Jan 4, 2021, 1:37 am
Last edit by: WineCountryUA
This is an archive thread, the archive thread is https://www.flyertalk.com/forum/united-airlines-mileageplus/1960195-b737max-cleared-faa-resume-passenger-flights-when-will-ua-max-flights-resume.html
Thread Topic
The reason for continuing this thread is to inform the UA traveler on the status of the MAX recertification and if / when UA might deploy the MAX aircraft. And UA flyer's thoughts about UA deploying the MAX if that was to happen.
United does not fly the 737 MAX 8 that has been involved in two recent crashes, but it does operate the 737 MAX 9.
How to tell if your flight is scheduled to be operated by the MAX 9:
View your reservation or flight status page, either on the web or on the app. United lists the entire aircraft type. Every flight that is scheduled to be on the 737 MAX will say "Boeing 737 MAX 9." If you see anything else -- for example, "Boeing 737-900," it is not scheduled to be a MAX at this time.
The same is true in search results and anywhere else on the United site.
For advanced users: UA uses the three letter IATA identifier 7M9 for the 737 MAX 9.
All 737 MAX aircraft worldwide (MAX 8, MAX 9, and MAX 10) are currently grounded.
Thread Topic
The reason for continuing this thread is to inform the UA traveler on the status of the MAX recertification and if / when UA might deploy the MAX aircraft. And UA flyer's thoughts about UA deploying the MAX if that was to happen.
READ BEFORE POSTING
Once again many posters in this thread have forgotten the FT rules and resorted to "Personal attacks, insults, baiting and flaming " and other non-collegial, non-civil discourse. This is not allowed.
Posters appear to be talking at others, talking about others, not discussing the core issues. Repeating the same statements, saying the same thing LOUDER is not civil discourse. These problems are not with one poster, they are not just one point of view, ...
As useful as some discussion here has been, continuing rules violations will lead to suspensions and thread closure. Please think about that before posting.
The purpose of FT is to be an informative forum that, in this case, enables the UA flyer to enhance their travel experience. There are other forums for different types of discussions. This thread was had wide latitude but that latitude is being abused.
Bottom line, if you can not stay within the FT rules and the forum's topic areas, please do not post.
And before posting, ask if you are bringing new contributing information to the discussion -- not just repeating previous points, then please do not post.
WineCountryUA
UA coModerator
Once again many posters in this thread have forgotten the FT rules and resorted to "Personal attacks, insults, baiting and flaming " and other non-collegial, non-civil discourse. This is not allowed.
Posters appear to be talking at others, talking about others, not discussing the core issues. Repeating the same statements, saying the same thing LOUDER is not civil discourse. These problems are not with one poster, they are not just one point of view, ...
As useful as some discussion here has been, continuing rules violations will lead to suspensions and thread closure. Please think about that before posting.
The purpose of FT is to be an informative forum that, in this case, enables the UA flyer to enhance their travel experience. There are other forums for different types of discussions. This thread was had wide latitude but that latitude is being abused.
Bottom line, if you can not stay within the FT rules and the forum's topic areas, please do not post.
And before posting, ask if you are bringing new contributing information to the discussion -- not just repeating previous points, then please do not post.
WineCountryUA
UA coModerator
This thread has engendered some strongly felt opinions and a great tendency to wander into many peripherally related topics. By all normal FT moderation standards, this thread would have been permanently closed long ago ( and numerous members receiving disciplinary actions).
However, given the importance of the subject, the UA Moderators have tried to host this discussion but odd here as UA is not the top 1 or 2 or 3 for MAX among North America carriers. However, some have allowed their passion and non-UA related opinions to repeatedly disrupt this discussion.
The reason for continuing this thread is to inform the UA traveler on the status of the MAX recertification and if / when UA might deploy the MAX aircraft. And UA flyer's thoughts about UA deploying the MAX if that was to happen.
Discussion of Boeing's culture or the impact on Boeing's future is not in scope. Nor is comments on restructuring the regulatory process. Neither is the impacts on COVID on the general air industry -- those are not UA specific and are better discussed elsewhere. And for discussion of UA's future, there is a separate thread.
Additionally repeated postings of essentially the same content should not happen nor unnecessarily inflammatory posts. And of course, the rest of FT posting rules apply including discuss the issue and not the posters.
The Moderator team feels there is a reason / need for this thread but it has been exhausting to have to repeated re-focus the discussion -- don't be the reason this thread is permanently closed ( and get yourself in disciplinary problems).
Stick to the relevant topic which is (repeating myself)
The reason for continuing this thread is to inform the UA traveler on the status of the MAX recertification and if / when UA might deploy the MAX aircraft. And UA flyer's thoughts about UA deploying the MAX if that was to happen.
WineCountryUA
UA coModerator
However, given the importance of the subject, the UA Moderators have tried to host this discussion but odd here as UA is not the top 1 or 2 or 3 for MAX among North America carriers. However, some have allowed their passion and non-UA related opinions to repeatedly disrupt this discussion.
The reason for continuing this thread is to inform the UA traveler on the status of the MAX recertification and if / when UA might deploy the MAX aircraft. And UA flyer's thoughts about UA deploying the MAX if that was to happen.
Discussion of Boeing's culture or the impact on Boeing's future is not in scope. Nor is comments on restructuring the regulatory process. Neither is the impacts on COVID on the general air industry -- those are not UA specific and are better discussed elsewhere. And for discussion of UA's future, there is a separate thread.
Additionally repeated postings of essentially the same content should not happen nor unnecessarily inflammatory posts. And of course, the rest of FT posting rules apply including discuss the issue and not the posters.
The Moderator team feels there is a reason / need for this thread but it has been exhausting to have to repeated re-focus the discussion -- don't be the reason this thread is permanently closed ( and get yourself in disciplinary problems).
Stick to the relevant topic which is (repeating myself)
The reason for continuing this thread is to inform the UA traveler on the status of the MAX recertification and if / when UA might deploy the MAX aircraft. And UA flyer's thoughts about UA deploying the MAX if that was to happen.
WineCountryUA
UA coModerator
United does not fly the 737 MAX 8 that has been involved in two recent crashes, but it does operate the 737 MAX 9.
How to tell if your flight is scheduled to be operated by the MAX 9:
View your reservation or flight status page, either on the web or on the app. United lists the entire aircraft type. Every flight that is scheduled to be on the 737 MAX will say "Boeing 737 MAX 9." If you see anything else -- for example, "Boeing 737-900," it is not scheduled to be a MAX at this time.
The same is true in search results and anywhere else on the United site.
For advanced users: UA uses the three letter IATA identifier 7M9 for the 737 MAX 9.
All 737 MAX aircraft worldwide (MAX 8, MAX 9, and MAX 10) are currently grounded.
B737MAX Recertification - Archive
Apr 3, 2019, 12:22 pm
#991
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All fine, but if you extend this particular line of thought, then you're strongly implying that there was nothing wrong with DC-10s operating without hydraulic fluid because one set of pilots in one situation (UA232) was able to get the plane down without total loss of life. <shrugs>
Apr 3, 2019, 12:50 pm
#992
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According to whom?
As R. John Hansman, a professor of aeronautics at the Massachusetts Institute of Technology, told me in a March 28 interview,As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft [emphasis mine] where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls.
As R. John Hansman, a professor of aeronautics at the Massachusetts Institute of Technology, told me in a March 28 interview,As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift. Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further. This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition. It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft [emphasis mine] where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls.
Too-light feel is a side effect if I understand it right, not the root of the problem. I'd rather believe MIT professor of aeronautics; how would you explain his " This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition"
He makes a number of statements, that are all individually true:
As I understand it, at high angles of attack the Nacelles -- which are the tube shaped structures around the fans -- create aerodynamic lift.
Because the engines are further forward, the lift tends to push the nose up -- causing the angle of attack to increase further.
This reinforces itself and results in a pitch-up tendency which if not corrected can result in a stall. This is called an unstable or divergent condition.
It should be noted that many high performance aircraft have this tendency but it is not acceptable in transport category aircraft where there is a requirement that the aircraft is stable and returns to a steady condition if no forces are applied to the controls.
No doubt the MAX, and the NG in some configurations, feel light in pitch. But no one, including your MIT professor, is actually claiming they're unstable. Less stable, but still positively stable.
Apr 3, 2019, 1:47 pm
#993
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Sorry, what were the faults of the ET flight crew? At this point the best information we have suggests that they correctly followed Boeing’s emergency procedures for MCAS malfunction, only to find that it was impossible to manually trim the aircraft at higher air speeds. At that point they started to improvise—which of course didn’t work—but certainly nothing in the Boeing-approved procedures was going to save them. Of course, we may subsequently learn of mistakes they made that doomed the aircraft, but at this time we don’t know of any, so why are we throwing them under the bus?
Apr 3, 2019, 2:04 pm
#994
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Sorry, what were the faults of the ET flight crew? At this point the best information we have suggests that they correctly followed Boeing’s emergency procedures for MCAS malfunction, only to find that it was impossible to manually trim the aircraft at higher air speeds. At that point they started to improvise—which of course didn’t work—but certainly nothing in the Boeing-approved procedures was going to save them. Of course, we may subsequently learn of mistakes they made that doomed the aircraft, but at this time we don’t know of any, so why are we throwing them under the bus?
Apr 3, 2019, 2:45 pm
#995
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That Boeing’s initial training-based mitigation for the MCAS problem was so deeply flawed and shortsighted, compounding the terrible design of MCAS to begin with, should really give one pause before jumping to the conclusion that Boeing’s next fix is definitely going to solve any and all problems with this aircraft.
Last edited by milypan; Apr 3, 2019 at 2:56 pm
Apr 3, 2019, 2:54 pm
#996
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Having difficulty understanding the nature of the MCAS "reset" phenomena being discussed in the aviation press
It resets to its original trim position or advances after the pilot resists by pulling the yoke?
Is the trim a series of stops or continuous?
Continues to the max 2.5 degrees?
It resets to its original trim position or advances after the pilot resists by pulling the yoke?
Is the trim a series of stops or continuous?
Continues to the max 2.5 degrees?
Under specific conditions including; autopilot off, flaps up, and a combination of bank angle and angle-of-attack, MCAS will activate.
When MCAS activates it provides a nose-down trim input for just short of ten seconds unless interrupted by activation of the primary electric trim. At the end of the nearly ten-second activation, or when interrupted by primary electric trim, MCAS pauses for five seconds. If, after the pause, the same conditions still exist, the pattern will repeat.
When the Stab Trim switches are selected to Cut Out all electric trimming is stopped. Pilots can continue to trim by manually turning the trim wheels. Each trim wheel has a fold-out handle for that purpose. The handles on the two wheels are located 90 degrees apart so that one of the two is always in a position where the pilot will have sufficient leverage to turn the wheel.
I don't know the context of the 2.5 degrees as the stab trim is displayed in units, not degrees, in the cockpit. I haven't seen it explained to what reference those degrees are being measured. We normally takeoff in the 4 to 6 units range. Full nose-down trim is, or slightly below, 0 units.
The software change that is under development will make several changes. One change is that an excessive disagreement between the two AoA sensors will disable MCAS. Another is that the MCAS activation will only occur once. It will not repeat even if the triggering conditions continue to exist.
Apr 3, 2019, 2:55 pm
#997
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Apr 3, 2019, 3:02 pm
#998
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Here's how MCAS works.
Under specific conditions including; autopilot off, flaps up, and a combination of bank angle and angle-of-attack, MCAS will activate.
When MCAS activates it provides a nose-down trim input for just short of ten seconds unless interrupted by activation of the primary electric trim. At the end of the nearly ten-second activation, or when interrupted by primary electric trim, MCAS pauses for five seconds. If, after the pause, the same conditions still exist, the pattern will repeat.
When the Stab Trim switches are selected to Cut Out all electric trimming is stopped. Pilots can continue to trim by manually turning the trim wheels. Each trim wheel has a fold-out handle for that purpose. The handles on the two wheels are located 90 degrees apart so that one of the two is always in a position where the pilot will have sufficient leverage to turn the wheel.
I don't know the context of the 2.5 degrees as the stab trim is displayed in units, not degrees, in the cockpit. I haven't seen it explained to what reference those degrees are being measured. We normally takeoff in the 4 to 6 units range. Full nose-down trim is, or slightly below, 0 units.
The software change that is under development will make several changes. One change is that an excessive disagreement between the two AoA sensors will disable MCAS. Another is that the MCAS activation will only occur once. It will not repeat even if the triggering conditions continue to exist.
Under specific conditions including; autopilot off, flaps up, and a combination of bank angle and angle-of-attack, MCAS will activate.
When MCAS activates it provides a nose-down trim input for just short of ten seconds unless interrupted by activation of the primary electric trim. At the end of the nearly ten-second activation, or when interrupted by primary electric trim, MCAS pauses for five seconds. If, after the pause, the same conditions still exist, the pattern will repeat.
When the Stab Trim switches are selected to Cut Out all electric trimming is stopped. Pilots can continue to trim by manually turning the trim wheels. Each trim wheel has a fold-out handle for that purpose. The handles on the two wheels are located 90 degrees apart so that one of the two is always in a position where the pilot will have sufficient leverage to turn the wheel.
I don't know the context of the 2.5 degrees as the stab trim is displayed in units, not degrees, in the cockpit. I haven't seen it explained to what reference those degrees are being measured. We normally takeoff in the 4 to 6 units range. Full nose-down trim is, or slightly below, 0 units.
The software change that is under development will make several changes. One change is that an excessive disagreement between the two AoA sensors will disable MCAS. Another is that the MCAS activation will only occur once. It will not repeat even if the triggering conditions continue to exist.
because they failed to anticipate that you wouldn’t be physically able to manually trim the aircraft if it were flying at higher air speeds. Which might happen if, say, you got an AoA sensor failure, which resulted in unreliable IAS (airspeed) messages and the aircraft being pushed nose down by MCAS.
Apr 3, 2019, 3:12 pm
#999
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@LarryJ Thanks as always for the information. Is there a system that would prevent manual trim from operating as stated by a previous poster?
More details: https://leehamnews.com/2019/04/03/et...as/#more-29790
Apr 3, 2019, 3:23 pm
#1000
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The software change that is under development will make several changes. One change is that an excessive disagreement between the two AoA sensors will disable MCAS. Another is that the MCAS activation will only occur once. It will not repeat even if the triggering conditions continue to exist.
So, then: Why have MCAS at all? What is its value if it does its job exactly once and then retires?
Apr 3, 2019, 3:37 pm
#1001
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To be clear, the issue is not simply that the procedures were poorly documented (though they surely were). It’s that the post-JT610 procedures that Boeing disseminated for MCAS failure literally did not work, because they failed to anticipate that you wouldn’t be physically able to manually trim the aircraft if it were flying at higher air speeds. Which might happen if, say, you got an AoA sensor failure, which resulted in unreliable IAS (airspeed) messages and the aircraft being pushed nose down by MCAS.
How about "find out why the plane was losing lift on take-off first and correct that -- whether it's plane design, software, or pilots"?
I read that as: We'll have sophisticated software that will try to correct a bad in-flight situation ONCE. Only ONCE. After that, the system essentially says, "I give up, you're the pilots."
So, then: Why have MCAS at all? What is its value if it does its job exactly once and then retires?
So, then: Why have MCAS at all? What is its value if it does its job exactly once and then retires?
Apr 3, 2019, 4:26 pm
#1002
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@LarryJ Thanks as always for the information. Is there a system that would prevent manual trim from operating as stated by a previous poster?
While hand-flying the airplane you keep it in-trim by using the primary electric trim. In an unscheduled MCAS event, as experienced by two Lion Air flights (same airplane) and one Ethiopian flight, the use of primary electric trim will temporarily stop MCAS and allow the aircraft to be returned to an in-trim condition. This was shown on the Lion Air accident flight in the DFDR data. There were 21 MCAS activations while the Captain was hand-flying. He stopped MCAS and retrimmed all 21 times. If you are keeping up with the retrimming, the aircraft will be close to in-trim when you deactivate the electric trim systems with the stab trim switches and manual trim can be used.
If you allow repeated activations of MCAS to progressively move the trim to the full nose-down position without correction, it will likely be difficult to trim it back using the manual backup system. Each trim wheel has a fold-out handle to aid in moving the wheel. The handles are positioned 90 degrees (of rotation) apart so that one of them always has leverage. This allows the two pilots to work together to trim if you're in a situation where one can't do it alone.
Apr 3, 2019, 4:52 pm
#1003
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And 350 people are dead now.
Apr 3, 2019, 5:34 pm
#1004
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Not to be pedantic, but I don't think the MCAS was ever expected to come on in "normal flight." My understanding is that MCAS is there only for a high-AOA situation, which as noted above will probably never happen for the average airliner.
