Boeing 737 MAX 8 grounded worldwide after second crash in less than a few months

[ganbaru]

Factbox: Boeing 737 MAX 8 groundings spread around the world
https://www.reuters.com/article/us-e...-idUSKBN1QT1YQ

U.S. grounds 737 MAX jets, Boeing shares fall again
https://www.reuters.com/article/us-e...-idUSKBN1QU15W

With now the US and Canada Following the EU, China and others, pretty uch the entire fleet is now grounded.

[Ithekro]

Have they finally pushed that airframe too hard, or is there a lack of maintenance?

[ganbaru]

I am not a aviation expert but with the comment from US pilots than had problem with the same model of airplane, it might be a problem related to a captor or the autopilot.

[Renegade334]

Originally Posted by Ithekro

Have they finally pushed that airframe too hard, or is there a lack of maintenance?

No. It might be linked to a new system called MCAS (Maneuvering Characteristics Augmentation System) they added on the Max 8. The M8 has bigger engines, which forced Boeing to change their position on their pylons (so that they don't have to install a taller landing gear or risk the engine casings scraping/banging on the runway during takeoff and landing), meaning that the aerodynamic and weight/balance characteristics of the Max 8 are different compared to the earlier 737s and some software amendment was therefore needed.

Simply put, the M8 now has a "natural" tendency to pitch up (the aircraft nose rises), which can be problematic at slow speeds because excessive angling can disrupt the airflow above the wings (thereby reducing the force known as "lift", which keeps the aircraft aloft) and increase the risk of a stall (leading to a bellyflop and a crash). So Boeing installed the MCAS software, which gives a few "extra" instructions to the horizontal stabilizers (the two small wings under the tail) and forces the plane to pitch down in order to counteract that natural pitch-up.

Given that some pilots, IIRC, testified that the plane sometimes had this weird and unexpected tendency to pitch down, there is some suspicion that there is a bug or a design issue with the sensor+software assembly that might have caused the two lost Max 8s to take a nosedive or "corrupted" the pilots' input. The other problem (IIRC again) is that Boeing omitted mentioning the MCAS in the airplane documentation that they hand over to their client airlines as well as the pilot schools, meaning that many pilots certified for the 737 were unaware that the MCAS existed, that it had a say in the automated handling of the Max 8 and also that it could be turned off.

[ganbaru]

Stakes rise for Boeing as EU, Canada step up scrutiny of 737 MAX after crashes
https://www.reuters.com/article/us-e...-idUSKCN1R0183

As the U.S. Federal Aviation Administration (FAA) analyses Boeing’s plans for a software fix prompted by the first crash five months ago, the European Union’s aviation safety agency EASA promised its own deep look at any design improvements.
“We will not allow the aircraft to fly if we have not found acceptable answers to all our questions,” EASA Executive Director Patrick Ky told an EU parliament committee hearing.
Canada said it would independently certify the 737 MAX in the future, rather than accepting FAA validation. It also said it would send a team to help U.S. authorities evaluate proposed design changes and decide if others were needed.

[mangamuscle]

Originally Posted by Renegade334

So Boeing installed the MCAS software, which gives a few "extra" instructions to the horizontal stabilizers (the two small wings under the tail) and forces the plane to pitch down in order to counteract that natural pitch-up.

Given that some pilots, IIRC, testified that the plane sometimes had this weird and unexpected tendency to pitch down, there is some suspicion that there is a bug or a design issue

IMO the problem is simple, you can't have two different pilots (human or computer) at the same time. It should be either one or the other, since the computer might think the plane is going to crash when the human pilot has it all under control and then they fight for control with catastrophic results. Same shit is going to happen sooner or later with those cars that have computer "enhanced" breaking systems.

[Sheba]

Originally Posted by mangamuscle

IMO the problem is simple, you can't have two different pilots (human or computer) at the same time. It should be either one or the other, since the computer might think the plane is going to crash when the human pilot has it all under control and then they fight for control with catastrophic results. Same shit is going to happen sooner or later with those cars that have computer "enhanced" breaking systems.

Dude, there is too many parameters in modern aviation. The idea of a computer aboard a plane is to assist the pilot and lighten the heavy burden that human pilots would have experienced without AI assistance. If it is indeed the program that is faulty, Boeing have nothing but themselves to blame.

[Renegade334]

Originally Posted by Sheba

The idea of a computer aboard a plane is to assist the pilot and lighten the heavy burden that human pilots would have experienced without AI assistance.

Correct, the autopilot and leveling systems became pretty much required when they started developing what would eventually become the modern-day passenger jet shape. Pioneer planes like the Boeing 367-80 (the precursor to the 707) encountered some issues such as the Dutch roll, which pretty much required constant pilot input to mitigate or eliminate it (in 1959, a Boeing 707 that had its anti-Dutch roll system deactivated for training purposes, ran into that problem and had three of its four engines shorn off its wings in mid-flight, leading to a fatal crash).

Not to mention, given the complexity of both the airframe and the commercial airspace, pilots need to be able to take their hands off the controls to perform other tasks, if not only to ward off fatigue.


That said, it seems to me Boeing neglected to modify the MCAS code to give the pilot's input complete priority over the autoleveling system's instructions. One of the two crashed Max 8s reportedly tried to gain altitude, but consistently failed to do so before it crashed. Sounds like they couldn't override the MCAS...probably because they weren't familiar with it or didn't know it could be turned off.

EDIT: judging by the Lion Air black box' audio recording, the crew was desperate to find a solution to their aircraft's obstination to pitch down (due to a stall alert, which is usually remedied by pitching down to increase speed and therefore restore proper airflow over the wings) and actually spent the last few minutes of their lives thumbing through manuals to find a technical fix to their increasingly dire predicament. The crew knew the sensor alert (stall warning) was erroneous and tried to gain altitude instead, but the autopilot kept forcing the plane down...until it finally crashed. Looks like Boeing is in a world of trouble right now, because the FBI is looking into the 737 Max 8's certification process. That can't be good.

[Key Board]

I learned that in order to pass FAA vetting, the certification is done by Boeing employees

Doesn't that mean that Boeing is vetting their own planes.

[mangamuscle]

Originally Posted by Renegade334

That said, it seems to me Boeing neglected to modify the MCAS code to give the pilot's input complete priority over the autoleveling system's instructions.--- Sounds like they couldn't override the MCAS...probably because they weren't familiar with it or didn't know it could be turned off.

... or maybe in a critical situation the computer has control priority over the pilot over the pretense that only a computer can make the split second maneuvers required to avert a catastrophe.

https://www.youtube.com/watch?v=ARJ8cAGm6JE

[Cosmic Eagle]

Originally Posted by Key Board

I learned that in order to pass FAA vetting, the certification is done by Boeing employees

Doesn't that mean that Boeing is vetting their own planes.

Yes. This whole thing is basically criminal negligence and greed on Boeing and the FAA's part. I mean just look how long it took for the FAA to ground the Max compared to everyone else

[mangamuscle]

https://www.bloomberg.com/news/artic...-later-crashed

The so-called dead-head pilot on the flight from Bali to Jakarta told the crew to cut power to the motor in the trim system that was driving the nose down

I am no pilot but outright unplugging motors in plain flight does not seem common sense.

[Ithekro]

Cutting motors to the thing trying to force your nose down when you can't override the sensor input to the computers (or possibly lose all ability to fly the plane at all I image.)

[mangamuscle]

Originally Posted by Ithekro

Cutting motors to the thing trying to force your nose down when you can't override the sensor input to the computers (or possibly lose all ability to fly the plane at all I image.)

Oh, but you don't really need to, you only have to buy these EXTRA (as in, they are not part of the airplane basic package) safety options that are NOT required by law to be included for the plane to take off.

https://www.nytimes.com/2019/03/21/b...es-charge.html

Heck, at this rate if seat belts in cars were not required by law, they would also be extra, everything to make the golden bull happy.

[scififan]

Originally Posted by mangamuscle

Oh, but you don't really need to, you only have to buy these EXTRA (as in, they are not part of the airplane basic package) safety options that are NOT required by law to be included for the plane to take off.

https://www.nytimes.com/2019/03/21/b...es-charge.html

Heck, at this rate if seat belts in cars were not required by law, they would also be extra, everything to make the golden bull happy.

Some people jokingly referred this extra purchases as DLC packs.

Doesn't Tesla also have numerous sensors installed around their cars. They don't seem to have any feedback control issue due to sensors malfunction.

[ganbaru]

Regulators knew before crashes that 737 MAX trim control was confusing in some conditions: document
https://www.reuters.com/article/us-e...-idUSKCN1RA0DP

The European Aviation and Space Agency (EASA) certified the plane as safe in part because it said additional procedures and training would “clearly explain” to pilots the “unusual” situations in which they would need to manipulate a rarely used manual wheel to control, or “trim,” the plane’s angle.
Those situations, however, were not listed in the flight manual, according to a copy from American Airlines seen by Reuters.

[ganbaru]

Pilot Speaks Out Against Boeing 737
https://www.youtube.com/watch?v=6PYkYy17r2o