Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed
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b1lance
We agree , I think. My wording is not necessarily certifiable.
But
Correct me if I am wrong:
All transport category aircraft MUST have positive stability inside the flight envelope . Period!
And what we are seeing here is neutral and possible negative stability, which is, if not corrected defined as deadly!
Periscope Down
Cpt B
But
Correct me if I am wrong:
All transport category aircraft MUST have positive stability inside the flight envelope . Period!
And what we are seeing here is neutral and possible negative stability, which is, if not corrected defined as deadly!
Periscope Down
Cpt B
Salute!
@ b1lanc..... and others.....
I think what some of us are talking about when we assert the jet is not stable is the stated purpose of MCAS, I also believe PEI is the most qualified to address this as he is a bonafide "golden arm" from both the USN and RAF and....
According to a graph from another blog, the plane requires less pitch control force per increased units of AoA rather than more force. In short, you should have to use more back pressure/movement to increase your AoA. But the MAX is like trimming nose up as you pull back, and it gets easier and easier to reach a stall AoA. That's the way I understand it. And the reason is not the 737 feel system implemntation, it's the actual aerodynamics of the plane due to the new engine mounting configuration and ssociated pitch moments and all that sort of thing.
So Boeing let the existing feel system work like before, and treated the problem with an aerodynamic solution. They moved the stabilizer angle. Problem is that other systems use AoA, and the damned FUBAR AoA vane not only activates MCAS but the stall warning systems and warning lights and....... Without the actual AoA that Boeing uses, I would guess that the stall AoA value for the shaker is higher than the value MCAS uses to trim nose down. Maybe FCeng, Dave or PEI can help here.
Anyway, THAT is what several of us are referring to as a stability issue. The plane should require more force to reach stall and not less.
Gums clarifies....
@ b1lanc..... and others.....
I think what some of us are talking about when we assert the jet is not stable is the stated purpose of MCAS, I also believe PEI is the most qualified to address this as he is a bonafide "golden arm" from both the USN and RAF and....
According to a graph from another blog, the plane requires less pitch control force per increased units of AoA rather than more force. In short, you should have to use more back pressure/movement to increase your AoA. But the MAX is like trimming nose up as you pull back, and it gets easier and easier to reach a stall AoA. That's the way I understand it. And the reason is not the 737 feel system implemntation, it's the actual aerodynamics of the plane due to the new engine mounting configuration and ssociated pitch moments and all that sort of thing.
So Boeing let the existing feel system work like before, and treated the problem with an aerodynamic solution. They moved the stabilizer angle. Problem is that other systems use AoA, and the damned FUBAR AoA vane not only activates MCAS but the stall warning systems and warning lights and....... Without the actual AoA that Boeing uses, I would guess that the stall AoA value for the shaker is higher than the value MCAS uses to trim nose down. Maybe FCeng, Dave or PEI can help here.
Anyway, THAT is what several of us are referring to as a stability issue. The plane should require more force to reach stall and not less.
Gums clarifies....
As I understand it ...
Boeing kept quiet about MCAS because they wanted to present it as "the same as an NG", and didn't want to do any additional simulator training. Not so much because it would be an issue to allocate crews for this as the aircraft came on line, but because no simulators would be available in time. And apparently they are still not, only a couple are available now, and some of the major owners have still not yet got one. That's the real delay there would have been in introduction of the aircraft.
One has to ask, of the few simulators already around, did they have the fidelity to represent an AoA failure accurately.
Now we have the prospect of the aircraft being offered for recertification, but these training aids are still not fully available. And are they going to represent the antics of the New MCAS properly ? So while the aircraft may get recertified, whatever will be required to get the crews up to standard before they first start using it. We already have accounts of established NG crews being presented with a Max one day, in revenue service, after just the PowerPoint training, and feeling it was far more different than they had been given to understand.
Boeing kept quiet about MCAS because they wanted to present it as "the same as an NG", and didn't want to do any additional simulator training. Not so much because it would be an issue to allocate crews for this as the aircraft came on line, but because no simulators would be available in time. And apparently they are still not, only a couple are available now, and some of the major owners have still not yet got one. That's the real delay there would have been in introduction of the aircraft.
One has to ask, of the few simulators already around, did they have the fidelity to represent an AoA failure accurately.
Now we have the prospect of the aircraft being offered for recertification, but these training aids are still not fully available. And are they going to represent the antics of the New MCAS properly ? So while the aircraft may get recertified, whatever will be required to get the crews up to standard before they first start using it. We already have accounts of established NG crews being presented with a Max one day, in revenue service, after just the PowerPoint training, and feeling it was far more different than they had been given to understand.
Yo gums, #804 You invite comment.
Your ‘The plane should require more force to reach stall and not less’, has the essentials. Pedantically, the stick force should increase with decreasing speed, similarly with nose up manoeuvre. Also, considering effects of increasing thrust.
- - -
It appears that the 737 Max, whilst retaining positive stick force stability throughout the flight envelope, does not exhibit sufficient to satisfy certification requirements. This ‘stability’ as sensed by the pilot (stick force) is ‘artificially’ increased by applying trim - MCAS. Because trim is so effective in the 737, the amount required is relatively small.
The small part of the fight envelope and flight conditions requiring enhancement suggest that flight without the MCAS trim would not be overly demanding; there is no step change between requiring trim (certification) and normal operation. However, the 737 in general appears very sensitive to nose up pitch change due to power increase - GA low speed, thus there is added concern.
Assuming that modification prevents any significant trim deviation due to system / sensor malfunction - it must, then all the crew need to know from training are the principles of MCAS (like STS), awareness of when MCAS is not available, and thus the need for careful handling. The points above suggest that the critical manoeuvre is GA - simulator training debatable.
The proposed mod does not provide a clear alert that MCAS is unavailable. MCAS inhibition has to be deduced from other indications; a minor point which might be forgotten during the surprise of a GA.
This would also be a basis for discussion by the certification team, as should the potential misleading indications from AoA display with disagreement.
The duration of the re-certification (flights / hours), as speculation, could indicate that other aspects have to be considered based on the accident findings - e.g. recovery from trim runaway. Are the assumptions that pilot identification and intervention in 737 NG, et al, still valid, and can these be assumed for the 737 MAX (grandfathers), given that the MAX appears to differ from other 737s due to the need for MCAS.
Perhaps even more surprises as long as there is no publication (or leak) of exactly what caused an erroneous value of AoA. How do you fix something what cannot be identified, nor repeated (software glitch, chaffed cable); you might be able to prevent a hazardous outcome (mod), but how sure - certification - public perception, lawyers; this could get interesting.
Your ‘The plane should require more force to reach stall and not less’, has the essentials. Pedantically, the stick force should increase with decreasing speed, similarly with nose up manoeuvre. Also, considering effects of increasing thrust.
- - -
It appears that the 737 Max, whilst retaining positive stick force stability throughout the flight envelope, does not exhibit sufficient to satisfy certification requirements. This ‘stability’ as sensed by the pilot (stick force) is ‘artificially’ increased by applying trim - MCAS. Because trim is so effective in the 737, the amount required is relatively small.
The small part of the fight envelope and flight conditions requiring enhancement suggest that flight without the MCAS trim would not be overly demanding; there is no step change between requiring trim (certification) and normal operation. However, the 737 in general appears very sensitive to nose up pitch change due to power increase - GA low speed, thus there is added concern.
Assuming that modification prevents any significant trim deviation due to system / sensor malfunction - it must, then all the crew need to know from training are the principles of MCAS (like STS), awareness of when MCAS is not available, and thus the need for careful handling. The points above suggest that the critical manoeuvre is GA - simulator training debatable.
The proposed mod does not provide a clear alert that MCAS is unavailable. MCAS inhibition has to be deduced from other indications; a minor point which might be forgotten during the surprise of a GA.
This would also be a basis for discussion by the certification team, as should the potential misleading indications from AoA display with disagreement.
The duration of the re-certification (flights / hours), as speculation, could indicate that other aspects have to be considered based on the accident findings - e.g. recovery from trim runaway. Are the assumptions that pilot identification and intervention in 737 NG, et al, still valid, and can these be assumed for the 737 MAX (grandfathers), given that the MAX appears to differ from other 737s due to the need for MCAS.
Perhaps even more surprises as long as there is no publication (or leak) of exactly what caused an erroneous value of AoA. How do you fix something what cannot be identified, nor repeated (software glitch, chaffed cable); you might be able to prevent a hazardous outcome (mod), but how sure - certification - public perception, lawyers; this could get interesting.
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Yes, lots of test flights and hours flown. It makes one wonder whether the Boeing Test Pilot fraternity went back and had a look at a particular part of the flight envelope and came back scratching their chins.
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I am beginning to become pedantic about the word trim as applied to MCAS. Let's be clear here trim in a conventional sense relieves pressure on the control column, at its simplest by a spring or small movable surface on the trailing edge of a control surface. Although the horizontal stabiliser is connected to the trim wheel in a 737 lets be clear that MCAS operates to give a nose down pitch CONTROL.
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-Thanks, you just brought back good old memories, my first job as a F/O. Entering 9 waypoints , mem couldn't take more and than sending them to the "PMS" I believe. Good old times was a lot of hand flying the classic, responsive/forgiving and humble, unlike the MD11 later. Sorry off topic.....
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Looking back, I wonder what the Boeing and FAA assumptions and plans originally were and now are on the subject of simulators for the new generation of MAX (7-8-9-10) aircraft ? Did the FAA and other regulators require a dedicated simulator series? Did Boeing assume these were or were not necessary? What does which regulation(s) say about this?
The only confirmation appears to be that Boeing had an E-CAB also usable for MAX. Some suggest that at the start of this year there were only 1 or 2 more basic sims useable for MAX. Simulator builders would have to prepare, get MAX drawings, get MAX data sets, etcetera. I have not heard about any of that.
If no in-depth plans were made and work started on building simulators, then requiring sim-time by new rules/regulations would put the availability of simulators on the critical time path.
Would be interesting to learn more about this subject.
The only confirmation appears to be that Boeing had an E-CAB also usable for MAX. Some suggest that at the start of this year there were only 1 or 2 more basic sims useable for MAX. Simulator builders would have to prepare, get MAX drawings, get MAX data sets, etcetera. I have not heard about any of that.
If no in-depth plans were made and work started on building simulators, then requiring sim-time by new rules/regulations would put the availability of simulators on the critical time path.
Would be interesting to learn more about this subject.
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We agree , I think. My wording is not necessarily certifiable.
But
Correct me if I am wrong:
All transport category aircraft MUST have positive stability inside the flight envelope . Period!
And what we are seeing here is neutral and possible negative stability, which is, if not corrected defined as deadly!
Periscope Down
Cpt B
But
Correct me if I am wrong:
All transport category aircraft MUST have positive stability inside the flight envelope . Period!
And what we are seeing here is neutral and possible negative stability, which is, if not corrected defined as deadly!
Periscope Down
Cpt B
As I understand it ...
Boeing kept quiet about MCAS because they wanted to present it as "the same as an NG", and didn't want to do any additional simulator training. Not so much because it would be an issue to allocate crews for this as the aircraft came on line, but because no simulators would be available in time.
Boeing kept quiet about MCAS because they wanted to present it as "the same as an NG", and didn't want to do any additional simulator training. Not so much because it would be an issue to allocate crews for this as the aircraft came on line, but because no simulators would be available in time.
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And because someone in Boeing Sales apparently told SWA that there would be no need for a MAX simulator qualification, and they were so sure this would be the case that they promised that Boeing would pay SWA one million dollars per airframe (or maybe knock a cool million off the price?) if simulator time was required.
Why is this suddenly not appropriate now?
Edmund
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Quote: " Didn't they have a way of training pilots without sims when the 737 was first certified? "
Yes, they did. In 1967 they flew circuits in the actual aircraft...doing touch and go's, stalls and other risky (in today's terms) stuff.
Yes, they did. In 1967 they flew circuits in the actual aircraft...doing touch and go's, stalls and other risky (in today's terms) stuff.
And there were a lot of training flight crashes in the early jet years.
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Didn't they have a way of training pilots without sims when the 737 was first certified? Why is this suddenly not appropriate now?
I dont know if I understand the quote correctly ... but for clarity would like to add ... yes, some aircraft were 'born' without the benefit of simulators... if you go through the history of accident investigations you find the reasons why simulators have become essential tools... in that sense they are always appropriate.
In this specific case they may turn out to be even more important because of the pilot training failure suggested by a number of posters.
If the plane would turn out to be causal then simulators will be important. If training turns out to be causal then simulators will be important.
Salute!
Yep, and one of the worst ones was in my home town and the trainee pilot had been a member of my Civil Air Patrol squad.
Classic case of letting trainee go too far, and then I have a hard time with trying a two-engine approach with the other two on the opposite wing in idle. And as the "sky gods" here ( mainly on other thread) will tellya - get the rudder in early, 'cause once the yaw starts you will get roll and if you pull back on the stick/yoke, then you get even more yaw and roll. In short, you're screwed. The report is better than the summary.
ASN Aircraft accident Douglas DC-8-51 N802E New Orleans, LA
As a matter of course, I taught single-engine go arounds in the Dragonfly, which had obscene motors versus the trainer. Each one had 50% more thrust than both of the trainer motors combined. If you pushed up the good motor before getting in the rudder, then you replicated the DC-8 accident scenario. Our first two non-combat losses were single-engine go arounds - fatals. So I would take my student up high and show them what happened if they crammed the throttle foward before putting in rudder. And we were a straight wing, not swept, which are worse.
..
Gums sends...
And there were a lot of training flight crashes in the early jet years.
Classic case of letting trainee go too far, and then I have a hard time with trying a two-engine approach with the other two on the opposite wing in idle. And as the "sky gods" here ( mainly on other thread) will tellya - get the rudder in early, 'cause once the yaw starts you will get roll and if you pull back on the stick/yoke, then you get even more yaw and roll. In short, you're screwed. The report is better than the summary.
ASN Aircraft accident Douglas DC-8-51 N802E New Orleans, LA
As a matter of course, I taught single-engine go arounds in the Dragonfly, which had obscene motors versus the trainer. Each one had 50% more thrust than both of the trainer motors combined. If you pushed up the good motor before getting in the rudder, then you replicated the DC-8 accident scenario. Our first two non-combat losses were single-engine go arounds - fatals. So I would take my student up high and show them what happened if they crammed the throttle foward before putting in rudder. And we were a straight wing, not swept, which are worse.
..
Gums sends...
But the key thing was they just trained for line operations rather than sustained problem training. And still the landing gear and structures used to take a pasting.
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And, more importantly, the main gear is also lengthened so that even with the bigger engines, the engine-to-ground clearance is only 2-3 inches less than the NG.
The 737 Max has a semi-levered main gear (a bit like that on the 777-300ER, mostly for tail strike protection on the Max 9) and also a "shrink-link" that in effect shortens the longer Max main leg on retraction so that it can still be accommodated in the bay.
The 737 Max has a semi-levered main gear (a bit like that on the 777-300ER, mostly for tail strike protection on the Max 9) and also a "shrink-link" that in effect shortens the longer Max main leg on retraction so that it can still be accommodated in the bay.
