737 MAX future
Mr Driver, Thanks for answering so many questions it really is appreciated.
I was more trying to see if if there was a self test of the STS system including MCAS (short of moving the vanes).
Obviously it would be preferable to know such things prior to take-off and or 400ft including that pesky stick shaker.
Should an AoA disagree (more than 5 degrees) MCAS can not function, so (and I am aware you stated you would not put them up) is flight with flaps up prohibited?
Did the brief include the conditions of MCAS override by the pilot/s and rest limits?
I was more trying to see if if there was a self test of the STS system including MCAS (short of moving the vanes).
Obviously it would be preferable to know such things prior to take-off and or 400ft including that pesky stick shaker.
Should an AoA disagree (more than 5 degrees) MCAS can not function, so (and I am aware you stated you would not put them up) is flight with flaps up prohibited?
Did the brief include the conditions of MCAS override by the pilot/s and rest limits?
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Again, if MCAS were somehow to activate when it was not supposed to with the new software in place, the response would probably still be the runaway stab trim procedure. I say "probably" because until the MAX is certified for flight, there may be new procedures developed.
However, retracting the flaps could (regardless of risk level) allow the aircraft to be flown in a condition that is known not to be certifiable.
One would expect that the aircraft could not be certified (?) with flaps retracted.
I think this will be the sticking point, the aircraft NEEDS MCAS, the fix has introduced many ways to limit and deactivate MCAS.
Nothing has changed, only the thing that is required is often not available anymore.
It is not just a case of the aircraft is safe to fly, but it must fly like it's little brother, in every part of the envelope all the time - and it can not do this without an active MCAS.
I think for certification it needs a fail safe system that keeps MCAS alive or very low probability of being shut down.
The fix is to remove MCAS basically! When we can all see by the data that it operated exactly as it was told (designed) to do - MCAS never made an error! 3 inputs would be a clever option.
One would expect that the aircraft could not be certified (?) with flaps retracted.
I think this will be the sticking point, the aircraft NEEDS MCAS, the fix has introduced many ways to limit and deactivate MCAS.
Nothing has changed, only the thing that is required is often not available anymore.
It is not just a case of the aircraft is safe to fly, but it must fly like it's little brother, in every part of the envelope all the time - and it can not do this without an active MCAS.
I think for certification it needs a fail safe system that keeps MCAS alive or very low probability of being shut down.
The fix is to remove MCAS basically! When we can all see by the data that it operated exactly as it was told (designed) to do - MCAS never made an error! 3 inputs would be a clever option.
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However, retracting the flaps could (regardless of risk level) allow the aircraft to be flown in a condition that is known not to be certifiable.
One would expect that the aircraft could not be certified (?) with flaps retracted.
I think this will be the sticking point, the aircraft NEEDS MCAS, the fix has introduced many ways to limit and deactivate MCAS.
Nothing has changed, only the thing that is required is often not available anymore.
It is not just a case of the aircraft is safe to fly, but it must fly like it's little brother, in every part of the envelope all the time - and it can not do this without an active MCAS.
I think for certification it needs a fail safe system that keeps MCAS alive or very low probability of being shut down.
The fix is to remove MCAS basically! When we can all see by the data that it operated exactly as it was told (designed) to do - MCAS never made an error! 3 inputs would be a clever option.
One would expect that the aircraft could not be certified (?) with flaps retracted.
I think this will be the sticking point, the aircraft NEEDS MCAS, the fix has introduced many ways to limit and deactivate MCAS.
Nothing has changed, only the thing that is required is often not available anymore.
It is not just a case of the aircraft is safe to fly, but it must fly like it's little brother, in every part of the envelope all the time - and it can not do this without an active MCAS.
I think for certification it needs a fail safe system that keeps MCAS alive or very low probability of being shut down.
The fix is to remove MCAS basically! When we can all see by the data that it operated exactly as it was told (designed) to do - MCAS never made an error! 3 inputs would be a clever option.
To be certifiable (and more to my way of thinking, cleared for dispatch) the 737 needs two functioning Inertial Reference Units (IRU). During the flight, let's say one of the IRU's fail. At this point, the aircraft is no longer "certifiable." However, I'm already in the air, so I pull out the appropriate non-normal checklist (which is quite involved), and let's say I am unable to reset the unit. I will then throw a switch to put both sides on a single IRU and continue to destination under certain additional restrictions. Once the plane is on the ground, it will stay on the ground until the faulty IRU is fixed or replaced. The same logic can be applied to numerous aircraft systems, not just the MCAS.
Every system on the aircraft is subject to failure, and some of those failures will put the aircraft out of its certifiable limit. The manufacturer does not eliminate those systems, but rather they develop non-normal procedures to deal with the failure until the aircraft is on the ground and the system can be repaired. This is the way it has been done in aviation since before I took my first flight.
There are certain components (like the wing) that really do fall in a fail-safe category, and they necessarily meet a much a higher standard. MCAS is not one of those items.
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To be certifiable (and more to my way of thinking, cleared for dispatch) the 737 needs two functioning Inertial Reference Units (IRU).
I see they have initialized the optional AoA dial on the flightdeck, and a light when AoA does not agree...(at 400 AGL?)
How does one determine MCAS is operational to dispatch? It must be on the ground, correct ? you cannot dispatch with a non-normal condition.
Have they added a MCAS INOP check prior to DEP?
Have they initialized MCAS on the ground (instead of 400 AGL?)
How can you check the operation of the AoA vanes while on the ground? (they all show 90 degrees?)
As part of the 'fix' there will be an AoA measurement shown on the screen. And this means what? As the saying goes, what would you do with the AoA measurement if you had one? Is is it showing the wing AoA or the fuselage AoA? How many pilots know the AoA of the wing vs the fuselage AoA?
Do pilots know the AoA and/or conditions when the engine nacelles provide the sudden pitch up?
How long have pilots been asking for the AoA ?
MCAS relies on the AoA vane measurements, which in reality, ac dont even report the AoA angle (case in point) nor has anyone paid that much attention to, yet now the automation does, and there begins the disconnect.
We are Boeing.
Resistance is futile
You will be assimilated.
Last edited by Smythe; 11th May 2019 at 03:50.
I hear what you're saying, but let me try this again with a simple example.
To be certifiable (and more to my way of thinking, cleared for dispatch) the 737 needs two functioning Inertial Reference Units (IRU). During the flight, let's say one of the IRU's fail. At this point, the aircraft is no longer "certifiable." However, I'm already in the air, so I pull out the appropriate non-normal checklist (which is quite involved), and let's say I am unable to reset the unit. I will then throw a switch to put both sides on a single IRU and continue to destination under certain additional restrictions. Once the plane is on the ground, it will stay on the ground until the faulty IRU is fixed or replaced. The same logic can be applied to numerous aircraft systems, not just the MCAS.
Every system on the aircraft is subject to failure, and some of those failures will put the aircraft out of its certifiable limit. The manufacturer does not eliminate those systems, but rather they develop non-normal procedures to deal with the failure until the aircraft is on the ground and the system can be repaired. This is the way it has been done in aviation since before I took my first flight.
There are certain components (like the wing) that really do fall in a fail-safe category, and they necessarily meet a much a higher standard. MCAS is not one of those items.
To be certifiable (and more to my way of thinking, cleared for dispatch) the 737 needs two functioning Inertial Reference Units (IRU). During the flight, let's say one of the IRU's fail. At this point, the aircraft is no longer "certifiable." However, I'm already in the air, so I pull out the appropriate non-normal checklist (which is quite involved), and let's say I am unable to reset the unit. I will then throw a switch to put both sides on a single IRU and continue to destination under certain additional restrictions. Once the plane is on the ground, it will stay on the ground until the faulty IRU is fixed or replaced. The same logic can be applied to numerous aircraft systems, not just the MCAS.
Every system on the aircraft is subject to failure, and some of those failures will put the aircraft out of its certifiable limit. The manufacturer does not eliminate those systems, but rather they develop non-normal procedures to deal with the failure until the aircraft is on the ground and the system can be repaired. This is the way it has been done in aviation since before I took my first flight.
There are certain components (like the wing) that really do fall in a fail-safe category, and they necessarily meet a much a higher standard. MCAS is not one of those items.
You have two functioning IRU's and with one going U/S, you are left with one IRU - the aircraft will function happily with one and there are no parameters of flight that will change. This is redundancy two "required" only one needed. Same with numerous of items like computers, one goes u/s the aircraft operates the same.
MCAS has no redundancy, and if there is a failure of MCAS the flight characteristics do change in certain areas of the envelope. You just will not know how abruptly or placid this change might be until you find yourself there (that may never happen just like an engine failure after take-off) or even amount of change v/s speed. What is the difference in a turn? will it try roll you also?
It is a bit like the flap selector braking off in your hand, no second handle. But the big difference is you know how the aircraft will fly regardless of the setting the handle broke. Chances are you had to do a flap-less landing during your original training - but I doubt for a broken handle! but you practice it at some stage.
Considering this all happens close to the stall and in manual flying condition. A condition almost prohibited at some airlines these days, the very least we expect is that the pilots have trained and practices for these known change of characteristics. But we all know that is not a consideration to be had.
To be certified to fly, MCAS needs to be operational to be dispatched.
I see they have initialized the optional AoA dial on the flightdeck, and a light when AoA does not agree...(at 400 AGL?)
How does one determine MCAS is operational to dispatch? It must be on the ground, correct ? you cannot dispatch with a non-normal condition.
Have they added a MCAS INOP check prior to DEP?
Have they initialized MCAS on the ground (instead of 400 AGL?)
How can you check the operation of the AoA vanes while on the ground? (they all show 90 degrees?)
As part of the 'fix' there will be an AoA measurement shown on the screen. And this means what? As the saying goes, what would you do with the AoA measurement if you had one? Is is it showing the wing AoA or the fuselage AoA? How many pilots know the AoA of the wing vs the fuselage AoA?
Do pilots know the AoA and/or conditions when the engine nacelles provide the sudden pitch up?
How long have pilots been asking for the AoA ?
MCAS relies on the AoA vane measurements, which in reality, ac dont even report the AoA angle (case in point) nor has anyone paid that much attention to, yet now the automation does, and there begins the disconnect.
We are Boeing.
Resistance is futile
You will be assimilated.
I see they have initialized the optional AoA dial on the flightdeck, and a light when AoA does not agree...(at 400 AGL?)
How does one determine MCAS is operational to dispatch? It must be on the ground, correct ? you cannot dispatch with a non-normal condition.
Have they added a MCAS INOP check prior to DEP?
Have they initialized MCAS on the ground (instead of 400 AGL?)
How can you check the operation of the AoA vanes while on the ground? (they all show 90 degrees?)
As part of the 'fix' there will be an AoA measurement shown on the screen. And this means what? As the saying goes, what would you do with the AoA measurement if you had one? Is is it showing the wing AoA or the fuselage AoA? How many pilots know the AoA of the wing vs the fuselage AoA?
Do pilots know the AoA and/or conditions when the engine nacelles provide the sudden pitch up?
How long have pilots been asking for the AoA ?
MCAS relies on the AoA vane measurements, which in reality, ac dont even report the AoA angle (case in point) nor has anyone paid that much attention to, yet now the automation does, and there begins the disconnect.
We are Boeing.
Resistance is futile
You will be assimilated.
I fly Airbus, and do not want to fly B737. Having said that, none of my 3 AOA indicators are tested before I am airborne. All my 7 flight computers self test to see if they are ok to fly, just like the FCCs(?) on the 737 will before flight. Does that mean that they will work once I rotate? No, but that is why I am there.
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The issues with Boeing run very deep. As with most industries, money (profit) is the only reason they exist. The CEO received more than $24m last year I believe. Just like the medical device industry here in Southern California: FDA or TUV auditors are wined and dined to go easy on the company and turn a blind eye....organizations are allowed to self regulate and report ( hey, how about selling a product, that surgeons use to treat brain aneurysms, to Europe and South America, even though a major shipment of the product contains traces of lead through the fault of a third party vendor? Self report ? Hell no!! And the FDA have no idea ). The need (obsession) to meet ever increasing numbers, to hold off the competition and to keep the stakeholders happy ($$$) ultimately results in complacency that is endemic throughout many industries ( yes...aviation included )....until people die and then the lawyers appear out of the woodwork to begin damage limitation...not out of remorse..but to simply protect the business. The documentary on the 787 below really is a mirror to many other industries. Everyone wants a piece of the pie but without the negative consequences and ownership. Maybe folk will view the 787 video below with even more contempt now we have lost two MAX aircraft...and more importantly...many innocent lives.
Pilots, passengers....all pawns to those playing the big game ( Thank goodness it was a little better during the Concorde years! )
Pilots, passengers....all pawns to those playing the big game ( Thank goodness it was a little better during the Concorde years! )
Dude, chill....
I fly Airbus, and do not want to fly B737. Having said that, none of my 3 AOA indicators are tested before I am airborne. All my 7 flight computers self test to see if they are ok to fly, just like the FCCs(?) on the 737 will before flight. Does that mean that they will work once I rotate? No, but that is why I am there.
I fly Airbus, and do not want to fly B737. Having said that, none of my 3 AOA indicators are tested before I am airborne. All my 7 flight computers self test to see if they are ok to fly, just like the FCCs(?) on the 737 will before flight. Does that mean that they will work once I rotate? No, but that is why I am there.
Your Airbus if something fails is still operating within the approved envelope as per certification requirements and required testing/training.
If one of your AoA fail at take off, nothing changes - it fly's the same.
I expect that when two fail, we have a problem? Was that iPad training you took?
The point is not a possible safety issue as most/many pilots have good flying skills and it may well be a non event. The point is when an AoA is U/S the aircraft is known to in certain parts of the envelope to be out of certification limits. Exactly where this is, and it varies it seems the physical effects are not known or experienced by airline pilots.
The basic problem is that the MAX can not meet certification without MCAS - How can shutting down MCAS be a solution?
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I got a brief on the new software yesterday. First, I would point out that while a third AOA would be nice, it is not necessary. The 737 has a number of double redundant systems. If there is a disagreement, we get a warning and we refer to a procedure to determine the bad system. We don't need a third AOA to figure out the bad one because we can cross check the airspeeds, mach numbers, altitudes, and power settings for reasonableness. The pilots are, in effect, the "third" system that sorts the good from the bad.
MCAS is part of the Speed Trim System (STS). There are two STS channels, and one is always required for dispatch. If one or both STS/MCAS systems became inop, we receive a warning annunciator on the flight deck. If both systems are inop, the annunciator comes on immediately - it doesn't wait until 400'. If both STS channels fail in flight, we have a non-normal procedure to address it - just like we have non-normals to address the failure of engines, hydraulics, electrics and all sorts of other things we would require for dispatch.
The new Flight Control Computer (FCC) software will inhibit any STS/MCAS input if the difference between AOA's is greater than about 5 degrees. This is more stringent that the current "AOA Disagree" trigger of greater than 10 degrees. The new software also has some other tests for reasonableness. and the total nose down input is adjusted for the conditions - it will input more stab trim at low airspeeds and less at high airspeeds.
Not sure what you are asking with your last question, but maybe it would be a helpful reminder that MCAS only activates with the flaps retracted. If the flight crew is operating the aircraft normally, the flaps will always be extended below 1000 feet.
MCAS is part of the Speed Trim System (STS). There are two STS channels, and one is always required for dispatch. If one or both STS/MCAS systems became inop, we receive a warning annunciator on the flight deck. If both systems are inop, the annunciator comes on immediately - it doesn't wait until 400'. If both STS channels fail in flight, we have a non-normal procedure to address it - just like we have non-normals to address the failure of engines, hydraulics, electrics and all sorts of other things we would require for dispatch.
The new Flight Control Computer (FCC) software will inhibit any STS/MCAS input if the difference between AOA's is greater than about 5 degrees. This is more stringent that the current "AOA Disagree" trigger of greater than 10 degrees. The new software also has some other tests for reasonableness. and the total nose down input is adjusted for the conditions - it will input more stab trim at low airspeeds and less at high airspeeds.
Not sure what you are asking with your last question, but maybe it would be a helpful reminder that MCAS only activates with the flaps retracted. If the flight crew is operating the aircraft normally, the flaps will always be extended below 1000 feet.
A feast.
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We have 3 artificial horizons in order to have a tie breaker if 1 goes wrong, same with the air speed indicators and usually IRSs. I can't see how 2 AoA sensors will meet requirements if 1 starts acting up. Boeing may have to come up with a completely new stall avoidance system, even if it means recertifying the aircraft as a new type and requiring pilots to obtain a new rating.
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That's not the "certified" state either and you haven't expressed concerns about it.
Having a third AoA sensor to fail functional with one failure is a feature the regulator could require from all transport aircraft built after date XYZ.
Would that improve safety? Maybe.
Still arguing that it's a non certified state is bogus.
When a system fails, some degradation can be declared acceptable.
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This is what needs to happen to restore confidence. IMHO.
1. Boeing management needs to develop a culture of accountability and get back its former culture of humility and engineering excellence with engineers at all levels of the organization. The MAX should only be built at Renton for the foreseeable future.
2. Address the issues at Charleston by unionizing and instituting a trust relationship between factory floor and management. Institute a mentoring program between sites to bring workforce skills, behaviours and product excellence up to par with other facilities.
Difficult? Yes. Impossible? No.
2. Address the issues at Charleston by unionizing and instituting a trust relationship between factory floor and management. Institute a mentoring program between sites to bring workforce skills, behaviours and product excellence up to par with other facilities.
Difficult? Yes. Impossible? No.
If it failed on 737 NG or Classic then you might have had continuous stick shaker which means you lose stall warning because it's already going off and no longer reliable.
That's not the "certified" state either and you haven't expressed concerns about it.
Having a third AoA sensor to fail functional with one failure is a feature the regulator could require from all transport aircraft built after date XYZ.
Would that improve safety? Maybe.
Still arguing that it's a non certified state is bogus.
When a system fails, some degradation can be declared acceptable.
That's not the "certified" state either and you haven't expressed concerns about it.
Having a third AoA sensor to fail functional with one failure is a feature the regulator could require from all transport aircraft built after date XYZ.
Would that improve safety? Maybe.
Still arguing that it's a non certified state is bogus.
When a system fails, some degradation can be declared acceptable.
The difference is in the MAX you get more than the stick shaker with an AoA failure you get a change of aircraft characteristics in certain areas. That change is "unknown in quantity" close to a stall and that change is known to be outside certifiable limits.
I expect it is very easy to get certification with a MCAS U/S, but I very much doubt it can be done without detailed training best done in the simulator - so there is a reduced startle factor with less experienced pilots.
Keep in mind where MCAS is actually required is in a small window of variable conditions and to NEED to be there, it is probably not a walk in the park day. So best not to have more surprises and start learning along the way when workload is already high.
Example - above 1,000 ft flaps up AP on - Birds! pull up, AP disengages miss birds, Another flock of birds again pull up in MCAS area now and it trims. You then trim to level as birds seem gone (MCAS deactivated) yet another flock of birds - pull back, this time the coulomb just comes right back aft into your crouch just like a cable has broken. Startle factor for more than a fraction of a second and it is in a stall, at best a few thousand feet AGL.
So you have just done two avoidance's in a B737, then third was in a fighter jet. Best to have some fighter jet training if that is what can happen.
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An Airbus can be dispatched with one ADIR inop. Why such strong comments from people that know so little about how aircraft are certified or flown? Airbus has had its own significant issues with undesired control imputs due to faulty sensors, it is only a matter of luck that more of them did not crash.
Listen to what 737 is saying and you may learn something about how systems are designed, how we deal with failures before dispatch and how we deal with failures in flight. This is not Boeing specific. There are many many aircraft out there that are trickier to fly and have been flying for decades than a 737MAX.
Does this all mean that Boeing has nothing to learn from this? of course not but there are lesson here for Lion Air, ET, the FAA and pilots on general. Simplifying this into " the MAX is unsafe and is all Boeing´s fault" means missing many important lessons here.
From a statistical point of view a 737 MAX is way safer than your car, your bike, taking the bus, etc,etc,etc a take it that you are not rushing out to buy a a brand new car every six months so ease up on the hysteria chaps.
Listen to what 737 is saying and you may learn something about how systems are designed, how we deal with failures before dispatch and how we deal with failures in flight. This is not Boeing specific. There are many many aircraft out there that are trickier to fly and have been flying for decades than a 737MAX.
Does this all mean that Boeing has nothing to learn from this? of course not but there are lesson here for Lion Air, ET, the FAA and pilots on general. Simplifying this into " the MAX is unsafe and is all Boeing´s fault" means missing many important lessons here.
From a statistical point of view a 737 MAX is way safer than your car, your bike, taking the bus, etc,etc,etc a take it that you are not rushing out to buy a a brand new car every six months so ease up on the hysteria chaps.
My sad prediction:
The next Max crash will involve a 3rd world airline without mature Western Airline training and experience with a crew so hyper vigilant about a MCAS runway that they will misdiagnose something else as a MCAS failure go to the stab cut out switches and now have to manually trim an out of trim aircraft, which is basically never done, get behind the airplane and fly it into the ground......
The next Max crash will involve a 3rd world airline without mature Western Airline training and experience with a crew so hyper vigilant about a MCAS runway that they will misdiagnose something else as a MCAS failure go to the stab cut out switches and now have to manually trim an out of trim aircraft, which is basically never done, get behind the airplane and fly it into the ground......
I had a Stickshake activate in the cruise at M.84 in a B747. Did we crash? No we evaluated the other flight parameters, disconnected the automatics for awhile, deactivating the false warnings and landed safely where the component was changed. Simples.
An Airbus can be dispatched with one ADIR inop. Why such strong comments from people that know so little about how aircraft are certified or flown? Airbus has had its own significant issues with undesired control imputs due to faulty sensors, it is only a matter of luck that more of them did not crash.
Listen to what 737 is saying and you may learn something about how systems are designed, how we deal with failures before dispatch and how we deal with failures in flight. This is not Boeing specific. There are many many aircraft out there that are trickier to fly and have been flying for decades than a 737MAX.
Does this all mean that Boeing has nothing to learn from this? of course not but there are lesson here for Lion Air, ET, the FAA and pilots on general. Simplifying this into " the MAX is unsafe and is all Boeing´s fault" means missing many important lessons here.
From a statistical point of view a 737 MAX is way safer than your car, your bike, taking the bus, etc,etc,etc a take it that you are not rushing out to buy a a brand new car every six months so ease up on the hysteria chaps.
Listen to what 737 is saying and you may learn something about how systems are designed, how we deal with failures before dispatch and how we deal with failures in flight. This is not Boeing specific. There are many many aircraft out there that are trickier to fly and have been flying for decades than a 737MAX.
Does this all mean that Boeing has nothing to learn from this? of course not but there are lesson here for Lion Air, ET, the FAA and pilots on general. Simplifying this into " the MAX is unsafe and is all Boeing´s fault" means missing many important lessons here.
From a statistical point of view a 737 MAX is way safer than your car, your bike, taking the bus, etc,etc,etc a take it that you are not rushing out to buy a a brand new car every six months so ease up on the hysteria chaps.
Just saying it should have had better training, and now will still need better training.
But certification to be called Big Brother is pretty hard to claim without correct training under version 1 & 2 from what details have been released.
The modified MCAS - https://www.boeing.com/commercial/73...e-updates.page (17Apr - any later version) would only require two sensors to disable MCAS.
The acceptability of this depends the ease of flight for ‘abnormal conditions’ and the probability of occurrence. This should not be a problem, MCAS is only used in a small part of the flight envelope, not likely to be encountered often. However, given that previous 737s are sensitive to nose up pitch with high thrust - GA mode, then the acceptability of ‘abnormal’ flight in the 737 Max without MCAS might be more questionable.
Also consider the extent of the differences between the 737 Max and previous models - ‘it will be the same’, except for MCAS, etc. Are the normal flight handling qualities of the MAX sufficiently similar to previous aircraft - margin to certification limit - this is not the same judgement as ‘same type rating’.
The confidence in the modified design might be further questioned by the discovery of inoperative AoA Disagree elements in some aircraft. The effect of this depends on interpretation - either a simple pin program error (customer option), or a software error preventing the option from working, N.B. where - AoA Disagree is now a major aspect of the modification. https://finance.yahoo.com/news/boein...205151888.html (In the ‘continued’ section)
The objective of the modification is to prevent large trim changes which could reduce the ability to fly the aircraft. If this is not assured, then MCAS would require much higher integrity - flight with MCAS disabled is judged unacceptable, or the software has insufficient integrity.
Then the system might require three vanes or alternative means of cross checking / use of sensors. Such integration will take time and may involve complex certification assessment given the history of events.
Re preflight vane checks; the validity of electrical connections might be checked, but not the accuracy of the AoA value, which like an aircraft requires the vane to be ‘flying’.
Re stick shake; AoA for Vsw is an alerting function - cross check with triple speed display.
AoA for MCAS is high-order safety action function - system disabling, no alternative.
The acceptability of this depends the ease of flight for ‘abnormal conditions’ and the probability of occurrence. This should not be a problem, MCAS is only used in a small part of the flight envelope, not likely to be encountered often. However, given that previous 737s are sensitive to nose up pitch with high thrust - GA mode, then the acceptability of ‘abnormal’ flight in the 737 Max without MCAS might be more questionable.
Also consider the extent of the differences between the 737 Max and previous models - ‘it will be the same’, except for MCAS, etc. Are the normal flight handling qualities of the MAX sufficiently similar to previous aircraft - margin to certification limit - this is not the same judgement as ‘same type rating’.
The confidence in the modified design might be further questioned by the discovery of inoperative AoA Disagree elements in some aircraft. The effect of this depends on interpretation - either a simple pin program error (customer option), or a software error preventing the option from working, N.B. where - AoA Disagree is now a major aspect of the modification. https://finance.yahoo.com/news/boein...205151888.html (In the ‘continued’ section)
The objective of the modification is to prevent large trim changes which could reduce the ability to fly the aircraft. If this is not assured, then MCAS would require much higher integrity - flight with MCAS disabled is judged unacceptable, or the software has insufficient integrity.
Then the system might require three vanes or alternative means of cross checking / use of sensors. Such integration will take time and may involve complex certification assessment given the history of events.
Re preflight vane checks; the validity of electrical connections might be checked, but not the accuracy of the AoA value, which like an aircraft requires the vane to be ‘flying’.
Re stick shake; AoA for Vsw is an alerting function - cross check with triple speed display.
AoA for MCAS is high-order safety action function - system disabling, no alternative.
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There’s another issue here.
MCAS will be solved and it appears BA are well on the way. However, there is little denying that they were somewhat disingenuous with it’s introduction and consequently their reputation & credibility has taken a hit. So, the question has to be what else slipped through the regulatory net? In other words, are there other things in the Max that customers have yet to discover?
If I had just bought a pile of Maxs at $100M a pop, I would want to get a warm feeling.
MCAS will be solved and it appears BA are well on the way. However, there is little denying that they were somewhat disingenuous with it’s introduction and consequently their reputation & credibility has taken a hit. So, the question has to be what else slipped through the regulatory net? In other words, are there other things in the Max that customers have yet to discover?
If I had just bought a pile of Maxs at $100M a pop, I would want to get a warm feeling.