Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed
From the above article: "The FAA last week said it planned to mandate changes in the system to make it less likely to activate when there is no emergency."
Hardly reassuring - hopefully EASA and others will look at the 4000+ still to be produced (if customers don't bale out) and demand a fix that isn't a bodge on top of a bodge.
Hardly reassuring - hopefully EASA and others will look at the 4000+ still to be produced (if customers don't bale out) and demand a fix that isn't a bodge on top of a bodge.
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From the above article: "The FAA last week said it planned to mandate changes in the system to make it less likely to activate when there is no emergency."
Hardly reassuring - hopefully EASA and others will look at the 4000+ still to be produced (if customers don't bale out) and demand a fix that isn't a bodge on top of a bodge.
Hardly reassuring - hopefully EASA and others will look at the 4000+ still to be produced (if customers don't bale out) and demand a fix that isn't a bodge on top of a bodge.
Sure, but my point is that the perspective for an aircraft is only beginning to be produced in huge numbers might be a bit different to a solution for an aircraft later on in production life. Especially where the processes of the original recent certification are being claimed to be imperfect. Hopefully other airworthiness authorities in Canada, Europe & Asia etc will take an independent, more clean-sheet view and not be steam-rollered into denying the use of hind sight now that the MAX is back on the ground.
Salute!
Brought this up on nother thread/post. But why can't Boeing modify the engine nacelles to "help" with the pitch coefficients/moments?
You know, right now the things act like canards, but maybe some tabs could be used that only exerted down moments when above a certain AoA? I have seen tabs on other engine configuration and always assumed they helped keep airflow smooth over/under the wing. But if these MAX suckers are that far forward and higher that they have pronounced aerodynamic effects, then why use them?
Gums wonders....
Brought this up on nother thread/post. But why can't Boeing modify the engine nacelles to "help" with the pitch coefficients/moments?
You know, right now the things act like canards, but maybe some tabs could be used that only exerted down moments when above a certain AoA? I have seen tabs on other engine configuration and always assumed they helped keep airflow smooth over/under the wing. But if these MAX suckers are that far forward and higher that they have pronounced aerodynamic effects, then why use them?
Gums wonders....
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WSJ: Is it the Pilot or the Robot That'sthe Problem?
As more information comes out about two B738 Max crashes, it’s clear that a big system malfunction was at work. Not the famed “MCAS” system, designed to help a pilot avoid an aerodynamic stall, whose snafu is strongly implicated in last October’s crash of a late-model 737 MAX in Indonesia and is suspected in last week’s crash of a 737 MAX in Ethiopia.
That system seems clearly to have been badly designed, in a way neither Boeing nor the Federal Aviation Administration would have approved if they had understood what they were doing. The truth is, their own bureaucratic systems seem accidently to have delivered into the cockpit a kludge that never should have been allowed near a plane that would be carrying passengers.
And yet the fact that the two planes were allowed to crash may not be blamable solely on faulty anti-stall software that, when fed improper data, can push the nose dangerously toward the ground.
U.S. airlines have been flying the new 737 MAX for nearly two years. Pilots seem to have coped with the plane’s troubled automation system with little fuss or bother. Before last year’s crash in Indonesia, a Lion Air crew flying the same jet appears to have had no trouble responding to the system’s flawed performance. After the Indonesia crash, 737 MAX pilots around the world were coached on the system’s flaws and given remedial training. The captain in last week’s Ethiopian Airlines crash was highly proficient. So why didn’t he avoid the crash if the accidents are as similar as now suspected?
While these questions remain unanswered, Boeing’s critics have widened the search for culprits to make what they know substitute for what they don’t. First it was the software, then it was shortchanging 737 MAX pilots of training. Boeing also was blamed for how it hung a new engine on the 737’s wing, and then for sticking with the 737 at all instead of building an all-new plane.There may be something to each of these complaints but an alternative rabbit hole has been to ask whether the industry’s growing reliance on computers has left pilots unready to intervene and compensate when something goes wrong.In reality, there is no good reason to fault Boeing’s decision to keep its 737 flying rather than seeking to certify an all-new aircraft. Likewise, the fact that new engines fitted on the 737 MAX cause it to generate more lift under certain circumstances than previous models is hardly a defect.
The real screw-up seems to have been Boeing’s decision to use software code not to fix an aerodynamic problem but to make the new jet, from the pilot’s point of view, seem to handle like the old jet. In essence, Boeing tried to make the 737 MAX a simulator of the 737 NG.That is, when manually flying the new plane, pilots could add the same amount of power and stick as they did in the old plane and get the same result—because software would secretly compensate for the tendency of the new plane’s nose to rise.Boeing compounded this choice with the hard-to-believe decision to make MCAS dependent on data from a single, fallible “angle of attack” indicator. We’ll see what comes out of the many investigations now under way, but the solution could be as easy as junking MCAS altogether and training pilots to fly the new plane in accordance with its actual flying characteristics.Still, Boeing has 4,600 outstanding orders for the 737 MAX. This would seem to refute definitively the argument that the market wanted an all-new aircraft. In fact, the mystery of recent crashes may be telling us the opposite: The time is not yet ripe for a new plane.Boeing, for one, has said its air-cargo customers already are clamoring for an aircraft that can fly itself. Unmanned aerial drones are acquiring operational experience and hours of flight data that may soon give us more information about how such systems perform under every kind of real-world scenario than we have about human pilots.Meanwhile, though automation is credited with improving safety, an important question is: Which automation? Should we thank the kind that helps airplanes stay on course and intervenes if the pilot makes an ill-advised maneuver? Or the kind that increasingly takes the pilot out of the loop altogether? Notice that Boeing’s faulty software was designed to operate in those rare moments when a pilot is flying the plane by hand.
These questions, sadly, relate to more than just accident prevention. As the overall crash rate declines, incidents of suicide-by-pilot have started to account for an alarming percentage of air fatalities. Think the Germanwings Airbus crash of 2015, the EgyptAir crash of 1999, and quite possibly the disappearance of Malaysian Airlines flight 370 in 2014.We hope the implications are clear. Replacements for the 737 or Airbus’s comparable A320 would be expected to carry the industry for the next 50 years. Before launching new planes, the companies and their customers and regulators need to decide what exactly they want the pilot to do in the future, and if they want a pilot at all.
And yet the fact that the two planes were allowed to crash may not be blamable solely on faulty anti-stall software that, when fed improper data, can push the nose dangerously toward the ground.
U.S. airlines have been flying the new 737 MAX for nearly two years. Pilots seem to have coped with the plane’s troubled automation system with little fuss or bother. Before last year’s crash in Indonesia, a Lion Air crew flying the same jet appears to have had no trouble responding to the system’s flawed performance. After the Indonesia crash, 737 MAX pilots around the world were coached on the system’s flaws and given remedial training. The captain in last week’s Ethiopian Airlines crash was highly proficient. So why didn’t he avoid the crash if the accidents are as similar as now suspected?
While these questions remain unanswered, Boeing’s critics have widened the search for culprits to make what they know substitute for what they don’t. First it was the software, then it was shortchanging 737 MAX pilots of training. Boeing also was blamed for how it hung a new engine on the 737’s wing, and then for sticking with the 737 at all instead of building an all-new plane.There may be something to each of these complaints but an alternative rabbit hole has been to ask whether the industry’s growing reliance on computers has left pilots unready to intervene and compensate when something goes wrong.In reality, there is no good reason to fault Boeing’s decision to keep its 737 flying rather than seeking to certify an all-new aircraft. Likewise, the fact that new engines fitted on the 737 MAX cause it to generate more lift under certain circumstances than previous models is hardly a defect.
The real screw-up seems to have been Boeing’s decision to use software code not to fix an aerodynamic problem but to make the new jet, from the pilot’s point of view, seem to handle like the old jet. In essence, Boeing tried to make the 737 MAX a simulator of the 737 NG.That is, when manually flying the new plane, pilots could add the same amount of power and stick as they did in the old plane and get the same result—because software would secretly compensate for the tendency of the new plane’s nose to rise.Boeing compounded this choice with the hard-to-believe decision to make MCAS dependent on data from a single, fallible “angle of attack” indicator. We’ll see what comes out of the many investigations now under way, but the solution could be as easy as junking MCAS altogether and training pilots to fly the new plane in accordance with its actual flying characteristics.Still, Boeing has 4,600 outstanding orders for the 737 MAX. This would seem to refute definitively the argument that the market wanted an all-new aircraft. In fact, the mystery of recent crashes may be telling us the opposite: The time is not yet ripe for a new plane.Boeing, for one, has said its air-cargo customers already are clamoring for an aircraft that can fly itself. Unmanned aerial drones are acquiring operational experience and hours of flight data that may soon give us more information about how such systems perform under every kind of real-world scenario than we have about human pilots.Meanwhile, though automation is credited with improving safety, an important question is: Which automation? Should we thank the kind that helps airplanes stay on course and intervenes if the pilot makes an ill-advised maneuver? Or the kind that increasingly takes the pilot out of the loop altogether? Notice that Boeing’s faulty software was designed to operate in those rare moments when a pilot is flying the plane by hand.
These questions, sadly, relate to more than just accident prevention. As the overall crash rate declines, incidents of suicide-by-pilot have started to account for an alarming percentage of air fatalities. Think the Germanwings Airbus crash of 2015, the EgyptAir crash of 1999, and quite possibly the disappearance of Malaysian Airlines flight 370 in 2014.We hope the implications are clear. Replacements for the 737 or Airbus’s comparable A320 would be expected to carry the industry for the next 50 years. Before launching new planes, the companies and their customers and regulators need to decide what exactly they want the pilot to do in the future, and if they want a pilot at all.
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Salute!
Brought this up on nother thread/post. But why can't Boeing modify the engine nacelles to "help" with the pitch coefficients/moments?
You know, right now the things act like canards, but maybe some tabs could be used that only exerted down moments when above a certain AoA? I have seen tabs on other engine configuration and always assumed they helped keep airflow smooth over/under the wing. But if these MAX suckers are that far forward and higher that they have pronounced aerodynamic effects, then why use them?
Gums wonders....
Brought this up on nother thread/post. But why can't Boeing modify the engine nacelles to "help" with the pitch coefficients/moments?
You know, right now the things act like canards, but maybe some tabs could be used that only exerted down moments when above a certain AoA? I have seen tabs on other engine configuration and always assumed they helped keep airflow smooth over/under the wing. But if these MAX suckers are that far forward and higher that they have pronounced aerodynamic effects, then why use them?
Gums wonders....
But in the end it's most likely: why bother with hardware when the fix is "just a few lines of code" (or even less - sounds like the "fix" was just changing the config to make original, probably relatively safe, system far more aggressive).
I've forgotten how many times I've heard "just a few lines of code", the phrase always makes the heart sink and the worry levels rise, and it is never uttered by people who actually realise the risk involved. Note that I say that having spent most of my software career outside of safety-critical and/or aviation work.
Software is easy to change, that is (one of) its strength. It's Achilles heel is that is is too damn easy to change and change requires far less thought than it should. Just because you can does not mean you should - but management will always ask if you can, and then tell you that therefore you should.
Offtopic prediction: Tesla is going to get bit in the arse by this some day with their OTA updates. Right now thousands of Tesla drivers wake up in the morning and their car drives differently and better than it did yesterday - and everyone thinks that is awesome. One day hundreds of thousands of Tesla drivers are going to wake up in the morning and find their car drives worse than it did yesterday, I really hope they find out on the driveway and not when they hit the highway...
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I've forgotten how many times I've heard "just a few lines of code", the phrase always makes the heart sink and the worry levels rise, and it is never uttered by people who actually realise the risk involved. Note that I say that having spent most of my software career outside of safety-critical and/or aviation work.
Software is easy to change, that is (one of) its strength. It's Achilles heel is that is is too damn easy to change and change requires far less thought than it should. Just because you can does not mean you should - but management will always ask if you can, and then tell you that therefore you should.
Software is easy to change, that is (one of) its strength. It's Achilles heel is that is is too damn easy to change and change requires far less thought than it should. Just because you can does not mean you should - but management will always ask if you can, and then tell you that therefore you should.
I would suspect that the Max software has a very concentrated team working on it and that the fix itself is 'just a few lines of code' and was completed a month after the first crash. The rest of the time is QA, testing, documentation and certification. The 'delay' may well be the effect on code certification of the spotlight on the process due to the second crash. The work will now be to rule therefore be very slow.
This thread requires a large placard reiterating the purpose of MCAS - a stability enhancement, it is not an aid to help pilots avoid, or be anti anything to do with stall.
Stability, in this case relates to the relationship between speed and trim, which translates to stick force - the feel of the aircraft. Changing trim would not normally change pitch attitude during manual flight, which MCAS is limited to (flaps up).
The 737 Max is not unstable; without MCAS, in a specific area of the flight envelope, the aircraft exhibits less stability margin than required for certification. The aircraft is flyable without MACS with low risk; however, the aircraft appears very difficult to fly with large trim offsets resulting in high stick forces, more so with distracting stick shake and alerting (more associated with UAS). Unfortunately these aspects and associated risk appear to be confirmed with hindsight.
Neither should we resort to hindsight in judging the quality of the design. Given the problem and resources (timescale), the design appears to be adequate in normal operation - as judged by many normal flights. The critical point in these accidents is that there was an erroneous input - probably from the AoA vane, but not yet proven. The effect of this error appears to differ from what might have been expected in design and certification.
The mechanism for managing this error in flight appears have made many assumptions about the severity of the fault, and the ability of human intervention; compounded by the lack of system information.
Stability, in this case relates to the relationship between speed and trim, which translates to stick force - the feel of the aircraft. Changing trim would not normally change pitch attitude during manual flight, which MCAS is limited to (flaps up).
The 737 Max is not unstable; without MCAS, in a specific area of the flight envelope, the aircraft exhibits less stability margin than required for certification. The aircraft is flyable without MACS with low risk; however, the aircraft appears very difficult to fly with large trim offsets resulting in high stick forces, more so with distracting stick shake and alerting (more associated with UAS). Unfortunately these aspects and associated risk appear to be confirmed with hindsight.
Neither should we resort to hindsight in judging the quality of the design. Given the problem and resources (timescale), the design appears to be adequate in normal operation - as judged by many normal flights. The critical point in these accidents is that there was an erroneous input - probably from the AoA vane, but not yet proven. The effect of this error appears to differ from what might have been expected in design and certification.
The mechanism for managing this error in flight appears have made many assumptions about the severity of the fault, and the ability of human intervention; compounded by the lack of system information.
This thread requires a large placard reiterating the purpose of MCAS - a stability enhancement, it is not an aid to help pilots avoid, or be anti anything to do with stall.
Stability, in this case relates to the relationship between speed and trim, which translates to stick force - the feel of the aircraft. Changing trim would not normally change pitch attitude during manual flight, which MCAS is limited to.
The 737 Max is not unstable; without MCAS, in a specific area of the flight envelope, the aircraft exhibits less stability margin than required for certification. The aircraft is flyable without MACS with low risk; however, the aircraft appears very difficult to fly with large trim offsets resulting in high stick forces, more so with distracting stick shake and alerting (more associated with UAS). Unfortunately these aspects and associated risk appear to be confirmed with hindsight.
Neither should we resort to hindsight in judging the quality of the design. Given the problem and resources (timescale), the design appears to be adequate in normal operation - as judged by many normal flights. The critical point in these accidents is that there was an erroneous input - probably from the AoA vane, but not yet proven. The effect of this error appears to differ from what might have been expected in design and certification.
The mechanism for managing this error in flight appears hold many assumptions about the severity of the fault, and the ability of human intervention; compounded by the lack of system information.
Stability, in this case relates to the relationship between speed and trim, which translates to stick force - the feel of the aircraft. Changing trim would not normally change pitch attitude during manual flight, which MCAS is limited to.
The 737 Max is not unstable; without MCAS, in a specific area of the flight envelope, the aircraft exhibits less stability margin than required for certification. The aircraft is flyable without MACS with low risk; however, the aircraft appears very difficult to fly with large trim offsets resulting in high stick forces, more so with distracting stick shake and alerting (more associated with UAS). Unfortunately these aspects and associated risk appear to be confirmed with hindsight.
Neither should we resort to hindsight in judging the quality of the design. Given the problem and resources (timescale), the design appears to be adequate in normal operation - as judged by many normal flights. The critical point in these accidents is that there was an erroneous input - probably from the AoA vane, but not yet proven. The effect of this error appears to differ from what might have been expected in design and certification.
The mechanism for managing this error in flight appears hold many assumptions about the severity of the fault, and the ability of human intervention; compounded by the lack of system information.
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It is a whole different game coding in a safety related environment. I have worked in maintenance areas where "just changing a comment will take 18 months" This has the contrary effect of urgent fixes having to be patched into systems without the 18month wait if the world ends if they cannot keep operating.
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I keep trying to ask this question in different ways but the mods don't publish so I'll try another way:
I see it stated that MCAS is only there because the size and forward placement of the engines on the Max results in stick force reduction as AoA increases and that this characteristic is contrary to FAR requirements.
I also see it stated that the Max is not unstable as a result of the new physical configuration. I ask innocently: Is this known for a fact?
I ask because the MCAS, as a solution, is a brutal way to simply correct a stick force irregularity. Surely a fail passive method to apply extra force to the stick is not a difficult thing to do.
The MCAS FMECA must make an interesting read! But if you absolutely must not stall then it might be justified.
Do we know for sure this version does indeed stall and recover normally like a typical stable aircraft?
I see it stated that MCAS is only there because the size and forward placement of the engines on the Max results in stick force reduction as AoA increases and that this characteristic is contrary to FAR requirements.
I also see it stated that the Max is not unstable as a result of the new physical configuration. I ask innocently: Is this known for a fact?
I ask because the MCAS, as a solution, is a brutal way to simply correct a stick force irregularity. Surely a fail passive method to apply extra force to the stick is not a difficult thing to do.
The MCAS FMECA must make an interesting read! But if you absolutely must not stall then it might be justified.
Do we know for sure this version does indeed stall and recover normally like a typical stable aircraft?
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As the Lion Air crew fought to control their diving Boeing Co. 737 Max 8, they got help from an unexpected source: an off-duty pilot who happened to be riding in the cockpit.That extra pilot, who was seated in the cockpit jumpseat, correctly diagnosed the problem and told the crew how to disable a malfunctioning flight-control system and save the plane, according to two people familiar with Indonesia’s investigation.The next day, under command of a different crew facing what investigators said was an identical malfunction, the jetliner crashed into the Java Sea killing all 189 aboard.
Salute!
@ Past......
Not sure if he "correctly diagnosed the problem" but he apparently correctly advised the crew to turn off the trim motor.
Have to wait for his testimony at one of the trials. Regardless, it worked.
Gums sends.
@ Past......
Not sure if he "correctly diagnosed the problem" but he apparently correctly advised the crew to turn off the trim motor.
Have to wait for his testimony at one of the trials. Regardless, it worked.
Gums sends.
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I keep trying to ask this question in different ways but the mods don't publish so I'll try another way:
I see it stated that MCAS is only there because the size and forward placement of the engines on the Max results in stick force reduction as AoA increases and that this characteristic is contrary to FAR requirements.
I also see it stated that the Max is not unstable as a result of the new physical configuration. I ask innocently: Is this known for a fact?
I ask because the MCAS, as a solution, is a brutal way to simply correct a stick force irregularity. Surely a fail passive method to apply extra force to the stick is not a difficult thing to do.
The MCAS FMECA must make an interesting read! But if you absolutely must not stall then it might be justified.
Do we know for sure this version does indeed stall and recover normally like a typical stable aircraft?
I see it stated that MCAS is only there because the size and forward placement of the engines on the Max results in stick force reduction as AoA increases and that this characteristic is contrary to FAR requirements.
I also see it stated that the Max is not unstable as a result of the new physical configuration. I ask innocently: Is this known for a fact?
I ask because the MCAS, as a solution, is a brutal way to simply correct a stick force irregularity. Surely a fail passive method to apply extra force to the stick is not a difficult thing to do.
The MCAS FMECA must make an interesting read! But if you absolutely must not stall then it might be justified.
Do we know for sure this version does indeed stall and recover normally like a typical stable aircraft?
737MAX is not unstable with or without MCAS in that starting from a 1g, wings level trim condition with zero column input it will not tend to increase or decrease AOA without the pilot applying column input. (This statement assumes that thrust and flight path are also trimmed to provide steady speed.) From that starting point a maneuver flown without adjustment to the horizontal stabilizer will require pull force as AOA increases over the range of AOA that must be demonstrated (stick shaker and beyond). Relaxing the column to its detent from any point along this AOA demonstration will result in AOA returning to near its trimmed condition. Pull to get nose up, relax to return = stable.
The 737MAX issue that gives rise to the need for MCAS is that the amount of pull column to stabilize at any given AOA along the way may decrease slightly from what was required at a slightly lower AOA. You still have to pull. It will still recover to a lower AOA if column force is removed. The characteristic, however, of not needing more column pull for every increment of higher AOA over the demonstration range is what does not meet the requirements.
Another point that has been discussed in PPRUNE is the idea that MCAS is only there to make the 737MAX handle like earlier 737 models. That is not what motivated MCAS and thus it would not be permitted to remove MCAS. Regardless of the desire for common handling between 737MAX and 737NG, 737MAX handling characteristics considered apart from any relation to 737NG handling characteristics do not meet the applicable FARs (see paragraph above) and thus need modification by one means or another in order to achieve certification.
As to the idea of a stick pusher rather than the MCAS use of the horizontal stabilizer, that has been discussed at great length. The 737 does not include the necessary hardware to implement such a stick pusher so the statement that "Surely a fail passive method to apply extra force to the stick is not a difficult thing to do." is not correct.
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As to the idea of a stick pusher rather than the MCAS use of the horizontal stabilizer, that has been discussed at great length. The 737 does not include the necessary hardware to implement such a stick pusher so the statement that "Surely a fail passive method to apply extra force to the stick is not a difficult thing to do." is not correct.
Stall identification and control is enhanced by the yaw damper, the Elevator Feel
Shift (EFS) module and the speed trim system. These three systems work together
to help the pilot identify and prevent further movement into a stall condition.
During high AOA operations, the SMYD reduces yaw damper commanded rudder
movement.
The EFS module increases hydraulic system A pressure to the elevator feel and
centering unit during a stall. This increases forward control column force to
approximately four times normal feel pressure. The EFS module is armed
whenever an inhibit condition is not present. Inhibit conditions are: on the ground,
radio altitude less than 100 feet and autopilot engaged. However, if EFS is active
when descending through 100 feet RA, it remains active until AOA is reduced
below approximately stickshaker threshold. There are no flight deck indications
that the system is properly armed or activated.
As airspeed decreases towards stall speed, the speed trim system trims the
stabilizer nose down and enables trim above stickshaker AOA. With this trim
schedule the pilot must pull more aft column to stall the airplane. With the column
aft, the amount of column force increase with the onset of EFS module is more
pronounced.
Shift (EFS) module and the speed trim system. These three systems work together
to help the pilot identify and prevent further movement into a stall condition.
During high AOA operations, the SMYD reduces yaw damper commanded rudder
movement.
The EFS module increases hydraulic system A pressure to the elevator feel and
centering unit during a stall. This increases forward control column force to
approximately four times normal feel pressure. The EFS module is armed
whenever an inhibit condition is not present. Inhibit conditions are: on the ground,
radio altitude less than 100 feet and autopilot engaged. However, if EFS is active
when descending through 100 feet RA, it remains active until AOA is reduced
below approximately stickshaker threshold. There are no flight deck indications
that the system is properly armed or activated.
As airspeed decreases towards stall speed, the speed trim system trims the
stabilizer nose down and enables trim above stickshaker AOA. With this trim
schedule the pilot must pull more aft column to stall the airplane. With the column
aft, the amount of column force increase with the onset of EFS module is more
pronounced.
Re #279 - Optional modification for AoA disagree and EFIS display. ‘…crew has more tools to identify an AOA signal error if one is present and to isolate as to which one seems more reasonable’.
I prefer to consider such displays as adding potential confusion; context is paramount.
‘Reasonability’ implies comparison. With only two inputs there is no direct way to established which AoA is correct (high is in error);
I assume that FCeng et al, are very familiar with these aspects, others less so.
A comparison with stick shake might incorrectly deduce that the high value is correct, or at least it is the immediate risk to flight - stall avoidance.
Similarly, comparison with speed, the mispositioned on-side low-speed awareness (stall) could add to the view that the high AoA is correct.
Subsequent cross check of speed could detect a difference in speed (AoA used for pressure correction), requiring a check of the standby ASI, but short of stalling the aircraft the relationship between an errant AoA input and airspeed cannot be determined. Although it might be concluded that the off-side speed is the better reference, and that with speed increase the stick shake is invalid - false correlation between AoA gauge and stick shake.
This would require a reversal the original mental picture - a demanding task; ‘first learned, best remembered’.
This context represents a piloting viewpoint of additional instrumentation, including mental activity - workload. The view (mental model) provides the reference situation for judging further action.
Many operators demand new, additional displays, yet few are able to argue why these would help avoid situations which they were unable to avoid with existing instruments. Similarly for recovery from upset situations of their own making - excluding system failures.
An engineering / certification argument must never invoke human management of an abnormal situation involving a system failure, which in the first instance was designed to replace human inability to manage the normal situation (boot strapping ?). Also consider the reasonableness of any piloting task.
_
An afterthought, in reversing the above - errant low AoA (high is really correct), then in MCAS terms there is no immediate problem, no stick shake, perhaps a stability weakness - no MCAS when required; other disagree alerts depend on the system logic.
This might imply that to-date, instances of low AoA have not been recorded (or equivalent maintenance flags), or that this type of failure is extremely remote.
Thus why did the AoA fail high - given a choice of direction; vane, wiring, logic ?
I prefer to consider such displays as adding potential confusion; context is paramount.
‘Reasonability’ implies comparison. With only two inputs there is no direct way to established which AoA is correct (high is in error);
I assume that FCeng et al, are very familiar with these aspects, others less so.
A comparison with stick shake might incorrectly deduce that the high value is correct, or at least it is the immediate risk to flight - stall avoidance.
Similarly, comparison with speed, the mispositioned on-side low-speed awareness (stall) could add to the view that the high AoA is correct.
Subsequent cross check of speed could detect a difference in speed (AoA used for pressure correction), requiring a check of the standby ASI, but short of stalling the aircraft the relationship between an errant AoA input and airspeed cannot be determined. Although it might be concluded that the off-side speed is the better reference, and that with speed increase the stick shake is invalid - false correlation between AoA gauge and stick shake.
This would require a reversal the original mental picture - a demanding task; ‘first learned, best remembered’.
This context represents a piloting viewpoint of additional instrumentation, including mental activity - workload. The view (mental model) provides the reference situation for judging further action.
Many operators demand new, additional displays, yet few are able to argue why these would help avoid situations which they were unable to avoid with existing instruments. Similarly for recovery from upset situations of their own making - excluding system failures.
An engineering / certification argument must never invoke human management of an abnormal situation involving a system failure, which in the first instance was designed to replace human inability to manage the normal situation (boot strapping ?). Also consider the reasonableness of any piloting task.
_
An afterthought, in reversing the above - errant low AoA (high is really correct), then in MCAS terms there is no immediate problem, no stick shake, perhaps a stability weakness - no MCAS when required; other disagree alerts depend on the system logic.
This might imply that to-date, instances of low AoA have not been recorded (or equivalent maintenance flags), or that this type of failure is extremely remote.
Thus why did the AoA fail high - given a choice of direction; vane, wiring, logic ?
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I know the 737 does not have a stick pusher, but, at least in the NG, it did increase stick power approaching a stall. That seems to be insufficient in the MAX, or not included in its systems. Below an excerpt from the NG FCOM, latest version i flew which is by now a few years old. If i understand it, there is now a fourth system with MCAS to aid in that situation.
I'll give this some more thought, but I feel you (and others making similar suggestions - my apologies for not recognizing those earlier) may be on to something here. I'll check with some people I know who are more expert on the associated requirements to see if this might be another approach that would satisfy the associated cert regulations.
Thanks, again - the value of the public square that PPRUNE is needs to be acknowledged and maintained.
FCeng84
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No training for the MAX!
Rant in progress....
To no- one in particular, BUT let me make it clear to all that no 737- 800 pilot has ever had any training on the MAX.
In my not so humble opinion!
Why say You?
Well , let me define training
1. Flying the MAX aircraft with an Instructor in the configurations different from the 738!
2. Flying a Level D or C full flight simulator with the exact flight characteristics of the MAX in an approved program!
That is training.
Thousands has studied for the MAX, including Yours Truly, the whole 4 hrs video and Q/A CBT from Boeing.
And voila , variant nr 8 is in the box .
Again , as per today there is no training on the MAX, as no sim is available.
MAX CBT home study is at best entertainment and clearly inadequate,
Rant over
Cpt B
To no- one in particular, BUT let me make it clear to all that no 737- 800 pilot has ever had any training on the MAX.
In my not so humble opinion!
Why say You?
Well , let me define training
1. Flying the MAX aircraft with an Instructor in the configurations different from the 738!
2. Flying a Level D or C full flight simulator with the exact flight characteristics of the MAX in an approved program!
That is training.
Thousands has studied for the MAX, including Yours Truly, the whole 4 hrs video and Q/A CBT from Boeing.
And voila , variant nr 8 is in the box .
Again , as per today there is no training on the MAX, as no sim is available.
MAX CBT home study is at best entertainment and clearly inadequate,
Rant over
Cpt B
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TLDR (Too Long Didn't Read)
Juan Browne's YouTube Video LIon Air B-737 Max NCAS Update Is far more informative than Boeing Pres. Dennis Muilenburgs full page NY Times Mar 20 apologram declaring Commitment Dedication and Values.