737 max nacelle lift generation
A good summary. I understand that, long ago and far away in the initial 1960s 737 design, the short gear legs were seen as a feature, as it enabled ground handling access to the baggage holds etc to be the same as competitors DC9 and One-Eleven, for which with rear mounted engines the engine clearance was not a problem. And the short legs folded up nicely between the main spars. Unfortunately that was never thought to present an issue for the future, but it has done ever since, as each new generation of 737 designers struggled with this bigger engine but same main spars design, doubtless along with plenty of "what idiot designed things like this" comments.
Because for each new generation there was this question of whether it was a new type. Commercial team to airlines it was "Yes, trade in your old fleet for this new one". Certification team to FAA it was "No, it's a 737, grandfather rules apply".
Because for each new generation there was this question of whether it was a new type. Commercial team to airlines it was "Yes, trade in your old fleet for this new one". Certification team to FAA it was "No, it's a 737, grandfather rules apply".
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The Nacelles produce drag, above the center of lift. Round permanent speed brakes.
Nacelle airflow and forces are considerably more complex than your assertion suggests, I'm afraid. Indeed, perhaps run some research into, say, Concorde's story on the subject which is in threads in this site. SR-71 Blackbird has a similar tale. At the end of the day, the nacelle can produce quite a good deal of lift force, not to mention thrust force.
above the center of lift.
This doesn't appear to make a lot of sense to me ?
galaxy flyer makes a good reference to the basic fact that any aeroplane design is a compromise and it is difficult to opine definite, specific views without considering and addressing that fact.
Nacelle airflow and forces are considerably more complex than your assertion suggests, I'm afraid. Indeed, perhaps run some research into, say, Concorde's story on the subject which is in threads in this site. SR-71 Blackbird has a similar tale. At the end of the day, the nacelle can produce quite a good deal of lift force, not to mention thrust force.
above the center of lift.
This doesn't appear to make a lot of sense to me ?
galaxy flyer makes a good reference to the basic fact that any aeroplane design is a compromise and it is difficult to opine definite, specific views without considering and addressing that fact.
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A good summary. I understand that, long ago and far away in the initial 1960s 737 design, the short gear legs were seen as a feature, as it enabled ground handling access to the baggage holds etc to be the same as competitors DC9 and One-Eleven, for which with rear mounted engines the engine clearance was not a problem. And the short legs folded up nicely between the main spars. Unfortunately that was never thought to present an issue for the future, but it has done ever since, as each new generation of 737 designers struggled with this bigger engine but same main spars design, doubtless along with plenty of "what idiot designed things like this" comments.
Because for each new generation there was this question of whether it was a new type. Commercial team to airlines it was "Yes, trade in your old fleet for this new one". Certification team to FAA it was "No, it's a 737, grandfather rules apply".
Because for each new generation there was this question of whether it was a new type. Commercial team to airlines it was "Yes, trade in your old fleet for this new one". Certification team to FAA it was "No, it's a 737, grandfather rules apply".
it is not like the aircraft is lifting its nose into a stall. It is the stick feel "only"
If the stick forces and gradients (OK, "feel") get a bit too far away from a nice region, then the aircraft can, indeed, lift its nose into a stall. That's one of the reasons why we have requirements for static stability. In this case the nacelle lip normal force "helps" the aircraft to become less statically stable.
not because a test pilot said it was too light at the top end.
If the stick forces and gradients (OK, "feel") get a bit too far away from a nice region, then the aircraft can, indeed, lift its nose into a stall. That's one of the reasons why we have requirements for static stability. In this case the nacelle lip normal force "helps" the aircraft to become less statically stable.
not because a test pilot said it was too light at the top end.
I would ask MAX pilots what their non normal says when a trim malfunction causes MCAS to be inop. Does the FAA say to declare an emergency and land ASAP because you are flying a dangerous aircraft? Do they tell you what flight region to avoid?
And even if it had, it would have been no help to Boeing as it would have still left a need for crews to be trained on a handling difference between the MAX and the NG - the very thing that MCAS was designed to obviate.
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Probably not.
I think a caution as Northup did with the T-38 would suffice. As it is I don't think MAX crews are exposed to the MCAS off handling characteristics now even though certain malfunctions would have them flying the MAX without MCAS.
I think a caution as Northup did with the T-38 would suffice. As it is I don't think MAX crews are exposed to the MCAS off handling characteristics now even though certain malfunctions would have them flying the MAX without MCAS.
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If the autopilot doesn't need MCAS a real pilot shouldn't either.
Except one would expect the automatics to have a much faster computation response compared to a human pilot's capability.
Except one would expect the automatics to have a much faster computation response compared to a human pilot's capability.
It's the concept that the pull back feel gets 'lighter' as you approach stall instead of 'heavier' - the exact sort of tactile feedback you don't want.
Of course, the PF when Asiana dumped that 777 during landing at SFO was having to pull back with something like 100 lbs. force but still didn't get the message that he was doing something wrong...
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If the autopilot doesn't need MCAS a real pilot shouldn't either. Just note the flight region where stick forces are lighter. Eg: T-38 "Minimum stick forces per G occur at approximately mach 0.9. Be careful not to overcontrol....."
I would ask MAX pilots what their non normal says when a trim malfunction causes MCAS to be inop. Does the FAA say to declare an emergency and land ASAP because you are flying a dangerous aircraft? Do they tell you what flight region to avoid?
I would ask MAX pilots what their non normal says when a trim malfunction causes MCAS to be inop. Does the FAA say to declare an emergency and land ASAP because you are flying a dangerous aircraft? Do they tell you what flight region to avoid?
Commercial aircraft are certified according to the average ability of the average line pilot, (I cannot remember the exact phrase they use). Hence control feel and reaction must be 'benign' and not have any marked changes throughout their range.
Test pilots and military fast jet pilots are selected for their well-above-average ability and awareness, so they would be aware of, and able to deal with, control non linearities
On your second point; in theory, a malfunctioning MCAS should have been noticed and seen as a THS runaway by the pilots, and the appropriate drill followed, (switch off the THS motor). But, we weren't in those cockpits, so I am not criticising nor passing comment, other than: since no pilots were told about the existence of MCAS, that made it a lot more tricky.
Had that been me, I would probably have declared a Mayday owing to control difficulties that I didn't understand at the time it happened.
Well, hang on a sec.......
Commercial aircraft are certified according to the average ability of the average line pilot, (I cannot remember the exact phrase they use). Hence control feel and reaction must be 'benign' and not have any marked changes throughout their range.
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Commercial aircraft are certified according to the average ability of the average line pilot, (I cannot remember the exact phrase they use). Hence control feel and reaction must be 'benign' and not have any marked changes throughout their range.
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We haven't had a MAX pilot chime in about what Boeing/Regulators say to do after a trim malfunction that has you turn off electric trim/MCAS......
Originally Posted by JimTx
Does the FAA say to declare an emergency and land ASAP because you are flying a dangerous aircraft? Do they tell you what flight region to avoid?
In this case, the aeroplane's handling is so different for normal, because of the engine config, that need for MCAS (a pretty complex system, by the sounds of it) is required at all indicates pretty clearly why you probably shouldn't fly it without it. As Uplinker says... normal line pilots are not test pilots.
STS on the other hand, is much more common, especially at low weights and high thrust (takeoff, go-around), but it's quite subtle - it trims slowly and typically only for a few seconds at the time. A proper trim runaway will typically result in a continous movement of the trim wheel in one direction.
We haven't had a MAX pilot chime in about what Boeing/Regulators say to do after a trim malfunction that has you turn off electric trim/MCAS. The possibility exists that the average line pilot will be hand flying a MAX without MCAS.
MCAS only activates at very high AoA, when approaching and exceeding the stall AoA, so the likelihood of a genuine MCAS activation on a line flight is very low.
STS on the other hand, is much more common, especially at low weights and high thrust (takeoff, go-around), but it's quite subtle - it trims slowly and typically only for a few seconds at the time. A proper trim runaway will typically result in a continous movement of the trim wheel in one direction.
As above, MCAS only really activates during stall, so I hope the average line pilot won't stall the aircraft if STS/MCAS become inoperative during flight. From what I remember from the simulator training, you have to keep pulling back after stick shaker to get MCAS to activate in the first place, so hopefully a qualified and competent pilot will recover from the stall way before that.
STS on the other hand, is much more common, especially at low weights and high thrust (takeoff, go-around), but it's quite subtle - it trims slowly and typically only for a few seconds at the time. A proper trim runaway will typically result in a continous movement of the trim wheel in one direction.
As above, MCAS only really activates during stall, so I hope the average line pilot won't stall the aircraft if STS/MCAS become inoperative during flight. From what I remember from the simulator training, you have to keep pulling back after stick shaker to get MCAS to activate in the first place, so hopefully a qualified and competent pilot will recover from the stall way before that.
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