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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

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MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures

Old 1st Jul 2019, 09:08
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Originally Posted by wonkazoo
Returning to the "They are among us" theme...

I was browsing another thread on the 787 and shall we say, ahem, issues with its production when I stumbled across the following.


Ironically, just a couple of days after those claims of "lack of evidence", evidence came out that it may have indeed been possible, since such a condition was discovered in a simulator test performed by FAA pilots.
Let's be fair here. The "evidence" you cite involved upgraded software/firmware that had not yet been certified for flight, much less installed on the accident aircraft, during a test that intentionally created a malfunction that was unrelated to MCAS. Until there are further details to the specifics of the test and the particular failure mode, there still is no evidence that there were any problems with the Main Electric Trim system on the accident aircraft. As you note, after many months of perhaps one of the most intense investigations in modern aviation history, not a single authority has suggested such a problem or called for any redesign work associated with this system.
Question 1: The preceding post was written by:

a) Boeing's Lawyer
b) An employee of Boeing with three kids to support
c) A Boeing corporate manager
d) A disinterested third party
e) Brittney Spears

Oh man, just hiccuped with beer- headed to an early demise-
dce
And yet the valid point the anonymous poster made remains unanswered by you.
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Old 1st Jul 2019, 14:41
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Originally Posted by DaveReidUK
But your proposition requires that
...
b) simultaneously there was an unrelated software/processor issue that prevented the pilots' trim inputs from being recorded on the FDR
I'm short on time to find the post, but there was compelling circumstantial evidence presented in this thread a couple of days ago that pilot trim inputs are sent to the FDR from the stab trim motor (whereas mcas/speed trim inputs are sent from the trim computer). In such a case, it is in fact very probable that failed pilot trim inputs will not be recorded by the FDR.
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Old 1st Jul 2019, 16:15
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Responses to above in no particular order:

1. The stab trim motor has four speeds - Main Electric fast/slow (0.4/0.2 deg/sec) and Automatic fast/slow (0.27/0.09 deg/sec) and two directions. If the previously posted schematics are to be taken at face value, then the commands for speed and direction come from outside the motor unit, but the actual processing of those commands into a specific speed and direction occur within a controller housed within the motor unit. While no documentation regarding this controller and how it operates has been publicly released, it is reasonable to assume that the accident investigating bodies would have access to it if they felt it was needed.

2. Overheating. This was a problem on early Boeing designs, but I am not aware of any such issues since introduction of the NG, and there is nothing is the manuals related to a thermal relief circuit. However, if there was an undocumented thermal relief, then it would temporarily disable the motor completely, and not just in one direction. No signs of this occurring. Again, if there was any history of this being an issue, one of the hundreds (or perhaps thousands?) of interested parties would have pointed to it by now.

3. Trimming forces. Speaking as someone who has actually used the manual trim wheel on the Boeing, I can assure you that the trim resistance increases in both directions. It is not like rolling a boulder uphill where it is very difficult in one direction and easy in the other. The increased resistance is due to binding forces at the jackscrew thread/nut interface. Not sure if it is strictly frictional force or some type of deformation or misalignment. Keep in mind that while the aerodynamic forces are acting roughly parallel to the jackscrew body, those forces are mostly perpendicular at the thread/nut interface. There will be some directional bias, but that is a relatively small component. BTW, this is one of the reasons why a jackscrew mechanism is used in the first place - to minimize those directional forces and make it easier for the motor. However, one point needs to be emphasized again: You completely avoid these issues by not letting the stab get out of trim in the first place. There is no, none, not one iota of evidence that the Main Electric Trim did not move the stab when it was used. And yes, by not being attentive to such matters, it is absolutely possible to place the aircraft in a state where things don't work as they should.

4. There is a lot of reference of what are perceived as anomalies in the trim system in the final moments of both accidents. Personally, that's not what I see, however I'm not going to claim I have a better microscope than anyone else here. That being said, I must again point out that in those final moments, the aircraft had exceeded the certified flight envelope. Engineering safety factors aside, there is not any expressed or implied guarantee that any system will work as it is supposed to once you exceed the limits of that system. The lesson here is that you keep that aircraft within its design envelope - just like the crew of the penultimate Lion Air 610 flight did.

5. There is far too much post hoc reasoning going on here. If your going-in assumption is, "Of course the Main Electric Trim must have malfunctioned," then your mind is going to work very hard to disregard any contrary evidence. As the initial data started coming in, one of the first and most obvious question to arise was whether there was a problem with the pilots' ability to trim the aircraft to oppose the MCAS input. That was certainly a concern of mine. I actually operate a 737 on a regular basis, and I have a keen interest in knowing. However, there is a big difference between asking if there was a malfunction in the pilot's trim system and assuming there was. In the first case, you go where the evidence leads, in the latter, you try to shoehorn the evidence into your assumptions.

6. Corollary to point 5. Whether or not the pilots had the tools to oppose the MCAS input is one of the top issues that the various accident investigators and certificate authorities must have looked at. Consider all the public discussions regarding the issues with the manual trim system. Consider the discussions regarding adequate pilot response time and whether the Runaway Stab Trim system checklist should be re-written. Concerns regarding these two items may, in fact, be some of the issues slowing down the process of getting the MAX back in service. Compare that to the absolute lack of any comments by any authoritative body that there was a problem with the Main Electric Trim system on the accident aircraft. You just can't assume that all of these parties with all of their vast resources are either that incompetent or part of some conspiracy to hide this information. This is the case of the dog that did not bark. It is not barking, because there is nothing there.

Last edited by yoko1; 1st Jul 2019 at 23:33.
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Old 1st Jul 2019, 16:41
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If the trim motor was stalled, could that somehow generate sufficient number of messages
on the 629 databus to overwhelm the computer?
I ask in the context of the FAA being able to overload the computer
in simulator tests (reported elsewhere).
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Old 1st Jul 2019, 17:03
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Great informative post, Thank you Yoko.

The problem mentioned in your final paragraph is that an official inquiry held by experts is one thing - a rumour panel with everybody from experts and concerned daily operators to schoolboys and air fans is another.

You are caught in the frustrating position (as are others) of trying to present reasoned arguments to a mixed bag of folk.

The other problem is that a few pages on, only the concerned operators will recall most of the clarifications and repetition often becomes necessary to “educate” others and late comers.

Thanks for taking the time. Only after the final report will speculation stop.

B
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Old 1st Jul 2019, 19:03
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Originally Posted by bill fly
Thanks for taking the time. Only after the final report will speculation stop.
Don’t really expect that to happen, but thanks for the comments.
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Old 1st Jul 2019, 19:06
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Originally Posted by yoko1
2. Overheating. This was a problem on early Boeing designs, but I am not aware of any such issues since introduction of the NG, and there is nothing is the manuals related to a thermal relief circuit. However, if there was an undocumented thermal relief, then it would temporarily disable the motor completely, and not just in one direction. No signs of this occurring. Again, if there was any history of this being an issue, one of the hundreds (or perhaps thousands?) of interested parties would have pointed to it by now.
Does it really seem feasible that there wouldn't be a thermal (or otherwise) protection device? Without thermal overload protection, one of the possible outcomes would be thermal overload & all that goes with it.

Regards the motor being disabled completely, in both directions / not just one, that's also not necessarily true & would depend on how smart the motor logic / protection is & how it's been designed.

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Old 1st Jul 2019, 21:33
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Originally Posted by Peter H
Nice find. I'm still having problems interpreting things though, any ideas on:
The deliberately broken microprocessor had become overwhelmed with data from the flight control system.
- If its "broken", how is it still working.
- If its "crippled" by how much.
- Or is it "restarting" after some sort of interrupt/reboot.
- Finally is the "overload" a transient effect, or the new status quo.
Re my question.
I now feel that the new "glitch" occurred when the tester faulted the "active" processor in the FCC, triggering a fail-over to the "standby" processor.
This gives obvious opportunities for disruption of normal service.
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Old 1st Jul 2019, 21:42
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I read a description where each of the 2 processors care for a specific subset of the 15 (or so) FCC processes. It is only in case a fault is detected that the valid processor take over all the processes.

I wrote in another thread : I wouldn't be surprised if the overload comes from the additional checks added to the MCAS process. If the MCAS trigger keeps being repeated and keeps being inhibited, if the new checks involve much I/O with wait states...
​​​​​
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Old 1st Jul 2019, 23:19
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Originally Posted by Thrust Augmentation
Does it really seem feasible that there wouldn't be a thermal (or otherwise) protection device? Without thermal overload protection, one of the possible outcomes would be thermal overload & all that goes with it.
Electric motors are not really my area of expertise, but I’ll throw out a few things and maybe someone who does work with this type of equipment can help.

The stab motor is reported to be a 3-phase DC brushless electric motor. The available circuit diagrams shows circuit protection on the AC side of the AC/DC power converter, but none between the power converter and the motor itself (doesn’t mean there isn’t one, but none are shown). Previous Boeing aircraft had op manual references to a thermal relief circuit. The NG and MAX have none. The non-normal procedures for an inoperative stab trim motor make no reference to any type of circuit breaker or cooling period.

I’ve given some more thought about what would actually happen if the stabilizer was physically prevented from moving. Just speculating here, but there is a clutch system that connects the stab trim motor drive to the jackscrew mechanism. This clutch system favors the manual trim system, which is why you can grab the trim wheel in the cockpit and keep the stab from moving any further. You can demonstrate this on the ground by activating the main electric trim and then stopping the trim wheel with your hand or foot as desired. When you do this, you can hear and feel the clutch slipping/disengaging. The important point here is that the trim motor will continue spinning against the clutch even though the stab is not moving. What I am suggesting is that the motor overload protection may be less electrical and more mechanical. When faced with a jackscrew load that exceeds the motor limit, rather than the motor stalling, perhaps the clutch will slip. If that were to happen, there would be sounds of the clutch slipping on the CVR and the FDR traces would show no stab movement while the yoke switch was engaged (none of which were actually reported). I really don’t know for sure because there is nothing in the available literature that discusses the system in this level of detail.

However, worth repeating, even though none of the participants here know for sure what happens in these circumstances, someone on one of the accident investigation teams certainly does. Again, there’s nothing in the official commentary regarding the stab motor having insufficient power to move the stab, no calls to redesign the motor or anything else in the Main Electric Trim system. No regulators are asking Boeing to do anything different with the Main Electric Trim system before allowing the MAX to fly again. All the concerns that have been raised so far about this aspect of the trim system have been reasonable, but none of them have been sustained after close examination.


Regards the motor being disabled completely, in both directions / not just one, that's also not necessarily true & would depend on how smart the motor logic / protection is & how it's been designed.
Again, not my area of expertise. I only know that on previous Boeing’s, the thermal relief circuit would shut down the motor entirely until it cooled off.

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Old 2nd Jul 2019, 00:29
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Originally Posted by yoko1


Electric motors are not really my area of expertise, but I’ll throw out a few things and maybe someone who does work with this type of equipment can help.

The stab motor is reported to be a 3-phase DC brushless electric motor. The available circuit diagrams shows circuit protection on the AC side of the AC/DC power converter, but none between the power converter and the motor itself (doesn’t mean there isn’t one, but none are shown). Previous Boeing aircraft had op manual references to a thermal relief circuit. The NG and MAX have none. The non-normal procedures for an inoperative stab trim motor make no reference to any type of circuit breaker or cooling period.

I’ve given some more thought about what would actually happen if the stabilizer was physically prevented from moving. Just speculating here, but there is a clutch system that connects the stab trim motor drive to the jackscrew mechanism. This clutch system favors the manual trim system, which is why you can grab the trim wheel in the cockpit and keep the stab from moving any further. You can demonstrate this on the ground by activating the main electric trim and then stopping the trim wheel with your hand or foot as desired. When you do this, you can hear and feel the clutch slipping/disengaging. The important point here is that the trim motor will continue spinning against the clutch even though the stab is not moving. What I am suggesting is that the motor overload protection may be less electrical and more mechanical. When faced with a jackscrew load that exceeds the motor limit, rather than the motor stalling, perhaps the clutch will slip. If that were to happen, there would be sounds of the clutch slipping on the CVR and the FDR traces would show no stab movement while the yoke switch was engaged (none of which were actually reported). I really don’t know for sure because there is nothing in the available literature that discusses the system in this level of detail.

However, worth repeating, even though none of the participants here know for sure what happens in these circumstances, someone on one of the accident investigation teams certainly does. Again, there’s nothing in the official commentary regarding the stab motor having insufficient power to move the stab, no calls to redesign the motor or anything else in the Main Electric Trim system. No regulators are asking Boeing to do anything different with the Main Electric Trim system before allowing the MAX to fly again. All the concerns that have been raised so far about this aspect of the trim system have been reasonable, but none of them have been sustained after close examination.




Again, not my area of expertise. I only know that on previous Boeing’s, the thermal relief circuit would shut down the motor entirely until it cooled off.

must be a really noisy clutch to be heard in the cockpit all the way from the tail...and recorded on the CVR, unless there are microphones on the tail.
the motor, according to the manual and info on the net is a DC servo motor, driven by a 3 phase AC/DC converter, with an unknown type of controller.
A decent converter has the capability to limit torque and current in order not to exceed the theoretical thermal limits, there is no need of breakers or clutches, it can be easily software mananged, however i do not know if such will be within the aviation certification requirments.

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Old 2nd Jul 2019, 00:44
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Originally Posted by FrequentSLF
must be a really noisy clutch to be heard in the cockpit all the way from the tail...and recorded on the CVR, unless there are microphones on the tail.
Well, it is probably more correct to say that the vibrations from the slipping clutch are transferred through the manual trim linkages to the cockpit where they do create a bit of a racket.

]the motor, according to the manual and info on the net is a DC servo motor, driven by a 3 phase AC/DC converter, with an unknown type of controller. A decent converter has the capability to limit torque and current in order not to exceed the theoretical thermal limits, there is no need of breakers or clutches, it can be easily software mananged, however i do not know if such will be within the aviation certification requirments.
Again, not my area of expertise, but it’s all pretty much a theoretical discussion since there were no signs of the trim motor not working when commanded to do so.
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Old 2nd Jul 2019, 00:44
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Originally Posted by Takwis
That question is near the top of my list, as well. Why change from individual cutouts for manual and autoplot trim? The higher ups don't seem to be asking it, and Boeing certainly is not giving any meaningful answers. That, and understanding the 'blips' would go a long way to solving some of the mystery.
While looking at the schematics for the electric trim system on the MAX posted by yoko1, and comparing them to the NG schematics, I noticed something interesting:

- on the NG the cutout switches were positioned between the thumb switches and the motor. So the thumb switches were powered directly from the circuit breaker panel.
- on the MAX the cutout switches are positioned between the circuit breaker and the thumb switches, so the cutout switches can disconnect the thumb switches from the circuit breaker.

This has some implications about what is recorded on the FDR when the cutout switches are used and you try to use the thumb switches.

Previously I had questions about how the thumb switch commands are recorded by the FDR, and if for some reason it can fail to record them. Reading the schematics cleared that out somewhat for me:

- on both the NG and the MAX the captain and F/O switches are connected together in parallel, so there is no possibility to distinguish between the captain switches and the F/O switches on the FDR.
- there are 3 outputs from the switches: "up" commands, "down" commands, and an "arm" command. The "up" / "down" commands are controlled by one half of the switch, the "arm" command is controlled by the other.
- to be able to control the motor the switches need to send one of the "up" / "down" commands and the "arm" command as well.
- the "up" and "down" and "arm" commands go through various relays and switches to the motor.
- the "up" and "down" commands go from the switches directly to the Flight Data Acquisition Unit so, as long as the thumb switches are powered, any use of the "up" / "down" half of the switches can be recorded by the FDR.
- I didn't find such a connection to the FDAU for the "arm" command, it seems that it is either not recorded on the FDR or, if it is recorded, it goes through a less direct path, possibly through the FCC, as the "arm" command seems to disable the autopilot interlock signal to the FCC.
- all this means that on NG using the cutout switches and then later trying to use the column trim switches would be communicated to the FDR as "up" / "down" main trim commands, without a corresponding stabilizer movement. However on the MAX any attempted "up" / "down" commands from the switches wouldn't show after the cutout switches are used, since the thumb switches are disconnected from the circuit breaker by the cutout.

Originally Posted by sadtraveller
I'm short on time to find the post, but there was compelling circumstantial evidence presented in this thread a couple of days ago that pilot trim inputs are sent to the FDR from the stab trim motor (whereas mcas/speed trim inputs are sent from the trim computer). In such a case, it is in fact very probable that failed pilot trim inputs will not be recorded by the FDR.
I was the one that assumed that was the case, but I was wrong, after looking at yoko1's schematics and other schematics in detail they are actually not sent from the trim motor.

For my analysis I used information from these sources:

MAX’s Return Delayed by FAA Reevaluation of 737 Safety Procedures
(Yoko1's post containing schematics of the stabilizer trim control system on the MAX)

https://www.satcom.guru/2018/11/stabilizer-trim.html
(contains a high level schematic for the NG version of the stabilizer trim)

https://aviaforum.ru/threads/katastr...2/post-2392734
(contains a more detailed schematic for the NG version).
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Old 2nd Jul 2019, 01:08
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Originally Posted by Takwis
That question is near the top of my list, as well. Why change from individual cutouts for manual and autoplot trim? The higher ups don't seem to be asking it, and Boeing certainly is not giving any meaningful answers.
This was actually covered in a news article (Seattle Times, I think) a month or so back.

As background, there was a time when the 737 had a procedure where the two cutout switches could be used separately to isolate the offending trim system. Quite a few years ago (early 2000’s if I recall correctly), Boeing changed the procedure so that both switches would always be used together. At the time I remember being told that this was part of a general trend in eliminating “troubleshooting” type actions plus the desire to shut down any runaway as quickly as possible.

Even today, if I had a runaway stab malfunction on a 737NG which I knew was being caused by the automatic trim system, I would have no legal procedure to use just the automatic trim cutout switch. That doesn’t mean I wouldn’t pull out the “Captain Emergency Authority” card, but I would be going out on a limb to diverge from the published procedure.

Fast forward to the MAX. Boeing wanted to maintain as much commonality with the 737NG as possible. The NG had two cutout switches, so the MAX would have two cutout switches. This would make the Runaway Trim procedure identical in both aircraft. However, Boeing’s philosophy had changed regarding what these switches should do. Since the original intent to isolate malfunctions had been replaced by a desire to shut down the entire trim systems as quickly as possible, they wired these switches to accomplish just that. Even though procedurally both switches were required, selecting just one switch (i.e. fat-fingered fumbling) would accomplish the job.




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Old 2nd Jul 2019, 02:03
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Originally Posted by yoko1


This was actually covered in a news article (Seattle Times, I think) a month or so back.

As background, there was a time when the 737 had a procedure where the two cutout switches could be used separately to isolate the offending trim system. Quite a few years ago (early 2000’s if I recall correctly), Boeing changed the procedure so that both switches would always be used together. At the time I remember being told that this was part of a general trend in eliminating “troubleshooting” type actions plus the desire to shut down any runaway as quickly as possible.

Even today, if I had a runaway stab malfunction on a 737NG which I knew was being caused by the automatic trim system, I would have no legal procedure to use just the automatic trim cutout switch. That doesn’t mean I wouldn’t pull out the “Captain Emergency Authority” card, but I would be going out on a limb to diverge from the published procedure.

Fast forward to the MAX. Boeing wanted to maintain as much commonality with the 737NG as possible. The NG had two cutout switches, so the MAX would have two cutout switches. This would make the Runaway Trim procedure identical in both aircraft. However, Boeing’s philosophy had changed regarding what these switches should do. Since the original intent to isolate malfunctions had been replaced by a desire to shut down the entire trim systems as quickly as possible, they wired these switches to accomplish just that. Even though procedurally both switches were required, selecting just one switch (i.e. fat-fingered fumbling) would accomplish the job.
i spent long time wondering why those switches function was changed, and your logic sounds exactly what a lawyer would tell to a court... it does not make any sense other than provide a legal justification for it.
The fix to your change of desire to shut down the enire system quickly would have been a AD with new wiring instructions to be implemented over a long time... oh damn i wonder why i waste my time to argue on this with you
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Old 2nd Jul 2019, 02:50
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Originally Posted by yoko1


This was actually covered in a news article (Seattle Times, I think) a month or so back.

As background, there was a time when the 737 had a procedure where the two cutout switches could be used separately to isolate the offending trim system. Quite a few years ago (early 2000’s if I recall correctly), Boeing changed the procedure so that both switches would always be used together. At the time I remember being told that this was part of a general trend in eliminating “troubleshooting” type actions plus the desire to shut down any runaway as quickly as possible.

Even today, if I had a runaway stab malfunction on a 737NG which I knew was being caused by the automatic trim system, I would have no legal procedure to use just the automatic trim cutout switch. That doesn’t mean I wouldn’t pull out the “Captain Emergency Authority” card, but I would be going out on a limb to diverge from the published procedure.

Fast forward to the MAX. Boeing wanted to maintain as much commonality with the 737NG as possible. The NG had two cutout switches, so the MAX would have two cutout switches. This would make the Runaway Trim procedure identical in both aircraft. However, Boeing’s philosophy had changed regarding what these switches should do. Since the original intent to isolate malfunctions had been replaced by a desire to shut down the entire trim systems as quickly as possible, they wired these switches to accomplish just that. Even though procedurally both switches were required, selecting just one switch (i.e. fat-fingered fumbling) would accomplish the job.
And of course you first MUST retrim to near neutral ( level ) trim before cutting all power to trim switches and otto pilot ?

And if your trim switch only moves at 1/2 to 1/4 rate of MCAS down stab, how much altitude do you lose ?

Or even without MCAS eg NG and prior ?

How much force to turn trim wheel how many times to move say .6 degree ? How many turns ? By yourself ?
And do it all within ?? seconds per regs ?



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Old 2nd Jul 2019, 02:57
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Given the latest MAX issue in the non related MCAS system encountered by the FAA and the difference in classifications used by Boeing compared to that of the FAA.

It is reasonable to believe that further changes (fix's) will be required once more testing is carried out by FAA and other regulators.

At what stage would Boeing need to give up on the requirements of Computer Based Training, hardware changes and/or Grandfather rights?

They have delivered a reasonable number of these aircraft to customers that will be wanting compensation, they are still building the aircraft at a reasonable rate and clearly they need to invest and expedite a Clean Sheet replacement - one assumes under closer scrutiny (less short cuts) by the regulator and expanding interest in the 787.
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Old 2nd Jul 2019, 05:42
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Originally Posted by MemberBerry
- all this means that on NG using the cutout switches and then later trying to use the column trim switches would be communicated to the FDR as "up" / "down" main trim commands, without a corresponding stabilizer movement. However on the MAX any attempted "up" / "down" commands from the switches wouldn't show after the cutout switches are used, since the thumb switches are disconnected from the circuit breaker by the cutout.
Your assumption is confirmed by the ET302 interim report.
The CVR indicates that the FO tried to action the trim via his trim thumb switches after having flipped the pedestal cutout switches.
None of his attempts appear on the DFDR.
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Old 2nd Jul 2019, 06:30
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Originally Posted by Luc Lion
The CVR indicates that the FO tried to action the trim via his trim thumb switches after having flipped the pedestal cutout switches.
Can you point to the entry on the CVR extract (i.e. the timestamp) where you believe that happened ?

I can't see it.

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Old 2nd Jul 2019, 06:55
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Originally Posted by yoko1
3. Trimming forces. Speaking as someone who has actually used the manual trim wheel on the Boeing, I can assure you that the trim resistance increases in both directions. It is not like rolling a boulder uphill where it is very difficult in one direction and easy in the other. The increased resistance is due to binding forces at the jackscrew thread/nut interface. Not sure if it is strictly frictional force or some type of deformation or misalignment. Keep in mind that while the aerodynamic forces are acting roughly parallel to the jackscrew body, those forces are mostly perpendicular at the thread/nut interface. There will be some directional bias, but that is a relatively small component. BTW, this is one of the reasons why a jackscrew mechanism is used in the first place - to minimize those directional forces and make it easier for the motor. However, one point needs to be emphasized again: You completely avoid these issues by not letting the stab get out of trim in the first place. .... And yes, by not being attentive to such matters, it is absolutely possible to place the aircraft in a state where things don't work as they should.
Yeah! That's right - you should NEVER let anyone(THING) trim the damned aeroplane ever further away from the correctly trimmed position. And you CERTAINLY would NEVER want to have anything SECRET, which pilots MUST NOT know about doing it SECRETLY and QUIETLY in the background whilst a badly designed and badly implemented system shakes the yoke violently whilst giving a number of other distracting URGENT warnings that you're stalling to steal your full attention and consume all you resources, leaving you nothing left to look out for any curved balls that Boeing snuck into the system secretly, which will effectively kill you and all aboard in a meter of a few tens of seconds, now would you?

Avoiding that nasty little killer should be avoided at all costs. What silly pilots, for "not being attentive to such matters". Shame on you Yoyo, shame on you, Boeing.
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