Luc Lion
Airbubba, the "control column actuated trim cutout switches" are switches located in the control column that stop an electric trim movement when the control column requests an elevator deflection contradicting the trim movement. This is the immediate response to a stuck electric trim button before using the STAB TRIM MAIN ELECT cutout switch on the control stand.
Thanks, seems like there was something like that on the 727.

Originally Posted by FCeng84
There seems to be some confusion with regard to 737 switches associated with pitch trim. That is very understandable as there are quite a few and it is easy to get them mixed up. Let me take a run at an overview:

I hope this helps.
It does, thanks!
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Old 13th Mar 2019, 00:56
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Originally Posted by hans brinker
There is no control column cutout switches, ....
There are such switches, although they are hidden in the column.
See FCOM 9.20 "Controls - System Description" - "Stabilizer Trim".
Read also the function of the "Stabilizer Trim Override Switch"
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Old 13th Mar 2019, 01:01
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Originally Posted by Icarus2001
Oh gawd here we go again, get rid of the pilots.

Q. Which form of transport is easiest to automate, rate in order?

Aircraft, trains, ships.

Now when you have thought about that ask why are there still train drivers.

FFS
Train Drivers aren't required. To run the London Underground Central Line at max capacity, drivers don't touch the controls. They run automatically. Drivers are there because the unions require them not because it's safer.
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Old 13th Mar 2019, 01:02
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Originally Posted by A0283
Just thinking ... not judging, just wondering... so nice to be naive sometimes...

Historically Boeing has always been quite clear and open about serious issues.
And thereby one, certainly not the only, of the companies and organizations that has made aerospace as safe as it is.
That reputation certainly got dented recently during the 787 program. Some are happy with it now, others still have professional reservations.
The Lion Air case caused other dents. The suggestion is that Boeing has been withholding information. They certainly have not been open.
Boeing did not open up about the design philosophy of MCAS, the design itself, the way in which it was tested, and certified, and documented and trained, etcetera.
This Ethiopian case magnifies this unusual lack of openness.
Simply said modern certification (not only in aerospace) puts a lot of proof and testing on the desk of the manufacturer rather than on the desk of the certification authority.
You wonder what was written and agreed about what kind of 'publication obligation of the certification process and results' this shift has caused.
To this day informed people know little of MCAS. Certainly not enough for peace of mind.

So what could Boeing do to start limiting the damage that is being done and still increasing rapidly. So rapid that it may dent the industry.
What would personally appeal to me is the chief engineer of the program giving an explanation about MCAS in general. So a very competent technical person with 'signature responsibility', don't think anyone else would do anymore.
This does not disrupt the Ethiopian investigation because we don't know if MCAS is even involved. So there would be no excuse not doing it citing this one, or for that matter even the Lion investigation. It is just basic historic knowledge and intent you might say.

You get the feeling that if they don't volunteer this now that at some stage they will be ordered to do this and add a number of other people and disciplines.

Chicago has a problem.

Thanks A0283
You've about summed up my feeelings, but better and more succinctly than ever I could have.
I'd just add that the certification authorities (In other industries as well) have a historical habit or even mandated practice of not getting into a dialogue of 'The how' of implementation for meeting design or behaviour requirements
In this case, once it was obvious to both parties that a 'workaround' was going to be necessary to handle native behaviour that flouted a requirement - for make no mistake, this is a 'workaround' just as the old shaker/stick pusher pair were for T-tailed aircraft - then I'd want a dialogue to begin if I worked in AW at Boeing or the Certificating Authority... but not about 'just meeting the requirement', but looking at every aspect of its necessity in the first place, from stretch design right through to the exact relevance of stick force per G or stick force per alpha - in each particular flight domain.
With CFD I imagine Boeing saw the pitching moment - alpha curves rearing their head very early on, at the project stage.. at least I hope so!
I can picture flies on the wall in certain offices back then raising their eyebrows in a knowing way as to me, it sounds awfully like they might have been handed to the S&C boys/girls for a solution far too early
I hope that makes sense...

Last edited by HarryMann; 13th Mar 2019 at 01:15.
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Old 13th Mar 2019, 01:03
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How many people are looking over the shoulder of the FDR/CVR analyst right now?
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Old 13th Mar 2019, 01:17
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@FCeng84 - I really appreciate your effort to help clarify a number of issues. Hope Boeing will elaborate on this in the end ;-)

For me there is a difference between an "AoA increase" and a "positive AoA rate". Hope you can clarify that during your further explanations.

I was wondering if you were talking about "positional feedback" with MCAS or "force feedback" or both. In another explanation you exclude the "positional".

If you use the cutout and remove the power you disable MCAS ... which would put you outside the 'normal' certified envelope... do I read that correctly? ... With MCAS aimed at the NNC part of things, using the cutout appears to push you in yet again an other area, and outside certification?... Or is that a wrong interpretation?
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Old 13th Mar 2019, 01:24
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Pretty sure the relevant curve here, would be Stick Force ~ Alpha not a derivative (e.g.Alpha rate)
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Old 13th Mar 2019, 01:26
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Originally Posted by FCeng84
I'm glad to be able to provide some clarity. MCAS operates as a function of AOA with no regard to column position. As you state, "MCAS is to essentially negate lift (more specifically pitching moment) of the engine cowling". By cancelling out the nose up pitching moment from the cowling with increased AOA, MCAS smooths out the overall Cm-alpha (pitching moment vs. AOA) characteristic of the airplane so that column required to command a maneuver to high AOA does not decrease along the way.
But if you can achieve the high AOA state on autopilot, it doesn't need MCAS and will just put the elevator and trim where it needs to be to get the attitude it wants, just like humans should be able to do. Shut off MCAS and tell pilots to be aware of stick lightening in the, as Boeing says, envelope that you won't likely encounter.
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Old 13th Mar 2019, 01:30
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@Harrymann
I'd want a dialogue to begin if I worked in AW at Boeing or the Certificating Authority, but not about 'just meeting the requirement', but looking at every aspect of its necessity in the first place, from stretch design right through to the exact relevance of stick force per G or stick force per alpha - in each particular flight domain ... at least I hope so! .... I hope that makes sense...
Ooooh yes ... we hope together ... it makes sense to me yes ...

And on your
Pretty sure the relevant curve here, would be Stick Force ~ Alpha not a derivative (e.g.Alpha rate)
I would join your question ... perhaps FCeng84 can answer that.

Thanks gents.
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