Boeing 737 Max Software Fixes Due to Lion Air Crash Delayed
Ian W, #698 / #696
‘Importance’ is in the context of a Fight Safety review and training requirements post MCAS accidents - learning from past events.
The argument for ‘feel awareness’ is both for normal operations, where the wider than normal flight envelope might be less familiar - automation dependency view; and in abnormal operation as experience of failure conditions in comparison.
Trim runaway - directional nose up/down and increasing force with trim deviation and speed, hence speed management, and for ‘feel shift’ with an overall increase of stick force (normally near stall but what about failures at other times).
There is supporting evidence for feel issues from incidents in the 737, I recall a severe roll upset due to fuel mismanagement, only apparent after autopilot disconnect (AAIB?). The crew expected the aircraft to fly wings level with zero force and stick central, thus their datum was offset and the aircraft continued to roll (try this as a surprise event in the sim).
Events in other aircraft show similar problems in pitch, where the expected norm - in trim, zero force, was taken as datum, but with trim offset the aircraft flight path continued to deviate ‘unexpectedly’, often interpreted as ‘loss of control’.
‘Importance’ is in the context of a Fight Safety review and training requirements post MCAS accidents - learning from past events.
The argument for ‘feel awareness’ is both for normal operations, where the wider than normal flight envelope might be less familiar - automation dependency view; and in abnormal operation as experience of failure conditions in comparison.
Trim runaway - directional nose up/down and increasing force with trim deviation and speed, hence speed management, and for ‘feel shift’ with an overall increase of stick force (normally near stall but what about failures at other times).
There is supporting evidence for feel issues from incidents in the 737, I recall a severe roll upset due to fuel mismanagement, only apparent after autopilot disconnect (AAIB?). The crew expected the aircraft to fly wings level with zero force and stick central, thus their datum was offset and the aircraft continued to roll (try this as a surprise event in the sim).
Events in other aircraft show similar problems in pitch, where the expected norm - in trim, zero force, was taken as datum, but with trim offset the aircraft flight path continued to deviate ‘unexpectedly’, often interpreted as ‘loss of control’.
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Has to be said that the two words that come to mind are "Bombardier" and "karma"...
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It is my understanding that this is why MCAS was invented in the first place. And once it is inop, pilots will be responsible for keeping the aircraft out of the stall regions of the performance envelope.
At what AoA, speed, winds, load, etc does one need to start thinking about that extra bump in lift and the nose kicking up?
EEngr...this was one of my first thoughts on this issue, we are all aware that at a certain point, the engine nacelles give it a bump in lift...What I would like to know, and I am certain pilots would like to know, what are these conditions?
At what AoA, speed, winds, load, etc does one need to start thinking about that extra bump in lift and the nose kicking up?
At what AoA, speed, winds, load, etc does one need to start thinking about that extra bump in lift and the nose kicking up?
But then again a slide show on a iPad will give you the same experience.
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Software?
So much has been posted on this subject that I must admit I have lost track, however this may be new and of interest.
https://spectrum.ieee.org/aerospace/...ware-developer
https://spectrum.ieee.org/aerospace/...ware-developer
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Whoa - FAA finds MCAS operationally suitable - initial training approved
https://www.bloomberg.com/news/artic...ing-on-737-max
The board last month conducted a new evaluation of MCAS as a result of the accidents.
How Boeing Safety Feature Became a Suspect in Crashes: QuickTake
“The MCAS system was found to be operationally suitable,” the report said.The report said that MCAS should be a “special emphasis” area for pilots being trained on the plane for the first time or transitioning to it from the most recent generation of 737 aircraft.“MCAS ground training must address system description, functionality, associated failure conditions and flight crew alerting,” the report said.
The board last month conducted a new evaluation of MCAS as a result of the accidents.
How Boeing Safety Feature Became a Suspect in Crashes: QuickTake
“The MCAS system was found to be operationally suitable,” the report said.The report said that MCAS should be a “special emphasis” area for pilots being trained on the plane for the first time or transitioning to it from the most recent generation of 737 aircraft.“MCAS ground training must address system description, functionality, associated failure conditions and flight crew alerting,” the report said.
Psychophysiological entity
Yes, Bend alot's naked statement says so much.
Keeping in mind, no other breed of the 737 would have put a nose down input to the stabiliser.
Psychophysiological entity
L39 Guy's comprehensive post contained:
I have wondered over these weeks if indeed prior knowledge of the MCAS effectively being inhibited by the autopilot, might have played a role in his hurried attempts. Yes, it would have been desperate action, perhaps born of the vivid Lion Air memory mingled with the feeling of unreality. Imagine just what was going on in his mind. Form the point of view of utter disbelief, it would almost have been better if he'd no prior imagery filling his thoughts. Of course, I'm assuming he knew the autopilot would inhibit MCAS.
Stall? I feel that after a few seconds he would have been fairly confident he wasn't stalling - given the power settings and assumed general feel but yes, there were two column, rather sharp forward pushes, the first coinciding with a marked UP attitude spike. He trimmed AND in what looks like a double pulse, but nothing that would make me think he's countering the STS at that point. I would need to compare these to a lot of normal flights to draw any conclusions,
. . .in the Ethiopian case, engaging the autopilot at 400 ft is a definite faux pas as it is contrary to the memory UAS drill and, if the aircraft was indeed stalled, another definite faux pas as one does not recover from a stall with the autopilot. cont.
I have wondered over these weeks if indeed prior knowledge of the MCAS effectively being inhibited by the autopilot, might have played a role in his hurried attempts. Yes, it would have been desperate action, perhaps born of the vivid Lion Air memory mingled with the feeling of unreality. Imagine just what was going on in his mind. Form the point of view of utter disbelief, it would almost have been better if he'd no prior imagery filling his thoughts. Of course, I'm assuming he knew the autopilot would inhibit MCAS.
Stall? I feel that after a few seconds he would have been fairly confident he wasn't stalling - given the power settings and assumed general feel but yes, there were two column, rather sharp forward pushes, the first coinciding with a marked UP attitude spike. He trimmed AND in what looks like a double pulse, but nothing that would make me think he's countering the STS at that point. I would need to compare these to a lot of normal flights to draw any conclusions,
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L39 Guy's comprehensive post contained:
I have wondered over these weeks if indeed prior knowledge of the MCAS effectively being inhibited by the autopilot, might have played a role in his hurried attempts. Yes, it would have been desperate action, perhaps born of the vivid Lion Air memory mingled with the feeling of unreality. Imagine just what was going on in his mind. Form the point of view of utter disbelief, it would almost have been better if he'd no prior imagery filling his thoughts. Of course, I'm assuming he knew the autopilot would inhibit MCAS.,
I have wondered over these weeks if indeed prior knowledge of the MCAS effectively being inhibited by the autopilot, might have played a role in his hurried attempts. Yes, it would have been desperate action, perhaps born of the vivid Lion Air memory mingled with the feeling of unreality. Imagine just what was going on in his mind. Form the point of view of utter disbelief, it would almost have been better if he'd no prior imagery filling his thoughts. Of course, I'm assuming he knew the autopilot would inhibit MCAS.,
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L39 Guy's comprehensive post contained:
I have wondered over these weeks if indeed prior knowledge of the MCAS effectively being inhibited by the autopilot, might have played a role in his hurried attempts. Yes, it would have been desperate action, perhaps born of the vivid Lion Air memory mingled with the feeling of unreality. Imagine just what was going on in his mind. Form the point of view of utter disbelief, it would almost have been better if he'd no prior imagery filling his thoughts. Of course, I'm assuming he knew the autopilot would inhibit MCAS.
Stall? I feel that after a few seconds he would have been fairly confident he wasn't stalling - given the power settings and assumed general feel but yes, there were two column, rather sharp forward pushes, the first coinciding with a marked UP attitude spike. He trimmed AND in what looks like a double pulse, but nothing that would make me think he's countering the STS at that point. I would need to compare these to a lot of normal flights to draw any conclusions,
I have wondered over these weeks if indeed prior knowledge of the MCAS effectively being inhibited by the autopilot, might have played a role in his hurried attempts. Yes, it would have been desperate action, perhaps born of the vivid Lion Air memory mingled with the feeling of unreality. Imagine just what was going on in his mind. Form the point of view of utter disbelief, it would almost have been better if he'd no prior imagery filling his thoughts. Of course, I'm assuming he knew the autopilot would inhibit MCAS.
Stall? I feel that after a few seconds he would have been fairly confident he wasn't stalling - given the power settings and assumed general feel but yes, there were two column, rather sharp forward pushes, the first coinciding with a marked UP attitude spike. He trimmed AND in what looks like a double pulse, but nothing that would make me think he's countering the STS at that point. I would need to compare these to a lot of normal flights to draw any conclusions,
Boeing would have been better off telling pilots to implement UAS procedure rather than runaway trim. If the flaps never go all the way up then MCAS can never be activated and the plane is kept below MCAS activation height. Boeing would have known all this after the first crash.
These seem the details recent active pilots on the MAX can not answer, first or third World.
The FDR data of ET302 shows automatic trim down after flap was selected up but before the trailing edge flap did reach zero degrees. That could be taken as a hint for flap handle position being used by the and not flap position...
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The flap position monitoring is a function of the Flap Slate Electronic Unit, so my guess is that the FSEU would send a signal to MCAS (which is a subroutine of the FCC) regarding flap position. There are one or more digital data busses which allow the various electronic components to exchange information, so I figure this would be the easier option than running a dedicated sensor to the flap handle. Reference the DFDR data from ET302 mentioned in the post immediately prior, there could be some threshold value beyond which the flaps are presumed up (i.e. < 0.2 degrees, slats retracted, etc.).
Last edited by 737 Driver; 20th Apr 2019 at 20:50. Reason: Added comment
the Boeing AD could have spelt all that out at the time. Instead they choose to play dumb and give out minimal information. Before MCAS could even kick in Boeing knew that a faulty AoA sensor would be already causing a heavy workload the moment the plane left the ground.
