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Ethiopian airliner down in Africa

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Ethiopian airliner down in Africa

Old 22nd Mar 2019, 02:23
  #2301 (permalink)  
 
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Originally Posted by edmundronald View Post
Gums,


But there is one interesting question though which is why those who survived such MCAS incidents prior to the Lion Air crash did not document them and raise a stink. Was it because they thought they had made an operational mistake?

Edmund
Nobody has reported a MCAS event prior to Lion Air. Where did you get such a story?
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Old 22nd Mar 2019, 02:37
  #2302 (permalink)  
 
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Originally Posted by PaxBritannica View Post
I can't see that a quick fix for MCAS is going to reassure the travelling public, ie me. If MCAS was a bodge, how many other bodges were found acceptable? If this was the only place in the design where engineers were asked to take a 'small' risk, I suspect whispers would have gotten around long before the plane flew. Therefore, it's likely that it was just one of many other design 'solutions' where the idea of tolerable risk was normalised.

No software patch will fix systemic management hubris.
Really? Do you think a crew will board then? As has been posted in many topics, most pax have no clue what aircraft type they are flying on. They fly by the dollar. If the crew boards, so will the pax.
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Old 22nd Mar 2019, 02:38
  #2303 (permalink)  
 
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Originally Posted by HarryMann View Post
Yes, though that Bob is why you as a manufacturer should Tell them what the heck you've done to the stab trim circuit... which it sounds ominously like was poorly or undocumented. Nor we are told, was much if anything made of it as a 'difference' feature in any training (?).
You're right, Harry, Boeing should have told the crews. "If you're out doing flaps up stalls in your MAX, you will get an intervention from MCAS. Also, if you get a continuous stick shaker on take off rotation & are stupid enough to accelerate, clean up the flaps, & try to continue the flight with the stick shaker, you MAY get a repeated intervention from MCAS 'cause it thinks the airplane is stalling".
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Old 22nd Mar 2019, 02:50
  #2304 (permalink)  
 
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Originally Posted by Kerosene View Post
Suppose MCAS becomes unavailable during flight e.g. due to Stab trim deactivation. The MAX’s flight characteristics in approach to stall scenarios proved not certifiable without MCAS as a fix. I’d like to ask the ones in the know (FcEng and others) how critical the loss of MCAS in flight would be in real life. For example, encountering a flight upset with approach to stall, how easily can this be recovered without MCAS? How was the risk of such an event assessed? Was it demonstrated in test flights? Why was it determined there would be no need to train flight crews on the simulator for the changed handling outside the certification parameters?

In a previous post I assumed such a scenario to be critcal, but perhaps it isn’t? Thanking you in advance for shedding light on this issue.
I have asked this before but in a different way.

Is there any recorded valid activation of MCAS?

Is it even possible that we have a tick box implementation for certification purposes that has achieved nothing other than promote accidents?
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Old 22nd Mar 2019, 03:14
  #2305 (permalink)  
 
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But, how do you design for an airline that flies an aircraft for three days with unreliable airspeed, maintenance that then compounds the problem with a bad AOA installation, & flight crews that still try to complete the flight with a continuous stick shaker? We don't know yet about Ethiopian, but if it was the same malfunction after all the warnings & publicity worldwide from Lion Air, then that is the height of incompetence.
Hard not to concur.A lot of Boeing bashing going on here.
Life isnt black and white like that.
Its not all Boeings fault.Its not all the pilots fault for not cutting out those 2 switches.
I think it was mentioned by FCENG84 that designers design safe
in the knowledge that airline pilots have a minimum standard
of airmanship and that line engineers know their job and
follow the MEL.Lionair's reputation is not a good one.
And frankly speaking,neither is Ethiopian.So its a difficult.situation
to analyse.Do I think either accident could have
happened in Southwest?No,I do not.

Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.They decided
that this failure scenario was one step shy of "catastrophic".
and that a crew would cope.Maybe they under-rated the
effect of the stick shaker on the pilots ability to react in the
correct manner.Those shakers can scramble your brain
and degrade reaction time and pilot response.They can cause
startle factor which I know is sometimes derided as an
excuse for poor airmanship.But it can happen and it can affect
quite a few crews.
Whats not okay is if they deliberately downgraded it below
"catastrophic" to rush certification and avoid further analysis
and fine-tuning of the design.If they genuinely miscalculated
the effect of unwanted MCAS at low altitude and so designed
it to work off one sensor only,then its just an error.
However,if they downgraded it below "catastrophic" to rush
certification then it was a cynical decision and thats negligence.
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Old 22nd Mar 2019, 03:31
  #2306 (permalink)  
 
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Originally Posted by Rananim View Post
Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.
It's not obvious to me that Boeing considered those possible consequences and it's not at all clear that any or every failure of an AoA sensor -- or another fault in raw data or processing upon which MCAS activation is dependent -- would result in identical systems behaviors, always in a single phase of flight. In fact, with all due respect, I seriously doubt whether either of those assumptions is defensible.
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Old 22nd Mar 2019, 03:34
  #2307 (permalink)  
 
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Originally Posted by Rananim View Post

Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.
Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
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Old 22nd Mar 2019, 03:37
  #2308 (permalink)  
 
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SLF here, but with a background in experimental physics dealing with personnel and equipment safety in large-scale, hazardous experimental situations.

Assuming that both 737 MAX crashes were the result (in large part) of faulty AOA probe data, then we already know, from sad experimental evidence, that relying on one probe is unacceptable. With 2 hull losses in N (? - not a terribly large number) flights of this aircraft, the reliability statistics are hardly at the flight-safety-critical level.

Having an "AOA disagree" warning or AOA readouts for pilots is not necessarily going to help. I suggest that as a minimum, with only two AOA probes (and that should be the minimum number), that MCAS should shut itself down in an AOA disagree situation (with notification to the pilots). The principle here is "primum non nocere". The aircraft is not going to have an upset just because MCAS is not there on these rare occasions.

Furthermore, if AOA data is going to be used in this way (possibly killing people if it is wrong), further sanity checks should be applied to the probe data (e.g., AOA pre-rotation on take-off, consistency with inertial and other air data, whatever).

MCAS as currently implemented seems like a horrid kluge to a non-pilot, but I'm inclined to believe, from what I've read here, that with better engineering (and not too drastic a change) the 737 MAX could be restored to safe service.
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Old 22nd Mar 2019, 03:54
  #2309 (permalink)  
 
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Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
BobM2
Yes you are of course correct but that doesnt alter the fact that crews who
elect to retract flaps and climb to MSA as per SOP would face
all 3 concurrently with flaps up.You assert that no crew would retract
flaps and climb to MSA to perform checklists and I hope you
are right.I agree with not retracting flaps and just landing from circuit height
but I dont assume thats what all crews would do,especially
if unfamiliar with MCAS.
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Old 22nd Mar 2019, 04:22
  #2310 (permalink)  
 
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Originally Posted by Rananim View Post
BobM2
Yes you are of course correct but that doesnt alter the fact that crews who
elect to retract flaps and climb to MSA as per SOP would face
all 3 concurrently with flaps up.You assert that no crew would retract
flaps and climb to MSA to perform checklists and I hope you
are right.I agree with not retracting flaps and just landing from circuit height
but I dont assume thats what all crews would do,especially
if unfamiliar with MCAS.
You are right. At least 2 crews, maybe 3 did accelerate, clean up, & got into a worse mess. These occurrences were all in good weather with long runways immediately available. There was no need to climb to an MSA, but you could if you felt a need to troubleshoot or read checklists. The main thing is don't change the take-off configuration as long as the airplane is flying normally. You are not paid or qualified to be a test pilot, especially with passengers on board.
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Old 22nd Mar 2019, 05:02
  #2311 (permalink)  
 
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Originally Posted by BobM2 View Post
You are right. At least 2 crews, maybe 3 did accelerate, clean up, & got into a worse mess. These occurrences were all in good weather with long runways immediately available. There was no need to climb to an MSA, but you could if you felt a need to troubleshoot or read checklists. The main thing is don't change the take-off configuration as long as the airplane is flying normally. You are not paid or qualified to be a test pilot, especially with passengers on board.
What we can only conclude as a design flaw requires recurring RTO above Vr?

Wrong focus.

Last edited by Turbine70; 22nd Mar 2019 at 05:21.
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Old 22nd Mar 2019, 05:14
  #2312 (permalink)  
 
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Originally Posted by BobM2 View Post
You are right. At least 2 crews, maybe 3 did accelerate, clean up, & got into a worse mess. These occurrences were all in good weather with long runways immediately available. There was no need to climb to an MSA, but you could if you felt a need to troubleshoot or read checklists. The main thing is don't change the take-off configuration as long as the airplane is flying normally. You are not paid or qualified to be a test pilot, especially with passengers on board.
In regards to cleaning up and accelerating, if one is dealing with stall indications and unreliable airspeed on climb out, the natural tendency would be to ensure you've got sufficient airspeed. Speed is life, in most cases. It would appear, unfortunately, that this was not one of those cases.
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Old 22nd Mar 2019, 06:11
  #2313 (permalink)  
 
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Originally Posted by Rananim View Post
Hard not to concur.A lot of Boeing bashing going on here.
Life isnt black and white like that.
Its not all Boeings fault.Its not all the pilots fault for not cutting out those 2 switches.
I think it was mentioned by FCENG84 that designers design safe
in the knowledge that airline pilots have a minimum standard
of airmanship and that line engineers know their job and
follow the MEL.Lionair's reputation is not a good one.
And frankly speaking,neither is Ethiopian.So its a difficult.situation
to analyse.Do I think either accident could have
happened in Southwest?No,I do not.

Boeing obviously considered the consequences of a faulty
sensor and its effect on MCAS prior certification.They knew
this would occur at flap retraction at low altitude and would result
in stick shaker,unreliable airspeed and considerable and
unexpected nose down trim all at once.They decided
that this failure scenario was one step shy of "catastrophic".
and that a crew would cope.Maybe they under-rated the
effect of the stick shaker on the pilots ability to react in the
correct manner.Those shakers can scramble your brain
and degrade reaction time and pilot response.They can cause
startle factor which I know is sometimes derided as an
excuse for poor airmanship.But it can happen and it can affect
quite a few crews.
Whats not okay is if they deliberately downgraded it below
"catastrophic" to rush certification and avoid further analysis
and fine-tuning of the design.If they genuinely miscalculated
the effect of unwanted MCAS at low altitude and so designed
it to work off one sensor only,then its just an error.
However,if they downgraded it below "catastrophic" to rush
certification then it was a cynical decision and thats negligence.
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
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Old 22nd Mar 2019, 06:20
  #2314 (permalink)  
 
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Originally Posted by BrandonSoMD View Post
Well, for most pilots in a commercial setting, AOA by itself means nothing.

For a military or airshow pilot who maneuvers to rather excessive AOAs regularly, or uses AOA as a primary reference for carrier landing, it makes a lot of sense to show some flavor of AOA. For example, nearly all Navy carrier aircraft are standardized to show something like15 units AOA in a properly configured approach, and something around 30 units AOA at stall. But there is no consistent units-to-degrees mapping, because the pilot doesn't care about absolutes; he just wants to know how close he is to some practical limit.

But for commercial pilots, AOA is relatively meaningless. In fact, it generally introduces needless concerns. What AOA is correct in a given setting: that's hugely dependent on a ton of factors. Which one (left or right) are you showing? How soon during takeoff roll should they come alive; with zero airspeed they can be at crazy values without any concern. They can be slightly different for various valid aerodynamic reasons (sideslip or roll rate). The only time you really care about AOA is when the two (or three or whatever) sensors dramatically disagree, or when they remain at excessive (very low or very high) values when they should not. That's all fairly easy to automatically check, if the FMC is programmed to do so.

WHY the FMC wasn't programmed to do so is a useful discussion. But showing the AOA to most pilots won't make things any better or safer. Principle #1 of human interface: only show what is important.
Well, for most pilots, and in a normal flying mode you are correct. But we are talking about when somethings going haywire.When you are not sure what the aircraft is doing, you might not be sure if you actually are stalling, you might not be sure about your airspeed. And we could go one step further for the more competent pilots, you wonder why just ONE stick shaker has activated, you wonder what the heck is the reason for the stabilizer trimming like crazy all the time, you wonder what is the reason for the IA showing different values on the left vs right display, and possibly reasons for other fault messages/warnings.

In such a scenario a displayed value of the AoA would in my opinion be VERY helpfull for the pilots in order to figure out what is really going on with the aircraft and what it's performance is.

Last edited by SteinarN; 22nd Mar 2019 at 06:41.
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Old 22nd Mar 2019, 06:41
  #2315 (permalink)  
 
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Reuters latest on Boeing cancelled orders

JAKARTA (Reuters) - National carrier Garuda Indonesia has sent a letter to Boeing Co asking to cancel an order for 49 737 MAX 8 narrowbody jets, Garuda Chief Financial Officer Fuad Rizal said on Friday.

The airline could switch the order, valued at $6 billion at list prices, to other Boeing models, Rizal told Reuters. He said negotiations with Boeing were ongoing and Airbus SE jets were not under consideration.

Garuda is the first airline to publicly confirm plans to cancel an order for the troubled jets after the second crash of a 737 MAX 8, which killed 157 people in Ethiopia last week.

Indonesian rival Lion Air has been reconsidering its orders since one of its 737 MAX jets crashed in October.

Garuda CEO Ari Askhara told Reuters on Friday that customers had lost trust in the 737 MAX 8.

The airline has only one in its fleet at present.

“They have been relooking at their fleet plan anyway so this is an opportunity to make some changes that otherwise may be difficult to do,” CAPA Center for Aviation Chief Analyst Brendan Sobie said.

Askhara said last week it was possible it would cancel the order for 20 of the jets, with a final decision depending on what the U.S. Federal Aviation Administration does after the Ethiopian crash.

He told Reuters before the crash that the airline had decided to reduce the Boeing 737 MAX order from 49 by swapping some to widebody Boeing models.

Boeing declined to comment on customer discussions.


Last edited by Mike Flynn; 22nd Mar 2019 at 06:52. Reason: typo
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Old 22nd Mar 2019, 07:04
  #2316 (permalink)  
 
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Minimum flap retraction altitude for B737 is 400 ft so possible MCAS-activation at low altitude.
This.
  1. High AOA (sensor fault) is the first condition
  2. Manual flight (is the second condition)
Taught to clean up and find altitude, clear the MSA is what all pilots are taught to do.
Induce another failure, like an engine failure at V1, at 400' commence the drills, up go the flaps.

3. Flaps are up (Third condition is met)

MCAS activates. Now things get sporting. Quite possibly a procedure trained for by pilots worldwide was just complicated and made more difficult by doing what all pilots do with a sub system bought into the mix that has a single point of failure a solitary AOA sensor.
That is bad process.
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Old 22nd Mar 2019, 07:53
  #2317 (permalink)  
 
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Originally Posted by Mike Flynn View Post
Reuters latest on Boeing cancelled orders
Lion Air are very displeased with Boeing and they have another 187 to come.

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Old 22nd Mar 2019, 07:56
  #2318 (permalink)  
 
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Originally Posted by dinbangkok View Post
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
And then make alarms an "optional extra"!
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Old 22nd Mar 2019, 08:21
  #2319 (permalink)  
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Originally Posted by BobM2 View Post
Rananim, a faulty AOA that would activate MCAS would produce a continuous stick shaker at rotation, not on flap retract. Why would any right-thinking pilot ever attempt to retract flaps & continue the flight with an active stick shaker, even if unaware that MCAS exists?
Do we know when the fault in the AoA system occured?
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Old 22nd Mar 2019, 08:27
  #2320 (permalink)  
 
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Originally Posted by dinbangkok View Post
Regardless of whether you're a pilot or not, surely the question that needs to be answered is simple: How is it remotely OK for Boeing (or any other manufacturer), to sell a passenger aircraft that needs software to correct an aerodynamic imbalance in the design of the aircraft (prone to pitching up)?
There are several exhibits of this out in the market: 777, 787, and soon to come 777X. These models all have full FBW systems that enable the bare airframe to have aerodynamic characteristics that with out any control system functionality at all would not be certifiable. The motivation is that these models have been able to design in improved performance because they have been able to take advantage of control system functions to yield certifiable handling qualities. The key, of course, is that the availability and reliability including any failure mode effects must be acceptable. Certification requirements cover all aspects of this.
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