Air Crash Thread: Boeing MAX and Other Problems

[Dotini]

Latest from Seattle:

By
Dominic Gates
Seattle Times aerospace reporter
The preliminary investigation into the crash of Ethiopian Airlines Flight 302 last month revealed Thursday that pilots began fighting the Boeing 737 MAX’s new automatic flight-control system barely a minute after leaving the ground, after a sensor failed shortly after takeoff.

Boeing Chief Executive Dennis Muilenburg reacted with a statement from the Renton 737 factory expressing “the immense gravity of these events across our company,” and acknowledging the role the new Maneuvering Characteristics Augmentation System, or MCAS, played in the crash.

“As pilots have told us, erroneous activation of the MCAS function can add to what is already a high-workload environment. It’s our responsibility to eliminate this risk,” Muilenburg said. “We own it and we know how to do it.”

The “black box” flight-recorder data shows that after MCAS swiveled the plane’s horizontal tail to push the nose sharply down three times in succession, the pilots hit the cut-off switches stopping the automatic action and tried to adjust the tail manually, according to the report by the Accident Investigation Bureau of Ethiopia’s Transport Ministry.

In doing so, they were following instructions provided by Boeing last November, following the crash of Lion Air Flight 610, on how to deal with such an inadvertent triggering of the new flight-control system.

Ahead of the release of the full report, Ethiopian Transport Minister Dagmawit Moges held a news conference in the capital, Addis Ababa, that was almost entirely focused on vindicating the actions of the pilots. “The crew performed all the procedures repeatedly provided by the manufacturer but was not able to control the aircraft,” she said.

The report says that while trying to follow Boeing’s directions, about three minutes into the flight, the two pilots found that the manual system for moving the horizontal tail — also known as the stabilizer — “was not working.” This meant they couldn’t move the large stabilizer wheel in the cockpit that is connected via cables to the tail.

Flight-control experts told The Seattle Times earlier this week that was probably because the forces on the tail of the plane moving at high speed — at that point, the airspeed was higher than the jet’s maximum operating speed limit — made it next to physically impossible to move the stabilizer wheel as Boeing had recommended.

-------------------

In previous models of the 737, the two cutoff switches for the stabilizer had different functions and it was possible to flip one that turned off automatic, noncommanded movement while not flipping the other, which would allow the pilot to continue to move the stabilizer with the thumb switches.

But on the MAX, the two cutoff switches have the same function; one is simply a backup to the other. These switches now cut all power to the motor that moves the stabilizer. So they cut off not only automatic movements not commanded by the pilot, including MCAS, but also the ability of the pilot to move the tail electrically.

More here:
https://www.seattletimes.com/busine...ts-fight-against-the-737-max-flight-controls/

 

[Danoff]

In previous models of the 737, the two cutoff switches for the stabilizer had different functions and it was possible to flip one that turned off automatic, noncommanded movement while not flipping the other, which would allow the pilot to continue to move the stabilizer with the thumb switches.

But on the MAX, the two cutoff switches have the same function; one is simply a backup to the other. These switches now cut all power to the motor that moves the stabilizer. So they cut off not only automatic movements not commanded by the pilot, including MCAS, but also the ability of the pilot to move the tail electrically.

 

[TenEightyOne]

Agreed. I think we're past the stage of worrying about if airlines did enough to prepare crews for MAX. Boeing created a flying disaster.

 

[Dotini]

IMHE, whatever the 21st Century Boeing Company does, it is motivated/justified by the highest of intentions to do good in the realms of progressive political correctness, corporate profit/shareholder value, and global warming fuel efficiency. Those are some pretty shaky altars upon which to sacrifice reputation, passenger safety and engineering standards of excellence.

 

[TenEightyOne]

IMHE, whatever the 21st Century Boeing Company does, it is motivated/justified by the highest of intentions to do good in the realms of progressive political correctness, corporate profit/shareholder value, and global warming fuel efficiency.

Motivated, yes. Justified, no, except to themselves.

Those are some pretty shaky altars upon which to sacrifice reputation, passenger safety and engineering standards of excellence.

Definitely. The FAA exists to stop companies being tempted to allow that to happen. The (seeming) failure of the FAA to correctly oversee the production launch of the new MAX features leaves them with questions to answer too.

 

[Eunos_Cosmo]

Seeing the data chart made me feel actually a little sick. To see the last-ditch attempt (just 30 seconds before impact) to trim up with the automated systems re-activated....only for the plane to respond again with much larger trim down commands immediately afterwards. They really did everything they could do. Once the AoA failed, there was almost nothing the pilots could have done, short of immediately known to disable MCAS. It's very tragic. A perfect storm of engineering failures. If ANY of these were true, the plane would not have crashed:

-MCAS verifies readings of AoA sensor against other data (such as from the other AoA sensor)
-MCAS is limited to 0.6 degree of adjustment, as originally certified
-MCAS does not have unlimited authority/has a maximum level of automated adjustment
-Disabling MCAS returns trim to 'neutral' position
-Disabling MCAS not disable electronic/hydraulic assistance to trim

And those are JUST related to the software implementation of that ONE system.

Also, it does appear that the AoA sensor failed some point after takeoff, rather than it being bad on the ground. I wonder if there was a bird strike?

 

[Danoff]

Seeing the data chart made me feel actually a little sick. To see the last-ditch attempt (just 30 seconds before impact) to trim up with the automated systems re-activated....only for the plane to respond again with much larger trim down commands immediately afterwards. They really did everything they could do. Once the AoA failed, there was almost nothing the pilots could have done, short of immediately known to disable MCAS. It's very tragic. A perfect storm of engineering failures. If ANY of these were true, the plane would not have crashed:

-MCAS verifies readings of AoA sensor against other data (such as from the other AoA sensor)
-MCAS is limited to 0.6 degree of adjustment, as originally certified
-MCAS does not have unlimited authority/has a maximum level of automated adjustment
-Disabling MCAS returns trim to 'neutral' position
-Disabling MCAS not disable electronic/hydraulic assistance to trim

And those are JUST related to the software implementation of that ONE system.

Also, it does appear that the AoA sensor failed some point after takeoff, rather than it being bad on the ground. I wonder if there was a bird strike?

I've got a non MCAS item for that list too...

- Manual adjustment of trim is possible given human strength while the control surface is heavily aerodynamically loaded

 

[TenEightyOne]

I've got a non MCAS item for that list too...

- Manual adjustment of trim is possible given human strength while the control surface is heavily aerodynamically loaded

You mean via the physical wheel, presumably, but it's note necessary - the conditions where that problem occurs are deep into a massive emergency that's already happened. Even during many overspeed/dive emergencies (super-rare in themselves) the trim can still be adjusted using the trim buttons or the yoke. The manual wheel is rarely used in any case (something I learnt today). To be clear this emergency was caused by the trim being massively, repeatedly offset by a system that continued to operate despite the crew following the named procedures to stop it from doing so. That's the problem, re-engineering the trim wheel is completely useless. I suspect we might even see it removed, it's effectively redundant.

-MCAS verifies readings of AoA sensor against other data (such as from the other AoA sensor)

It needs two sensors, a single verification is impossible... unless the pilots get clear Disagree messages on the PFD.

-MCAS is limited to 0.6 degree of adjustment, as originally certified

No, 2.5 is acceptable. It needs to be certified and tested but I trust the aero engineers in their judgement that it's the correct adjustment margin. The new certification should reflect that but the plane shouldn't be allowed to arbitrarily, uncontrollably apply it.

-MCAS does not have unlimited authority/has a maximum level of automated adjustment

Maximum level, no. If it needs to act then it needs to act. Unlimited authority, see above comment. I agree that this shouldn't be allowed.

-Disabling MCAS returns trim to 'neutral' position

No. The aircraft would need to know the neutral position (different at different speeds and atmospheres) and would require the same action authority that you want to limit. The pilots should be able to set trim, which they already are.

-Disabling MCAS not disable electronic/hydraulic assistance to trim

It doesn't, one of the earlier articles is being misunderstood. The hydraulics can not physically move the tailplane at gross overspeed. Adding to that problem in the earlier article was opposing hydraulic pressure from the yoke.

 

[Dotini]

Their (seeming) failure of the FAA to correctly oversee the production launch of the new MAX features leaves them with questions to answer too. like a rich, fat old lady caught swimming naked when the tide goes out.

Fixed that.

 

[Danoff]

You mean via the physical wheel, presumably, but it's note necessary - the conditions where that problem occurs are deep into a massive emergency that's already happened. Even during many overspeed/dive emergencies (super-rare in themselves) the trim can still be adjusted using the trim buttons or the yoke. The manual wheel is rarely used in any case (something I learnt today). To be clear this emergency was caused by the trim being massively, repeatedly offset by a system that continued to operate despite the crew following the named procedures to stop it from doing so. That's the problem, re-engineering the trim wheel is completely useless. I suspect we might even see it removed, it's effectively redundant.

It's the redundant system for the hydraulic actuation of the trim. So if the hydraulic system fails, the automatic trim adjustment is out AND the yoke controls are out. At that point, you need a manual adjustment. If the manual adjustment is going to work, it should work. Meaning you should be able to manually adjust the trim tabs even when they're loaded. It's nonsense to have a backup system that doesn't work under certain flight conditions. In those flight conditions you're relying entirely on the hydraulic systems to function, and (while I'm sure that there is redundancy within the hydraulics) that's a single-point failure from a system level perspective.

 

[TenEightyOne]

It's the redundant system for the hydraulic actuation of the trim. So if the hydraulic system fails, the automatic trim adjustment is out AND the yoke controls are out. At that point, you need a manual adjustment. If the manual adjustment is going to work, it should work. Meaning you should be able to manually adjust the trim tabs even when they're loaded. It's nonsense to have a backup system that doesn't work under certain flight conditions. In those flight conditions you're relying entirely on the hydraulic systems to function, and (while I'm sure that there is redundancy within the hydraulics) that's a single-point failure from a system level perspective.

Not a single-point failure at all, the control is not meant to work in that envelope and it doesn't. For any stab trim the airspeed needs to come down using airbrakes, thrust, slats, and stabilisers via the yoke. If it can't be trimmed at overspeed it can't be trimmed, it doesn't matter how you command it. The aircraft is already in a catastrophic flight envelope if you can't move the wheel or the handle, you're already looking at a forced landing if you can't glide whatever remains into an airport. It's like you're complaining that a sunroof doesn't work when the car's upside down.

I'll repeat that the earlier article pointed out the wheel wouldn't move against yoke pressure. Again, it's not a system failure of the trim adjust if the pilot doesn't want to let go of the yoke because the plane's in a terminal dive.

 

[Danoff]

Not a single-point failure at all, the control is not meant to work in that envelope and it doesn't. For any stab trim the airspeed needs to come down using airbrakes, thrust, slats, and stabilisers via the yoke. If it can't be trimmed at overspeed it can't be trimmed, it doesn't matter how you command it.

No, I don't accept that as an explanation. And it's not because i don't follow it, and it's not because I think the sunroof won't work when the car is upsideown.

This is not a case of the control surface being not supposed to work or somehow fundamentally unable to work in those conditions. And in fact I think you yourself are relying on the notion that it will work under hydraulic actuation in those conditions. Because if it wouldn't do that, then I think you have an inherent failure mode designed into the system, not even a single-point failure, just a system that is designed to cause a crash in certain conditions with zero faults.

It's not the case that the manual control isn't supposed to work but the hydraulic control is supposed to work in the same flight conditions. The manual just doesn't, and it's not inherent to it being manual, it's designed badly.

I'll repeat that the earlier article pointed out the wheel wouldn't move against yoke pressure. Again, it's not a system failure of the trim adjust if the pilot doesn't want to let go of the yoke because the plane's in a terminal dive.

No it's not a system failure, it's a system that is designed not to work when it should. It's a system that is designed to crash without a failure which is worse than a failure. The only thing that makes this a single-point failure scenario is that the hydraulic system (in non MAX planes) is not also designed to crash in the same scenario.


Edit:

Give me another example of a control that if you adjust it fully you put yourself into a situation where you cannot adjust it back unless you remove input from other controls.

 

[TenEightyOne]

Give me another example of a control that if you adjust it fully you put yourself into a situation where you cannot adjust it back unless you remove input from other controls.

Sluice gates are a good one and apt due to the fluid forces that can stop you closing a gate/valve that's been over-opened. Another good parallel would be a car with dual steering controls. The pupil is steering hard left and the instructor needs to steer hard right. They're both acting across the same steering pump.

The initial MCAS deployment in the Ethiopian Air crash was recoverable if the pilots had been properly informed. It kept deploying to the point where it was unrecoverable despite the pilots following all the "correct" steps.

You seem to be focussing on the trim wheel's operation at fatal overspeed, you're really focussing on the wrong thing. If a self-driving car erroneously swerves left and the driver doesn't have the time/strength to recover before an accident then the failure point is at the intervention of the autonomy, not in the steering system which has worked perfectly well for billions of system miles.

EDIT: Further to the above... the procedure (however erroneous the investigation might show that to be) after the Lion Air crash was to use the electric trim. The manual trim was not in the procedure (no reason why it would be) and crews were clearly trained in the fact that the manual wheel would not work in certain envelopes. You'll see that the yoke (column) force needs to be neutralised before manual trimming. That's not bad design, it's physics. After that point manual trimming would work although it's hard to imagine why the pilot would use it.

 

[GTV0819]

Agreed. I think we're past the stage of worrying about if airlines did enough to prepare crews for MAX. Boeing created a flying disaster.

I concur. But still, why the hell are they so confident about this aircraft before these incidents happened? I wonder.

 

[TenEightyOne]

I concur. But still, why the hell are they so confident about this aircraft before these incidents happened? I wonder.

I can only guess that they thought this situation could never happen. Given that it clearly did in the Lion Air crash I wonder why the MAX wasn't grounded at that point.

 

[GTV0819]

I can only guess that they thought this situation could never happen. Given that it clearly did in the Lion Air crash I wonder why the MAX wasn't grounded at that point.

Well, they thought that this was just an isolated case since Lion Air has so many poor records already by the time this incident happened. Until the recent EA incident happened, they were proved wrong lol.

 

[Danoff]

Sluice gates are a good one and apt due to the fluid forces that can stop you closing a gate/valve that's been over-opened. Another good parallel would be a car with dual steering controls. The pupil is steering hard left and the instructor needs to steer hard right. They're both acting across the same steering pump.

I should have specified that it should be in an aircraft environment (or similar civilian environment where redundancy is required for all systems to prevent catastrophic loss of life).

The initial MCAS deployment in the Ethiopian Air crash was recoverable if the pilots had been properly informed. It kept deploying to the point where it was unrecoverable despite the pilots following all the "correct" steps.

EDIT: Further to the above... the procedure (however erroneous the investigation might show that to be) after the Lion Air crash was to use the electric trim. The manual trim was not in the procedure (no reason why it would be) and crews were clearly trained in the fact that the manual wheel would not work in certain envelopes. You'll see that the yoke (column) force needs to be neutralised before manual trimming.

The MCAS cutoff also removes hydraulic adjustment of the trim. So while the MCAS was on, the runaway trim would occur. And when it was off, they could only use the manual system. They'd have needed to know that they should release the yoke and allow the plane to head for the ground (at 500 ft altitude) before attempting to manually adjust the trim, which would probably also have killed them. I don't see how it was recoverable.

You seem to be focussing on the trim wheel's operation at fatal overspeed, you're really focussing on the wrong thing. If a self-driving car erroneously swerves left and the driver doesn't have the time/strength to recover before an accident then the failure point is at the intervention of the autonomy, not in the steering system which has worked perfectly well for billions of system miles.

I understand that other things went wrong, but they shouldn't have been unrecoverable. The fact that the manual adjustment didn't work effectively reduced redundancy to single-failure. Once the MCAS failed, they were done. Step 1, disable the MCAS. Step 2 manually adjust the trim... can't, too much aerodynamic load due to failed MCAS. Step 3, release the yoke and re-attempt manual adjustment... can't, too close to the ground. There appears to be no Step 4.

That's not bad design, it's physics.

It's not physics. The hydraulic system can do it. You literally just need to exert enough force. The manual system is not designed to impart that much force, which is a bad design.

 

[TenEightyOne]

The MCAS cutoff also removes hydraulic adjustment of the trim. So while the MCAS was on, the runaway trim would occur. And when it was off, they could only use the manual system.

No, they can also use the electronic trim afer using the "stab trim cutout" switches which disable MCAS. It's in the document above. The pilots use the electronic trim to neutralise yoke pressure (the feedback that helps to 'level' the controls) and can then use manual trim. At no time is use of the manual trim specified in those procedures, they can continue using the electronic trim buttons on the yoke and the yoke itself.

It's hard to imagine why they might use manual trim and it doesn't seem to have been attempted during the Indonesian or Ethiopian crashes.

Well, they thought that this was just an isolated case since Lion Air has so many poor records already by the time this incident happened. Until the recent EA incident happened, they were proved wrong lol.

We don't know what they thought but we know the FAA saw fit to order them to improve the documentation. With that said I think the FAA had it in their hands to save some lives too, which they arguably didn't.

 

[GTsail]

No, they can also use the electronic trim afer using the "stab trim cutout" switches which disable MCAS. It's in the document above. The pilots use the electronic trim to neutralise yoke pressure (the feedback that helps to 'level' the controls) and can then use manual trim. At no time is use of the manual trim specified in those procedures, they can continue using the electronic trim buttons on the yoke and the yoke itself. *****

Can you clarify the above procedures further for me?

It seems from the instructions above in post # 223, the pilots can use the electronic trim to neutralize yoke pressure before they set the stab trim switches to "cutoff", however, once they set these switches to "cutoff", this would no longer be possible. The instructions above seem to imply that only the manual trim wheel could be used once the electronic trim switch was set to "cutoff". Is there another step that I'm overlooking?

Is it possible to turn off the MCAS but leave on the electronic trim mechanism?

 

[TenEightyOne]

It seems from the instructions above in post # 223, the pilots can use the electronic trim to neutralize yoke pressure before they set the stab trim switches to "cutoff", however, once they set these switches to "cutoff", this would no longer be possible. The instructions above seem to imply that only the manual trim wheel could be used once the electronic trim switch was set to "cutoff". Is there another step that I'm overlooking?

Is it possible to turn off the MCAS but leave on the electronic trim mechanism?

I thought the first setting (override) left the switches in operation until after cutout, the manual trim wheel is never used. In this case it's still academic, the aircraft was at terminal overspeed (beyond Vmo) and likely beginning to break up.

STATEMENT OF ISSUE:

The aisle stand trim switches can be used to trim the airplane throughout the flight envelope and fully complies with the reference regulation.

Simulation has demonstrated that the thumb switch trim does not have enough authority to completely trim the aircraft longitudinally in certain corners of the flight envelope, e.g. gear up/flaps up, aft center of gravity, near Vmo/Mmo corner, and gear down/flaps up, at speeds above 230 kts. In those cases, longitudinal trim is achieved by using the manual stabilizer trim wheel to position the stabilizer.

The trim wheel can be used to trim the airplane throughout the entire flight envelope. In addition, the autopilot has the authority to trim the airplane in these conditions. The reference regulation and policy do not specify the method of trim, nor do they state that when multiple pilot trim control paths exist that they must each independently be able to trim the airplane throughout the flight envelope. Boeing did not initially consider this to be a compliance issue because trim could always be achieved, even during the conditions where use of the aisle stand trim switch was required. Subsequent to flight testing, the FAA-TAD expressed concern with compliance to the reference regulation based on an interpretation of the intent behind “trim”. The main issue being that longitudinal trim cannot be achieved throughout the flight envelope using thumb switch trim only.

EASA POSITION

Boeing set the thumb switch limits in order to increase the level of safety for out-of-trim dive characteristics (CS 25.255(a)(1)). The resulting thumb switch limits require an alternative trim method to meet CS 25.161 trim requirements in certain corners of the operational envelope. The need to use the trim wheel is considered unusual, as it is only required for manual flight in those corners of the envelope. The increased safety provided by the Boeing design limits on the thumb switches (for out-of-trim dive characteristics) provides a compensating factor for the inability to use the thumb switches throughout the entire flight envelope. Furthermore, the additional crew procedures and training material will clearly explain to pilots the situations where use of the trim wheel may be needed due to lack of trim authority with the wheel mounted switches. The trim systems on the 737Max provide an appropriate level of safety relative to longitudinal trim capability.

 

[Keef]

I wonder if the NTSB will recommend the MAX have a separate type rating from the other 737s.

 

[Danoff]

No, they can also use the electronic trim afer using the "stab trim cutout" switches which disable MCAS.

From Dotini's article.

In previous models of the 737, the two cutoff switches for the stabilizer had different functions and it was possible to flip one that turned off automatic, noncommanded movement while not flipping the other, which would allow the pilot to continue to move the stabilizer with the thumb switches.

But on the MAX, the two cutoff switches have the same function; one is simply a backup to the other. These switches now cut all power to the motor that moves the stabilizer. So they cut off not only automatic movements not commanded by the pilot, including MCAS, but also the ability of the pilot to move the tail electrically.

 

[TenEightyOne]

From Dotini's article.

Have they removed the override function from MAX? That would be crazy. It seems that the manual (electric) trim control still had authority towards the end of the Ethiopian flight as the pitch trim was still altering in response to thumb commands. The fact remains that controlling the manual wheel over certain airspeeds is difficult due to the physics of it, that can't really be designed out. At those sorts of speeds yoke control would be used to level/unload the plane before cruise trimming. It would be a suicidal pilot who took the trim to such an offset by themselves, and we've only seen an aircraft consistently repeat trim runaways in these two recent accidents.

I wonder if the NTSB will recommend the MAX have a separate type rating from the other 737s.

The differences now seem significant enough for that to be possible. That's ultimately what Boeing have been trying to avoid, I think. The common type was a big selling point.

 

[Dotini]

Latest from the The Emerald City:

The Fraud Section of the U.S. Justice Department’s Criminal Division has convened a grand jury in a sweeping and aggressive criminal investigationinto the jet’s certification that is being carried out by the Transportation Department’s Inspector General. The FBI has also joined that investigation and subpoenas have been issued.

Talk to us
We continue to seek information on the design, training and certification of the Boeing 737 MAX. If you have insights, please get in touch with aerospace reporter Dominic Gates at 206-464-2963 or dgates@seattletimes.com. To communicate on a confidential and encrypted channel, follow the options available at https://st.news/newstips.

The House Committee on Transportation and Infrastructure has requested records from Boeing and the FAA as part of its investigation into the 737 MAX certification process.

And the Federal Aviation Administration (FAA) has set up a review chaired by former National Transportation Safety Board Chairman Chris Hart and including experts from the FAA, NASA, and international aviation regulatory authorities to evaluate all aspects of MCAS, including its design and how pilots interact with the system.

See more here: https://www.seattletimes.com/busine...or-board-review-of-airplane-design-processes/

 

[TenEightyOne]

@Keef, @Danoff, re the override switches, I'm looking to see if they're no longer present on MAX. They work as follows and should allow electrical trim to continue to be used after the stab trim cutoff stage. As I said, the Ethiopian pilots were still using manual electric trim and didn't appear to move the manual wheel trim, although it's impossible to say if they tried or not.

STAB TRIM OVERRIDE switch
NORMAL
- normally guarded to ensure normal operation of the column actuated cutout switch
OVERRIDE
- bypasses the column cutout switches (if both fail)
- restores power to the stabilizer trim switches
- when this switch is placed in override, the main electric trim will operate when commanded regardless of control column position because the column cutout switches are bypassed
- if the stab is jammed you may be up against the column cutout switch (opposite force)
- use STAB TRIM OVRD switch to enable use of main electric stab trim again
- operational test of column cutout switches and OVRD switch:
- do this at the gate during your preflight
- while trimming with electric stab trim, oppose the trim by moving the column in the opposite direction
- column cutout switches should engage, stopping the electric stab trim input
- move the stab trim OVRD switch to OVRD
- trim should resume

See more here: https://www.seattletimes.com/busine...or-board-review-of-airplane-design-processes/

I've used up my free reads for this month. Bah.

 

[Dotini]

I've used up my free reads for this month. Bah.

There wasn't much more to it, just news of corporate scrambling. When/if I quote more from ST, I'll quote the entire thing.

• • Boeing & Aerospace
  • Business

  After 737 MAX crashes, Boeing CEO asks for board review of airplane design processes
  April 5, 2019 at 3:37 pm Updated April 5, 2019 at 8:30 pm
  
  By
  Dominic Gates
  Seattle Times aerospace reporter
  
  
  Addressing criticism of the design of the Boeing 737 MAX’s flight-control systems, the company’s board of directors has created a committee to review how the jet maker designs and develops its new airplanes.
  
  Boeing Chief Executive Dennis Muilenburg said Friday he asked for the review to “confirm the effectiveness of our policies and processes for assuring the highest level of safety on the 737 MAX program, as well as our other airplane programs,” and to “recommend improvements.”
  
  “Safety is our responsibility, and we own it,” Muilenburg said. “When the MAX returns to the skies, we’ve promised our airline customers and their passengers and crews that it will be as safe as any airplane ever to fly.”
  
  The review follows the launching of several external probes looking closely at the certification and safety of the MAX.
  
  A Seattle Times story last month described flaws in the safety analysis of the MAX’s new automatic flight-control system — known as the Maneuvering Characteristics Augmentation System, or MCAS — that was conducted by Boeing as part of the certification of the airplane.
  
  The MCAS is now known to have played the major role in both recent fatal MAX crashes, of a Lion Air jet in October and an Ethiopian Airlines last month.
  
  The Fraud Section of the U.S. Justice Department’s Criminal Division has convened a grand jury in a sweeping and aggressive criminal investigationinto the jet’s certification that is being carried out by the Transportation Department’s Inspector General. The FBI has also joined that investigation and subpoenas have been issued.
  
  Talk to us
  We continue to seek information on the design, training and certification of the Boeing 737 MAX. If you have insights, please get in touch with aerospace reporter Dominic Gates at 206-464-2963 or dgates@seattletimes.com. To communicate on a confidential and encrypted channel, follow the options available at https://st.news/newstips.
  The House Committee on Transportation and Infrastructure has requested records from Boeing and the FAA as part of its investigation into the 737 MAX certification process.
  
  And the Federal Aviation Administration (FAA) has set up a review chaired by former National Transportation Safety Board Chairman Chris Hart and including experts from the FAA, NASA, and international aviation regulatory authorities to evaluate all aspects of MCAS, including its design and how pilots interact with the system.
  
  The committee of Boeing board members will be chaired by Adm. Edmund Giambastiani Jr., former vice chairman of the U.S. Joint Chiefs of Staff. Its other members are Robert Bradway, chairman and CEO of Amgen; Lynn Good, chairman and CEO of Duke Energy; and Edward Liddy, former chairman and CEO of Allstate.
  
  RELATED
  MORE ON THE BOEING 737 MAX
  

  • FAA official tells senator that Boeing 737 MAX inspectors were ‘fully qualified’
  • Boeing will slow 737 production by one-fifth; no layoffs planned
  • Ethiopian pilots fought the Boeing 737 MAX flight controls almost from takeoff, preliminary report shows

 

[Imari]

The fact remains that controlling the manual wheel over certain airspeeds is difficult due to the physics of it, that can't really be designed out.

Of course it can, it's a matter of cost. If they wanted redundant and independent power assist for the "manual" wheel then that could absolutely be included, but it would cost money.

Obviously, the job of an aircraft designer is to make the aircraft as safe as reasonably practicable at the lowest cost. Unfortunately, while engineers tend to understand this pretty well, the businessmen holding the checkbooks have less appreciation for the real world implications of lowering safety standards. It's hard to explain to those not mathematically inclined that a low individual probability of a major accident with a machine actually means a near certainty of a major accident once you have thousands of those machines operating.

 

[GTV0819]

We don't know what they thought but we know the FAA saw fit to order them to improve the documentation. With that said I think the FAA had it in their hands to save some lives too, which they arguably didn't.

They failed to handle their duty properly and now lies the problem. They really should put in their minds that safety should be top priority above all.

 

[TenEightyOne]

Of course it can, it's a matter of cost. If they wanted redundant and independent power assist for the "manual" wheel then that could absolutely be included, but it would cost money.

"Older" aircraft had the ability to go into "override" which re-authorised the manual electric switches (rocker buttons on the yoke) without re-engaging flight computers. I'm still not clear if MAX had this removed, at the moment nothing would surprise me.

The manual wheel is a final redundant system, there's no need to make it hydraulic as a triple-redundant hydraulic trim system already exists in two forms in the 737 (the switches and the yoke). As far as I'm aware this cascade of systems hasn't caused a crash until the two MAX incidents where MCAS trimmed the aircraft into a dramatically nose down position. That took the aircraft beyond the situations for which the QRH gives perfectly recoverable advice. The procedure in the QRH (and for all 737 pilots as far as I can see from pro forums) is to unload the aircraft by changing speed/attitude to reduce the immense aero forces on the elevators that an overspeed gives. Tragically the Lion Air and Ethiopian Air crashes seem to have been caused by MCAS pointing the plane downwards during the heaviest, slowest, lowest part of the flight.

Having read back through the thread I agree with you, @Danoff, @Keef et al - being able to quickly/easily alter the trim wheel may have worked, although we don't know what MCAS might have done next. That means another hydraulic system that isn't affected by the first (on MAX maybe only) stab trim cutoff command, and effect which needs design analysis in itself.

Still, to my mind the aircraft shouldn't ever be in a position where the manual trim wheel is the only solution, the manual electric trim should have maintained authority. The yoke clearly maintained authority until it was out of the trim envelope, it correlated with pitch changes on the Ethiopian Air 737 until the end of the data, but when that ceases it looks to have been in the fully-back position.

They failed to handle their duty properly and now lies the problem. They really should put in their minds that safety should be top priority above all.

It certainly appears so. Clearly Boeing have made some conscious design decisions and we need to see how they justify those in the months to come, and the FAA need to be thoroughly examined with regards to their oversight of that process.

 

[Novalee]

Boeing's legal troubles grew Tuesday as a new lawsuit accused the company of defrauding shareholders by concealing safety deficiencies in its 737 MAX planes before two fatal crashes led to their worldwide grounding.

The proposed class action filed in Chicago federal court seeks damages for alleged securities fraud violations, after Boeing's market value tumbled by $34 billion within two weeks of the March 10 crash of an Ethiopian Airlines 737 MAX.

https://www.nbcnews.com/news/us-new...ass-action-lawsuit-over-737-max-plane-n992796