Ethiopian airliner down in Africa
Join Date: Dec 2018
Location: Nyc
Posts: 49
Originally Posted by Kerosene
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.
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.
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?
Join Date: Sep 1999
Posts: 542
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.
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.
Join Date: Apr 2015
Location: Under the radar, over the rainbow
Posts: 707
Originally Posted by Rananim
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.
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.
Join Date: Jun 2007
Location: NC, USA
Age: 76
Posts: 92
Originally Posted by Rananim
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.
Join Date: Mar 2019
Location: Seattle
Posts: 1
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.
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.
Join Date: Sep 1999
Posts: 542
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?
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.
Join Date: Jun 2007
Location: NC, USA
Age: 76
Posts: 92
Originally Posted by Rananim
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.
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.
Join Date: Dec 2018
Location: Nyc
Posts: 49
Originally Posted by BobM2
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.
Wrong focus.
Last edited by Turbine70; 22nd Mar 2019 at 05:21.
Join Date: May 2008
Location: us
Posts: 16
Originally Posted by BobM2
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.
Join Date: Nov 2005
Location: London
Posts: 16
Originally Posted by Rananim
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.
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.
Join Date: Jul 2013
Location: Norway
Age: 54
Posts: 135
Originally Posted by BrandonSoMD
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.
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.
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.
Join Date: Feb 2016
Location: S.E.Asia
Posts: 1,807
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.
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
Join Date: Sep 2017
Location: Europe
Posts: 1,679
Minimum flap retraction altitude for B737 is 400 ft so possible MCAS-activation at low altitude.
- High AOA (sensor fault) is the first condition
- Manual flight (is the second condition)
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.
Join Date: Feb 2010
Location: Thailand
Posts: 455
Originally Posted by dinbangkok
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)?
Gender Faculty Specialist
Join Date: Mar 2002
Location: Stop being so stupid, it's my turn
Posts: 1,719
Originally Posted by BobM2
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?
Join Date: Feb 2009
Location: Seattle
Posts: 379
Originally Posted by dinbangkok
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)?
Join Date: Jul 2013
Location: Norway
Age: 54
Posts: 135
Chilling reading by Bjørn at Leeham explaining that the elevator blow back problem - which our excellent Fceng84 explained in details a few pages ago - might have been a significant contributory cause for both of these crashes.
Bjørn at Leeham
I know all about blowback problems of elevators. It was the most dangerous shortcoming of the fighter I flew, the SAAB J35 Draken. Even more dangerous than its famous “Super stall”, a Pugachev Cobra like deep stall behavior the aircraft would only exit from if you “rock it out” of the stall (more on this some other time). While “Super stall” is scary, Blowback is deadly.
What could have been done?
The only remedy to the blowback induced dive would have been a full nose up trim application, for a long time (throttles to idle and air brake would also have helped). But the reaction to trim is slow and the aircraft was now heading for earth. The reflex is not to trim but to pull for all there is, by both pilots, you have seconds to stop the dive. It didn’t help. If this is confirmed as the scenario for the end of both JT610 and ET302 I wonder why the danger of flying to fast at low altitude, while sorting out a raiding MCAS, was not communicated when the MCAS Airworthiness Directive was released after the JT610 crash. MCAS forcing the stabilator to full nose down should not have doomed JT610 or ET302. Their applied speed margins did. The JT610 crew knew nothing about MCAS and a potential blowback problem. The ET302 crew knew about the MCAS problem but not about the danger of flying to fast while sorting MCAS.
I have checked with longtime pilots of the 737. They have not heard of a Blowback problem when flying at elevated speeds at low altitude.
And before MCAS there was no reason to, it was beyond normal flying practice. But the JT610 investigators saw what can happen when you run into the MCAS rodeo. Why didn’t they warn to keep speeds within normal speed range?
What could have been done?
The only remedy to the blowback induced dive would have been a full nose up trim application, for a long time (throttles to idle and air brake would also have helped). But the reaction to trim is slow and the aircraft was now heading for earth. The reflex is not to trim but to pull for all there is, by both pilots, you have seconds to stop the dive. It didn’t help. If this is confirmed as the scenario for the end of both JT610 and ET302 I wonder why the danger of flying to fast at low altitude, while sorting out a raiding MCAS, was not communicated when the MCAS Airworthiness Directive was released after the JT610 crash. MCAS forcing the stabilator to full nose down should not have doomed JT610 or ET302. Their applied speed margins did. The JT610 crew knew nothing about MCAS and a potential blowback problem. The ET302 crew knew about the MCAS problem but not about the danger of flying to fast while sorting MCAS.
I have checked with longtime pilots of the 737. They have not heard of a Blowback problem when flying at elevated speeds at low altitude.
And before MCAS there was no reason to, it was beyond normal flying practice. But the JT610 investigators saw what can happen when you run into the MCAS rodeo. Why didn’t they warn to keep speeds within normal speed range?
Last edited by SteinarN; 22nd Mar 2019 at 08:52.
Join Date: Mar 2006
Location: England
Posts: 917
Originally Posted by Chesty Morgan
Do we know when the fault in the AoA system occured?
But where did the fault occur, and why did the AoA value ‘fail’ up .
Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed
Join Date: Jan 2008
Location: US/EU
Posts: 694
Ethiopian pilots raised safety concerns years before fatal crash, records show
Washington Post reporting on FAA complaints years ago about allegedly flawed training programs and poor safety procedures at Ethiopian Airlines.
Ethiopian pilots raised safety concerns years before fatal crash, records show
Ethiopian pilots raised safety concerns years before fatal crash, records show
One pilot said the airline didn’t “have the infrastructure” to support the fleet of Boeing and Airbus jets it ordered, and alleged the airline had a “fear-based” management culture in which “safety is being sacrificed for expansion and profit margin.” The pilot also accused the airline of failing to update pilot manuals and leaving out certain checklists designed to help pilots respond to “non-normal” situations. Another pilot criticized Ethiopian regulators for maintaining lax standards with respect to crew flight and rest time. The FAA’s data does not identify the pilots by name.
