Wonder if Trump shorted Boeing stock before the decision?

Not likely even if he was trading the stock..

The time to short was before Monday's drop. IMO Boeing stock is unlikely to crater because of what happened today.

 

https://arstechnica.com/information...te-data-provided-link-between-boeing-crashes/

The source of the data in question is a combination of telemetry feeds from the flights' Automatic Dependent Surveillance(ADS) system. Introduced in the US in 2001 and more widely worldwide in the wake of the crash of Malaysian Airlines flight 370 in 2014, Europe has required most aircraft to carry the UHF-band ADS-Broadcast (ADS-B) system since 2017, and the FAA has mandated ADS-B for most aircraft by 2020.
...
The investigation is not complete, and a direct link between the crashes is not certain. Witnesses to the ET302 crash said that they saw smoke coming from the aircraft before the crash. But the vertical speed profile of ET302 transmitted via the aircraft's ADS-B telemetry showed a similar pattern of sudden dives to that of JT610. ADS-B data recorded for ET302 by FlightRadar24 shows that the aircraft, after reaching an altitude of 8,025 feet above sea level, suddenly dipped, plunging 400 feet before recovering briefly. But the aircraft's vertical speed remained unstable, and a few minutes later it dove into the ground. For reference, the airport the flight took off from is at 7,631 feet above sea level—so the aircraft never reached more than 500 feet above the ground, not leaving much room for correction.

 

It's hard for me to believe that plane only got 500 ft high. How far is that wreck site from airport?

Aren't most planes several hundred ft just leaving runway?

 

It's hard for me to believe that plane only got 500 ft high. How far is that wreck site from airport?

Aren't most planes several hundred ft just leaving runway?

Sure, that's why this one crashed IMO. It looks like the plane tried to increase speed to gain flight stability in a last ditch effort to gain altitude but for some reason (confused pilot/bad sensor data/software bug) the control system commanded the nose down. You can flip the manual switch but a manual disconnect of MCAS transforms the flight characteristic of the plane from a traditional 737 (that the pilots do simulator training on) to what looks like a bucking horse at low altitude maybe because the larger engines and different wing/body construction changed stability in a negative fashion. It seems the effect is much like a person trying to take manual control of a powerful but heavily driver-assisted car to prevent an accident. The change-over time needed to get in front of events is small if the driving feel changes from a mild-mannered SUV in a skid to a NASCAR stock car in a skid.

https://www.boldmethod.com/learn-to...-of-static-and-dynamic-stability-in-aircraft/

Two Types Of Stability
Stability is the ability of an aircraft to correct for conditions that act on it, like turbulence or flight control inputs. For aircraft, there are two general types of stability: static and dynamic.

Most aircraft are built with stability in mind, but that's not always the case. Some aircraft, like training airplanes, are built to be very stable. But others, like fighter jets, tend to be very unstable, and can even be unflyable without the help of computer controlled fly-by-wire systems.

http://www.aviatorjoe.net/go/compare/737-800/737_MAX_8/

 

A post on the Pro Pilots Rumor Network cited earlier by @nsaspook describes the aerodynamic reasons for MCAS and why it's on the Max8/9 and not on the original 737. Interesting reading.
https://www.pprune.org/showpost.php?p=10418385&postcount=1348

For those who want to understand how we came to this amateur job:

It’s unique to the MAX because the 737 MAX no longer has the docile pitch characteristics of the 737NG at high Angles Of Attack (AOA). This is caused by the larger engine nacelles covering the higher bypass LEAP-1B engines. The nacelles for the MAX are larger and placed higher and further forward of the wing,

By placing the nacelle further forward of the wing, it could be placed higher. Combined with a higher nose landing gear, which raises the nacelle further, the same ground clearance could be achieved for the nacelle as for the 737NG.

The drawback of a larger nacelle, placed further forward, is it destabilizes the aircraft in pitch. All objects on an aircraft placed ahead of the Center of Gravity will contribute to destabilize the aircraft in pitch.

The 737 is a classical flight control aircraft. It relies on a naturally stable base aircraft for its flight control design, augmented in selected areas. Once such area is the artificial yaw damping, present on virtually all larger aircraft (to stop passengers getting sick from the aircraft’s natural tendency to Dutch Roll = Wagging its tail).

Until the MAX, there was no need for artificial aids in pitch. Once the aircraft entered a stall, there were several actions described l which assisted the pilot to exit the stall.

The larger nacelles, called for by the higher bypass LEAP-1B engines, changed this. When flying at normal angles of attack (3° at cruise and say 5° in a turn) the destabilizing effect of the larger engines are not felt.

The nacelles are designed to not generate lift in normal flight. It would generate unnecessary drag as the aspect ratio of an engine nacelle is lousy. The aircraft designer focuses the lift to the high aspect ratio wings.

But if the pilot for whatever reason manoeuvres the aircraft hard, generating an angle of attack close to the stall angle of around 14°, the previously neutral engine nacelle generates lift. A lift which is felt by the aircraft as a pitch up moment (as its ahead of the CG line), now stronger than on the 737NG. This destabilizes the MAX in pitch at higher Angles Of Attack (AOA). The most difficult situation is when the manoeuvre has a high pitch ratio. The aircraft’s inertia can then provoke an over-swing into stall AOA.

To counter the MAX’s lower stability margins at high AOA, Boeing introduced MCAS. Dependent on AOA value and rate, altitude (air density) and Mach (changed flow conditions) the MCAS, which is a software loop in the Flight Control computer, initiates a nose down trim above a threshold AOA.

It can be stopped by the Pilot counter-trimming on the Yoke or by him hitting the CUTOUT switches on the center pedestal. It’s not stopped by the Pilot pulling the Yoke, which for normal trim from the autopilot or runaway manual trim triggers trim hold sensors. This would negate why MCAS was implemented, the Pilot pulling so hard on the Yoke that the aircraft is flying close to stall.

It’s probably this counterintuitive characteristic, which goes against what has been trained many times in the simulator for unwanted autopilot trim or manual trim runaway, which has confused the pilots of JT610. They learned that holding against the trim stopped the nose down, and then they could take action, like counter-trimming or outright CUTOUT the trim servo. But it didn’t. After a 10 second trim to a 2.5° nose down stabilizer position, the trimming started again despite the Pilots pulling against it. The faulty high AOA signal was still present.

How should they know that pulling on the Yoke didn’t stop the trim? It was described nowhere; neither in the aircraft’s manual, the AFM, nor in the Pilot’s manual, the FCOM. This has created strong reactions from airlines with the 737 MAX on the flight line and their Pilots. They have learned the NG and the MAX flies the same. They fly them interchangeably during the week.

They do fly the same as long as no fault appears. Then there are differences, and the Pilots should have been informed about the differences.

Source: https://leehamnews.com/2018/11/14/bo...to-the-pilots/

Unfortunately the lion and Ethiopian's pilots have not had this chance

The software apparently doesn't do a good job of detecting/compensating for defective sensors which control MCAS. Bloomberg reports that the elevator trim jackscrew shows that it was trimmed nose-down, lending support that MCAS thought the AOA was too great and trimmed for nose down.
https://www.bloomberg.com/news/arti...ash-wreckage-said-to-show-jet-was-set-to-dive

The idea that basic aerodynamic stability was compromised in the quest for the more-efficient engines and then pasted over with software is disturbing. Civil aircraft are designed for positive static and dynamic stability so that the aircraft will naturally seek a more or less normal flight attitude. Having to rely on sensors and software to jury-rig an unstable airframe to make it flyable (and be certifiable) has the potential for catastrophic failures if you don't get it perfect - and if the electronics don't stay perfect. Considering that airlines and pilots were not told of MCAS or the need for it in the first place before the Lion crash is an indicator of how bogus the whole thing is - or how much hubris Boeing carried into the design.

JMHO

 

A post on the Pro Pilots Rumor Network cited earlier by @nsaspook describes the aerodynamic reasons for MCAS and why it's on the Max8/9 and not on the original 737. Interesting reading.
https://www.pprune.org/showpost.php?p=10418385&postcount=1348


The software apparently doesn't do a good job of detecting/compensating for defective sensors which control MCAS. Bloomberg reports that the elevator trim jackscrew shows that it was trimmed nose-down, lending support that MCAS thought the AOA was too great and trimmed for nose down.
https://www.bloomberg.com/news/arti...ash-wreckage-said-to-show-jet-was-set-to-dive

The idea that basic aerodynamic stability was compromised in the quest for the more-efficient engines and then pasted over with software is disturbing. Civil aircraft are designed for positive static and dynamic stability so that the aircraft will naturally seek a more or less normal flight attitude. Having to rely on sensors and software to jury-rig an unstable airframe to make it flyable (and be certifiable) has the potential for catastrophic failures if you don't get it perfect - and if the electronics don't stay perfect. Considering that airlines and pilots were not told of MCAS or the need for it in the first place before the Lion crash is an indicator of how bogus the whole thing is - or how much hubris Boeing carried into the design.

JMHO

A bad implementation or bad engineering principles for a set of given specifications? Boeing designs and builds planes for customers. The air carriers want these characteristics for their pilots and bottom line expenses. We, the flying public want cheap tickets. Boeing seems to have badly muffed the failure modes on this plane but there are very sound reasons this plane was build the way it was.

 

A bad implementation or bad engineering principles for a set of given specifications? Boeing designs and builds planes for customers. The air carriers want these characteristics for their pilots and bottom line expenses. We, the flying public want cheap tickets. Boeing seems to have badly muffed the failure modes on this plane but there are very sound reasons this plane was build the way it was.

Boeing competes with Aerobus? And came out with this plane for a specific reason rushing it to production it seems. At least based on what I have read.

While we all want something for nothing, we have no way of knowing how it is achieved. This is why we have regulatory agencies set up to oversee that this does not happen. Boeing chose to modify and not redesign. Much simpler approval process.

Software is back up. It cannot compensate for flawed design or for undertraining. Perhaps this disaster will drive the point home for some people.

In healthcare industry there was a similar example with infusion pumps, a company was given years by FDA to fix what was a fundamentally flawed charging circuit design causing multiple issues (resulting in patient harm). They kept introducing software fixes instead of going back to the drawing board. It was years before FDA decided to pull the plug on them.

The point I am trying to make is that multiple parties are reaponsible for creating this situation

 

Boeing competes with Aerobus? And came out with this plane for a specific reason rushing it to production it seems. At least based on what I have read.

While we all want something for nothing, we have no way of knowing how it is achieved. This is why we have regulatory agencies set up to oversee that this does not happen. Boeing chose to modify and not redesign. Much simpler approval process.

Software is back up. It cannot compensate for flawed design or for undertraining. Perhaps this disaster will drive the point home for some people.

In healthcare industry there was a similar example with infusion pumps, a company was given years by FDA to fix what was a fundamentally flawed charging circuit design causing multiple issues (resulting in patient harm). They kept introducing software fixes instead of going back to the drawing board. It was years before FDA decided to pull the plug on them.

The point I am trying to make is that multiple parties are reaponsible for creating this situation

Yes, they compete with Aerobus and Aerobus uses the same types of systems in their planes because of customer needs.

Software is not a backup with this plane and hasn't been a backup on aircraft for a long time on many types. The software is designed to emulate a earlier models flight characteristics in normal operations to save retraining costs by using the skills pilots have gained over many years flying the earlier models. Properly implemented it is neither a flawed design philosophy or more dangerous than training the pilots on a 'new' plane that looks almost exactly like a 'old' plane.

 

Software is not a backup with this plane and hasn't been a backup aircraft for a long time on many types. The software is designed to emulate a earlier models flight characteristics in normal operations to save retraining costs by using the skills pilots have gained over many years flying the earlier models. Properly implemented it is neither a flawed design philosophy or more dangerous than training the pilots on a 'new' plane that looks almost exactly like a 'old' plane.

Agreed. And I get your point about software being an integral part of modern flight controls but that is not the whole story here.

Of course, tuning the control response with software to make a new, larger and more powerful MAX allowed a simple transition from earlier 737s. That's common. Cockpits and systems are kept as close as possible to each other to make transitions between planes easier and to allow multiple type-certifications with minimal cross-training. All good.

But the secondary problem is that MCAS was also used to correct a stability defect in the airplane that was introduced as a result of the new bigger engines. That's new. In the MAX, stick forces don't uniformly increase as the stick is pulled back due to the additional pitch-up moments from the engines in the extended nacelles. That problem is serious enough that the aircraft could not be certified at all with that characteristic - FARs say that the stick pressure must increase with increasing AOA so that releasing pressure drops the nose. That inherent stability problem is addressed by MCAS which resets the horizontal stab trim to add some nose-down force to compensate for the nose-up force from the new engine installation. But MCAS has failure modes - in Lion's case it looks like the AOA vane - that are not adequately handled by the software. Pilots were not advised that a simple sensor failure could leave the plane in a very difficult to handle control situation. 737 type rated pilots had a quick on line briefing on the new plane but nothing to indicate how much the normal flight regime shrunk with MCAS inop, let alone the apparently very real prospect that a sensor failure that the system didn't detect and discard would render the aircraft unresponsive to pilot inputs. Even disabling the system in time reverts to a plane with potential control issues due to the inherent pitch-up instability in addition to rectifying the resulting hard-nose-down trim. American and Southwest pilots are not happy about not knowing that. I suspect other aviation authorities are not either thus the reason for other countries grounding the plane before the US. FAA oversight of the test and certification process will come under review as well.

Anyway, that's how I understand the issue IMHO.
J

EDIT: and yeah, getting way out front of the official analyses and reports.. Probably shouldn't do that.

EDIT2: Boeing says software upgrade in 10 days.

 

Great explanation. One wonders whether that new system will have the unwanted effect of requiring extensive retraining in the MAX series? Even then, it seems like a problem waiting to happen again. Hard to imagine such a high performance airplane without an appropriate stick feel.

 

Great explanation. One wonders whether that new system will have the unwanted effect of requiring extensive retraining in the MAX series? Even then, it seems like a problem waiting to happen again. Hard to imagine such a high performance airplane without an appropriate stick feel.

Thanks! I read that American has ordered a 737 MAX simulator. They train pilots from other airlines as well. I'd bet that they'll run that thing through the wringer and develop their own procedures or at least verify Boeing's.

 

Agreed. And I get your point about software being an integral part of modern flight controls but that is not the whole story here.

Of course, tuning the control response with software to make a new, larger and more powerful MAX allowed a simple transition from earlier 737s. That's common. Cockpits and systems are kept as close as possible to each other to make transitions between planes easier and to allow multiple type-certifications with minimal cross-training. All good.

But the secondary problem is that MCAS was also used to correct a stability defect in the airplane that was introduced as a result of the new bigger engines. That's new. In the MAX, stick forces don't uniformly increase as the stick is pulled back due to the additional pitch-up moments from the engines in the extended nacelles. That problem is serious enough that the aircraft could not be certified at all with that characteristic - FARs say that the stick pressure must increase with increasing AOA so that releasing pressure drops the nose. That inherent stability problem is addressed by MCAS which resets the horizontal stab trim to add some nose-down force to compensate for the nose-up force from the new engine installation. But MCAS has failure modes - in Lion's case it looks like the AOA vane - that are not adequately handled by the software. Pilots were not advised that a simple sensor failure could leave the plane in a very difficult to handle control situation. 737 type rated pilots had a quick on line briefing on the new plane but nothing to indicate how much the normal flight regime shrunk with MCAS inop, let alone the apparently very real prospect that a sensor failure that the system didn't detect and discard would render the aircraft unresponsive to pilot inputs. Even disabling the system in time reverts to a plane with potential control issues due to the inherent pitch-up instability in addition to rectifying the resulting hard-nose-down trim. American and Southwest pilots are not happy about not knowing that. I suspect other aviation authorities are not either thus the reason for other countries grounding the plane before the US. FAA oversight of the test and certification process will come under review as well.

Anyway, that's how I understand the issue IMHO.
J

EDIT: and yeah, getting way out front of the official analyses and reports.. Probably shouldn't do that.

EDIT2: Boeing says software upgrade in 10 days.

I'm pretty sure Boeing never called it a defect when they modeled the aircraft characteristics long before an actual production MAX 8 was flying. Stability augmentation is not new or novel in aircraft.
https://www.law.cornell.edu/cfr/text/14/23.672

As usual it's all about trust. At MAX 8 introduction, if Boeing told the FAA "we've got this' stability 'defect' under control so pilots get what they expect from flight controls I think we all would have said OK two years ago.

 

I'm pretty sure Boeing never called it a defect when they modeled the aircraft characteristics long before an actual production MAX 8 was flying. Stability augmentation is not new or novel in aircraft.
https://www.law.cornell.edu/cfr/text/14/23.672

As usual it's all about trust. At MAX 8 introduction, if Boeing told the FAA "we've got this' stability 'defect' under control so pilots get what they expect from flight controls I think we all would have said OK two years ago.

Great link! Thanks. I think you're spot-on re: everyone's acceptance Boeing's self-certification of the system. They have some 'splainin' to do.

 

(3) The trim, stability, and stall characteristics are not impaired below a level needed to permit continued safe flight and landing.

That problem is serious enough that the aircraft could not be certified at all with that characteristic - FARs say that the stick pressure must increase with increasing AOA so that releasing pressure drops the nose. Et seq.

Putting 1 and 1 together, will those planes need major modification and then need re-certification to fly? It seems like a CG/engine thrust-line issue. Now, if it were a model, we'd just put a couple of washers behind the top engine mounts. It seems unlikely the solution on a 737 will be that simple.

 

Putting 1 and 1 together, will those planes need major modification and then need re-certification to fly? It seems like a CG/engine thrust-line issue. Now, if it were a model, we'd just put a couple of washers behind the top engine mounts. It seems unlikely the solution on a 737 will be that simple.

I guess we will find out after a test pilot flies the previously failures crash profiles a few dozen times without crashing with the new software fix.

 

They'll hope no airframe mods will be necessary.

I would guess they'll revamp the software with redundancies out the wazoo and notifications to the pilots when all is not just peachy.
They'll test the snot out of it in the simulator and likely in the air too.
When they know they have a fix, pilots will have to be trained to recognize when the system is degraded or inop and have clear, tested procedures to handle all anticipated events.
I'd expect simulator sessions to train pilots to recognize various stages of problems and handle them using learned, ingrained procedures and aircraft handling under various failure scenarios.

 

Wired has a pretty good article on this as well:

https://www.wired.com/story/boeing-737-max-8-ethiopia-crash-faa-software-fix-lion-air/

I do not see where they address the sensor issue or why there is only one sensor with no back up?

They'll hope no airframe mods will be necessary.

I would guess they'll revamp the software with redundancies out the wazoo and notifications to the pilots when all is not just peachy.
They'll test the snot out of it in the simulator and likely in the air too.
When they know they have a fix, pilots will have to be trained to recognize when the system is degraded or inop and have clear, tested procedures to handle all anticipated events.
I'd expect simulator sessions to train pilots to recognize various stages of problems and handle them using learned, ingrained procedures and aircraft handling under various failure scenarios.

Which is putting the responsibility on the user for something that should have been done differently by the manufacturer.

Example:

I have a problem with corrosion developing on contacts of a charging circuit every 2 months on a brand new unit. This was brought up to the manufacturer. Their reply was to advise to clean contacts every 2 months. What I expect is for them to give me a part that does not corrode.

 

They'll hope no airframe mods will be necessary.

I would guess they'll revamp the software with redundancies out the wazoo and notifications to the pilots when all is not just peachy.
They'll test the snot out of it in the simulator and likely in the air too.
When they know they have a fix, pilots will have to be trained to recognize when the system is degraded or inop and have clear, tested procedures to handle all anticipated events.
I'd expect simulator sessions to train pilots to recognize various stages of problems and handle them using learned, ingrained procedures and aircraft handling under various failure scenarios.

Working as a software developer on these kind of systems seems like it would be kind of cool. I developed an energy management system application that included multiple terminals and a scripting language for the operators. The system would talk to field interface panels which had binary and analog inputs and outputs. I really enjoyed creating something that interfaced to hardware. But if my code screwed up (and it never did after it was in the field, to my knowledge it worked better than the legacy system I replaced) I would shut down an air handler when I was not supposed to. Srcew up in something like this that gets by testing and you can kill a lot of people.

 

Some detail about the Lion Air crash and MCAS system operation.
https://www.satcom.guru/2018/11/stabilizer-trim.html

 

Some detail about the Lion Air crash and MCAS system operation.
https://www.satcom.guru/2018/11/stabilizer-trim.html

Another great find! Thanks. This one was at the bottom of the one you linked.
https://www.satcom.guru/2018/11/737-mcas-failure-is-option.html
Hmmmm..