MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
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The concern is about entering service after a long storage period and the sheer number of airplanes they will want to ticket in a short period.
Last edited by Dave Therhino; 28th Nov 2019 at 00:29.
Oldn, #4178 "2.2. On the peculiarities of the trim (relief) of forces" beginning on page 159.
Also from the recommendations: - It is recommended that the Boeing Company. Page 175
“5.21. Consider the practicability to implement the design changes of the stabilizer control system to reduce the risk for the pilot to set stabilizer in-flight into out of trim position.”
And the objection and rebuttal in the note:-
“In the Comments to the draft Final Report the aircraft manufacturer suggested to remove this recommendation, reasoning that the Boeing Company design philosophy implies the pilot can fully operate with the available deflection of flight controls, including the stabilizer control. This may be required in a variety of non-normal situations, for example at the total loss of hydraulic system/hydraulic circuits’ pressure. At the same time according to the manufacturer, the aircraft design provides for reasonable amount of engineering concepts for the PM to stop the inflight stabilizer setting into the out of trim position by the PF.
The investigation team agrees that the aircraft design allows for it. But, the air accidents investigation practice shows that the PM, who monitors the flight management and aircraft control actions by the PF, is not always able to promptly identify the out-of-trim stabilizer position, as well as to detect the mere fact of the stabilizer prolonged motion. The investigation team notes that at the current level of technological development the combination of the mentioned engineering concepts is a possible solution: the limitation of the stabilizer deflection angles, when this could result in the adverse consequences, and the full travel/deflection when actually necessary.”
If the Max, after MCAS modification, remains similar to the NG, then the above applies - particularly if the operation of the aircraft depends on the assumption of timely crew awareness and action, then this cannot be assured in all circumstances.
As designed (work as imagined) is not the same as work as done, a gap between theory and practice, identified by accident investigation ?
Also from the recommendations: - It is recommended that the Boeing Company. Page 175
“5.21. Consider the practicability to implement the design changes of the stabilizer control system to reduce the risk for the pilot to set stabilizer in-flight into out of trim position.”
And the objection and rebuttal in the note:-
“In the Comments to the draft Final Report the aircraft manufacturer suggested to remove this recommendation, reasoning that the Boeing Company design philosophy implies the pilot can fully operate with the available deflection of flight controls, including the stabilizer control. This may be required in a variety of non-normal situations, for example at the total loss of hydraulic system/hydraulic circuits’ pressure. At the same time according to the manufacturer, the aircraft design provides for reasonable amount of engineering concepts for the PM to stop the inflight stabilizer setting into the out of trim position by the PF.
The investigation team agrees that the aircraft design allows for it. But, the air accidents investigation practice shows that the PM, who monitors the flight management and aircraft control actions by the PF, is not always able to promptly identify the out-of-trim stabilizer position, as well as to detect the mere fact of the stabilizer prolonged motion. The investigation team notes that at the current level of technological development the combination of the mentioned engineering concepts is a possible solution: the limitation of the stabilizer deflection angles, when this could result in the adverse consequences, and the full travel/deflection when actually necessary.”
If the Max, after MCAS modification, remains similar to the NG, then the above applies - particularly if the operation of the aircraft depends on the assumption of timely crew awareness and action, then this cannot be assured in all circumstances.
As designed (work as imagined) is not the same as work as done, a gap between theory and practice, identified by accident investigation ?
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Oldn, #4178 "2.2. On the peculiarities of the trim (relief) of forces" beginning on page 159.
Also from the recommendations: - It is recommended that the Boeing Company. Page 175
“5.21. Consider the practicability to implement the design changes of the stabilizer control system to reduce the risk for the pilot to set stabilizer in-flight into out of trim position.”
And the objection and rebuttal in the note:-
“In the Comments to the draft Final Report the aircraft manufacturer suggested to remove this recommendation, reasoning that the Boeing Company design philosophy implies the pilot can fully operate with the available deflection of flight controls, including the stabilizer control. This may be required in a variety of non-normal situations, for example at the total loss of hydraulic system/hydraulic circuits’ pressure. At the same time according to the manufacturer, the aircraft design provides for reasonable amount of engineering concepts for the PM to stop the inflight stabilizer setting into the out of trim position by the PF.
The investigation team agrees that the aircraft design allows for it. But, the air accidents investigation practice shows that the PM, who monitors the flight management and aircraft control actions by the PF, is not always able to promptly identify the out-of-trim stabilizer position, as well as to detect the mere fact of the stabilizer prolonged motion. The investigation team notes that at the current level of technological development the combination of the mentioned engineering concepts is a possible solution: the limitation of the stabilizer deflection angles, when this could result in the adverse consequences, and the full travel/deflection when actually necessary.”
If the Max, after MCAS modification, remains similar to the NG, then the above applies - particularly if the operation of the aircraft depends on the assumption of timely crew awareness and action, then this cannot be assured in all circumstances.
As designed (work as imagined) is not the same as work as done, a gap between theory and practice, identified by accident investigation ?
Also from the recommendations: - It is recommended that the Boeing Company. Page 175
“5.21. Consider the practicability to implement the design changes of the stabilizer control system to reduce the risk for the pilot to set stabilizer in-flight into out of trim position.”
And the objection and rebuttal in the note:-
“In the Comments to the draft Final Report the aircraft manufacturer suggested to remove this recommendation, reasoning that the Boeing Company design philosophy implies the pilot can fully operate with the available deflection of flight controls, including the stabilizer control. This may be required in a variety of non-normal situations, for example at the total loss of hydraulic system/hydraulic circuits’ pressure. At the same time according to the manufacturer, the aircraft design provides for reasonable amount of engineering concepts for the PM to stop the inflight stabilizer setting into the out of trim position by the PF.
The investigation team agrees that the aircraft design allows for it. But, the air accidents investigation practice shows that the PM, who monitors the flight management and aircraft control actions by the PF, is not always able to promptly identify the out-of-trim stabilizer position, as well as to detect the mere fact of the stabilizer prolonged motion. The investigation team notes that at the current level of technological development the combination of the mentioned engineering concepts is a possible solution: the limitation of the stabilizer deflection angles, when this could result in the adverse consequences, and the full travel/deflection when actually necessary.”
If the Max, after MCAS modification, remains similar to the NG, then the above applies - particularly if the operation of the aircraft depends on the assumption of timely crew awareness and action, then this cannot be assured in all circumstances.
As designed (work as imagined) is not the same as work as done, a gap between theory and practice, identified by accident investigation ?
I'm just a grounded -- and now retired -- engineer, but that very thorough report on the Rostov-on-Don crash seems to me to contain some very powerful and disturbing insights into the realities of the human-machine interface and the sometimes-scary distance between expected systems behaviors and the way things work when, for instance, the humans get outside their usual envelope.
Because I was primed to do so by your including the link to the report in this thread, the possible relevance to the MAX dawned on me early in the reading. Overall, as someone said in the thread on the report, the reading experience was extremely informative and seriously dreadful.
I hope others here will consider the elements we've highlighted and weigh in with their thoughts.
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That there are a lot of aircraft to deal with after a long period of storage doesn't make the case that the FAA needs to do this.
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But the whole point of delegating such functions is that the FAA (and other authorities, this isn't just an FAA issue) do not have the manpower to do all these tasks under normal circumstances. I frankly don't see an (presumably small) group of (likely) overworked FAA employees doing a task they are less familiar with (due to it having been the OEM's responsibility of late) doing any better job the the Boeing guys.
That there are a lot of aircraft to deal with after a long period of storage doesn't make the case that the FAA needs to do this.
That there are a lot of aircraft to deal with after a long period of storage doesn't make the case that the FAA needs to do this.
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Maybe the implied rationale behind that idea is that they don't **trust** Boeing to do it thoroughly? In no way do I wish to suggest that the technicians on the ground (literally!) are not up to the job or would cut corners, it is more a case of the Boeing management looking for shortcuts, therefore the FAA will have a final say (they've had their fingers burnt once already).
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I don't think FAA overriding Boeing for MAX delivery "wrap up" is solely public image "looking tough" based.
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Psychophysiological entity
Congress is now looking at the manual trim wheel issue and why the FAA certified the MAX with the issue against their own safety engineers recommendations.
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But the whole point of delegating such functions is that the FAA (and other authorities, this isn't just an FAA issue) do not have the manpower to do all these tasks under normal circumstances. I frankly don't see an (presumably small) group of (likely) overworked FAA employees doing a task they are less familiar with (due to it having been the OEM's responsibility of late) doing any better job the the Boeing guys.
That there are a lot of aircraft to deal with after a long period of storage doesn't make the case that the FAA needs to do this.
That there are a lot of aircraft to deal with after a long period of storage doesn't make the case that the FAA needs to do this.
Yup, that's it. The FAA doesn't trust Boeing, for the very good reason that the fallout from the MAX debacle has caused much of the world to lose trust in the FAA (see the news articles, linked above, about EASA and UAE doing their own certifications of the 777X). I'm sure the FAA would prefer not to do this, but it must -- correctly, IMHO -- see it as necessary to help preserve American aviation's position in the world.
The FAA lives in a fishbowl and most of the high level decision making has to do with appearances, not substance. Hopefully, the FAA inspectors will actually have the authority to make findings of airworthiness, unhindered by higher micromanagement, so that the appearance they want to make is actually matched by reality.
Last edited by GlobalNav; 30th Nov 2019 at 21:10.
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Would Denzel Washington have saved ET302?
Would it work, or am I completely insane?
In the movie "Flight" Denzel Washington rolls a plane inverted that is stuck in a dive.
In the ET302 accident, the pilots turned the trim motor back on because they were trying to relieve back pressure, and the manual trim was stiff. Would rolling a 737-MAX inverted and relaxing the column have the plane gain altitude, buying the pilots more time to work the trim wheel manually, maybe even while the plane was inverted, with relaxed elevator forces, or not? I"m sure Boeing isn't considering this, to include in their flight manuals, and you wouldn't win any applause from the passengers, but, would it work? Would you be able to roll inverted, quickly enough, and would then relaxing back pressure, and even pushing forward on the controls, gain altitude?
In the movie "Flight" Denzel Washington rolls a plane inverted that is stuck in a dive.
In the ET302 accident, the pilots turned the trim motor back on because they were trying to relieve back pressure, and the manual trim was stiff. Would rolling a 737-MAX inverted and relaxing the column have the plane gain altitude, buying the pilots more time to work the trim wheel manually, maybe even while the plane was inverted, with relaxed elevator forces, or not? I"m sure Boeing isn't considering this, to include in their flight manuals, and you wouldn't win any applause from the passengers, but, would it work? Would you be able to roll inverted, quickly enough, and would then relaxing back pressure, and even pushing forward on the controls, gain altitude?
The ET302 crew was also trying to re-enable the autopilot as seen by the auto-pilot alarm indication in the data traces.
In any case, they did not have enough altitude to invert the plane. The plane does not have sufficient roll authority to do a snap-roll and not enough altitude to make up for the loss when, in the middle of the roll, the lift from the wings is no longer resisting gravity, but is pointing horizontally. Normally the roll to inversion is started with pitch up to avoid altitude loss, and is often done in very small planes where the side of the fuselage can supply significant lift.
There was a real life crash of an Alaska Air flight that "Flight" was modeled on.
In any case, they did not have enough altitude to invert the plane. The plane does not have sufficient roll authority to do a snap-roll and not enough altitude to make up for the loss when, in the middle of the roll, the lift from the wings is no longer resisting gravity, but is pointing horizontally. Normally the roll to inversion is started with pitch up to avoid altitude loss, and is often done in very small planes where the side of the fuselage can supply significant lift.
There was a real life crash of an Alaska Air flight that "Flight" was modeled on.
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From the accident report findings: "46. The Federal Aviation Administration (FAA) did not fulfill its responsibility to properly oversee the maintenance operations at Alaska Airlines, and at the time of the Alaska Airlines flight 261 accident, FAA surveillance of Alaska Airlines had been deficient for at least several years."
No doubt they don't want to see a similar statement any time soon.
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At MCT at low altitude in a 737 you have maybe 7-10 seconds of fuel in the lines before the engines flame out if you were to attempt sustained inverted flight.
Last edited by Dave Therhino; 1st Dec 2019 at 01:28.
maybe 7-10 seconds of fuel in the lines before the engines flame out
The first part of an aileron roll in anything (even an Extra with its 400 degree/second roll rate) is to pull the nose up 30 degrees or more - 45 degrees in a Citabria. If you don't, you will finish the manouevre with the nose pointing pretty much straight down. No idea what a 737's roll rate is, but probably not very high. My aerobatics instructor explained to me once how you decide whether it's safe to roll a non-aerobatic type (he says C130s roll very nicely) and it's not just a case of bang over the stick and wait, far from it.
Not to mention the total pandemonium in the cabin. OK, it's better than dying. But still.
Way off topic now, are we?
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Salute!
Well, having done hundreds of rolls and "things you have not dreamed of", to borrow a line from High Flight.
You can roll easily without initially getting the nose high if in a small, or nimble plane. Problem with the big boys is inertia, and nose will dig in easily. Hence nose high to start. OTOH....
The ET flight had extreme nose down trim, so every degree of roll from normal erect provides less of a lift vector below the horizon, right? Eventually, all of its lift vector is above the horizon when completely inverted. So a technique I used on most jets to avoid the nose high entry was applying forward stick and a touch of nose down trim as bank angle increased past 90 deg, and maybe some top rudder until over 90 deg of bank. Could literally roll within 20 feet of initial altitude, and the T-birds and Bluers and Arrows and Snowbirds show this every performance. So Denzel's manuever is theoretically possible. And worry about motors quiting later. 737 flies O.K in glider mode due to the mechanical connections, right? We need "wonkazoo" to comment, as he flew aerobatic demos all the time.
The Alaska folks should get a post humous medal of honor for even trying the Denzel trick, as they had nothing to loose. And IMHO biggest mistake was not trying to land when things started acting up. Of course if they didn't turn off the electric trim motor, then they could have lost it over L.A.
I feel the complete ET flight report will assign some contributing factor to the crew for not slowing down, and likely mention CRM. I feel that they did not know enough about the mechanization of MCAS that kept applying nose down trim when they were not countering it with the button of the wheel, plus the 5 second delay, plus......
Gums opines...
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Salute!
Well, having done hundreds of rolls and "things you have not dreamed of", to borrow a line from High Flight.
You can roll easily without initially getting the nose high if in a small, or nimble plane. Problem with the big boys is inertia, and nose will dig in easily. Hence nose high to start. OTOH....
The ET flight had extreme nose down trim, so every degree of roll from normal erect provides less of a lift vector below the horizon, right? Eventually, all of its lift vector is above the horizon when completely inverted. So a technique I used on most jets to avoid the nose high entry was applying forward stick and a touch of nose down trim as bank angle increased past 90 deg, and maybe some top rudder until over 90 deg of bank. Could literally roll within 20 feet of initial altitude, and the T-birds and Bluers and Arrows and Snowbirds show this every performance. So Denzel's manuever is theoretically possible. And worry about motors quiting later. 737 flies O.K in glider mode due to the mechanical connections, right? We need "wonkazoo" to comment, as he flew aerobatic demos all the time.
The Alaska folks should get a post humous medal of honor for even trying the Denzel trick, as they had nothing to loose. And IMHO biggest mistake was not trying to land when things started acting up. Of course if they didn't turn off the electric trim motor, then they could have lost it over L.A.
I feel the complete ET flight report will assign some contributing factor to the crew for not slowing down, and likely mention CRM. I feel that they did not know enough about the mechanization of MCAS that kept applying nose down trim when they were not countering it with the button of the wheel, plus the 5 second delay, plus......
Gums opines...
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What we are talking about here is manufacturing inspectors issuing the initial standard airworthiness certificate for all the new aircraft that were produced since the order that grounded the aircraft type. No standard airworthiness certificates have been issued for a Max since that date. The FAA's manufacturing inspectors are imminently qualified to perform that task, and there are quite a few of them available in the Puget Sound area. They do it all the time at Boeing for various reasons, and for many other aircraft types. The benefit of having the FAA inspectors do it is theoretically they won't be subjected to the same pressures to hurry up the process as the Boeing inspectors would. You can argue whether this is necessary, but don't think the FAA inspectors are less qualified. That is absolutely not true.
What will happen with the 737 Max’s that are grounded overseas? Will the FAA need to send staff there, or do they need to fly those planes back to the USA to get their certificate?
Jeroen
